Method for suppressing fruit peel damage and materials used in the method

Abstract

To provide a method for suppressing pericarp damage that occurs on the pericarp of fruits including Citrus maxima that belongs to the same classification as the novel variety Mizuki and further citruses, and to provide a material used in the method.SOLUTION: A problem can be solved by a method for suppressing pericarp damage occurring in growing fruits of citrus and a material used in the method, the method comprising coating the surface of the citrus with a material having a light transmittance of 43.9% or less in the entire wavelength range corresponding to the wavelength of visible light, during the period to the harvest time from any time that is within the period until the cumulative total solar radiation from the day when the above citrus is in full bloom is 1246 MJ / m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for suppressing peel damage occurring on the peel of citrus fruits and materials used in this method. [Background technology]

[0002] Mizuki (Ministry of Agriculture, Forestry and Fisheries Variety Registration No. 27604), a variety registered in 2019, is a new variety of pomelo, a type of citrus fruit, and is not yet available on the market. Mizuki is a hybrid variety of Suisho Buntan (seed parent) and Southern Yellow (pollen parent). It has a bright yellow peel, a large fruit size of approximately 11 cm in diameter, high sugar content and good taste, very few seeds, and is juicy, making it suitable for cut fruit. It can be shipped during the citrus off-season from mid-April onwards, has good storage properties, is expected to be a popular gift item, and is anticipated to sell at a high price.

[0003] However, as shown in Figure 1, yellow spots, which are yellow spots about 5 mm in size each, appear on the green peel of the fruit during the summer months from August to mid-November. These yellow spots occur in large numbers on the sun-exposed side of the fruit on the outer perimeter of the tree. When the locations of occurrence are divided into the fruit-bearing parts of the tree and the parts of the fruit, in descending order of frequency, as shown in Table 1, the order is the sun-exposed upper part of the outer perimeter, the sun-exposed lower part of the outer perimeter, the sun-exposed inner part, and the shaded parts of the outer perimeter and inner part. In particular, the occurrence is remarkably high in the upper and lower parts of the outer perimeter.

[0004] The aforementioned yellow spots sometimes turn brown during the harvest season, leaving marks on the bright yellow skin. This results in a lower grade during sorting before shipment, hindering sales in the higher price range.

[0005] While no similar disorders have been observed in citrus varieties to date, the aforementioned yellow spots are a potential issue that may occur in new citrus varieties as breeding progresses. Furthermore, since the yellow spots do not affect the fruit pulp, even if they occur, the fruit pulp retains its characteristic high sugar content, good taste, extremely low seed content, and abundant juice.

[0006] One disorder in which the green peel of citrus fruits turns yellow is called sunburn. However, sunburn differs from the yellow spots mentioned above in terms of size, color, and symptoms. Sunburn occurs when the surface of the fruit is exposed to strong sunlight for several hours during hot summer days, especially after a period of rain, and the peel surface temperature exceeds 40°C. This results in a widespread yellow to brownish discoloration and indentation of the peel across almost the entire sun-exposed surface of the green fruit. The difference between sunburn and yellow spots is that sunburn affects a large area per spot and causes indentations of yellow to brownish skin. As a countermeasure against sunburn, for example, the fruit is covered with a stretchable synthetic fabric from late July to around August.

[0007] Patent Document 1 discloses a fruit growing bag made of a film having the function of transmitting visible light and blocking ultraviolet rays, and having an opening for inserting fruit.

[0008] Patent Document 2 describes a fruit bag made of a resin film that is transparent to visible light, wherein when the transmittance of the resin film at a wavelength of 540 nm is T540 and the transmittance of the resin film at a wavelength of 850 nm is T850, the value of T850 / T540 is 0.85 or less, and the water vapor transmission rate of the resin film at 40°C and 90% RH is 100 to 2000 g / (m²). 2 A fruit bag is disclosed that is (day). Paragraph

[0128] states, "The cause is thought to be the rise in temperature inside the bag due to excessive transmission of infrared rays and sunburn due to the transmission of ultraviolet rays," indicating that the cause of sunburn is the excessive transmission of infrared rays and ultraviolet rays.

[0009] Patent Document 3 discloses a fruit bag containing titanium dioxide that reflects near-infrared light, wherein the light transmittance measured by a spectrophotometer is 12% or less in the 300-780 nm range and 33% or less in the 300-2500 nm range. Furthermore, regarding Examples 1 to 3 of Patent Document 3, Figure 1 shows that the transmittance in the 300-780 nm range includes wavelengths with transmittance of 12% or less and wavelengths with transmittance exceeding 12%.

[0010] Patent Document 4 discloses a fruit protection bag for covering and protecting fruit, comprising a bag body made of a transparent or translucent thermoplastic resin film, with at least both side edges excluding the opening heat-sealed and numerous breathable micropores provided across the entire surface, and a light-scattering member made of thermoplastic resin that is superimposed on one or both sides of the bag body and is peelably heat-sealed to both side edges near the opening. The fruit protection bag is used, for example, for grapes, from June until the harvest season in early September.

[0011] Patent Document 5 discloses a fruit bag containing at least one material selected from the group consisting of far-infrared radiating material, ethylene gas adsorbent, ultraviolet absorber, humidity control material, and heat insulating material. It also states that the material of the fruit bag may be a material with appropriate strength and flexibility, such as recycled paper, synthetic resin such as polyethylene film, nonwoven fabric, or metal foil, and that the timing and duration of covering the fruit with the fruit bag should be adjusted appropriately depending on the type of fruit.

[0012] Non-patent document 1 discloses a stretchable fruit bag made of Tetron yarn, manufactured by Toyo Shokusan Co., Ltd., with the trade name "Sante," which is used to prevent sunburn, promote coloring, and allow citrus fruits to overwinter on the tree. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2021-58150 [Patent Document 2] Japanese Patent Application Laid-Open No. 2020-5563 [Patent Document 3] Japanese Patent No. 5877441 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-268404 [Patent Document 5] Japanese Patent Application Laid-Open No. 2000-37142 [Non-Patent Document]

[0014] Catalog of the fruit bag Sante (product name) for citrus fruits on the homepage of Toyo Shokusan Co., Ltd. (http: / / www.toyoshokusan.co.jp / business / bus001.html) Summary of the Invention Problems to be Solved by the Invention

[0015] The invention of Patent Document 1 uses a fruit-growing bag that transmits visible light and shields ultraviolet light for the purpose of improving the sugar content and deliciousness of fruits such as grapes, pears, persimmons, or citrus fruits and enhancing the appearance of the fruits. Since visible light is sufficiently irradiated onto the sunny side of the citrus fruits, there is a problem that it is impossible to expect suppression of the occurrence of the yellow spots generated on the green fruit skin.

[0016] The invention of Patent Document 2 uses a transparent bag in which the fruit bag transmits visible light and hardly transmits infrared light, and the light transmittance is 25% to 95%. Since visible light is sufficiently irradiated onto the sunny side of the citrus fruits, there is a problem that it is impossible to expect suppression of the occurrence of the yellow spots generated on the green fruit skin.

[0017] ​​​​​​​​​​​​The invention described in Patent Document 3 aims to provide a fruit bag that can prevent delays in fruit harvesting and suppress fruit pulp damage. Therefore, in order to suppress the rise in fruit temperature during the pre-harvest period, it is essential that the fruit bag be formulated with a pigment containing titanium dioxide, which reflects near-infrared rays that are easily converted into heat in sunlight, in addition to light transmittance. Regarding the use of the fruit bag, for example, in the case of pears, it is described that the fruit bag is placed over the fruit 40 days or more before harvest, from early September to early October, after the summer, in order to suppress the rise in fruit temperature. Therefore, there was a problem in that it could not be expected to suppress the occurrence of the aforementioned yellow spots, which occur not only during the limited period before harvest but also from the young fruit stage to the mature stage, and which cannot be said to be caused by a rise in fruit temperature.

[0018] The invention described in Patent Document 4 uses a transparent or translucent thermoplastic resin film for the fruit protection bag. For example, in the case of thermoplastic resin, the light transmittance is 75% to 93%, so visible light is sufficiently irradiated onto the sun-exposed surface of citrus fruits. Therefore, it has the problem that it cannot be expected to suppress the occurrence of the yellow spots that occur on the green peel.

[0019] The invention described in Patent Document 5 aims to improve the sugar content of fruits and prevent sunburn, but it states that the bag material is not limited to highly transparent synthetic resin films such as polyethylene film, and therefore includes fruit bags in which visible light is sufficiently irradiated onto the sun-exposed surface of citrus fruits. As a result, there was a problem in that it could not be expected to suppress the occurrence of the aforementioned yellow spots that occur on the green peel.

[0020] Non-patent document 1 describes a fruit bag (product name: Sante) used for approximately 2-3 weeks from late July to August to prevent sunburn and promote coloring of citrus fruits, or as a cold-weather protection material for overwintering on the tree. However, it also mentions that if the bag is left covering the fruit for a long period to promote coloring, the color may fade, meaning that in rare cases the entire fruit may turn whitish instead of orange or yellow. This raises concerns that it cannot be relied upon to prevent the aforementioned yellowing, which requires long-term measures from at least August in the summer to mid-November in late autumn.

[0021] This invention was conceived in view of these problems, and aims to provide a method for suppressing the occurrence of yellow spots on the peel of fruits, including pomelos and citrus fruits, which belong to the same classification as the new variety Mizuki, and materials used in this method. [Means for solving the problem]

[0022] In this invention, the wavelength of visible light is defined as having a lower limit of 360 nm to 400 nm and an upper limit of 760 nm to 830 nm, the wavelength of infrared light is defined as being longer than the wavelength of visible light and including near-infrared light, and the wavelength of ultraviolet light is defined as being shorter than the wavelength of visible light.

[0023] In this invention, cumulative total solar radiation means the cumulative amount of energy from all sunlight irradiated per unit area of ​​the Earth's surface.

[0024] In this invention, the full bloom day refers to the day when approximately 80% of the flower buds have opened.

[0025] The method for suppressing peel damage described in claim 1 is a method for suppressing peel damage occurring in citrus fruits during their growth, wherein the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². 2 The method is characterized by covering the surface of the citrus fruits with a material whose light transmittance is 43.9% or less across the entire wavelength range corresponding to the wavelengths of visible light, from any point within the period up to the harvest season.

[0026] The method for suppressing peel damage described in claim 2 is a method for suppressing peel damage occurring in citrus fruits during their growth, wherein the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². 2 The method is characterized by covering the surface of the citrus fruits with a material whose light transmittance is less than 31.7% across the entire wavelength range of 423 nm to 720 nm, from any point within the period up to the harvest season.

[0027] The method for suppressing peel damage described in claim 3 is a method for suppressing peel damage occurring in citrus fruits during their growth, wherein the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². 2 The method is characterized by covering the surface of the citrus fruits with a material whose light transmittance is less than 11.0% across the entire wavelength range of 423 nm to 660 nm, from any point within the period up to the harvest season.

[0028] The method for suppressing peel damage according to claim 4 is characterized in that, in any one of claims 1 to 3, the citrus fruit is a pomelo.

[0029] The method for suppressing peel damage according to claim 5 is characterized in that, in any one of claims 1 to 4, the citrus fruit is Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604).

[0030] The method for suppressing peel damage according to claim 6 is characterized in that, in any one of claims 1 to 5, the peel damage is yellow spotting.

[0031] The method for suppressing peel damage described in claim 7 is a method for suppressing peel damage occurring in the fruit of Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604) during its growth, wherein the cumulative total solar radiation of Mizuki from the day of full bloom is 1246 MJ / m². 2 The method is characterized by covering the surface of the Mizuki with a material whose light transmittance is less than 11.0% across the entire wavelength range of 423 nm to 660 nm, from any point in the period up to the harvest season.

[0032] The method for suppressing peel damage according to claim 8 is the method for suppressing peel damage according to claim 1, wherein the material covering the citrus fruits does not contain an additive that has the function of reflecting infrared rays, has a light transmittance of 43.9% or less in the range of all wavelengths corresponding to the wavelength of visible light, and the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². 2The material is a bag-like body with an opening large enough to cover the fruit from any point within the period up to the harvest season, and is characterized in that the opening of the material, or the area around the opening, is sealed with a fruit covering maintenance means.

[0033] The material described in claim 9 is A material used in the method for suppressing peel damage described in claim 1, which is for suppressing the occurrence of yellow spots, It does not contain additives that have the function of reflecting infrared rays. Without incorporating or adding additives that have the function of reflecting ultraviolet rays or making it difficult for ultraviolet rays to pass through, It is characterized by having a bag-like form with a light transmittance of 43.9% or less across the entire wavelength range corresponding to the wavelengths of visible light.

[0034] The material described in claim 10 is one in which the cumulative total solar radiation from the full bloom date of the citrus fruits in claim 9 is 1246 MJ / m². 2 It is characterized by having a size that is capable of covering the citrus fruit from any point within the period up to the following time until the harvest time of the citrus fruit.

[0035] The material described in claim 11 is characterized in that, in claim 9 or 10, the material has an opening, the opening can be opened or closed, and the size when open is greater than or equal to the size of the fruit at harvest, and the size when closed is greater than or equal to the thickness of the branch and less than or equal to the size of the fruit when covered, and is provided with a fruit covering maintenance means. [Effects of the Invention]

[0036] The method for suppressing peel damage described in any of claims 1 to 8 has the effect of suppressing yellow spots that occur on the peel of fruits, including pomelos and citrus fruits of the same classification as the new variety Mizuki.

[0037] The material according to claim 9 or 10 can achieve a light transmittance at a level that can suppress the occurrence of yellow spots, and the cumulative total solar radiation from the full bloom date of the citrus fruits is 1246 MJ / m². 2 The fruit can be covered from any point within the period up to the following time until it is large enough for harvest.

[0038] The material described in claim 11 has the effect of reliably covering the fruit until harvest, even in wind and rain. [Brief explanation of the drawing]

[0039] [Figure 1] This is an explanatory diagram showing the percentage of fruits at different stages of development when new yellow spots appeared on the peel of Mizuki peanuts since the last survey. [Figure 2] This diagram illustrates the results of an investigation into the relationship between fruit surface temperature and the occurrence of yellow spots. (a) shows the changes in fruit surface temperature and ambient temperature inside the covering material from early morning to midnight, and (b) shows the degree of yellow spot occurrence for each type of material. [Figure 3] This diagram illustrates the results of an investigation into the effects of materials with different wavelength transmittances in the ultraviolet range on the macula. (a) is a diagram showing the wavelength transmittance of each material, and (b) is a diagram showing the results of comparing the degree of macular degeneration for each material. [Figure 4] This figure shows the results of an investigation into the effect of materials with the same transmittance in the infrared wavelength range on the macula, and is an explanatory diagram showing the transmittance of each material at different wavelengths. Figure 2(b) shows an explanatory diagram comparing the degree of macula occurrence for each material. [Figure 5] The diagrams illustrate the relationship between the type of synthetic fiber fabric and the degree of macular eczema occurrence. (a) shows the results of the 2018 survey, and (b) shows the results of the 2019 survey. The numbers (without parentheses) in the bar graphs for each synthetic fiber fabric indicate the degree of macular eczema occurrence, while the numbers in parentheses represent the percentage of macular eczema occurrence relative to the untreated sample (100%). [Figure 6] This is an explanatory diagram showing the transmittance of each synthetic fiber fabric at different wavelengths, indicating that a transmittance of 43.9% or less was determined in the visible light wavelength range. [Figure 7] This is an explanatory diagram showing the wavelength transmittance of each synthetic fiber fabric, indicating that a transmittance of less than 31.7% was obtained for wavelengths between 423 nm and 720 nm. [Figure 8] This is an explanatory diagram showing the wavelength transmittance of each synthetic fiber fabric, indicating that a transmittance of less than 11.0% was obtained for wavelengths between 423 nm and 660 nm.

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] The method for suppressing fruit disorders of the present invention is a method for suppressing the occurrence of yellow spots on the fruit skins of citrus fruits including pomelos. The yellow spots refer to yellow spots with a size of about 5 mm per spot on the green fruit skin, and a part of them turns brown during the harvesting period and leaves a mark, which means a disorder in which brown spots remain on the fresh yellow fruit skin. The yellow spots are fruit skin disorders that appear on Ruiji, a new variety of pomelos, but are fruit skin disorders that may occur in various fruits due to future variety improvement.

[0041] In the present invention, the degree of yellow spot occurrence is evaluated as none, few (about 1 to 5), medium (about 6 to 20), or severe (21 or more) for the degree of yellow spot occurrence in one fruit, and is calculated by ((1 × number of fruits with few spots + 3 × number of fruits with medium spots + 5 × number of fruits with severe spots) / (5 × number of surveyed fruits) × 100). Also, the yellow spot incidence rate refers to the ratio of fruits in which the yellow spots have occurred among all fruits. Therefore, the yellow spot incidence rate compares the ratio of fruits in which one or more yellow spots have occurred among the surveyed fruits, while the degree of yellow spot occurrence compares the frequencies calculated based on the number of fruits according to the degree of yellow spot occurrence of the surveyed fruits, and can make a comparison taking into account the degree of yellow spot occurrence.

[0042] The method for suppressing fruit skin disorders of the present invention is a method for suppressing fruit skin disorders that occur in fruits of citrus fruits during growth, and the integrated total solar radiation amount from the full bloom date of the citrus fruits is 1246 MJ / m 2 The period from any time within the period until the following time to the harvesting period is a method of covering the surface of the fruits of the citrus fruits with a material having a light transmittance of 43.9% or less in the range of all wavelengths corresponding to the wavelengths of visible light. The wavelength of visible light ranges from a lower limit of 360 nm to 400 nm and an upper limit of 760 nm to 830 nm.

[0043] Also, the method for suppressing fruit skin disorders of the present invention is a method for suppressing fruit skin disorders that occur in fruits of citrus fruits during growth, and the integrated total solar radiation amount from the full bloom date of the citrus fruits is 1246 MJ / m2 This method involves covering the surface of the citrus fruits with a material whose light transmittance is less than 31.7% across the entire wavelength range of 423 nm to 720 nm, from any point within the period up to the harvest season.

[0044] Furthermore, the present invention provides a method for suppressing peel damage that occurs in citrus fruits during their growth, wherein the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². 2 This method involves covering the surface of the citrus fruits with a material whose light transmittance is less than 11.0% across the entire wavelength range of 423 nm to 660 nm, from any point within the period up to the harvest season.

[0045] The citrus fruits include pomelos, and the pomelos include Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604). Therefore, the pomelos are one type of citrus fruit, and Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604) is one type of citrus fruit and also one type of pomelos.

[0046] The aforementioned peel disorders include yellow spots, cracking of the fruit stalk, blackening of the fruit stalk, and black spot disease, with yellow spots being one of the aforementioned peel disorders.

[0047] Therefore, the present invention provides a method for suppressing peel damage that occurs in the fruit of Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604) during its growth, wherein the cumulative total solar radiation from the day of full bloom of Mizuki is 1246 MJ / m². 2 This method involves covering the surface of the Mizuki with a material whose light transmittance is less than 11.0% across the entire wavelength range of 423 nm to 660 nm, from any point in the period up to the harvest season.

[0048] First, we will explain that the aforementioned yellow spots occur due to exposure to sunlight. Table 1 shows the locations on the peel of the citrus fruit Mizuki where the yellow spots occur. Table 1 divides the fruit's location into the upper outer perimeter of the tree, the lower outer perimeter of the tree, and the interior of the tree, and further divides the fruit into a sun-exposed side and a shaded side, and investigates the yellow spot occurrence rate and degree of yellow spot occurrence. The survey date was November 24, 2016.

[0049] [Table 1]

[0050] Table 1 suggests that the incidence of yellow spots is more than twice as high on the outer edges of the tree compared to the interior. Therefore, it is suggested that yellow spots are more likely to occur in areas exposed to sunlight. From this, it follows that measures to reduce the amount of sunlight that hits the fruit are necessary to suppress the occurrence of yellow spots.

[0051] Next, the period for covering the fruit with the material is determined based on the cumulative total solar radiation from the full bloom date of the citrus fruits being 1246 MJ / m². 2 The following will be explained as the period from any point within the timeframe up to the harvest season.

[0052] When investigating the timing of the new yellow spots on the peel of citrus fruits in the Mizuki variety, as shown in Figure 1, the yellow spots were newly developed on 40.4% of the fruits surveyed on trees during the 9-day period from August 18th to August 27th, 2020, and on 92.6% of the fruits surveyed during the 12-day period from September 18th to September 29th, 2020. This indicates a high incidence of yellow spots during the period from August to mid-November. Furthermore, even in late November and early December, although the incidence of yellow spots decreases to about 10% or less, new occurrences are still observed. Therefore, it is suggested that some form of yellow spot suppression measure is necessary until mid-November, and that yellow spot suppression measures are necessary until harvest.

[0053] Next, we investigated the timing of covering with materials effective in suppressing yellowing. Table 2 shows the results of investigating the relationship between the date on which covering of citrus trees was started and the yellowing rate and degree of yellowing after harvest. The full bloom date was May 19, 2019. The materials mentioned above are not limited to any particular material and may include fabrics made of synthetic fibers such as polyester or nylon, regenerated fibers such as rayon, or semi-synthetic fibers such as acetate. The yellowing suppression effect was evaluated as follows: ◎ if the yellowing degree was 50% or less of the untreated yellowing degree, ○ if it was between 50% and 70%, △ if it was between 70% and 85%, and × if it was above 85%.

[0054] [Table 2]

[0055] Table 2 shows that the degree of yellow spotting in fruits covered with material from June 19 until harvest was 5.8 and the yellow spotting rate was 12.5%, the degree of yellow spotting in fruits covered with material from July 25 until harvest was 6.7 and the yellow spotting rate was 18.3%, the degree of yellow spotting in fruits covered with material from August 23 until harvest was 22.0 and the yellow spotting rate was 50.0%, the degree of yellow spotting in fruits covered with material from September 24 until harvest was 31.4 and the yellow spotting rate was 57.8%, and the degree of yellow spotting in untreated fruits until harvest was 23.8 and the yellow spotting rate was 70.0%.

[0056] Regarding the incidence of yellow spots, it was shown that the later the covering start date, that is, the higher the cumulative total solar radiation from full bloom to the covering start date, the greater the number of fruits with yellow spots. Similarly, regarding the degree of yellow spot occurrence, it was shown that covering from an early stage, that is, from a period when the cumulative total solar radiation is low, is more effective in suppressing yellow spots than untreated fruit. However, it was also shown that if the covering is delayed, that is, when the cumulative total solar radiation increases, the occurrence of yellow spots may be equal to or worse than untreated fruit.

[0057] Table 2 shows that to suppress the occurrence of yellow spots compared to the untreated state, the cumulative total solar radiation from the day of full bloom must be 1246 MJ / m². 2 It was shown that coverage is necessary up to the following point.

[0058] Therefore, the period during which materials are covered as a measure to suppress yellowing is when the cumulative total solar radiation from the day of full bloom is 1246 MJ / m². 2 It was indicated that the period would be from any point within the following timeframe until the harvest season.

[0059] Next, we investigated whether measures to suppress sunburn, a type of fruit peel damage caused by sunlight, are also effective in suppressing the development of macula, another type of fruit peel damage caused by sunlight.

[0060] Fruit bags designed to prevent sunburn are available for fruits, including citrus fruits. Sunburn is known to occur when the fruit surface temperature rises to 40°C for 3 hours or more, and becomes more pronounced when it exceeds 45°C. Paragraph

[0128] of Patent Document 2 states that the cause is thought to be an increase in the temperature inside the bag due to excessive transmission of infrared rays and sunburn due to the transmission of ultraviolet rays. Therefore, we investigated whether yellow spot suppression could be achieved using the same fruit bags as for sunburn.

[0061] The results of the investigation into the relationship between fruit surface temperature and the occurrence of yellow spots are shown in Figures 2(a) and (b). As shown in Figure 2(a), on September 5, 2021, there was almost no difference between the air temperature and the temperature before 7:00 AM and after 7:00 PM. However, between 7:00 AM and 9:00 PM, the highest air temperature was 37.2°C and the lowest average temperature was 28.2°C. The highest fruit surface temperature for synthetic fiber cloth D was 47.1°C and the highest average temperature was 31.9°C. The untreated and synthetic fiber cloth E samples had higher fruit surface temperatures than the ambient temperature but lower than the fruit surface temperature of synthetic fiber cloth D, with a highest value of 42.7°C and an average temperature of 30.4°C. The fruit surface temperatures for synthetic fiber cloth E and the untreated samples were almost the same, as the lines almost overlap as shown in Figure 2(a).

[0062] Furthermore, as shown in Figure 2(b), the degree of yellow spotting was 93.0% lower for synthetic fiber cloth D, where the maximum fruit surface temperature was 47.1°C, higher than that of synthetic fiber cloth E, where the maximum fruit surface temperature was 42.7°C, lower than that of synthetic fiber cloth D. Note that for both synthetic fiber cloth D and synthetic fiber cloth E, the cumulative total solar radiation from the day of full bloom was 917 MJ / m². 2 The covering was applied on July 13, 2021. The synthetic fiber fabric is not limited to any particular type of fabric, and may include any fabric made from synthetic fibers such as polyester or nylon, regenerated fibers such as rayon, or semi-synthetic fibers such as acetate.

[0063] This indicates that there is little correlation between fruit surface temperature, which affects sunburn, and the occurrence of yellow spots, and that it is difficult to suppress the occurrence of yellow spots using materials with the same function as sunburn countermeasures.

[0064] The inventors conceived the present invention by focusing on the relationship between the wavelength range and transmittance and the occurrence of macula, given that macula, like sunburn, is a peel disorder that occurs in areas exposed to sunlight. Sunlight includes ultraviolet, visible, and infrared rays depending on the wavelength. Transmittance, for example, indicates the percentage of sunlight that passes through the material.

[0065] First, as shown in Figure 3, the relationship between the transmittance of wavelengths near the boundary between ultraviolet and visible light and the occurrence of macula was investigated. Since the lower limit of visible light wavelengths is 360 nm to 400 nm, the wavelength of ultraviolet light is less than 360 nm to 400 nm. Material A was made of UV-cut polyolefin, Material B was made of polyolefin, and Material C was made of UV-transmitting polyolefin. The cumulative total solar radiation from the day of full bloom was 917 MJ / m². 2 It was covered on July 13, 2021.

[0066] As shown in Figure 3(a), the transmittances of materials A, B, and C differ significantly at wavelengths below 423 nm, including the ultraviolet range, but they have almost the same transmittance at wavelengths above 423 nm in the visible light range. Furthermore, as shown in Figure 3(b), the results showed almost no difference in the degree of macular degeneration. From this, it is suggested that the difference in transmittance at wavelengths below 423 nm, including the ultraviolet range, is not related to the degree of macular degeneration, and that the wavelengths that affect the degree of macular degeneration are above 423 nm. Therefore, there is no need to add additives or materials that have the function of reflecting ultraviolet light or making ultraviolet light less permeable. The transmittances of each material were measured at 1 nm intervals using a spectrophotometer (JASCO Corporation, V-670).

[0067] Next, as shown in Figure 4, the relationship between wavelength, transmittance, and yarrow formation near the boundary between infrared and visible light was investigated. Since the upper limit of visible light wavelengths is 760nm to 830nm, the wavelength of infrared light is greater than 760nm to 830nm. The synthetic fiber fabrics D and E used both had a cumulative total solar radiation of 917 MJ / m² from the day of full bloom. 2 The coating was applied on July 13, 2021. The transmittance was measured at 1 nm intervals using a spectrophotometer (JASCO Corporation, V-670) to determine the transmission wavelength of each material.

[0068] As shown in Figure 4, the transmittance of synthetic fiber fabric D and synthetic fiber fabric E differs significantly in the visible light range below 733 nm, but the transmittance of synthetic fiber fabric D and synthetic fiber fabric E is almost the same in the infrared range above 733 nm. Furthermore, as shown in Figure 2(b), the degree of macular degeneration was 93% lower with synthetic fiber fabric D than with synthetic fiber fabric E. This suggests that while the difference in transmittance below 733 nm has an effect on the occurrence of macular degeneration, the transmittance in the infrared range above 733 nm has little correlation with the degree of macular degeneration. Therefore, it is not necessary to incorporate additives or materials that have the function of reflecting infrared rays or making infrared rays less permeable.

[0069] Therefore, it became clear that the degree of macular degeneration is greatly influenced by wavelengths of sunlight between 423 nm and 733 nm. Since the wavelength range of visible light is from 360 nm to 400 nm at the lower limit and from 760 nm to 830 nm at the upper limit, wavelengths between 423 nm and 733 nm are visible light.

[0070] Next, as shown in Figure 5, the relationship between each synthetic fiber fabric and the degree of yellow spot occurrence was investigated. Figure 5(a) shows the results of the 2018 survey, where the cumulative total solar radiation from the day of full bloom was 885 MJ / m². 2 The plants were covered on July 12, 2018, and harvested and surveyed on March 7, 2019. Figure 5(b) shows the cumulative total solar radiation from the day of full bloom, which was 1247 MJ / m². 2 The plants were covered on July 25, 2019, harvested on March 4, 2020, and then surveyed.

[0071] Comparing the incidence of macular degeneration in 2018 and 2019 for synthetic fiber fabric A and untreated samples, it was found that the level of macular degeneration differed between years, even for the same type of synthetic fiber fabric or untreated samples. Therefore, the target for suppressing macular degeneration was set not as an absolute numerical target of macular degeneration, but as 50% of the macular degeneration rate of the untreated sample.

[0072] For example, in 2018, only synthetic fiber cloth A (2.0) had a yellowing incidence of 6.3 or less, which is 50% of the untreated yellowing incidence of 12.6. In 2019, synthetic fiber cloth A (6.7) and synthetic fiber cloth A+C (4.0) had a yellowing incidence of 7.35 or less, which is 50% of the untreated yellowing incidence of 14.7. If we evaluate the yellowing incidence per fruit in four stages: none, slight, moderate, and severe, for example, a yellowing incidence level of 7.35 means that out of 20 fruits, 12 to 13 fruits have no yellowing and 7 to 8 fruits have slight yellowing, so the commercial value of the fruit is hardly reduced.

[0073] From Figures 5(a) and (b), the macular suppression effect of synthetic fiber fabric A was 15.9% of the untreated macular susceptibility of 12.6, given that the macular susceptibility in 2018 was 2.0, and 45.6% of the untreated macular susceptibility of 14.7, given that the macular susceptibility in 2019 was 6.7. The macular suppression effect of synthetic fiber fabric A+C was 27.2% of the untreated macular susceptibility of 14.7, given that the macular susceptibility in 2019 was 4.0. Therefore, the macular suppression effect of synthetic fiber fabric A and synthetic fiber fabric A+C was less than 50% of the untreated macular susceptibility. Furthermore, the macula suppression effect of synthetic fiber fabric B is as follows: in 2018, the macula incidence of 7.9 was 62.7% of the macula incidence of 12.6 in the untreated area, so it is classified as ○ (over 50% to 70% of the macula incidence of the untreated area). The macula suppression effect of synthetic fiber fabric C is as follows: in 2019, the macula incidence of 12.0 was 81.8% of the macula incidence of 14.7 in the untreated area, so it is classified as △ (over 70% to 85% of the macula incidence of the untreated area). The evaluation results of the macula suppression effect of each synthetic fiber fabric are summarized in Table 3. In the peel damage suppression method of the present invention, an evaluation of ◎, ○, and △ for macula suppression effect indicates that there is a macula suppression effect, while an evaluation of × indicates that there is no macula suppression effect.

[0074] [Table 3]

[0075] Therefore, the transmittance of synthetic fiber fabrics A, A+C, B, and C, which were evaluated as having a macular suppression effect of ◎, ○, or △, was determined. In this process, based on experimental results showing that the transmittance in the ultraviolet range as shown in Figure 3, or the infrared range as shown in Figure 4, has a very weak causal relationship with macular development, the transmittance of the aforementioned synthetic fiber fabrics A, A+C, B, and C was determined at wavelengths in the visible light range of 360 nm to 830 nm, corresponding to the maximum range of visible light with a lower limit of 360 nm to 400 nm and an upper limit of 760 nm to 830 nm.

[0076] As shown in Figure 6, the maximum transmittance of the synthetic fiber fabrics A, A+C, B, and C in the visible light range of 360 nm to 830 nm is 43.9%. The transmittance was measured at 1 nm intervals using a spectrophotometer (JASCO Corporation, V-560) to capture the transmitted wavelength of each material.

[0077] Therefore, the cumulative total solar radiation from the day of full bloom of the citrus fruits is 1246 MJ / m². 2 A method was derived for covering the surface of the citrus fruits with a material whose light transmittance is 43.9% or less across the entire wavelength range corresponding to the wavelengths of visible light, from any point within the period up to the harvest season.

[0078] Next, the transmittance and wavelength were determined when synthetic fiber fabric C, which has a macular suppression effect of △, was excluded. From Figures 3 and 4, it was found that the wavelength range affecting macular development is between 423 nm and 733 nm, and that synthetic fiber fabrics A and A+C have a macular suppression effect of ◎. Therefore, the upper limit of transmittance for synthetic fiber fabric A and synthetic fiber fabric A+C in the wavelength range of 423 nm to 733 nm was investigated, and the results are shown in Figures 7 and 8. The transmittance was measured at 1 nm intervals using a spectrophotometer (JASCO Corporation, V-560) to determine the transmission wavelength of each material.

[0079] From Figure 7, in the wavelength range of 423 nm to 733 nm, the maximum transmittance of synthetic fiber fabric A is 37.1% compared to synthetic fiber fabric A+C, but the minimum transmittance of synthetic fiber fabric C is 31.7%. Therefore, the upper limit of the wavelength range was set to 720 nm, where the transmittance of synthetic fiber fabric A is less than 31.7%. Furthermore, synthetic fiber fabric B, which has a macular suppression effect (○), has wavelength ranges in the wavelength range of 423 nm to 720 nm where the transmittance is not less than 31.7%. For this reason, the transmittance of synthetic fiber fabric A and synthetic fiber fabric A+C was set to less than 31.7% across the entire wavelength range of 423 nm to 720 nm.

[0080] Therefore, from Figure 7, the cumulative total solar radiation from the day of full bloom of the citrus fruit is 1246 MJ / m². 2 It was found that the occurrence of yellow spots can be suppressed by covering the surface of the citrus fruits with a material whose light transmittance is less than 31.7% in the entire range of wavelengths from 423 nm to 720 nm, from any point within the period up to the harvest season.

[0081] Furthermore, the transmittance and wavelength were determined when synthetic fiber fabric B, which has a macular suppression effect of ○, and synthetic fiber fabric C, which has a macular suppression effect of △, were excluded. As shown in Figure 8, the range of wavelengths and transmittances that include only the transmittances of synthetic fiber fabric A and synthetic fiber fabric A+C, which have a macular suppression effect of ◎, were investigated, while completely excluding the transmittances of synthetic fiber fabric B (○) and synthetic fiber fabric C (△). From Figure 8, in the wavelength range of 423 nm to 733 nm, the range of wavelengths and transmittances that include only the transmittances of synthetic fiber fabric A and synthetic fiber fabric A+C, while completely excluding the transmittances of synthetic fiber fabric B and synthetic fiber fabric C, was found to be less than 11.0% in the entire wavelength range of 423 nm to 660 nm, since the transmittance of synthetic fiber fabric B in the wavelength range of 423 nm to 733 nm is 11.0% or more.

[0082] Therefore, from Figure 8, the cumulative total solar radiation from the day of full bloom of the citrus fruit is 1246 MJ / m². 2 It was found that the occurrence of yellow spots can be suppressed by covering the surface of the citrus fruits with a material whose light transmittance is less than 11.0% in the entire range of wavelengths from 423 nm to 660 nm, from any point within the period up to the harvest season.

[0083] The present invention was developed for the pomelo variety Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration No. 27604), which belongs to the pomelo family of citrus fruits. However, this method of suppressing pomelo damage may also occur in other fruit trees, including citrus fruits, depending on future improvements to fruit varieties.

[0084] Next, the materials used to cover the citrus fruits will be described. The materials may take the form of a bag or a cloth, but any form is acceptable as long as it can cover the citrus fruits.

[0085] The material is a bag-like body that does not contain additives that reflect infrared rays and has a light transmittance of 43.9% or less across the entire wavelength range corresponding to the wavelength of visible light. Furthermore, the material is used when the cumulative total solar radiation from the full bloom day of the citrus fruits is 1246 MJ / m². 2It has a size that allows it to provide coverage from any point within the period up to the following time until the harvest season.

[0086] Alternatively, the material is a bag-like body that does not contain additives with infrared-reflecting properties and has a light transmittance of less than 31.7% across the entire wavelength range from 423 nm to 720 nm, or less than 11.0% across the entire wavelength range from 423 nm to 660 nm. Furthermore, the material is used when the cumulative total solar radiation from the full bloom date of the citrus fruits is 1246 MJ / m². 2 It has a size that allows it to provide coverage from any point within the period up to the following time until the harvest season.

[0087] Table 4 compares the timing and size of covering materials for citrus fruits, specifically Unshu mandarin, Shiranui, and Mizuki. The cumulative total solar radiation from the full bloom date for the aforementioned citrus fruits is 1246 MJ / m². 2 For the Mizuki variety, the size that can be used to cover the area from any point within the period up to the harvest time is as follows: In the case of Mizuki, as shown in Table 4, the horizontal diameter increases from approximately 5 cm when covered to approximately 11 cm at harvest time, which is about 2.2 times larger.

[0088] [Table 4]

[0089] As shown in Table 4, citrus fruits are generally covered with materials during cold periods to protect against frost damage, and some fruits are covered for several weeks to prevent sunburn. As a result, as shown in Table 4, the percentage of fruit that grows significantly during the period of covering is as follows: Unshu mandarins covered to prevent sunburn, and Shiranui covered to protect against frost damage, do not grow very large, while Mizuki fruits grow to approximately 2.2 times their original size, showing the highest growth rate. For this reason, the material used to cover Mizuki fruits to suppress yellowing must be applied when the fruit's diameter is less than 50% of its harvest size, and the material must be large enough to accommodate fruits that are 2 to 2.5 times larger than their size at the time of covering. This is a requirement not seen in fruit bags used for other citrus fruits.

[0090] Therefore, for a period of time after covering, the material covers fruits that are 50% or less in size than the material itself. As a result, there is too much of a gap between the material and the fruit for it to catch, and the material easily falls off due to wind or other factors. To prevent this falling, a fruit covering retention mechanism is provided at the opening of the material.

[0091] The opening will now be described. The material has an opening, which can be opened or closed, and is equipped with a fruit covering maintenance means such that when open the opening is larger than the size of the fruit at harvest, and when closed the opening is larger than the thickness of the branch but smaller than the size of the fruit when covered. The material has at least one opening, and the form of the material may be a bag with four sides, or a cylindrical bag, but any form is acceptable as long as it has the opening.

[0092] The means for maintaining fruit covering include, firstly, the use of shape-adjustable devices such as cable ties, wires, or twist ties; secondly, an opening opening structure that includes a form in which rubber or string is inserted into the opening and pulled to tie the opening, or a form in which the opening is closed with hook-and-loop fasteners or snap buttons; and thirdly, the use of components with a clamping function such as staplers, clips, or pinches. Any means for maintaining fruit covering is acceptable, but is not limited to these.

[0093] Furthermore, the materials of the present invention can be applied not only to evergreen fruit trees such as citrus fruits, but also to deciduous fruit trees.

[0094] Therefore, the method for suppressing peel damage involves using a material covering citrus fruits that does not contain additives that reflect infrared rays, has a light transmittance of 43.9% or less across the entire wavelength range corresponding to the wavelength of visible light, and has a cumulative total solar radiation of 1246 MJ / m² from the day of full bloom of the citrus fruits. 2 This method involves a bag-like body with an opening large enough to cover the fruit from any point within the period up to the harvest time, and involves sealing the opening of the material or the area around the opening with a means for maintaining fruit covering, thereby suppressing damage to the fruit peel.

[0095] Next, we investigated the effect of the method for suppressing peel damage using the materials of the present invention on the occurrence of peel damage, and the results are shown in Table 5. In Table 5, the applied material is the application of calcium carbonate wettable powder, and "untreated" means that no material was applied and no measures were taken. The "yellow spot" column represents the yellow spot occurrence rate. The cumulative total solar radiation from the full bloom day is 1246 MJ / m². 2 The plants were covered on July 25, 2019, and harvested and surveyed on March 4, 2020.

[0096] [Table 5]

[0097] Table 5 shows that synthetic fiber fabric A is also effective against peel disorders other than the aforementioned yellow spots. Therefore, it has become clear that the peel disorder suppression method of the present invention and the materials used in this method are effective not only in suppressing yellow spots but also in suppressing peel disorders other than the aforementioned yellow spots. Thus, it can be seen that the peel disorder suppression method of the present invention is effective not only in suppressing yellow spots but also in suppressing multiple peel disorders.

[0098] Next, we investigated the relationship between the covering date of the material and fruit quality when using the material of the present invention, and the results are shown in Table 6. In Table 6, synthetic fiber cloth A was used as the material, and the cumulative total solar radiation from the full bloom date was 1246 MJ / m². 2 The plants were covered on July 25, 2019, harvested on March 4, 2020, and fruit analysis was conducted on April 14.

[0099] [Table 6]

[0100] Table 6 shows that, compared to untreated fruit, covering the fruit with the material improved the a* value of the peel color regardless of the covering period, specifically resulting in a brighter yellow peel color. There was almost no difference in internal quality such as flesh and sugar content, suggesting that good taste could be maintained.

Claims

1. A method for suppressing peel damage that occurs in citrus fruits during growth, The cumulative total solar radiation from the full bloom date of the aforementioned citrus fruits was 1246 MJ / m². ２ The period from any of the following times until the harvest season, A method for suppressing damage to the fruit peel, characterized by covering the surface of the citrus fruit with a material whose light transmittance is 43.9% or less across the entire wavelength range corresponding to the wavelength of visible light.

2. A method for suppressing peel damage that occurs in citrus fruits during growth, The cumulative total solar radiation from the full bloom date of the aforementioned citrus fruits was 1246 MJ / m². ２ The period from any of the following times until the harvest season, A method for suppressing damage to the fruit peel, characterized by covering the surface of the citrus fruit with a material whose light transmittance is less than 31.7% across the entire range of wavelengths from 423 nm to 720 nm.

3. A method for suppressing peel damage that occurs in citrus fruits during growth, The cumulative total solar radiation from the full bloom date of the aforementioned citrus fruits was 1246 MJ / m². ２ The period from any of the following times until the harvest season, A method for suppressing damage to the fruit peel, characterized by covering the surface of the citrus fruit with a material whose light transmittance is less than 11.0% in the entire range of wavelengths from 423 nm to 660 nm.

4. The method for suppressing peel damage according to any one of claims 1 to 3, characterized in that the citrus fruits are pomelos.

5. The method for suppressing peel damage according to any one of claims 1 to 4, characterized in that the citrus fruit is Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604).

6. A method for suppressing peel damage according to any one of claims 1 to 5, characterized in that the peel damage is yellowing.

7. A method for suppressing peel damage occurring in the fruit of Mizuki (Ministry of Agriculture, Forestry and Fisheries variety registration no. 27604) during growth, wherein the cumulative total solar radiation from the day of full bloom of Mizuki is 1246 MJ / m². ２ A method for suppressing peel damage, characterized by covering the surface of the Mizuki fruit with a material whose light transmittance is less than 11.0% in the entire range of wavelengths from 423 nm to 660 nm, from any point in the period up to the harvest period.

8. In the method for suppressing peel damage according to claim 1, the material covering the citrus fruits does not contain additives that have the function of reflecting infrared rays, has a light transmittance of 43.9% or less in the range of all wavelengths corresponding to the wavelength of visible light, and the cumulative total solar radiation of the citrus fruits from the day of full bloom is 1246 MJ / m². ２ A method for suppressing damage to the fruit peel, characterized by a bag-like body with an opening large enough to cover the fruit from any point within the period up to the harvest time, and the opening of the material, or the area around the opening, being sealed with a fruit covering maintenance means.

9. A material used in the method for suppressing peel damage described in Claim 1, characterized in that it is for suppressing the occurrence of yellow spots, does not contain any additives that have the function of reflecting infrared rays, does not contain or add any additives that have the function of reflecting ultraviolet rays or making ultraviolet rays less permeable, and has the form of a bag-like body having a light transmittance of 43.9% or less in the range of all wavelengths corresponding to the wavelength of visible light.

10. The cumulative total solar radiation from the full bloom date of the aforementioned citrus fruits was 1246 MJ / m². ２ The material according to claim 9, characterized in that it is large enough to cover the citrus fruit from any point within the period up to the following time until the harvest time of the citrus fruit.

11. The material according to claim 9 or 10, characterized in that the material has an opening, the opening can be opened or closed, and the size when open is greater than or equal to the size of the fruit at harvest, and the size when closed is greater than or equal to the thickness of the branch and less than or equal to the size of the fruit when covered.

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