Method for suppressing tomato blister disease

Abstract

This method for suppressing tomato blister disease includes irradiating tomato seedlings with red light for a duration of 4 hours or more and less than 12 hours per day, and irradiating the tomato seedlings with blue light for a duration of 16 to 24 hours inclusive, per day. The duration of red light irradiation to the tomato seedlings is, for example, 4 to 10 hours inclusive, per day. As a light source for irradiating the blue light, for example, a light-emitting diode having a peak wavelength of 420-470 nm is used, and as a light source for irradiating the red light, for example, a light-emitting diode having a peak wavelength of 600-680 nm is used.

Description

Methods to suppress blister disease in tomatoes

[0001] The present invention relates to a method for suppressing blister disease in tomatoes.

[0002] The use of light-emitting diodes (LEDs) as artificial light sources for cultivating plants in closed greenhouses, that is, greenhouses where the cultivation environment, including temperature, humidity, and light exposure time and intensity, can be artificially controlled, is increasing. Since the most efficient wavelengths of light for plant photosynthesis are blue light around 450 nm and red light around 660 nm, LED chips that emit blue light (blue LEDs) and LED chips that emit red light (red LEDs) are often used as light sources for plant growth.

[0003] However, when tomato seedlings are grown in a closed greenhouse equipped with the LED light source described above, some varieties may develop a physiological disorder called blistering disease (leaf gall disease). When blistering disease occurs, the value of the seedlings is significantly reduced, resulting in a large economic loss. Since blistering disease is not observed when the light source is fluorescent lamps or other types of lights in the same closed greenhouse, it has been suggested that irradiation with ultraviolet (UV) light is effective (see, for example, Patent Documents 1, 4, and Non-Patent Document 1).

[0004] However, using ultraviolet (UV) irradiation presents several challenges, including the need for significant additional investment, the accelerated degradation of resins within the greenhouse due to UV irradiation, and the relatively short lifespan of UV light sources. Furthermore, the effects of UV radiation on the human body must also be considered.

[0005] Patent No. 7238947 Patent No. 7472788 Patent No. 7137739 Patent No. 7129906

[0006] Demonstration Research Manual for Vegetable Seedling Production Technology for Establishing a Cutting-Edge Seedling Industry, Fukushima Prefectural Agricultural Research Center, March 2018, pp. 7-10, [online], March 2018, [Retrieved February 26, 2025], Internet<URL:https: / / www.pref.fukushima.lg.jp / uploaded / attachment / 272402.pdf>

[0007] As an alternative to the ultraviolet irradiation described above, a technique has been proposed to suppress vesicular disease in tomatoes by devising a method of irradiation using blue and red LEDs. For example, Patent Document 2 describes that vesicular disease can be suppressed by setting the ratio of the photon flux density of blue light to the total photon flux density of blue and red light within a predetermined range during simultaneous irradiation with blue and red light. Patent Document 3 also describes that the occurrence of vesicular disease can be suppressed by setting the ratio of the photon flux density of blue light to red light within a predetermined range.

[0008] However, these methods still had room for improvement in terms of their effectiveness in suppressing blistering diseases or the efficiency of seedling cultivation.

[0009] This invention has been made in view of the above points, and its objective is to provide a method that can efficiently cultivate tomato seedlings while effectively suppressing the occurrence of blistering disease.

[0010] The tomato blister disease suppression method according to the present invention, which was developed to solve the above problems, involves irradiating tomato seedlings with red light for 4 hours or more but less than 12 hours per day, and with blue light for 16 hours or more but 24 hours per day.

[0011] According to the tomato blister disease suppression method of the present invention described above, it is possible to efficiently cultivate tomato seedlings while effectively suppressing the occurrence of blister disease.

[0012] The inventors investigated a method to suppress bullous disease without reducing growth by utilizing blue and red light, which are widely used in plant cultivation in closed greenhouses. As a result, they found that the duration of red light irradiation greatly affects the occurrence of bullous disease, that the onset of bullous disease can be suppressed by shortening the duration of red light irradiation, and that although seedling growth is stunted by shortening the duration of red light irradiation, this can be avoided by lengthening the duration of blue light irradiation. This led to the present invention.

[0013] In other words, the method for suppressing tomato blister disease according to the present invention involves irradiating tomato seedlings with red light for 4 hours or more but less than 12 hours per day (preferably 4 to 10 hours, more preferably 4 to 9 hours), and irradiating them with blue light for 16 hours or more but less than 24 hours per day (preferably 18 to 24 hours, more preferably 20 to 24 hours). Here, "~" represents a range including the numbers before and after it (the same applies in the following explanation).

[0014] The irradiation of red light over the above-mentioned period may be carried out continuously (referred to as continuous irradiation) or in multiple sessions (referred to as fractional irradiation). Similarly, the irradiation of blue light over the above-mentioned period may be carried out continuously or in fractional irradiation. Furthermore, the period of red light irradiation (the time period during which red light is irradiated) within a day may or may not overlap with the period of blue light irradiation (the time period during which blue light is irradiated).

[0015] The present invention is effective in suppressing the onset of blistering disease in tomato seedlings of various varieties. It is desirable to adjust the red light irradiation time in the present invention according to the susceptibility of the tomato variety to blistering disease. For example, for varieties with low susceptibility to blistering disease, the red light irradiation time should be set longer within the above time range, while for varieties with high susceptibility to blistering disease, the red light irradiation time should be set shorter within the above time range.

[0016] Furthermore, while the present invention is preferably applied to tomato seedlings from immediately after germination until the end of seedling cultivation (preferably from the cotyledon development stage until the seedlings are removed from the closed greenhouse), it is not limited thereto.

[0017] For irradiating tomato seedlings with the aforementioned red light, it is desirable to use an LED with a peak wavelength of 600 nm to 680 nm (i.e., a red LED) as the light source. On the other hand, for irradiating tomato seedlings with the aforementioned blue light, it is desirable to use an LED with a peak wavelength of 420 nm to 470 nm (i.e., a blue LED) as the light source. The photosynthetic photon flux density (PPFD) of the red light is 100 μmol·m －２·s －１ to 200 µmol·m －２ ·s －１ A level of is preferable, and the PPFD of blue light is 50 µmol·m －２ ·s －１ to 150 µmol·m －２ ·s －１ A level of is preferable, but the present invention is not limited thereto.

[0018] In order to investigate the relationship between the irradiation time of blue light and red light and the onset severity of blight, the following seedling raising test was conducted.

[0019] Said seedling raising test was carried out using a container-type cultivation system (Eco Nursery (registered trademark), Elm Co., Ltd.), which is configured by arranging, inside a transport container: a shelf on which a plant cultivation tray (such as a cell tray) is placed; an LED light source composed of a red LED and a blue LED provided on each tier of said shelf; an air conditioning facility that adjusts the temperature and humidity inside said container; an automatic water supply device that supplies water to said tray; and a control device that controls said LED light source, air conditioning facility, and automatic water supply device.

[0020] Note that, as said red LED, an LED with a peak wavelength of 660 nm was used, and the PPFD of red light was approximately 150 µmol·m －２ ·s －１ to 190 µmol·m －２ ·s －１ . In addition, as said blue LED, an LED with a peak wavelength of 450 nm was used, and the PPFD of blue light was approximately 90 µmol·m －２ ·s －１ to 110 µmol·m －２ ·s －１ . PPFD was measured near the upper surface of said cell tray using a photometer (MQ-610, manufactured by APOGEE).

[0021] As the tomato variety to be used for seedling raising, the tomato rootstock variety "Arnold" (Syngenta Japan K.K.), which is markedly prone to blight onset, was used (the same applies to Examples 3 and 4 described later).

[0022] First, a 128-cell seedling tray was filled with seedling growing medium (Sumisoil® N-150, Sumika Agricultural Materials Co., Ltd.), and one seed of the aforementioned tomato variety was sown in each cell, followed by covering with soil. Immediately after sowing, the seedlings were watered from the bottom for 10 minutes, and then germinated under dark conditions for 3 days. From the 4th to the 6th day after sowing, the seedlings were grown with 18 hours of blue and red light irradiation from the aforementioned LED light source per day.

[0023] From the 7th to the 15th day after sowing, multiple test plots with different light irradiation conditions were set up, and light irradiation was carried out under different conditions for each test plot. Specifically, there was a plot (conventional plot) where both red and blue light irradiation time was 18 hours per day, a plot where both blue light irradiation time was 24 hours per day and red light irradiation time was 0, 4, 8, 12, 16, or 20 hours per day, respectively, a plot where both red light irradiation time was 24 hours per day and blue light irradiation time was 0, 4, 8, 12, 16, or 20 hours per day, respectively, and a plot where both red light irradiation time was 9 hours per day and blue light irradiation time was 0, 4, 8, 12, 16, 20, or 24 hours per day, respectively.

[0024] Aside from light irradiation, cultivation conditions followed the conventional practices for tomato seedling cultivation in closed greenhouses. Specifically, the temperature was set to 26°C during the light period (3:00 AM to 9:00 PM) and 18°C ​​during the dark period (9:00 PM to 3:00 AM) in the conventional plot. Temperature control was also performed in other test plots so that the temperature during the same time period was approximately the same as the conventional plot. The carbon dioxide concentration was set to 500 ppm to 700 ppm. Humidity was set to 70%, but in reality, fluctuations were observed within the range of 50% to 80%. Irrigation was performed by bottom watering for 10 minutes daily or every other day.

[0025] Subsequently, at the end of the experiment on the 15th day after sowing, the severity of blistering disease in each test plot was evaluated on a multi-level scale from 0 (none) to 5 (severe), and the above-ground weight (fresh weight) of the seedlings in each plot was investigated.

[0026] Table 1 shows the onset severity of blister disease, above-ground weight (fresh weight), and the overall evaluation based thereon in each test plot on the 15th day after sowing. In the overall evaluation, ○ means "good", △ means "fairly good", and × means "poor" (the same applies to Tables 2 to 4 described below).

[0027]

[0028] As shown in Table 1, severe blister disease occurred in the conventional plot irradiated with red light and blue light for 18 hours each. On the other hand, in each test plot where the irradiation time of blue light was set to 24 hours, the onset severity of blister disease increased as the irradiation time of red light became longer. Although no onset of blister disease was observed in the test plot where the irradiation time of blue light was 24 hours and the irradiation time of red light was 0 hours, growth (above-ground fresh weight) was somewhat poor. Furthermore, in all test plots where the irradiation time of red light was set to 24 hours, high onset severity was exhibited in all plots. In addition, in each test plot where the irradiation time of red light was set to 9 hours, the onset of blister disease was suppressed in all plots, but it was confirmed that the shorter the irradiation time of blue light, the more growth was retarded.

[0029] From the above, it was found that the irradiation time of red light affects the onset of blister disease, and that blue light irradiation does not affect the onset of blister disease. It was also confirmed that reducing the irradiation time of red light decreases the growth amount, but this problem can be solved by extending the irradiation time of blue light.

[0030] Next, the relationship between the irradiation times of blue light and red light and the onset severity of blister disease was investigated using multiple varieties of tomatoes that are considered to have relatively high onset severity of blister disease. In the present example, for the period from the 7th day after sowing to the end of the test (15th day after sowing), a conventional plot in which the daily irradiation time of red light and the daily irradiation time of blue light were each set to 18 hours was set, and plots in which the daily irradiation time of blue light was set to 24 hours in all cases, and the daily irradiation time of red light was set to 0 hours, 8 hours, or 12 hours respectively were set. Cultivation conditions other than those described above were the same as in Example 1.

[0031] Table 2 shows the incidence severity of fruit puffing and the above-ground weight (fresh weight) for each variety and each test plot on the 15th day after sowing. In this table, tomato variety names are listed in descending order of the incidence severity of fruit puffing. In this table, the number immediately after "R" indicates the irradiation time (h) of red light, and the number immediately after "B" indicates the irradiation time (h) of blue light (the same applies to Table 3 described below). Furthermore, the numbers written below these irradiation times are the integrated photosynthetically active photon flux (DLI: daily light integral, unit: mol·m －２ ·d －１ ), which is the daily integrated value of PPFD.

[0032]

[0033] As shown in Table 2, fruit puffing occurred in all varieties used in the present example in the conventional plot where red light and blue light were each irradiated for 18 hours. In contrast, no incidence of fruit puffing was observed in any variety in the plot where the red light irradiation time was set to 0 hours, and the number of varieties developing fruit puffing increased as the red light irradiation time became longer. In addition, in the plot where the red light irradiation time was set to 0 hours, the growth amount (above-ground fresh weight) was low, and disorders such as spindling and mottled leaf albinism occurred, but growth was favorable in the plot where the red light irradiation time was set to 8 hours and the plot where it was set to 12 hours. Furthermore, the comprehensive evaluation considering both the incidence severity of fruit puffing and the growth amount was particularly favorable in the plot where the red light irradiation time was 8 hours.

[0034] Next, in order to verify whether light intensity (PPFD) of red light or irradiation time has a greater influence on the incidence of fruit puffing, the relationship between the light intensity and irradiation time of red light and the incidence severity of fruit puffing was investigated. In the present example, during the period from the 7th day after sowing to the end of the test (the 15th day after sowing), the PPFD of red light was set to 150 µmol·m －２ ·s －１ , with test plots in which the daily irradiation time of the red light was 4 hours, 8 hours, 12 hours, or 16 hours, and the PPFD of red light was set to 75 µmol·m －２ ·s －１The experiment consisted of two sections: one with a daily irradiation time of 4 hours, 8 hours, 12 hours, or 16 hours of red light, and the other with a daily irradiation time of 24 hours of blue light in each section. All other cultivation conditions were the same as in Example 1.

[0035] Table 3 shows the incidence of bullous disease, above-ground weight (fresh weight), and overall evaluation for each test plot 15 days after sowing.

[0036]

[0037] As shown in Table 3, the DLI of red light is the same at 4.4 mol·m. －２ d －１ In comparison to the other test plots, the test plot that was exposed to strong light for a short time (PPFD was 150 μmol·m) －２ ・s －１ Therefore, the test group that was exposed to weaker light for a longer period of time (PPFD was 75 μmol·m) was better than the group that was exposed to red light for 8 hours. －２ ・s －１ The group exposed to red light for 16 hours had a greater incidence of bullous disease. This indicates that the duration of exposure to red light has a greater influence on the development of bullous disease than the amount of red light.

[0038] Next, we investigated the incidence of bullous disease when red light was irradiated continuously and when it was irradiated in fractions.

[0039] In this embodiment, two test plots were established: one receiving red light for 12 hours per day from the 7th day after sowing until the end of the experiment, and the other receiving red light for 8 hours per day. In both plots, the blue light irradiation time was 24 hours per day. For the test plot receiving red light for 12 hours per day, the test period according to this embodiment was until the 16th day after sowing, and for the test plot receiving red light for 8 hours per day, the test period according to this embodiment was until the 13th day after sowing.

[0040] In the aforementioned test plots, the plot irradiated with red light for 12 hours a day (referred to as plot R12B24) was further divided into a plot irradiated with red light continuously for 12 hours (referred to as plot R12), a plot irradiated in two 6-hour sessions (referred to as plot R6×2), a plot irradiated in three 4-hour sessions (referred to as plot R4×3), and a plot irradiated in four 3-hour sessions (referred to as plot R3×4). In plot R6×2, a 4-hour period without red light irradiation (referred to as the "dark period" in this embodiment) was inserted between the two red light irradiation sessions. In plot R4×3, a 3-hour dark period was inserted between each of the three red light irradiation sessions, and in plot R3×4, a 2-hour dark period was inserted between each of the four red light irradiation sessions.

[0041] Furthermore, within the group that received red light irradiation for 8 hours a day (referred to as the R8B24 group), two subgroups were established: one that received red light irradiation continuously for 8 hours (referred to as the R8 group), and another that received red light irradiation in two 4-hour sessions. Of these, the latter subgroup was further divided into groups with a 1-hour dark period between the two red light irradiation sessions (referred to as the R4-1-4 group), a 2-hour dark period (referred to as the R4-2-4 group), a 3-hour dark period (referred to as the R4-3-4 group), a 4-hour dark period (referred to as the R4-4-4 group), a 5-hour dark period (referred to as the R4-5-4 group), a 6-hour dark period (referred to as the R4-6-4 group), and a 7-hour dark period (referred to as the R4-7-4 group).

[0042] In this embodiment, the daily red light irradiation period (the time period during which red light is irradiated) for each of the above-mentioned districts was set as follows. [R12B24 wards] R12 wards 6:00-18:00 R6×2 wards 4:00-10:00, 14:00-20:00 R4×3 wards 4:00-8:00, 11:00-15:00, 18:00-22:00 R3×4 wards 3:00-6:00, 8:00-11:00, 13:00-16:00, 18:00-21:00 [R8B24 Ward] R8 Ward 8:00-16:00 R4-1-4 Ward 8:00-12:00, 13:00-17:00 R4-2-4 Ward 7:00-11:00, 13:00-17:00 R4-3-4 Ward 7:00-11:00, 14:00-18:00 R4-4-4 ward 6:00-10:00, 14:00-18:00 R4-5-4 ward 6:00-10:00, 15:00-19:00 R4-6-4 ward 5:00-9:00, 15:00-19:00 R4-7-4 Ward 5:00-9:00, 16:00-20:00

[0043] Other than the above, the cultivation conditions were the same as in Example 1.

[0044] Table 4 shows the degree of bullous disease incidence, above-ground weight (fresh weight), and overall evaluation for each test plot at the end of the test period (i.e., 16 days after sowing for plot R12B24 and 13 days after sowing for plot R8B24).

[0045]

[0046] As shown in Table 4, in both the group exposed to red light for 12 hours a day (R12B24 group) and the group exposed to red light for 8 hours a day (R8B24 group), no difference was observed in the incidence of bullous disease between the group exposed to red light continuously and the group exposed to it in fractions. However, a slight decrease in growth was observed in the groups with a larger number of fractions of exposure time (i.e., the R4×3 group and the R3×4 group).

[0047] [Embodiments] It will be apparent to those skilled in the art that the exemplary embodiments described above are specific examples of the following embodiments.

[0048] (Section 1) A method for suppressing tomato blister disease according to one aspect of the present invention involves irradiating tomato seedlings with red light for 4 hours or more but less than 12 hours per day, and irradiating them with blue light for 16 hours or more but 24 hours per day.

[0049] (Paragraph 2) The method for suppressing tomato blister disease according to Paragraph 2 is the method for suppressing tomato blister disease according to Paragraph 1, wherein the daily irradiation time of the red light to the tomato seedlings is 4 hours or more and 10 hours or less.

[0050] (Article 3) The method for suppressing bullous disease in tomatoes according to Article 3 is the method for suppressing bullous disease in tomatoes according to Article 1 or Article 2, wherein a light-emitting diode having a peak wavelength of 420 nm to 470 nm is used as the light source for irradiating with the blue light.

[0051] (Article 4) The method for suppressing blistering disease in tomatoes according to Article 4 is the method for suppressing blistering disease in tomatoes according to any one of Articles 1 to 3, wherein a light-emitting diode having a peak wavelength of 600 nm to 680 nm is used as the light source for irradiating with the red light.

Claims

1. A method for suppressing blistering disease in tomatoes, which involves irradiating tomato seedlings with red light for 4 hours to less than 12 hours per day, and with blue light for 16 hours to 24 hours per day.

2. The method for suppressing blistering disease in tomatoes according to claim 1, wherein the daily irradiation time of the red light to the tomato seedlings is 4 hours or more and 10 hours or less.

3. The method for suppressing blister disease in tomatoes according to claim 1, wherein a light-emitting diode having a peak wavelength of 420 nm to 470 nm is used as a light source for irradiating the blue light.

4. The method for suppressing blister disease in tomatoes according to claim 1, wherein a light-emitting diode having a peak wavelength of 600 nm to 680 nm is used as a light source for irradiating the red light.

Images