Methods for selecting plants, and plant groups

Abstract

This invention provides a method for selecting plants that possess desired traits regarding the internode length of the main stem. [Solution] One aspect of the present invention is a selection method that includes a step of selecting plants using the length of the young shoot at the third leaf development stage as an indicator.

Description

Technical Field

[0001] The present invention relates to a method for selecting plants and a group of plants obtained by the selection.

Background Art

[0002] In the harvesting operation of pumpkins, it is said that 85% of the total harvesting operation time is occupied by the time for searching for fruits. For pumpkin varieties with short internodes that set fruits near the base of the plant, since the fruit-setting location can be assumed, the time for searching for fruits can be shortened. Also, since the timing of fruit-setting is generally uniform among fruits, simultaneous harvesting is possible. Furthermore, the ease of finding fruits is also a property suitable for future mechanization of harvesting. Therefore, for labor-saving in pumpkin cultivation, the breeding of short-internode varieties is required.

[0003] As a method for selecting short-internode varieties of pumpkins, the currently established method is to measure the vine length of pumpkin individuals and compare it with a predetermined standard. More specifically, the cultivated pumpkin seedlings are planted in the field, cultivated for about one month or more, and when the difference in vine length between short-internode varieties / vine varieties becomes clear, the vine length is measured to select the variety.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above method has problems such as a long cultivation period until selection, a large field being required, a large number of personnel being required for cultivation management, and a large cost burden for field materials and the like.

[0006] Regarding watermelons, there are reports that the difference in main stem length between short-internode varieties and climbing varieties becomes clearer earlier, making it possible to select short-internode varieties (Non-Patent Literature 1). However, this method is difficult to apply to plants where the difference in main stem length between short-internode varieties and climbing varieties does not become clear early, such as pumpkins.

[0007] One aspect of the present invention has been made to solve the above problems and aims to provide a new method for early selection of candidate plants that have desired traits with respect to the internode length of the main stem. [Means for solving the problem]

[0008] The inventors of the present invention diligently investigated the above-mentioned problem. As a result, they discovered for the first time that the length of young shoots in plants at a specific growth stage correlates with the internode length of the main stem at a later growth stage, leading to the invention of the present invention.

[0009] The present invention aims to solve the above problems and includes the following:

[0010] 1) A selection method that includes a step of selecting plants using the length of the young shoot at the third leaf development stage as an indicator. 2) A selection method comprising the step of selecting plants using at least one indicator selected from the length of the young shoot at the third leaf development stage, the length of the young shoot at the fourth leaf development stage, and the length of the young shoot at the fifth leaf development stage. 3) A group of plants comprising multiple plants selected by the method described in 1) or 2) above. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to provide a novel method for early selection of candidate plants that have a desired trait with respect to the internode length of the main stem. [Brief explanation of the drawing]

[0012] [Figure 1]Figure 1 is a diagram illustrating the flow of selection technology according to one embodiment of the present invention. [Figure 2] Figure 2 illustrates the measurement of young shoot length, vine length, and determination of plant form according to one embodiment of the present invention. [Figure 3] Figure 3 shows the results according to an embodiment of the present invention. [Figure 4] Figure 4 shows another result according to an embodiment of the present invention. [Figure 5] Figure 5 shows yet another result according to an embodiment of the present invention. [Figure 6] Figure 6 shows yet another result according to an embodiment of the present invention. [Modes for carrying out the invention]

[0013] [1. Selection Method] (overview) A selection method according to one embodiment of the present invention includes a step (selection step A) of selecting plants using the length of the young shoot at the third leaf development stage as an indicator. The selection method according to this embodiment was completed by discovering for the first time that the length of the young shoot of a plant at the third leaf development stage correlates with the subsequent plant morphology (particularly the internode length of the main stem). According to this selection method, for example, it is possible to select plants having desired traits (particularly traits related to the internode length of the main stem) at an early stage.

[0014] (Selection Process A) • Types of plants: The types of plants to be selected are not particularly limited, but plants that exhibit differences in plant form due to differences in the internode length of the main stem are preferred, and in particular, plants that exhibit both climbing and short-internode (dwarf) forms are preferred. Preferably, these are plants of the Cucurbitaceae family such as watermelon, melon, pumpkin, and cucumber, and particularly preferably pumpkin plants. In a broad sense, the term "pumpkin plant" refers to plants belonging to the genus Cucurbita L., and among these, pumpkin plants selected from the group consisting of C. argyrosperma (to which the main cultivated varieties belong), Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata, Cucurbita pepo, and intraspecific or interspecific hybrids thereof are preferred, and in some cases, pumpkin plants selected from the group consisting of C. argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata, and intraspecific or interspecific hybrids thereof are more preferred. The plants to be selected are preferably seed-propagating.

[0015] • Target group for selection: The plants to be selected are the seedlings (young plants) at the third leaf unfolding stage of the above plants. The third leaf refers to the third true leaf, and the number of cotyledons in dicotyledonous plants is not counted. At the same time, the number of plants to be selected may be one individual, but usually it is a plant group composed of multiple individuals of the same species. The lower limit of the number of individuals constituting the plant group is not particularly limited, but for example, it is 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 100 or more, 500 or more, or 1000 or more. The upper limit of the number of individuals constituting the plant group is also not particularly limited, but for example, it is 10,000 or less, 5000 or less, or 1000 or less. The plants to be selected are preferably those grown in containers such as seedling pots or cell trays, and more preferably those grown in seedling pots. However, the plants to be selected may also be seedlings planted in the field. From the perspective of the efficiency of selection and the efficiency of transplanting seedlings, the number of individuals grown in each cell of a seedling pot or cell tray is preferably one individual.

[0016] The plants to be selected may be those in a seedling facility (such as a greenhouse) or outdoors. The plants to be selected may, for example, be placed on a rack such as a seedling bench.

[0017] In the aspect of selection for breeding, the plants to be selected are, for example, seedlings at the third leaf unfolding stage obtained by sowing a plurality of seeds obtained by crossing. The crossing is carried out, for example, between parent plants with differences in plant form (such as vining and short internode (dwarf) traits) due to differences in the internode length of the main stem, between the obtained hybrids (F1), or between the obtained hybrid progeny (F2 and later). Also, crossing between vining varieties or between short internode varieties may be carried out. The crossing may be backcrossing or the like, and the combination of parent plants is not particularly limited as long as crossing is possible.

[0018] ·Timing and criteria for selection: The timing for selecting plants is when the third leaf emerges. At this time, the length of the third leaf seedling is measured. The length of the third leaf seedling refers to the length from the base of the leaf axil to the tip of the leaf (generally the leaf before it unfolds). When the true leaf emerges from the leaf axil, the main vein of the leaf is bent inward and folded, and over time the main vein of the leaf becomes almost straight (as shown in Figure 2). Although not particularly limited, it is sometimes preferable to measure the length of the third leaf seedling when the main vein of the leaf has become almost straight. The seedling length can be measured by directly measuring the length (determining the length in mm) or by relative measurement (comparing it to a predetermined standard to determine if it is longer or shorter). Depending on the conditions of seedling cultivation, in pumpkin plants, the third leaf emergence period is generally around 20 days after sowing (for example, between days 16 and 23, or between days 18 and 21, etc.).

[0019] Plant selection is performed, for example, by comparing the length of the young shoot at the third leaf emergence stage with a predetermined standard. The predetermined standard could be, for example, the length of the young shoot at the third leaf emergence stage in climbing varieties and / or short-internode varieties belonging to the same plant species as the plant being selected (e.g., pumpkin plants). More specifically, the predetermined standard could be, for example, the mean, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage in climbing varieties belonging to the same plant species as the plant being selected (e.g., pumpkin plants). Alternatively, for example, the mean, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage in short-internode varieties belonging to the same plant species as the plant being selected (e.g., pumpkin plants) could be used. Here, the climbing varieties and short-internode varieties used to provide the predetermined standard are not particularly limited, but representative climbing varieties and short-internode varieties may be selected from the same plant species as the plant being selected (in the case of pumpkin plants, for example, the varieties described in the examples may be used). Alternatively, in the case of hybridization (including hybrid progeny) between a climbing variety and a short-internode variety, parent varieties may be selected as the climbing or short-internode variety that provides the specified criteria. In the case of hybridization between climbing varieties or between short-internode varieties (including hybrid progeny), parent varieties may also be selected as the climbing or short-internode variety that provides the specified criteria. It is preferable that seedlings of the plant varieties that provide the specified criteria are grown under substantially the same conditions as seedlings of the plant varieties to be selected.

[0020] The following is an example of selecting candidates for short-internode varieties. When selecting candidates for short-internode varieties, a predetermined criterion is used, for example, a criterion based on climbing varieties, to select candidates whose young shoot length at the third leaf emergence stage is shorter than this criterion, 10% or more shorter than this criterion, 15% or more shorter than this criterion, 20% or more shorter, 25% or more shorter than this criterion, or 30% or more shorter than this criterion. In other cases where candidates for short-internode varieties are selected, a predetermined criterion is used, for example, a criterion based on short-internode varieties, to select candidates whose young shoot length at the third leaf emergence is shorter than 80% (0.8 times) of this criterion, shorter than 90% (0.9 times) of this criterion, shorter than 95% (0.95 times) of this criterion, shorter than this criterion, shorter than 110% (1.1 times) of this criterion, shorter than 115% (1.15 times) of this criterion, or shorter than 120% (1.2 times) of this criterion. In yet another case of selecting candidates for short-internode varieties, selection can be made based on criteria such as the length of the young shoot at the third leaf emergence stage being 25 mm or less, 24 mm or less, 23 mm or less, 22 mm or less, 21 mm or less, 20 mm or less, 19 mm or less, 18 mm or less, 17 mm or less, 16 mm or less, or 15 mm or less, although these values ​​will vary depending on the conditions of seedling cultivation, etc. In yet another case of selecting candidates for short-internode varieties, a method is to select only those with the shortest young shoot length at the third leaf emergence stage from the group of plants to be selected, for example, within the top 40%, 30%, 20%, or 10% from the shortest.

[0021] In the above explanation, we described an example in which selection process A is performed using the length of the young shoot at the third leaf development stage as an indicator. However, selection process A can also be carried out as a process to select plants using at least one indicator selected from the length of the young shoot at the third leaf development stage, the length of the young shoot at the fourth leaf development stage, and the length of the young shoot at the fifth leaf development stage. However, from the perspective of earlier selection, it is preferable to perform selection process A using the length of the young shoot at the third leaf development stage as an indicator.

[0022] • Selection results: This selection method makes it possible to select candidates for plants with desired traits (particularly traits related to the internode length of the main stem) at an early stage. More specifically, it makes it possible to select candidates for climbing varieties and / or short-internode varieties at an early stage. This allows for narrowing down the number of individual plants to be used in the transplanting-selection process B described later, which in turn enables more efficient use of the field, reduces the number of personnel required for cultivation management after transplanting, and reduces the cost burden of field materials, etc.

[0023] (Planting ~ Selection process B) The candidate plants (seedlings) selected in selection process A are, for example, planted in a field. It is preferable to cultivate the plants after planting until the desired traits (especially traits related to the internode length of the main stem) are reflected in the plant's form, and then perform the final selection process (selection process B). For example, in the case of pumpkin plants, the traits of being a climbing variety or a short-internode variety become clearly reflected in the plant's form approximately one month after planting, so selection process B is performed at this time.

[0024] In selection process B, the plants selected in selection process A as candidates for plants possessing the desired traits are evaluated based on whether they actually possess those traits. For example, plants selected in selection process A as candidates for short-internode varieties are evaluated based on whether they actually exhibit short internodes. Alternatively, plants selected in selection process A as candidates for climbing varieties are evaluated based on whether they actually exhibit climbing characteristics. Selection may be performed by measuring the length of the vines (main stem length), or it may be performed without measuring the length of the vines. The plants selected in selection process B are then cultivated in the field, while the plants that were not selected are discarded, for example. The selected plants are then subjected to artificial pollination under controlled conditions (either self-pollination or cross-pollination), and the fruits are harvested and seeds are collected.

[0025] (Selection process from other perspectives) The selection processes A and B described above focus particularly on traits related to the internode length of the main stem (e.g., climbing nature / short internodes). In breeding, there is a need to select plants that inherit the superior traits of the parent varieties (e.g., disease resistance, fruit storability, etc.) and also have short internodes. In such cases, in addition to selection processes A and B, further selection focusing on traits such as disease resistance and fruit storability can be performed.

[0026] (Specific selection schemes for breeding) Figure 1 illustrates the early selection technique for short-internode pumpkin plants according to this embodiment, in comparison with conventional methods. The early selection technique according to this embodiment is performed in the following order: (1) to (11). Note that (1) to (4) below are also performed in the conventional selection method, and although the number of individuals transplanted in (7) to (11) differs significantly, the method itself is the same as in the conventional selection method. (1) Cross-pollination: Around May to July, artificial pollination is performed on the female flowers of the female pumpkin plant that will be the father plant using pollen from the father plant. The female flowers of the mother pumpkin plant are controlled to prevent pollination by other pollen. (2) Seed collection: By autumn of the same year, collect and store the seeds from the fruits obtained as a result of (1). (3) Sowing: In the spring of the following year, sow the seeds collected in (2) one by one into seedling pots or similar containers. The seedling raising process ((3) to (6)) is carried out, for example, in a greenhouse. When raising 100 seedlings, the required greenhouse area is approximately 4m². 2 That is the case. (4) Seedling cultivation: Cultivate seedlings until the third leaf emerges. This is approximately 20 days from sowing in (3). (5) Measurement (sprout length): Measure the length of the young shoot of the third leaf of the seedlings grown in (4). (6) Selection process A: The seedlings whose seedling length was measured in (5) are selected according to the prescribed criteria (in this case, the seedling length of the third leaf is less than 20 mm). Of the 100 seedlings, 40 meet the prescribed criteria (Yes) and 60 do not meet the prescribed criteria (No). The 60 seedlings that do not meet the prescribed criteria are discarded. (7) Transplanting (planting): Transplant the 40 individuals that meet the specified criteria in (6) to the field. The required field area is approximately 84 m². 2 Therefore, when transplanting 100 seedlings (the required field area is approximately 210m²) 2 Compared to [another method], the required field area is significantly smaller. (8) Cultivation: The seedlings transplanted in (7) are grown in the field. Pumpkin plants grow to a size where it is possible to distinguish between climbing and short-internode varieties after about one month of cultivation. (9) Measurement (vine length): Measure the vine length of the pumpkin plants cultivated in (8). (10) Selection process B: Pumpkin plants whose vine length measured in (9) is below the predetermined selection standard are finally selected, and cultivation of the selected pumpkin plants is continued. The selected plants are then subjected to artificial pollination under control (either self-pollination or cross-pollination) by approximately July, for example, to produce fruit. (11) Yield survey and selection: By autumn of the same year, harvest the fruits obtained through (10) and conduct a yield survey, etc. Based on the results of the yield survey, etc., select the fruits, collect the seeds, and store them. If necessary, repeat the process from (3) to (11) in subsequent years.

[0027] [2. Plant groups] A group of plants according to one embodiment of the present invention is a group of plants obtained by performing the selection process A described in the [1. Selection Method] section above. For example, the following group of plants is an example. A group of plants consisting only of multiple plants that meet the selection criteria in selection process A (i.e., have been selected). A group of plants consisting of multiple plants (1) that meet the selection criteria in selection process A, and multiple plants (2) that have not yet undergone selection in selection process A. The multiple plants (1) and the multiple plants (2) constitute the group of plants in a manner that is distinguishable from each other (for example, by being grouped as separate groups). A group of plants consisting of multiple plants (1) that meet the selection criteria in selection process A, multiple plants (2) that have not yet undergone selection in selection process A, and multiple plants (3) that do not meet the selection criteria in selection process A. The multiple plants (1), multiple plants (2), and multiple plants (3) constitute the group of plants in a way that makes them distinguishable from each other (for example, by being grouped as separate groups). A group of plants consisting of multiple plants (1) that meet the selection criteria in selection process A, and multiple plants (3) that do not meet the selection criteria in selection process A. The multiple plants (1) and the multiple plants (3) constitute the group of plants in a way that makes them distinguishable from each other (for example, by being grouped as separate groups).

[0028] There is no particular lower limit to the number of individuals that make up a plant community, but for example, it could be 10 or more individuals, 20 or more individuals, 30 or more individuals, 40 or more individuals, 50 or more individuals, 100 or more individuals, 500 or more individuals, or 1000 or more individuals. There is no particular upper limit to the number of individuals that make up a plant community, but for example, it could be 10,000 or less individuals, 5,000 or less individuals, or 1,000 or less individuals. An example of a plant that makes up a plant community is a seedling grown in a nursery pot. [3. Summary] 1) A selection method that includes a step of selecting plants using the length of the young shoot at the third leaf development stage as an indicator. 2) The method according to 1), wherein the length of the young shoot at the third leaf development stage is compared with a predetermined standard for selection. 3) The method according to 2), wherein the prescribed criteria include at least the length of the young shoot at the time of third leaf development in a climbing variety and / or a short-internode variety belonging to the same plant species as the plant to be selected. 4) As the prescribed criteria, use the average, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage for climbing varieties belonging to the same plant species as the plant being selected, The method according to 3), using the mean, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage in short-internode varieties belonging to the same plant species as the plant to be selected. 5) The above-mentioned plant belongs to the Cucurbitaceae family, and the method is one of 1) to 4). 6) Plants belonging to the Cucurbitaceae family include pumpkins, as described in 5). 7) A method according to any one of 1) to 6) for selecting climbing varieties and / or short-internode varieties. 8) A selection method comprising the step of selecting plants using at least one indicator selected from the length of the young shoot at the third leaf development stage, the length of the young shoot at the fourth leaf development stage, and the length of the young shoot at the fifth leaf development stage. 9) A group of plants comprising multiple plants selected by any of the methods described in 1) to 8) above. The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Examples]

[0029] One embodiment of the present invention is described below.

[0030] [Example 1: Correlation between young shoot length and vine length in pumpkins] (Experimental method) Pumpkin seeds were sown one by one in 10.5cm black plastic pots filled with Takii seedling growing medium, and seedlings were grown. After measuring the length of the seedlings (which would develop into the third true leaves) (seedling length), the seedlings were transplanted to a field at the Hokkaido Agricultural Research Center of the National Agriculture and Food Research Organization (Hitsujigaoka, Sapporo, Hokkaido). The seedling cultivation process was carried out in a glass greenhouse where sunlight constantly entered during the day, with the black plastic pots placed on seedling stands, and watered daily. No heating was used, and if the room temperature exceeded 25℃, the windows were opened to lower the room temperature.

[0031] Next, the pumpkin plants were cultivated in the field for approximately one month after transplanting, and the length of the vines (main stem length) was measured in the field. The relationship between seedling length and vine length (main stem length) was then analyzed. Figure 2 illustrates the measurement of seedling length, vine length, and determination of plant form (whether it is a climbing plant or a short-internode (dwarf) plant). Seedling length was measured from the base of the leaf axil to the tip of the leaf (generally a leaf before unfolding). Vine length was measured from the base to the tip of the main stem. Plant form was determined by whether or not the vines grew.

[0032] The schedule for conducting the tests is as follows: (1) 2021: Sowing on 5 / 17, seedling measurement on 6 / 6, transplanting on 6 / 7, vine length survey on 7 / 7 (2) 2022: Sowing on 5 / 19, seedling measurement on 6 / 6, transplanting on 6 / 7, vine survey on 7 / 7 (3) 2023: Sowing on 5 / 18, seedling measurement on 6 / 5, transplanting on 6 / 7, vine survey on 7 / 6 Furthermore, the pumpkin seeds that were sown are of the following varieties. (1) Bush buttercup (B: dwarf): Examined in 2021 and 2022. (2) Seinaiji (S: climbing type): Tested in 2021 and 2022 (3) F1(B(above (1)) × S(above (2)): 2021 and 2022 exams (4) F2 (Self-pollination of F1 (above (3) above)): Tests conducted in 2022 and 2023.

[0033] The results are shown in Figures 3 and 4. Figure 3 is a histogram showing the relationship between seedling length and plant form for the F2 varieties. The horizontal axis represents seedling length (millimeters), and the vertical axis represents the number of individuals. Of the individuals whose seedling length before transplanting was less than 20 mm, 80% showed short internodes (dwarfism) one month after transplanting. Figure 4 is a plot showing the relationship between seedling length before transplanting and vine length approximately one month after transplanting for the F2 varieties. The horizontal axis represents seedling length before transplanting (millimeters), and the vertical axis represents vine length approximately one month after transplanting (mm). There was a positive correlation between seedling length before transplanting and vine length approximately one month after transplanting (mm).

[0034] Although the relationship between seedling length and plant form in Bush buttercup, Seinaiji, and F1 varieties is not shown in the diagram, similar to the F2 varieties, Bush buttercup (B: dwarf) had relatively short seedling lengths, while Seinaiji (S: climbing) had relatively long seedling lengths. In the F1 varieties, similar to the F2 varieties, those with relatively short seedling lengths tended to be dwarf, and those with relatively long seedling lengths tended to be climbing. We also measured the length of seedlings that would develop into the second true leaves and seedlings that would develop into the first true leaves, but no clear relationship was found between these lengths and plant form.

[0035] [Example 2: Correlation between young shoot length and vine length in existing pumpkin varieties] Using the same method as in Example 1, seeds of existing pumpkin varieties were sown, and the length of the seedlings that would develop into the third true leaf (seedling length) was measured. Then, the relationship between the measured seedling length and the known plant characteristics (vining / short internodes) of each variety was evaluated.

[0036] The pumpkin varieties used were Yukigesho (climbing), Tsurunashiyakko (short internodes), Cold Naget (short internodes), Jeje J (short internodes), and Ebisu (climbing). 30-40 individuals of each variety were measured, and the average value was calculated. The results are shown in Figure 5. On day 15 and 18 after sowing, the third true leaf had not yet unfolded in any of the measured individuals, and they were still in the bud stage. On day 21 after sowing, the third true leaf had not yet unfolded in many of the measured individuals, and they were still in the bud stage, although some individuals had already developed their third true leaf. When true leaves emerge from the leaf axil, the main vein of the leaf is curved inward and folded, and over time the main vein becomes almost straight (as shown in Figure 2). On day 18 after sowing, the main vein of the leaf was almost straight in almost all individuals (as shown in Figure 2).

[0037] [Example 3: Correlation between young shoot length and vine length in existing pumpkin varieties (2)] In this example, four pumpkin varieties with known plant characteristics (climbing / short internode) were grown in an artificial climate chamber, and the length of the third leaf bud was measured. The artificial climate chamber was set to 25°C for 16 hours during the light period, 18°C ​​for 8 hours during the dark period, and a light intensity of approximately 470-580 μmol / m² (PPFD). 2 The environment was fixed at / s (LED output 100%). The pumpkin varieties used were Yukigesho (climbing), Tsurunashiyakko (short internodes), Jeje J (short internodes), and Ebisu (climbing), and five individuals of each variety were measured to calculate the average value. Pumpkin seeds were sown one by one in 6.5 cm black poly pots filled with Takii seedling soil, and seedlings were grown. The length of the seedlings, which will develop into the third true leaves, was measured. Seedling length was measured from the base of the leaf axil to the tip of the leaf (generally a leaf before development, but a developing leaf was used if applicable).

[0038] The results are shown in Figure 6. The vertical axis in Figure 6 represents the seedling length (unit: mm). The results showed a similar trend to that of Example 2. On day 15 after sowing, as in Example 2, the third true leaf had not yet unfolded in any of the plants, and they were still in the seedling stage. More specifically, on day 15 after sowing, the second true leaf was unfolding in Yukigesho and Tsurunashiyakko, but the second true leaf was fully unfolded in Jeje J and almost fully unfolded in Ebisu. However, on day 18 after sowing, unlike in Example 2, the third true leaf was already unfolding in all varieties except Tsurunashiyakko (short internodes) (although not fully unfolded). More specifically, on day 18 after sowing, the third true leaf had just begun to unfold in Yukigesho, and in Jeje J and Ebisu, the third true leaf was mostly unfolded, with the unfolded fourth true leaf visible as a seedling. On the 21st day after sowing, the third true leaves of Yukigesho and Tsurunashiyakko were mostly unfolded, with the unfolded fourth true leaves visible as buds. Ebisu had its fourth true leaves unfolding, and Jeje J had its fourth true leaves mostly unfolded.

[0039] Compared to Example 2, the difference in growth stages between varieties after the same number of days following sowing was larger. Therefore, Figure 6 shows the results of comparing sprout lengths with the growth stages (number of unfolded leaves) roughly matched between varieties. In the left figure, which compares the sprout lengths of the third true leaves, Yukigesho and Tsurunashiyakko are 18 days after sowing, while Jeje J and Ebisu are 15 days after sowing. In the right figure, which compares the sprout lengths of the fourth true leaves, Yukigesho and Tsurunashiyakko are 21 days after sowing, while Jeje J and Ebisu are 18 days after sowing. [Industrial applicability]

[0040] This invention can be used, for example, in the field of plant breeding.

Claims

1. A selection method that includes a step of selecting plants based on the length of the young shoot at the third leaf development stage.

2. The method according to claim 1, wherein the length of the young shoot at the third leaf development stage is selected by comparing it with a predetermined standard.

3. The method according to claim 2, wherein the prescribed criteria include at least the length of the young shoot at the time of third leaf development in a climbing variety and / or a short-internode variety belonging to the same plant species as the plant to be selected.

4. As the prescribed criteria, the mean, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage in climbing varieties belonging to the same plant species as the plant being selected may be used. The method according to claim 3, wherein the mean, median, lower limit, and / or upper limit of the young shoot length at the third leaf emergence stage are used for short-internode varieties belonging to the same plant species as the plant to be selected.

5. The method according to claim 1, wherein the above-mentioned plant is a plant belonging to the family Cucurbitaceae.

6. The method according to claim 5, wherein the plant belonging to the Cucurbitaceae family is a pumpkin plant.

7. The method according to claim 1, for selecting climbing varieties and / or short-internode varieties.

8. A selection method comprising the step of selecting plants using at least one indicator selected from the length of the young shoot at the third leaf emergence stage, the length of the young shoot at the fourth leaf emergence stage, and the length of the young shoot at the fifth leaf emergence stage.

9. A group of plants comprising a plurality of plants selected by the method described in claim 1.

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