JPH01225427A - Efficient production of rice hybrid seed - Google Patents

Abstract

PURPOSE:To efficiently produce rice hybrid seeds, by inducing a gene related to the grain character to each parent line related to production of rice hybrid seeds and producing differences in the grain character between both parent lines. CONSTITUTION:A gene related to the grain character is introduced into each parent line related to production of rice hybrid seeds to produce differences in the grain character between both parent lines. Both parent lines are then raised and harvested after full maturity of the seeds. One parent line is excluded to purely and effectively produce a rice F1 seed and maintain the male sterility line.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing rice F1 seeds and maintaining male sterile lines in a pure and efficient manner in rice hybrid seed production.

[Conventional technology]

In general, it has been known for a long time that when plants are hybridized (hybrid, Fl ('F1 m) = first hybrid generation), they become more vigorous than either of their parents with respect to many traits, and yield and quality are improved. This is called hybrid vigor, and it is used in hybrid rice.

However, rice is a self-fertilizing crop, meaning that both the mother (pistil) and father (stamen) are present in one spikelet (“eika” = flower wrapped in rice husk), thus obtaining hybrid seeds. Remove all stamens just before flowering (
Traditionally, in rice breeding, each seedling must be emasculated before flowering, then covered with a bag to avoid confusion, and then pollinated with the pollen from the father stamen. Crossing was carried out by pollinating the pollen of the parent and then covering it with a bag.

Although such methods are feasible for laboratory-scale operations such as breeding, they are completely unusable on a commercial scale, where large quantities of hybrid seeds must be produced.

Therefore, attempts were made to introduce a seed collection system that utilizes male sterility in order to obtain large quantities of hybrid seeds even for self-fertilized crops such as rice. Regarding the production of hybrid rice, currently the main axis is the cytoplasmic male sterile line, and lines for maintaining it, as well as fertility recovery lines for producing F1 hybrids (^-1ine, B-1ine, and R -1i
The ``Three Fundamental Law'' has been established based on three systems of ``ne''. In this system, A-1ine is the mother, R-
A-1ine is used as the father to produce 11 seeds, but since the 11 seeds are produced on the mother A-1ine plant, the father line is completely unnecessary when collecting seeds. In addition, as the name suggests, male sterile lines do not produce any fertile fruit on their own, so the line must be maintained using B-1ine as the father, but in that case, F1
It is fraught with the same problems as seed production.

The method of seed production currently used is to plant the mother and father lines in separate rows in the field and cross them, and when the seeds are harvested, the hybrid seeds grown on the mother plant are mixed with the hybrid seeds on the father plant. This is done by separating the unneeded seeds that have ripened and harvesting them separately.

[Problem to be solved by the invention]

The reason behind this cultivation method is that it is not easy to distinguish between necessary hybrids and unnecessary paternal lines. If these different types of seeds are mixed together, not only will the quality be extremely unfavorable, but it will also be impossible to maintain pure strains. Therefore, as mentioned above, the strains of both parents must be cultivated with clearly separated rows.

However, since this method cannot reduce the distance between the parent plants, the pollination rate is low and the amount of hybrid seeds produced per unit area is low. At each stage, the mother line and the father line must be clearly distinguished, which requires a great deal of effort in cultivation management.

Furthermore, in order to maintain the purity of each line in hybrid rice production, it is essential to remove contamination from different lines, but traditionally this work has had to rely mainly on uncertain identification based on experience. Ta.

In order to solve these problems, it is necessary to make it easy to distinguish between the maternal lineage and the paternal lineage.

In addition, in order to improve the production of hybrid seeds, it is desirable to increase the pollination rate by planting a mixture of both parental lines, which have been planted separately in rows.

[Means to solve the problem]

It is known that there are differences in some traits among plant varieties and lines. Therefore, we attempted to efficiently produce rice hybrid seeds by utilizing the fact that such differences in traits are expressed by introducing a gene that controls the traits, and thus arrived at the present invention.

That is, the present invention introduces genes related to grain traits into the parent line involved in the production of rice hybrid seeds,
By creating differences in grain traits between the parental lines and identifying the differences, one parent line can be removed after seed harvest, and 11 seeds and male sterile line seeds can be efficiently obtained while maintaining purity. By introducing the method and genes related to grass type traits into the parental lines involved in the production of rice hybrid seeds, differences in grass type traits are generated between the parental lines, and by identifying the differences, one of the parental lines is This is a method for efficiently obtaining 11 seeds and male sterile line seeds while maintaining their purity by removing them before harvesting the seeds.

In the present invention, grain traits refer to phenotypic traits that appear in seeds, such as chaff color, grain weight, grain shape, and grain weight,
In addition, plant type traits refer to phenotypic traits that appear in young seedlings or grown plants, such as plant height or leaf color.

Below, we will specifically describe a method for producing rice with such clearly distinguishable traits, as well as an efficient method for producing hybrid seeds using the method.

Mutation is a method of introducing clearly distinguishable grain and carriage traits into the parental lines involved in the production of rice hybrid seeds. Examples of mutagenesis techniques include methods that use radiation or methods that do not require special treatment in cell culture. Either method can impart distinctly distinguishable traits to plants, although the frequency varies.

Induce callus (cell mass) from rice seeds.

This callus is repeatedly subcultured in a growth medium (a method that does not require any special treatment), or the suspension cultured cells obtained by subculture are irradiated. Then, after growing in growth medium,
The callus is transplanted to a plant regeneration medium (differentiation medium). After the differentiated plant is acclimated, it is transplanted onto soil.

From the plants regenerated in this way, individuals with clearly distinguishable traits in their grains or racks are selected. The resulting clearly distinguishable traits are stably inherited in many strains.

The clearly distinguishable traits thus obtained can then be introduced into other cultivars by conventional cross breeding methods.

Hybrid seeds are produced using the rice varieties with clearly distinguishable traits obtained as described above.

As a first method, seedlings of the mother and father lines are raised separately, then planted in rows as usual, and only the mother line is harvested when the seeds are fully ripe. In this case, at each stage of cultivation, the contamination of different strains is eliminated based on the differences in traits in the carriages of each strain.

The second method is to mix the seeds of the mother and father lines to make seedlings and cultivate them in the field. This method is called mixed planting. When the seeds are fully ripe, the seeds in the field are harvested without selection. After harvesting, the mother line is selected based on the differences in grain traits between the lines.

[Effect]

By introducing genetic factors for grain or plant type traits into the parental lines involved in rice hybrid seed production, clear differences in these traits can be generated between the parental lines, making it possible to distinguish between the parental lines. This can be done with a probability of 9% or more. Thereby, production of 11 seeds and maintenance of male sterile lines can be performed with high purity and high efficiency.

〔Example〕

The present invention will be explained below with reference to Examples.

Example 1 Fertility recovery line (MT-1?V5) derived from Chinese rice C57
) calli were induced from seeds. This callus is MSi book, Sigt1. c3χ), agar (0,8χ), and 2.
The cells were cultured for one month in a medium containing 4-D (lpp■) (hereinafter referred to as growth medium). The proliferated callus was further subcultured in a growth medium for 1 month. The obtained callus is N6
The plants were transplanted to a medium (differentiation medium) containing inorganic salts and Mta<3χ), and the plants were regenerated. From these regenerated plants, individuals that were clearly taller than the original C57 were selected, and 35 long-culm fertile lines were obtained. Among these, two lines (MT-RV5-TXI and MT-RV5-TX2) that reliably restored fertility were obtained through a cross test with a male sterile line (MT-0MS4).

Using the thus obtained long culm fertility restored line as the father, a cultivation test was conducted to produce 11 seeds by mixed planting according to a conventional method. At this time, a similar cultivation test was conducted using C57 as the father, and the fruiting rate was compared. The results are shown in Table 1, and the cultivated long culm fertile lines showed a high fruiting rate.

Furthermore, when a conventional fertility recovery line (MT-RV-5) was used, this father line had almost the same plant height as the F1 plants after fruiting, making it impossible to remove; When the fertility restored line was used, the plant height was clearly higher than that of the Fl plants, and the panicles could be easily removed.

Table 1 Example 2 Line with cytoplasmic male sterility (M
Callus was induced from the seeds of T-0MS7). This callus is basically LS! II! (3χ) and 2,4-ro (1 ppm) were subcultured every week to obtain suspension cultured cells. These suspension cultured cells were irradiated with 20 kR gamma rays, and agar (0,8
%) (hereinafter referred to as growth medium) for one month. The surviving callus was further transferred to a growth medium and allowed to grow. The obtained callus was treated with N6 inorganic salts and Si!
! Medium containing sugar (3z) (hereinafter referred to as differentiation medium)
The plants were regenerated. From these regenerated plants, 24 lines with red seeds (rice husks) were selected by test crossing with rice (MT-BT) with normal seed color.

Among these, a fertility-recovered line with normal seed color (MT
-RL9), three lines with red fruiting seeds (MT-0MS7-AXI, MT-0MS7-A
X2, and MT-0MS7-AX3) were obtained. These lines were maintained by division.

Using the line thus obtained as the mother tree, cultivation tests were conducted to obtain 11 seeds by mixed planting and row planting according to conventional methods. When 0 seeds were fully ripe, all seeds in the field were harvested without selection. . By identifying the surface color of the obtained seeds, we can use a commercially available sorter to clearly distinguish whether the seeds were self-fertilized by the father and set fruit (normal color) or those with 11 seeds (red). Table 2 shows the fruit set rate of 11 seeds when using the 0-plant method.

Using the similarly obtained male sterile line as a mother tree, cultivation tests were conducted to maintain the male sterile line by mixed planting and row planting according to conventional methods. Fully ripened seeds were harvested without selection. By identifying the color of the surface of the obtained seeds, we can use a commercially available sorter to clearly determine whether the seeds are self-fertilized by the father (normal color) or are male-sterile lines (red). Table 3 shows the fruiting rates of the male sterile lines propagated using the 0 line method, which were able to differentiate between the two.

Table 2 Cytoplasmic male sterile line Fruiting rate (%) Planted by row
Mixed planting MT-0MS7-AXI 30.1
68.7MT-0MS7-AX2 41.8
75.41'lT-0MS7-AX3
37.5 70.2 Table 3 Cytoplasmic male sterile line Fruiting rate (%) Planted by row
Mixed planting MT-0MS7-AXI 40.3
75.1MT-0MS7-AX2 49.5
81.8MT-0MS7-AX3 45
．． 2 77.4 Example 3 Fertility restorer line derived from Philippine rice IR24 (IIT-
Regenerated plants were obtained from seeds of RV2) according to Example 2. From these regenerated plants, 29 lines with large seeds were selected. Among these, cytoplasmic male sterile line (MT-CMS12
), two lines that reliably recovered fertility were found through test crosses with (
MT-RV2-GXl and MT-RV2-GX2) were obtained.

Using the thus obtained large-grained fertility restored line as the father plant, a cultivation test was conducted to obtain 11 seeds by mixed planting according to a conventional method. When the seeds were fully ripe, all seeds in the field were harvested without selection. By using a commercially available grain size sorter and seed specific gravity sorter, the obtained seeds could be easily separated into FIM seeds and self-pollinated paternal line seeds.

Example 4 Rice (MT-0MS2) having a cytoplasmic male sterility factor derived from Chinsurah Boro II was used as a mother,
Crossing was conducted using rice (MT-VTZ413), which has a reddish-purple color in leaf ears (nodes located between the leaf blade and sheath) as the father. Callus was induced from the obtained hybrid seeds, and suspension cultured cells were obtained according to Example 2. The suspension cultured cells were irradiated with 40kR gamma rays and cultured in a growth medium for one month. Surviving calli were grown in growth medium. The obtained callus was transplanted to a differentiation medium to regenerate a plant.

Among these regenerated plants, what is the color of the leaf ears that is reddish-purple? l
A strain that is morphologically indistinguishable from T-CMS2 (MT-0M
S2-PAI) was obtained. This line is cytoplasmic male sterile, and using the newly obtained line as the mother, a cultivation test was conducted to obtain F1 seeds by planting in rows according to the conventional method. At the seedling raising and cultivation stages, it was possible to clearly distinguish between the male sterile line and the fertile restored line (both leaf ear colors are white), and contamination by different lines was eliminated. the result,
F1 seeds were obtained with 99.9% purity.

〔effect〕

According to the present invention, in the production of hybrid rice,
By identifying the differences in traits caused by the expression of genetic factors related to grain and plant shape traits between the parental lines, we have completed a technology to selectively remove one of the parental lines to efficiently obtain hybrid seeds. This method not only made it possible to significantly reduce the effort required to obtain hybrid seeds, but also
Multiplication cultivation became possible, and the pollination rate and fruit set rate improved dramatically, and the amount of seeds produced per unit area increased significantly. Furthermore, by using this technology, it has become possible to maintain a high level of purity for each strain in the three-base method.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. By introducing genes related to grain traits into the parental lines involved in the production of rice hybrid seeds, differences in grain traits are created between the parental lines, and by identifying the differences, one A method for efficiently obtaining rice seeds while maintaining purity by removing the parent line after harvesting the seeds. 2. By introducing genes related to grass-type traits into the parental lines involved in the production of rice hybrid seeds, differences in grass-type traits are created between the parental lines, and by identifying the differences, one parent line can be differentiated from the other. A method for efficiently obtaining rice F1 seeds while maintaining purity by removing the seeds before harvesting. 3. A method for efficiently obtaining male sterile line seeds while maintaining purity by using the method according to claim 1 in the production of rice hybrid seeds. 4. A method for efficiently obtaining male sterile line seeds while maintaining purity by using the method according to claim 2 in the production of rice hybrid seeds.