Detailed Explanation of Key Points of Cotton Male Sterile Line Seed Production Technology

The cotton male sterile line seed production technology uses the insect-assisted pollination male sterile line hybrid seed production method, which overcomes the shortcomings of the currently widely applied cotton hybrid seed production method - the manual emasculation and pollination hybrid seed production method, such as being time-consuming and labor-intensive, high work intensity, complex management of seed production fields, and high seed production costs. The labor usage can be reduced by more than 50% compared with it, and the purity of hybrid seeds can be further improved. It is the most ideal way to produce cotton hybrid seeds.

The cotton male sterile line seed production technology is to breed a transgenic insect-resistant nuclear double recessive male sterile line with a recessive low-gossypol marker trait and carry out insect-assisted pollination seed production, so as to solve a series of problems in the current cotton hybrid seed production technology, such as being time-consuming and labor-intensive, high work intensity, and resulting in many false hybrids.

This technology uses the insect-assisted pollination male sterile line hybrid seed production method, which overcomes the shortcomings of the currently widely applied cotton hybrid seed production method - the manual emasculation and pollination hybrid seed production method, such as being time-consuming and labor-intensive, high work intensity, complex management of seed production fields, and high seed production costs. The labor usage can be reduced by more than 50% compared with it, and the purity of hybrid seeds can be further improved. It is the most ideal way to produce cotton hybrid seeds.

Brief Technology

This technology uses the transgenic insect-resistant nuclear double recessive male sterile line Zhongkang A as the basic material to breed a transgenic insect-resistant nuclear double recessive male sterile line with a low-gossypol marker trait for insect-assisted pollination breeding. It not only simplifies the seed production procedure and reduces the breeding workload, but also makes it possible to distinguish true and false hybrids by visually inspecting the presence or absence of pigment glands on the seedling bed or in cut seed kernels. Those with pigment glands are true hybrids, otherwise they are false hybrids, thereby avoiding economic losses and making it usable for large-scale production of hybrid seeds.

Through sexual hybridization, the recessive glandless gene is transferred into Zhongkang A. In the fertility segregation population of its progeny, plant-to-plant crosses are made (sterile x fertile), and seeds are harvested and planted separately. The fertility segregation ratio and the presence or absence of glands in the progeny are investigated, and combined with observations of agronomic traits, after many years and multiple directional selections, sterile line materials with stable insect resistance, low gossypol, and a sterile plant rate of 50% are finally screened out, as follows:

1. Transfer breeding of the recessive low-gossypol semi-maintainer line. A recessive low-gossypol insect-resistant cotton line is used as the male parent and Zhongkang A as the female parent for hybridization. The F1 is taken to Hainan Island for generation advancement. From the F2 generation, low-gossypol fertile plants are selected as male parents and crossed plant-to-plant with segregated sterile plants. Seeds are harvested separately by plant and planted the next year to investigate fertility, retaining plant rows with a sterile plant rate of 50%.

2. Purification of the low-gossypol double recessive nuclear male sterile line. Gland observation is carried out on plant rows with a sterile plant rate of 50%, and low-gossypol fertile plants and low-gossypol sterile plants are selected for plant-to-plant crossing. Hybrid seeds and testcross seeds are harvested separately by plant. Using Hainan Island for winter generation advancement, two seasons per year, after 3 consecutive years of plant-to-plant crossing and testcrossing, an insect-resistant low-gossypol double recessive nuclear male sterile line with stable traits is bred. This sterile line has excellent comprehensive agronomic traits, is highly resistant to cotton bollworm, has a tower-shaped plant, moderate leaves, strong boll-setting ability, thin boll shell, and smooth boll opening. The sterility degree is 100%, and the sterility is stable and complete.

Application Prospects

1. Compared with the existing manual emasculation and pollination hybrid seed production method, the present invention can greatly reduce the labor intensity in seed production fields, reduce workload, and improve seed production efficiency, thereby greatly lowering seed production costs.

2. Using the sterile line of the present invention as the female parent makes it easy to distinguish true and false hybrids, and they can be easily removed on the seedling bed. It can be used for large-area, large-scale field seed production of insect-assisted pollination male sterile lines.

3. The sterile line of the present invention has a wide range of restorer sources. Generally, upland cotton varieties (lines) can all serve as its restorers. The heterosis is obvious, the competitive advantage is 115%-136%, and the insect resistance effect is good.