The following technical points should be paid attention to in the production of cotton hybrid seeds by artificial castration:
(1) Selection of isolation zone. In order to avoid the introduction of other varieties of pollen and ensure the purity of hybrid seed production, the seed production field must be square and contiguous, densely planted, and isolation belts should be set around it. The general isolation distance should be above 100 meters. The outcrossing rate of cotton is directly proportional to the population density of pollinators and inversely proportional to the square of the distance between different varieties. Therefore, if there are honey crops and pollinators in the isolation area, the isolation distance should be appropriately increased. If natural barriers such as hills, rivers, forest belts, villages and towns or tall buildings can be used for isolation, the effect will be better.
(2) Standardize sowing. Pay attention to adjusting the sowing date of parents when sowing, so that parents can meet at flowering stage. When the growth period of parents is not much different, sowing can be done at the same time; When there is a big difference in the growth period between parents, the sowing date of early-maturing parents can be postponed appropriately.
The ratio of parents to parents is 1: 5 ~ 6. The planting density of female parent is 37500 ~ 49500 plants/hectare, and that of male parent is 56500 ~ 60000 plants/hectare. The general planting method is large and small rows, with large row spacing of 80 ~ 65,438+000 cm and small row spacing of 60 ~ 70 cm.
In order to improve the sowing quality, the seed-making field should choose a plot with flat terrain, convenient irrigation and drainage and good water and fertilizer conditions. Apply farmyard manure and appropriate amount of chemical fertilizer as base fertilizer, and topdressing in time.
(3) Artificial removal of impurities and emasculation. According to the characteristics of parents, impurities are removed at seedling stage, flowering stage and harvest stage to ensure the purity of parents and hybrid seeds.
In large-scale artificial emasculation seed production, all buds are removed before July 5 and after August 15, and artificial emasculation pollination is carried out between July 5 and August 15. During this period, every day from 2 pm to before dark, the flowers to be opened the next day are selected for castration, and they are searched again before 6: 30 am the next day to ensure the purity of seed production. When it is found that the corolla is about to open or the anther begins to break and loose powder, flowers should be picked.
Manual emasculation of cotton is generally done by bare hands. Select the corolla with suitable growth, separate the bud leaves with your fingers, cut off the thumb nails from the base of the calyx, gently peel it off to the right, peel off the corolla together with the stamens to expose the pistil, and then mark it for later pollination. When castrating, you should pay attention to not pinching your nails too deeply, so as not to hurt your ovaries, break the white membrane of your ovaries and peel off your bracts. Corolla with moderate tension to prevent stigma from breaking; When emasculating, it should be thoroughly cleaned, and the removed stamens should be taken out; To prevent self-pollination caused by loose pollen.
(4) Artificial pollination. Artificial pollination is usually carried out at 8 ~ 12 in the morning. Usually, several stamens stripped from the male parent are tied together and then smeared on the stigma of the female parent. This method saves time and effort and has good effect. Another method is to take pollen from the flowers whose parents have opened at 7 ~ 8 am the next day after castration, dry them in the sun to make the pollen grains fully dispersed, put them into a small bottle with holes in the cork, and pollinate them with the pollen in the small bottle. When pollinating with a small bottle, you should pay attention to gently holding the castrated bud with your left hand, inverting the small bottle with your right hand, aligning the small hole on the bottle cap with the stigma, moving the small bottle left and right or gently holding the small bottle with your fingers, and then removing the small bottle and the mark. No matter which pollination method is adopted, it is required to pollinate fully and evenly to reduce crooked peaches.
During cotton hybrid seed production, if it rains, it will bring a lot of inconvenience to artificial emasculation and pollination, and the following methods can be considered to solve it. Before it rains, put a waterproof plastic hose or straw (about 2 ~ 3 cm long and sealed at one end) on the stigma. Before pollination, the sleeve can prevent rain from washing the stigma and affecting the attachment and germination of pollen grains. After pollination, the sleeve can prevent rain from washing away the pollen scattered on the stigma. Because the viability of cotton stigma can generally last for about 2 days, it can be pollinated again after the rain stops, and some losses can be recovered.
(5) Seed harvesting and preservation. In order to ensure the fullness and purity of hybrid seeds, cotton bolls must be dehydrated normally before they can be harvested. When harvesting, the mother storehouse should be harvested first, and then the mother storehouse should be harvested to prevent the cotton in the mother storehouse from mixing with the mother storehouse. Different kinds and grades of cotton should be collected, dried, twisted and stored separately, and all work should be done by special personnel to prevent mechanical mixing.