The flowering time of beet seed plants is slightly different due to different climatic conditions in different places. Generally, flowering begins in the first half of June, and the whole flowering period lasts for 30 ~ 40 days. Then, with the decrease of temperature, seed plants grow slowly, and the number of flowers decreases day by day. Even only a few small flowers at the top of the flower branches open every day, which generally cannot bear fruit.
During the whole flowering process, the number of flowers per day is different. Generally, it reaches its peak in 5 ~ 7 days after flowering, when the number of daily flowers is the highest, and the number of daily flowers can account for 50% ~ 70% of the total flowers within 3 days, and the number of daily flowers in the early and late stages is less.
During the day, from morning till night, the amount spent at different times is different. There are few flowers before 5 am, only a few. The first flowering peak is from 6 am to 9 am, and almost 50% of the total flowers are open during this time. Secondly, the second peak is around noon 1 1 ~ 12, which can reach 15% ~ 20% of the total flowers in the whole day. After 3 pm, the number of flowers is very small. Generally, the second peak is not obvious. But in the case of cloudy morning and clear afternoon, the second peak is more obvious, even better than the first peak. In rainy weather, the flowering process is affected, and the number of flowers per day is obviously reduced.
As far as the flowering sequence of the whole plant is concerned, the lateral branches near the top of the whole plant open first, then the main stem moves from bottom to top, and the lateral branches gradually move around and outward from top to bottom (upper branches first, lower branches later). Generally, 5-7 flowers bloom on the main stem, and the back branches begin to bloom in 20-40 hours. Starting from each side branch, from bottom to top, the branch near the main stem opens first, and the branch away from the main stem opens later. Therefore, the flowering sequence of the whole plant has formed a spiral movement from the inside out and from the center to the periphery.
According to this flowering rule and the ripening process of pollen grains, when artificial hybridization and emasculation are carried out, the mature and uncracked pollinator anthers should be pinched on the first day of cross-pollination and put into a Petri dish with a dryer for cross-pollination the next morning. The female parent plants to be emasculated should also pinch off the anthers gently without damaging the stigma the day before hybridization, and put on kraft paper bags for artificial pollination the next morning. An artificial cross combination should be pollinated 1 ~ 2 times.
In order to avoid cross-pollination between different strains and types of sugar beet, which leads to the mixing of seeds and plants, attention should be paid to maintaining a certain isolation distance when collecting seeds from multiple different strains or varieties. As a small part of breeding materials, the isolation distance between different single strains from the same parent source is close, which can be about 10m apart, covered with large gauze, or planted between two farmers' plots with a distance of 100 ~ 200 m, and the isolation distance between a single seed and multiple seeds is more than 3km. The isolation distance between diploid and polyploid is 1 ~ 2 km.
When collecting seeds in a large area, the above distance should be appropriately increased, depending on the number, area and topography of the mother roots. Between open spaces, the distance should be far; If there are tall obstacles such as trees and houses as natural barriers in the middle, the isolation distance can be slightly closer. The isolation distance between different varieties of the same type or between different parents of the same variety is 2 ~ 4 km. The isolation distance of seed collection plots between different varieties (multi-seed and single seed, male sterile hybrid and common diploid or polyploid varieties) is 5 ~ 8 km. The distance between sugar beet and feed sugar beet or leaf sugar beet varieties is more than 20 kilometers.