(1) Parents were selected according to the dominant and recessive laws of various related traits.
If you want to cultivate the first generation hybrid with crack resistance, both parents should have crack resistance. If the first generation hybrid resistant to one or more diseases is to be bred, it is necessary for one parent to be highly resistant to one or more diseases and the other to be moderately resistant, so that it is possible to obtain a disease-resistant combination. The composition of yield depends not only on the number of plants planted, but also on the number of fruits per plant and the quality of single fruit. The fruit size of the first generation hybrid is related to parents and specific combinations. If the difference of single fruit weight between parents is small, the single fruit weight of the first generation hybrid may show superiority (also different from the combination); If there is a big difference in single fruit weight between parents, the single fruit weight of the first generation hybrid will not be dominant, and it will show different degrees of intermediate type, and the middle is often too small, which tends to favor the small fruit parents. Therefore, in order to gain the advantage of fruit weight, parents with medium fruit size and little difference should be selected as far as possible to prepare hybrid combinations. The number of fruit per plant plays an important role in yield composition. When selecting hybrid combinations, we should try to choose varieties with more fruits as parents. Generally speaking, the inheritance of quality traits (such as tall and short seedlings, purple stems and green stems, red fruits and yellow fruits, etc.). ) is completely recessive, while quantitative traits (such as fruit size, crack resistance, disease resistance, maturity, fruit shape, etc.) are inherited. ) is not completely dominant, among parents.
(2) Parents are required to complement each other in outstanding characteristics and excellent personality.
Choosing parents requires that both parents have different advantages, so that they can learn from each other and concentrate their advantages on the first generation hybrids. For example, the hybrid Hongza 16 bred by Institute of Vegetables and Flowers of Chinese Academy of Agricultural Sciences, namely Hongza 100 with short seedlings, self-capping, early maturity, multiple fruits, bright red fruits and high hardness, and 8753 hybrid combination with Mabel Miao stem and tobacco mosaic virus resistance gene as parents, has the characteristics of early maturity, disease resistance, high yield and high quality. The complementary scope is relatively wide, and it is necessary to carefully observe and analyze the original materials. For example, both varieties are precocious, but "early" is different. One is the speed from flowering to fruit expansion, and the other is the speed of fruit color change. The hybridization between the two varieties may complement each other, making the first generation hybrid more early.
(3) The selected parents should have different ecotypes.
According to the different populations of processed tomatoes developed under certain historical and environmental conditions. It has obvious advantages to select varieties with different ecotypes to prepare the first generation hybrid. There are many kinds of processed tomatoes, including wild subspecies, semi-cultivated subspecies and cultivated subspecies. The heterosis can also be improved by using varieties with different geographical, climatic conditions and latitudes to prepare the first generation hybrids.
(4) It is best for the parent varieties to have seedling marker traits.
In order to keep the purity of parents and the high order of first-generation hybrids, it is best to choose varieties with seedling marker traits as parents, which is convenient for parents to remove impurities and maintain purity and first-generation hybrids to remove impurities and maintain fidelity. Seedling landmarks such as green stems, potato leaves and yellow seedlings.
(5) Requirements for female parents.
In addition to the above requirements, we should also pay attention to the following two points: first, choose varieties with more seeds in fruits as female parents, and varieties with smaller and more fruits generally receive more seeds than varieties with larger fruit types and fewer fruits; Single inflorescence has more seed collection than compound inflorescence; Early-maturing varieties collect more seeds than late-maturing varieties. Secondly, the varieties whose flower organs are easy to emasculate are selected as female parents to improve work efficiency and reduce costs.
After the parents are selected, the parents should be purified first to ensure the uniformity and heterosis of the first generation of hybrids. For specific methods, please refer to the section on improved seed breeding. After the parents are purified, it is necessary to expand reproduction. Increase the number of seeds to meet the needs of hybrid seed production, that is, carry out original seed reproduction. The original seed breeding farm should be separated from the production farm, and strict isolation and screening should be carried out to ensure the purity of the original seed. The original species can be reproduced every year or once every few years.