| Pak-choi [Brassica campestris L. ssp. Chinensis(L) Makino var. Communis Tsen et Lee], also known as non-heading Chinese cabbage, Chinese cabbage, rape, etc., is one of the vegetable crops that are most rich in minerals and vitamins, occupying an important status in vegetables’ annual production and supply at the Yangtze River region. However, because of different ecological conditions in China and large numbers of crop introduction from place to place recently, seed market is not standard and mixing of variety is a serious problem, it is normal to find the phenomena of homonym and synonyms. This brings many problems for production and operation and challenges for breeders in parental choice of genetic breeding. This project collects 78 pak-choi materials from all over the market, by analyzing genetic diversity in two aspects of agronomic traits and SSR markers to understand the phylogenetic relationships among the various varieties of pak-choi. By agronomic traits investigating, screen the materials of heat-resistant and bolting resistance in field preliminary and then choose the excellent performing strains to set aside for seed. Through the laboratory of physiological and biochemical tests, we authenticate the heat-resistance and bolting resistant of the screened materials, taking effective advantage of the excellent performing germplasm resources, laying the foundation for future breeding. The main results are as follows:(1)Screened 560 pairs of SSR primers, obtained 51 polymorphic primer pairs and amplified 240 polymorphic bands. The genetic similarity coefficient is calculated using NTSYSpc2.10 e software, using UPGMA method to do cluster analysis for 78 packoi material. Clustering results showed that: 78 pak-choi material’s genetic similarity coefficiency is between 0.57-0.93, divided the 78 cultivars into seven categories using the genetic similarity coefficiency 0.75 as criteara.(2)Survey of 78 pak-choi materials for agronomic traits, using NTSYS- pc2.10 e software for the materials for clustering analysis of agronomic traits. At the genetic similarity coefficiency of 1.58, materials will be divided into 5 categories. In the process of investigating the agronomic traits, we selected a heat-resistant material and a material highly resistant to bolting.(3)Indoor physiological and biochemical test are conducted for control plant and the the heat-resistant material X72 which is identified from preliminary screening. The results show that in presence of heat stress content of MDA and conductivity for both X72 and CK continued to increase after plantation, but the X72 content is always lower than that of CK; POD content showed decreased after the first rising trend, but the content of the X72 is always higher than CK; SOD content showed a gradual upward trend, but the content of X72 is always higher.(4)Indoor and field tests for the late bolting material X48, which is obtained from preliminary screening are conducted, and sow those materials’ seeds which are going through low temperature treatment at different periods, then investigate the flower bud stage and stem height of these materials. The results showed that the longer the vernalization time, the shorter the flower bud stage and higher the bolting is, but the late bolting materials had not bolted in the measurement period; The content of protein first decreased, then increased and decreased last, but the content of X48 was always higher than that of the CK; The content of POD is showing a rising trend, X48 is always lower than that of the CK. Identification of indoor and outdoor tests coincide.(5) Backcross the heat-resistant pak-choi and flowering Chinese cabbage cytoplasmic male sterile line to get the BC3 generation which have the uniform offspring and stable fertility; Using heat-resistant pak-choi and bolting resistant pak-choi as parents and to build six generations, laying a foundation for the initial positioning of pak-choi heat resistant gene and resistance to bolting gene. |
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