Inheritant Law And Molecular Markers Of The Head-Splitting Trait In Heading Chinese Cabbage

In order to understand the head-splitting character and speed the head-splitting resistance breeding in Chinese cabbage, two separate groups of Chinese cabbage were applied to establish head-splitting grading standard, analyse its inheritance and screen linkage molecular marker for it. The main results were as follow:1. By continuously observing the head-splitting in two sets of materials, it was showed that the best date for surveying heading-splitting is at around 20th day later leaf-heading ripeness. The observations of heading-splitting are more accurate and reliable at this time. In practice, when the average air temperature in the growing season is higher , the best observing time can be relatively shifted to a eariler date, on the contrary, properly postponed.2. By analysing the variance of head-splitting trait in reciprocal F1, the result showed that differences between reciprocals were not significant in the two sets of matericals, which indicate that the head-splitting trait was controlled by nuclear genes.3. This study investigated head-splitting in two separate groups and tested its fitness. The results showed that the head-splitting trait is a qualitative and quantitative trait. The seperated proportion of no head-spliting plants to head-splitting plants is fitted to 3:1 with the surveying data at the best date, which means that at least there is a pair of major recessive genes controlling the performance of head-splitting. Moreover, some minor genes and environmental conditions also modify the head splitting degree and speed at head-splitting plant.4. F2 segregating population of material A used as template, RAPD molecular markers linked to related genes of head-splitting were screened with 600 random primers by BSA (bulked segregant analysis) method, we obtained three markers: (1) a special band S15-222 is linked to splitting-resistance genes, the distance between them is not more than 8.876 cM; (2) S1398-500 is linked to splitting-resistance genes with distance less than or equal 13.858cM; (3) S1289-200 is linked to splitting-resistance genes with distance less than or equal 32.196cM.5. F2 segregating population of material A used as template, SRAP molecular markers linked to related genes of head-splitting were screened with 88 pairs by BSA method. It was found two specific primers em1me6, em3me6. Primer pairs em1me6 and em3me6 amplified a specific band about 250bp in head-splitting plants and splitting-resistance plants respectively.