Identification Of Bolting Resistance And QTL Mapping Of Chinese Cabbage

Chinese cabbage（Brassica campestris L.ssp.pekinensis）is an important vegetable originally produced in China.with an annual planting area of 1.8 million hm2,which is the second largest vegetable in our country.It plays an important role in stabilizing vegetable price and market supply.With the Chinese cabbage industry mode change,the area of spring sowing and cold area Chinese cabbage cultivationis increasing day by day,and gradually form the planting scale.The premature bolting is the main harm in the production of spring Chinese cabbage,which will cause bolting before the cabbage head are formed or the cabbage head are not fully compact,and will lose the commercial value,affect the quality,yield and annual supply.It is an effective way to select varieties that are resistant to early bolting to solve the production problem of spring Chinese cabbage,and it is an effective means to select varieties that are resistant to early bolting to use molecular marker technology to locate related bolting genes.Constructing a scientific identification method and evaluation system for the early bolting tolerance of immature is a key link in the bolting research of Chinese cabbage,and it is also a key technology for the creation of spring Chinese cabbage germplasm resources.In this study,properties were selected.By investigating 17 Chinese cabbage parent materials with large differences in bolting phenotypic traits,the identification and evaluation criteria of their tolerant to premature bolting were established.Analyze the correlation between the traits and the changes of physiological and biochemical indexes before and after bolting,finally found the best identification index for rapid evaluation of resistance to premature bolting.Based on htis,the study selected the extremely bolting resistant Chinese cabbage self-incompatibility line13DS9 and extremely easy bolting Chinese cabbage inbred line 12DS134 as the female parent and male parent to obtain the F₂ generation,and constructed the genetic linkage Map and QTL mapping,which provides a theoretical basis for further mining of Chinese cabbage tolerant genes of immature early bolting.The results of this research are as follows:1.According to the identification and evaluation criteria of bolting resistance,the bolting resistance of Chinese cabbage was identified during the budding stage,the bolting stage and the 5 cm length of the shoot.The results of the study show that there is a very significant positive correlation between the three indicators,and they can all be used alone as the resistance to bolting.Among them,the budding stage is considered to be the best identification index for quickly evaluating the early bolting tolerance of Chinese cabbage.2.The soluble protein content of Chinese cabbage that has not been vernalized is higher than that of Chinese cabbage that has been vernalized,and the difference is more obvious after vernalization bolting.The SOD enzyme activity of Chinese cabbage before vernalization and bolting is higher than that of Chinese cabbage after vernalization and bolting,and The enzyme activity of unvernalized Chinese cabbage is at a moderate level.After vernalization,the soluble protein content of boltingtolerant Chinese cabbage was lower than that of bolting-easy Chinese cabbage,and the SOD activity was higher than that of bolting-easy Chinese cabbage.These two physiological indicators can be used as auxiliary indicators for the identification of early bolting resistance.3.Using 13DS9×12DS134 to construct an F₂generation population including 180individual plants,625 pairs of SSR molecular markers were screened,and a total of 90 pairs of polymorphic primers were screened out,of which 74 pairs were linked to the map,forming a sheet containing Genetic map of 10 linkage groups.The map covers the genome length of 1966.22 c M,the average distance between markers is 21.85 c M,and the number of markers per chromosome ranges from 3-18.4.Using the constructed genetic map,combined with the phenotypic data of the F₂generation population in the field test,QTL mapping was performed on the traits of early bolting tolerance in Chinese cabbage.A total of 11 QTL loci were detected.The specific distribution is that there are 4 QTL loci on chromosome A01,2 QTL loci on chromosomes A03,A05 and A09,and 1 QTL loci on chromosome A04.