Linkage Map Construction And QTL Analyses For Agronomic Traits In Chinese Cabbage

Chinese cabbage (Brassica campestris L. ssp. pekinensis) is one of the largest plant area and the most widespread of vegetable crops. Chinese cabbage various in cultivars, has long history of cultivation. Complex genetic basis of this crop make it difficult to improve some important agronomic traits are quantitative trait for instance quality, yield, growth period and so on. It is necessary to exploit existing genetic variation to dissect agronomic and quality traits in B. rapa at molecular levels for utilising efficiently key genes in breeding.1.A molecular genetic map was constructed based on74InDels markers and37SSRs markers using DNA samples extracted from a doubled haploid population obtained through microspore culture from the F1between two homozygous parents: B120and Black227. By using Joinmap4.0software analysis, the map consisted12linkage groups, included108genetic markers and covered1004.7cM with an average distance of9.30cM. The map will contribute to following location and analysis of QTL of tipburn in Chinese cabbage.2. Based on doubled haploid population from B120X Black227and the genetic linkage map? MapQTL5.0is used to investigate QTL of the10agronomic traits in Chinese cabbage.24QTLs controlling10agronomic traits related to morphology traits were mapped on12linkages. These QTLs included2for plant height,2for plant diameter,3for leaf length,3for leaf width,5for leaf length/leaf width,2for head height,3for head diameter,2for head height/head diameter,1for head weight,1for length of internal stem. There are unequal gene additive effect on the expression of10agronomic traits and the variation explained ranged from5.6%-36.3%.These detected QTLs will be useful for genetic analysis and for MAS in breeding program for bolting new cultivars.3.The explained variances were different ranged from5.6%-36.3%,19QTL can explain more than10.0%. Control the leaf length/leaf width QTL on A06have the lowest rate, Control the length of internal stem QTL on A07have the highest rate.in the study, the detection of co-localised M-QTL occurred in three genomic regions. The first one was for ph-1(plant height),11-1(leaf length)and1w-1(leaf width)on A07,the second one was for pd-2(plant diameter),1w-2(leaf width) and hd-1(head diameter) on A09, the third one was for hd-3(head diameter) and hhhd-2(head height/head diameter)4.Based on doubled haploid population from B120X Black227and the geneticlinkage map, MapQTL5.0is used to investigate QTL of tipburn traits in Chinese cabbage. Control marginal rot traits QTL on A03, explained variances12.3%.