Mapping QTL For The Main Agronomic Traits Of DH Population In Chinese Cabbage (Brassica Rapa L. Ssp. Pekinensis)

Chinese cabbage (Brassica rapa L. ssp. pekinensis) is one of the most important vegetable crops in China with,among vegetable crops, the largest cultivation area and per capita consumption. Chinese cabbage, various in cultivars,has long history of cultivation,many nutrition value and important status in China. Complex genetic basis of this crop make it difficult to improve some important agronomic traits are quantitative trait for instance yeild,quality, 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.In our study, The BrIVFhn mapping population of 183 DH lines was derived from a cross between two DH Chinese cabbage lines. Y177 is originated from a winter type Japanese cultivar'Jianchun'and Y195 is derived from a summer type Chinese cultivar'Xiayang'. These two parents have extreme differences in leaf hairiness, leaf blistering, leaf glossiness, leaf size and plant size etc. Based on a linkage map with 287 markers, MapQTL4.0 is used to investigate QTL of the major traits related to leaf and plant morphology and yield using the data collected under 3 different eviroments by interval mapping and multiple-QTL model mapping (MQM) methods. Main conclusions are listed as below:1.QTL for leafy morphological traits: Twenty-one QTLs located on nine linkage groups were detected, including three for leaf hairiness, six for leaf blistering, five for leaf serration of margin, seven for leaf glossiness. The variation explained ranged from 5.7 % to 80.5 %. QTL analysis found three QTLs in same location of R6 under three different environments about leaf hairiness trait. The variation explained is 80.5%.2.QTL for yeild related traits: Thirty-five QTLs located on eight linkage groups were detected, including five for leaf length, two for length of sessile part, two for length of petiolate parts, one for leaf width, five for midrib length, two for midrib width, one for leaf length/leaf width Ratio, one for leaf area,one for Lamina area , one for area of midrib.And four for leaf wight,four for Lamina wight, three for wight of midrib, three for wight of midrib / Lamina wight Ratio.The variation explained ranged from 6.4 % to 18.9 %. QTL analysis found that the QTL of leaf length , midrib length, lamina area ,leaf area and area of midrib ;leaf width and midrib width were co-localized .3. QTL for plant morphological related traits. Fifteen QTLs located on five linkage groups were detected, including seven for plant attitude, four for plant extent, three for plant height, one for number of leafs. The variation explained ranged from 6.7% to 16.5 %. QTL analysis found QTLs in same location of R9 under three different environments about plant attitude trait.;The QTLs of plant extent measured in different environments have similar locations on the map. In conclusion, our research provided useful information for molecular marker assistant selection in breeding programmes of Chinese cabbage for complicated agronomical traits.