Assessment Of Inbred Line’s Heterosis And Breeding Of Double Haploid Lines For The Third Generation New Type Brassica Napus

In Brassica crops, there are three basic genomes (A, B, C) and three sets of corresponding subgenomes (Ar/An/Aj,Bn/Bj/Bc,Co/Cn/Cc). Obvious genetic differentiation between and within different sets of subgenomes has been well demonstrated previously. To utilize the exotic subgenomic differentiation for rapeseed breeding, a kind of new type B. napus (ArArCcCc) has been developed by replacing the An and Cn genome by Ar genome of B. rapa and Cc genome of B. carinata respectively, which could significantly broaden the genetic basis of B. napus and result in a dramatic intersubgneoimc heterosis potential when the new type B. napus is crossed to the traditional B. napus. A novel gene pool with hundreds of the third generation lines of new type B. napus has been obtained so far in our lab, which has been introgressed with diverse genomic components Ar/Cc subgenomes. The objective of this study is to evaluate the heterosis potential of the intersubgenomic hybrids derived from the gene pool by crossing the third generation lines of new type B. napus to traditional cultivars, and selected elite lines of the third generation of new type B. napus will be processed into microspore culturing for further study.In this study,40F5lines of the third generation new type B. napus were randomly selected from the gene pool but derived from different interspecific crosses between B. rapa and B. carianta ensuring representative.80intersubgenomic hybrids between the40lines and two B. napus testers (an Europe cultivar, Tapidor, and a Chinese semi-winter cultivar, Zhongshuang9) were made with thousands of seeds for two-year field trials in the year of2009. The hybrids along with all of the parents were grown with three replications in the field of Huazhong Agricultural University in the year of2009-2010and2010-2011, respectively. An elite commercial hybrids cultivar of B. napus, Huaza7, was used as hybrid control in two trials. The general combining ability and special combining ability of the40new type lines has been analyzed, which finally helped to select9elite lines with the best general combining ability. The results of the first yield trial showed that great variation on flowering time of the new type B. napus lines.10%and25%of the new type B. napus lines showed higher seed yield and oil content than commercial hybrid control respectively. However,42.5%of the intersubgenomic hybrids showed higher seed yield than commercial hybrid control. The best hybrid combination, Tapidor×8B1380, even showed25.5%higher seed yield than hybrid control. A total of seven and twelve hybrid combinations surpassed the control on seed yield at the significant level under P<0.01and P<0.05, respectively. The oil content of the hybrids was increased with3.6%averagely compared with the parents. Similar results were presented in the second year.35.5%of the hybrids surpassed the control on seed yield, and three hybrids shower better seed yield performance significantly (P<0.01). The hybrid combination, Tapidor×8B1227, surpassed the control on seed yield repetitively with28.5%.The approach of microspore culture was conducted for the40lines. DH lines have been developed for14lines successfully, and five lines with ten plants achieved good seed quality with double-low. Further approach to improve the novel gene pool of the new type B. napus has been discussed, as well as for how to further exploring intersubgenomic heterosis in Brassica.