通过标记辅助回交育种改良优质水稻保持系金山B-1的稻瘟病抗性

金山B-1是本室育成的一个优质水稻雄性不育保持系。为了改良金山B-1的稻瘟病抗性,我们以水稻品系75-1-127为供体,通过标记辅助连续回交将显性广谱抗稻瘟病基因Pi-9导入到金山B-1中。已知Pi-2与Pi-9等位或紧密连锁。根据前人报道的Pi-2的双侧标记和公共数据库提供的水稻基因组序列信息,我们开发了一个在金山B-1和75-1-127之间表现多态的SSR标记SRM22。该标记与Pi-9基因紧密连锁,估计与Pi-9的物理距离为309Kb,换算成遗传距离为0.73cM。在各世代皆利用SRM22对目标基因进行跟踪,并结合形态性状进行背景选择。在BC3F1代,将中选单株与不育系金山A-1进行杂交并检查其后代的育性,以测验这些单株的不育保持性。在BC3F2代,根据抗病标记、不育保持性(根据BC3F1推断)及形态性状,选得5个符合需要的单株,由此得到5个抗病性得到改良的金山B-1近等基因系(BC3F2:3)。抗病鉴定表明,所有育成株系的抗性水平皆显著高于金山B-1,说明抗病基因确实已经导入金山B-1,利用SRM22标记进行选择是可靠的。但值得注意的是,所有育成株系的抗性水平都略低于75-1-127,说明Pi-9的抗病能力会受到遗传背景的影响。

Improving the Resistance of Jinshan B-1, a Male Sterile Persistence Line of Rice with Good Quality, to Rice Blast via Marker-assisted Backcross Breeding

Jinshan B-1 is a male-sterility maintainer line of rice with good quality bred by our lab. In order to improve the resistance of Jinshan B-1 to rice blast, we introduced Pi-9, a dominant gene with wide-spectrum resistance to rice blast, into Jinshan B-1 from donor line 75-1-127 via successive backcrosses with the help of molecular markers. According to reported markers flanking gene Pi-2, which had been known to be allelic or very tightly linked to Pi-9, and rice genomic sequence information available from public database, we exploited an SSR marker named SRM22, which was expected to be closely linked (309Kb) to Pi-9 and showed polymorphism between 75-1-127 and Jinshan B-1. The marker SRM22 was employed to trace the target gene in every generation, combined with background selection according to morphological traits. The male-sterility maintainability of individual plants was tested in BC3F1 generation by crossing the plants to male-sterile line Jinshan A-1 and examining the fertility of their hybrids. Five desirable plants were selected in BC3F2 according to their blast resistance marker, male-sterility maintainability (deduced from BC3F1 generation) and morphological traits and corresponding near isogenic (BC3F2:3) lines of Jinshan B-1 with improved blast resistance were obtained. We found that the resistance levels of the isogenic lines were all much higher than that of Jinshan B-1, suggesting that the resistant gene had been really introduced into Jinshan B-1 and so using marker SRM22 for the selection was reliable. However, it is noted that the resistance levels of the isogenic lines were all a little lower than that of 75-1-127. This suggests that the resistance ability of gene Pi-9 may be influenced by genetic background.