Improving The Resistance Of Zhenshan97B To Bacterial Blight By Molecular Marker-Assisted Selection

The rice bacterial blight (BB) is one of the most serious diseases in China. Breeding resistant varieties has proved to be the most effective and economical means to control the disease. Xa21 is a wide-spectrum resistance gene to rice bacterial blight. The objective of this study was to improve the rice bacterial blight resistance of Zhenshan 97B by introgressing Xa21 gene from IRBB21 into it using MAS. Main results are as follows:1.The introgression of Xa21 into the receptor parent (Zhenshan 97B) was conducted based on both molecular markers and resistance testing. A STS marker pTA248 was used for the selection. The genetic distance between Xa21 and pTA248 is only 1.2cM. The exactitude rate of MAS based on pTA248 is 94.74% in BC1F1, and 94.44% in BC2F1 and 96% in BC3F1. It was estimated that Xa21 could decrease 5.13cm of the lesion length.2.Base on the published SSR linkage map,67 polymorphic SSR markers were found between parents Zhenshan 97B and IRBB21.These SSR markers are evenly distributed on the 12 chromosomes of rice. These SSR markers were used to analyze the genomes of 13 BC2F1 individuals with bacterial blight resistance. In the 13 individuals, the highest percentage of recurrent parent genetic background is 89.4%, and the lowest is 80.3%, and the average is 85.7%,lower than the theory level(87.5%). Individuals 4,5,7,8,9,1 land 13 had less linkage drag.3.The BC3F1 individuals with bacterial blight resistance obtained showed similar agronomic performance to the Zhenshan 97B.