Utilization Situation and Prospect of Gene xa5 Against Pathotype Ⅴ of Rice Bacterial Blight

In recent years,the strong virulence pathotype Ⅴ of rice bacterial blight grew up quickly in Southern China,which has become a major population and spread to the rice regions of Jiangsu and Zhejiang provinces in Southern China.Since pathotype Ⅴ caused serious bacterial blight disease in rice production regions,it is urgent to breed and promote resistant varieties against pathotype Ⅴ.The most economic and effective measure to control rice bacterial blight is to breed resistant cultivars for widely planting using resistance genes.The Institute of Plant Protection,Guangdong Academy of Agricultural Sciences,and Agricultural Science Research Institute of Panyu District of Guangzhou used IRBB5 carrying the recessive xa5 gene from IRRI that is resistant to pathotype Ⅴ to breed resistant varieties with rice blast resistance source,through hybridization,multiple cross,pedigree selection and synchronous resistance evaluation.We successfully bred series of new resistant rice varieties such as Baijiangzhan,Baijingzhan and Baisizhan,which showed resistance to strong virulence pathotype Ⅴ(grade 1-3)of bacterial blight and rice blast(mediate to high resistance),good grain quality(level 3 of rice quality of Guangdong),and yield equivalent to major cultivars(compared with region trial control cultivars of Guangdong).These new resistant varieties were promoted and planted in the strong virulence pathotype Ⅴ region along the west coast of Guangdong,which showed favorable superiority and wide application prospect in controlling rice bacterial blight with resistance varieties.

RICE TRANSFORMATION WITH A PHYTOALEXIN GENE AND BIOASSAY OF THE TRANSGENIC PLANTS

Immature embryos, mature embryos and embryogenic calli of 6 rice (Oryza sativa L.) materials were transformed with particle bombardment. The plasmids pSSVstl and pVE5+ were used, both containing the phytoalexin gene from grapevine coding for stilbene synthase, but driven by 35S and its own promoter respectively. Through resistance selection for G418 (100 to 150 mg/L) or hygromycin (50 mg/L), 54 independent transgenic plants were isolated and further assessed by PCR, Southern blot and Dot blot analyses. The transgenic plants and their progenies were tested for resistance to blast ( Pyricularia oryzae ) and bacterial blight of rice ( Xanthomonas oryzae ). Preliminary results indicated that the stilbene synthase gene could enhance the resistance of transgenic plants and their progenies to both pathogens.