The mechanism of resistance loss of the super rice varieties to rice blast

Abstract

In order to clarify the mechanism of the resistance loss of super rice varieties to rice blast, we monitored the resistance of 10 super rice varieties to rice blast for four consecutive years under different ecological conditions. The results showed that the disease index of all the tested varieties exhibited an increasing trend, and the resistance level decreased every year. We focused on the analysis of Ganxin 203 and Zhuliangyou 02, which were cultivated for four years, and the number of dominant race and the average virulence frequency of strains from the two varietes increased every year for four consecutive years. We tested the avirulence gene in the strains from the two varieties, the result indicated that the frequency of the avirulent genes gradually decreased in the two varieties for four years. Compared with the results of the resistance gene test of the two varieties, the number of avirulent genes that corresponded to resistance genes of Zhuliangyou 02 was higher than that of Ganxin 203, and these avirulent genes also had higher frequency. It was evident that the main cause of resistance loss of the super rice varieties was the selection of a dominant physiological species of the rice blast, while the occurrence frequency of the avirulent genes that induced the occurrence of resistance with the resistance genes of the rice variety was decreasing every year. The present study is of great scientific significance with regard to the distribution and extension of the life of the super rice varieties.