The Distribution Of An Avirulencegene AVRPiz-t In The Field

Avirulence gene is the genetic factor of pathogen, whose encoding products could interact with the resistance gene of host plants directly or indirectly, triggering a series of defense reaction in plants and resulting in the disease resisting reaction.This study using strains to infect IRBL11 containing Piz-t, Li Jiang Xin Tuan Hei Gu, transgenic rice from Ri Ben Qing and Ri Ben Qing. Those strains include 70 strains that collected before the year of 1996 from Fujian province, 31 strains collected from Fujian province and isolated in 2006, 28 strains collected from hunan province, 26strains collected from Jilin province and 22 strains provided by China Agricultural University. Moreover, we use three pairs of primers to amplify the total length, promoter and ORF regions of the AVRPiz-t gene in those strains.According to the corresponding relation between the results of infection and PCR, we cloned and sequenced AVRPiz-t gene of five strains provided by China Agricultural University. Sequence analysis suggested that, point mutation in the 40thor 41st amino acid of three strains led to their loss of avirulence .But a 1.8kb insertion in the upstream 427bp of AVRPiz-t led not to its loss of avirulence .This study reveals that the virulence of the M. grisea strain to Piz-t in Fijian province increases from 14.5% to 100% during the 10 years, the reason for such an enormous variation in virulence is awaiting for further investigation.