Abstract:

【Objective】Rice blast seriously threatens rice production in Heilongjiang Province and the breeding and utilization of anti-blast varieties are the most economical, safe and effective measures to control it. This study explored the resistance of rice varieties in Heilongjiang Province; clarified the resistance effect of disease resistance genes, and provided a basis for the selection and utilization of germplasm resources of rice blast in Heilongjiang Province. 【Method】 In the autumn of 2018, 134 rice strains were collected from the main rice area in Heilongjiang Province, and the resistance of 50 dominant rice varieties was analyzed. For the reported 35 rice blast resistance genes, a comparison was made between the varieties and positive control varieties. Sequencing results of some positive control varieties were compared with the reference sequence published in the National Centre for Biotechnology Information to analyze the existence of rice blast resistance genes in the corresponding varieties. Through the correlation analysis of gene aggregation type and breed resistance performance, the genotypes related to the resistance performance of rice varieties in Heilongjiang Province were clarified. 【Result】 Among 50 rice varieties in Heilongjiang Province, Longgeng 20 had the best resistance (R). Longgeng 67, Longken 202, Longgeng 40, Longgeng 31, Longgeng 57 and Longgeng 43 had moderate disease resistance; whereas, 43 varieties such as Jiahe 1 had relatively low resistance. Through the analysis of variety combination resistance, we found that 33 pairs of Longgeng 20 + Longgeng 67 had a high RAC（resistance association coefficient) value, low VAC (virulence association coefficient) value and good combined disease resistance. The matching structure showed potential for application. The identification of resistance genes carried by specific primers showed that Pish, Pi36, Pi33 and Pi-CO39 were detected, and Pi63, Ptr, Pi37, Pi64, pi21, Pi9, Pi54, Pikh, Pia, Pikp, Pi35, Pikm and Pik were between 50%-100% of occurences frequency, indicating that such genes were widely used in rice breeding in Heilongjiang Province. The detection rate of Pita, Pib, Pii, Pi5, Piz-t, Pi50 and Pi2 was between 10% and 50%; Pid2 was detected in in two varieties, and Pigm was detected in Jigeng 88. However, Pit, Pid3, Bsr-d1, Pi25, Pid3-A4, Pi56, Pi1, Pike and Pb1 were not detected in the cultivars, indicating that such genes are less distributed in rice varieties in Heilongjiang Province. The variety genotype analysis found that the varieties carried 12-19 resistant genes, with a total of 58 genotypes, indicating that the test varieties had rich blast resistance gene combination types. By analysis, the single gene and gene polymerization with disease resistance showed that the distribution frequency of Pi2, Piz-t, Pi50, Pi5 and Pii corresponded to frequency of resistance. We found that the more varieties carrying resistance genes, the higher the frequency resistance, and six varieties that carrying Pi2+Piz-t+Pi50+α polymerization types showed resistance. 【Conclusion】 Our results have demonstrated the following: the resistance of rice germplasm resources in Heilongjiang province is low; combination planting of different varieties could be usefully applied; the distribution of blast resistance genes is different in the participating varieties; Pi2, Piz-t, Pi50, Pi5 and Pii play a leading role in disease resistance, and Pi2+Piz-t+Pi50+α gene polymerization type could contribute to improving rice blast resistance.

Key words: rice, rice blast, resistance frequency, blast resistance evaluation, blast resistance gene