Analysis of avirulence genes of Magnaporthe oryzae and resistance association of monogene against blast from rice blast nursery in Hunan Taojiang

Abstract:

[Objective] We identified avirulence genes of rice blast fungus in Taojiang, Hunan Province, to deploy rice blast resistant varieties and blast resistant breeding in Hunan. [Methods] We collected samples of leaf blast of Lijiangxintuanheigu (LTH) in Taojiang and isolated blast fungi through single spore isolation. Avirulence genes of these fungi were identified by in vitro after being inoculated onto the 5th leaf of the 24 monogenic near-isogenic lines against blast at 5 leaves stage which is cultivated from LTH with known blast-resistance gene. We analyzed the interactions between the blast-resistance genes combining pathogenicity association coefficient (PCA) with resistance association coefficient (RAC). [Results] The total 92 strains of M. oryzae contain the whole 24 avirulent genes based on 24 near-isogenic lines, and they also showed different levels of virulence, where the anti-stain frequency of Pi-20 was the highest up to 54.35%. Moreover, the optimal combination of resistant genes was Pi-20×Pi-ks (RAC=0.28, PAC=0.23). [Conclusion] The virulence of M. oryzae was strong and 24 blast-resistant monogenes were nearly diseased in Taojiang rice blast nursery of Hunan Province. At present, rice cultivars carrying resistant genes combinations (Pi-20 with Pi-k, Pi-ks, Pi-3) can be popularized in Hunan Province, but new blast resistance genes must be further imported.

Key words:Magnaporthe oryzae, Near-isogenic lines (NILs), resistance genes, Pathogenicity association coefficient (PAC), Resistance association coefficient (RAC)