Abstract:

To elucidate the resistance spectra of resistance genes and the feasibility of breeding the cultivar with durable and broad-spectrum resistance by integrating resistance genes, the monogenic NILs bred by IRRI with the background of LTH, a native variety in yunnan without any major resistance gene and their 8 combinations were identified by inoculating 31 Magnaporthe grisea isolates. The results indicated that the resistance spectra were remarkably different among the lines, and the resistance frequencies of IRBLZ-Fu(Pi-z), IRBLZ5-CA(Pi-z-5), IRBLZt-T(Pi-z-t), IRBL9-W(Pi-9(t)) were 93％，97％，90％ and 96％, respectively, showing that the four genes Pi-z, Pi-z-5, Pi-z-t, and Pi-9(t) were perceived preliminarily to be broad-spectrum resistance genes. At the same time, to avoid to the linkage, the resistance genes in different chromosomes were accumulated except for Pi-k-s and Pi-k-p. The resistance spectra of the combinations were broader than those of their parents because of complement effect and additive effect. Namely, on the one hand, the lines with single resistance gene were susceptible to some isolates, or some was susceptible, and some resistant, but the combination was resistant. On the other hand, some lines with single resistance gene and some combinations were susceptible to some isolates, but the size and the number of the lesion of the combinations were less than those of the lines with single resistance genes. Integrating several resistance genes into a cultivar would be useful for expanding resistance spectrum and durability. Pi-z, Pi-z-5, Pi-z-t and Pi-9(t) had great potential in resistance breeding, in spite of that the mechanism of their broad spectrum was not known. In addition, the resistance spectrum of the combination was broader than those of Pi-k-s and Pi-k-p. It’s not clear whether the mechanism of the broader spectrum was similar or same to the relation between EDS1 and PAD4 in Arabidopsis thaliana.

Key words: Rice blast, Near-isogenic line, Major resistance gene, Resistance identification