[Relationship between genetic lineage and pathotype of Pyricularia grisea in Yunnan Plateau]

Rice blast caused by Pyricularia grisea is the most destructive disease in Yunnan Plateau, China. In order to elucidate the relationship between genetic lineage and pathotype of P. grisea of Yunnan Plateau as well as the variability of the fungus at DNA level,the repetitive element-based PCR (rep-PCR) of Pot2, an element found in approximately 100 copies in the fungus genome,was exploited. Two hundred and thirty-six isolates of P. grisea collected from 15 main rice-growing counties of Yunnan Plateau were fingerprinted by using rep-PCR. A linkage graph of the rep-PCR fingerprints from 134 representative isolates was generated using an unweighted pair-grouped average program (UPGMA) of the STATISTICAL 5.0 software. The isolates were classified into 8 genetic lineages (G1 approximately G8) at the level of 1.75 genetic linkage distance, of which the G1, G2 and G4 were the dominant lineages. The isolates in a certain area generally belonged to one correspondent genetic lineage and the isolates from the same plot and host rice variety mostly shared one linkage group though different genetic lineages within one lesion. Furthermore, 29 isolates representing the eight genetic lineages were inoculated on 33 rice cultivars of Yunnan at the stage of 3 approximately 4 leaves in greenhouse. The isolates were divided into 6 pathotype groups (P1 approximately P6) according to its compatibility, which demonstrated that some isolates of one genetic lineage sharing two or three pathotype groups, alternatively, one or four pathotype groups. The isolates from each genetic lineage, however, may share one pathotype group such as P2. The preliminary results implicated that the relationship between genetic lineages and pathotype groups of P. grisea in Yunnan Plateau was complicated rather than simple. On the other hand,2 rice cultivars including HeXi 16 and JingGuo 92 were resistant to the 29 isolates but YunJing 20 and HeXi 30 both susceptible to all of them, which was helpful for deploying the blast-resistant genes in rice production of Yunnan Plateau. Therefore, the rice blast-resistance spectrum of the tentative new rice cultivars should be evaluated before its release considering the blast-resistant rice breeding and the practice of rice production in Yunnan Plateau.