Diversity of Pathotypes and DNA Fingerprint Haplotypes in Populations of Magnaporthe grisea in Korea over Two Decades

Abstract

Using isolates collected over 2 decades, we determined the population structure and dynamics of the rice blast fungus, Magnaporthe grisea, in Korea at both the genotypic and phenotypic levels. Pathotype analysis on 6,315 isolates collected from 328 rice cultivars from 1981 to 2000 revealed the presence of a total of 91 pathotypes. Among these 91 patho-types, nine dominated, comprising 76.5% of the isolates. The expected number of pathotypes (corrected for sample size) increased significantly during the course of this study. On average, six (ranging from 0 to 20) new commercial cultivars were introduced annually between 1981 and 1998. However, the overall cultivar diversity, estimated using the Shannon index, was low. Most of the new cultivars were not planted to a large area because the seven most common cultivars each year occupied over 70% of the rice-cultivated area. The frequencies of the nine dominant patho-types from these seven cultivars were highly correlated with those from the entire set of cultivars. To understand genetic diversity within and between pathotypes, 176 isolates collected from 1984 to 1999 were randomly sampled and analyzed by DNA fingerprinting. High similarities were observed among isolates; overall similarities were greater than 63% in combined MGR586 and MAGGY DNA fingerprints. Unlike most other populations of M. grisea, DNA fingerprints showed no clear lineage structure. No groups were supported by bootstrap values greater than 10%. Furthermore, there was no significant correlation between DNA fingerprint similarities and pathotypes. Genetic similarity was significantly greater (P < 0.001) within years than between years, although the difference was small. Our data suggest that M. grisea populations in Korea have been mostly dominated by a single clonal lineage. We cannot conclude from these data that selection by the host population has been a major force in the evolution of M. grisea in Korea.

Virulence and rep-PCR analysis of Pyricularia grisea isolates from two Brazilian upland rice cultivars

“…Studies on genetic structure of P. grisea population using MGR-DNA fingerprinting showed that even though each isolate had a unique fingerprint, they could be grouped into distinct lineages The results of the analysis of isolates from Primavera and Maravilha using rep-PCR in the present study are in accordance with the observations made in earlier investigations (Levy et al, 1991;Levy et al, 1993;Xia et al, 1993;Chen et al, 1995;Roumen et al, 1997;Don et al, 1999;Park et al, 2003;Rathour et al, 2004). Information on the interactions between cultivars and lineages can be used to improve the diversity of pathogen populations at screening sites .…”

“…Distinct DNA fingerprint groups or lineages were identified using the probe MGR586 (Filippi et al, 1999;Hamer, 1991;Zeigler et al, 1995). Many of these clonal lineages have been shown to exhibit restricted diversity (Levy et al, 1993;Xia et al, 1993;Chen et al, 1995;Roumen et al, 1997;Don et al, 1999;Park et al, 2003;Rathour et al, 2004). Because of difficulties in large scale use of RFLP analysis, a rep-PCR technique with two primer sequences from Pot2 has been developed.…”

Characterisation of Magnaporthe oryzae isolates from rice in peninsular Malaysia.

“…Although the results of RAPD analysis showed quite good congruence with the results obtained from ISSR studies, a greater effective ratio of multi-locus Table 1 Coefficient doi: 10.17221/102/2016-CJGPB markers as well as a higher number of private alleles were observed using ISSR markers (Nasehi et al 2014). (Mishra et al 2006), Korea (Park et al 2003), China (Ngueko et al 2004), Iran (Javan-Nikkhah et al 2004 and India (Chadha & Gopalakrishna 2005), which is in agreement with the findings of this study. To the best of our knowledge, this is the first report on the genetic diversity of M. oryzae isolates using ISSR and RAPD markers in Malaysia, and evaluating these two types of markers to differentiate rice blast pathogen populations.…”

Genetic and phenotypic diversity of Magnaporthe oryzae from leaves and panicles of rice in commercial fields in the State of Goiás, Brazil

“…On the other hand, continuous genotypic variation and lack of association between genetic and virulence patterns was observed in other countries (Mekwatanakarn et al, 2000;Park et al, 2003;Rathour et al, 2004). Observations from different countries indicate the possibility of genetic recombination in the pathogen population.…”

“…In Korea, the genetic analysis of 176 isolates of M. oryzae collected in farmers' fields and nurseries did not show a well defined lineage structure (Park et al, 2003). Rathour et al (2004), in the northwestern Himalyan region of India, also showed the presence of high genetic diversity and continuous variation in 48 isolates, using RAPD markers.…”