Assessment of Genetic Diversity in Thai Isolates ofPyricularia griseaby Random Amplification of Polymorphic DNA

Abstract

One hundred and seventy-four isolates of Pyricularia grisea were collected from various hosts such as barley, rice, weed and wild rice in Thailand. Seven arbitrary decamer primers from the set of University of British Columbia were employed and nine lineages were classified. Lineages B, C and H were predominant, contributing up to 70% of total pathogens in this study. Analysis showed that the distribution of each lineage differs from the predominant lineages across Thailand in such that other lineages were restricted in particular area. For instance, lineage A was limited only in southern Thailand, whereas wide distribution of lineages B and C reflected an influence of both biological and physical effects on pathogen variation. Principal component analysis resulted in a total of four groups of blast pathogen with small distinctions between barley-, rice-, weed-and wild rice-infected blast. Bridging relationships occurred among border isolates of weed and rice blast suggesting a chance of migrations between hosts. Higher diversity was observed in northern, north-eastern and central Thailand while eastern and southern parts were rather low. Genetic diversity indices elucidated an abundance of pathogen lineages existing in northern Thailand suggesting that it should be the centre of diversity.

Characterisation of Magnaporthe oryzae isolates from rice in peninsular Malaysia.

“…Therefore the high level of polymorphism within M. oryzae isolates used in this study is attributed to the fact that isolates were collected from different agro-climatic regions of Malaysia reinforcing the hypothesis of different geographical regions being more important than different plant parts. This result is in agreement with those reported by Sirithunya et al (2008), who did not observe any clear relationship between genetic variability and different plant parts while isolates represented accordance between their genetic diversity and geographical origins.…”

“…Thailand, Malaysia and other Asian countries are considered as ancient rice-growing regions; therefore, the high diversity of the pathogen could be due to the long period of co-existence, development and evolution, while the introduction of rice planting into America and Europe occurred a few centuries ago, leading seldom to the variation of the pathogen (Chadha & Gopalakrishna 2005). Previous studies have also demonstrated that the geographical origin was a dominant factor in determining the genetic diversity of the rice blast pathogen (Sirithunya et al 2008;Srivastava et al 2014). In contrast, an assessment of the genetic diversity of the rice blast fungus in China indicated that the clustering of the isolates was not harmonious with their geographical origins (Ngueko et al 2004).…”

“…The RAPD and ISSR markers have been proved as highly powerful tools in studies of genetic diversity and fingerprinting of Magnaporthe spp. isolates (Chadha & Gopalakrishna 2007;Sirithunya et al 2008), as well as other plant pathogenic fungi (Nasehi et al 2014).…”

“…Genetic diversity among rice blast pathogen populations has been studied using ISSR and RAPD markers (Chadha & Gopalakrishna 2007;Sirithunya et al 2008). The application of RAPD markers combined with other reproducible markers such as ISSR provides more accurate assessments of genetic diversity in pathogen populations (Schlotterer 2004).…”

Pyramiding of four blast resistance QTLs into Thai rice cultivar RD6 through marker-assisted selection

“…Eight virulent M. oryzae isolates from diverse outbreak areas (Figure 2) (Sirithanya et al 2008) were used for evaluation against 16 combination groups of resistance QTLs. Fungal isolates used in the pathogenicity test were grown on rice flour agar media (Korinsak 2009).…”