Rice Blast Management Through Host-Plant Resistance: Retrospect and Prospects

Abstract

Rice (Oryza sativa) plays a significant role in achieving global food security. However, it suffers from several biotic and abiotic stresses that seriously affect its production. Rice blast caused by hemibiotropic fungal pathogen Magnaporthe oryzae is one of the most widespread and devastating diseases of rice. The crop rice is vulnerable to this pathogen from seedlings to adult plant stages affecting leaves, nodes, collar, panicles and roots. This disease can be effectively managed through host resistance. Of the 100 blast resistance genes, identified and mapped in different genotypes of rice, 19 genes have been cloned and characterized at the molecular level. Most of these genes belong to nucleotide binding sites and leucine rich repeats. Besides more than 350 quantitative trait loci (QTLs) have also been identified in the rice genome. These blast resistance genes and QTLs have been successfully mobilized in the commercial cultivars by using standard plant breeding techniques and also by marker assisted backcross breeding. With the advent of latest molecular biology techniques and our understanding of the basic mechanisms of Magnaporthe-rice pathosystem, the strategies for broadspectrum resistance to M. oryzae can be designed in future.

Natural variation of rice blast resistance gene Pi-d2

“…Searching and stacking R genes with different resistance specificities has been a priority for rice breeders and pathologists worldwide (Hao et al, 2009). To date, over hundreds of major and minor rice blast R genes have been identified, 19 of which (including Pi-d2) have been cloned (Ballini et al, 2008;Sharma et al, 2012).…”

Evaluation of DNA markers linked to blast resistant genes, Pikh, Pit (p), and Pita, for parental selection in Sri Lankan rice breeding

“…In this research, to identify polymorphism in Sri Lankan rice germplasm, simple sequence repeats markers (RM206, RM246) and gene marker (YL87/YL155) were incorporated based on a genealogy study that was conducted on the highly blast resistant variety Tetep by us prior to this study. It identified several IR varieties such as IR64, IR24, IR8, IR36 and mainly a Vietnamese variety Tetep (Sharma et al, 2012) contributed blast resistant genes to Sri Lankan germplasm. The markers RM206, RM246 and YL87/YL155 are linked to the blast resistant genes, Pita, Pit (p) and Pikh respectively in variety Tetep (McCouch et al, 1997).…”

Positive selection pressure on rice blast resistance allelePiz-tmakes it divergent in Indian land races

“…The identification and isolation of additional host R-genes and pathogen avirulence genes is important to understand the molecular mechanisms involved in the hostÁpathogen interaction. So far, about 100 major rice blast resistance genes have been identified, and few of them have been characterized (Sharma et al 2012). All the cloned R-genes have been classified into five groups based on their predicted protein structure (Hammond-Kosack & Jones 1997).…”

“…From the present study, it can be concluded that the LRR domain is more diversified as compared to the NB-ARC domain. Most isolated R genes encode proteins possessing a LRR domain, of which the majority also contains a NBS domain (Sharma et al 2012). Two basic strategies have evolved for an R protein to recognize a pathogen effector (which is also called avirulence [Avr] factor): direct physical interaction and indirect interaction via association with other host proteins targeted by the Avr factor.…”