Association of lesion mimic trait with spot blotch resistance in wheat

Abstract

Lesion mimic creates necrosis in the leaf tissue and promotes the growth of necrotrophic/hemibiotrophic pathogens. The presence of lesion mimic locus and their effect on spot blotch disease, days to heading, black point index and thousand kernel weight of wheat were investigated in parents Sujata, Avocet-YRA and their 146 recombinant inbred lines (RILs). The study conducted during two cropping seasons showed that some lines with higher expression of lesion mimic phenotypes exhibited significant increase in AUDPC. Three markers (Xbarc181, Xwmc674 and Xgwm513) were deployed to reveal the presence of lesion mimic locus (lm, lm1 and lm2). Three lesion mimic loci were detected in combinations of lm+lm1+lm2, lm+lm2, lm2 and lm. The three loci combination (lm+lm1+ lm2) expressed highest lesion mimic severity and early heading while lowest expression was recorded in the RILs with lm2 locus alone. Lesion mimic grade showed positive and significant correlation with AUDPC and negatively significant association with days to heading. Black point index and thousand kernel weight was not correlated with the lesion mimic grade. These lm loci expression showed differential production of ROS and were characterized by DAB and NBT staining. The combination of the three loci showed increased accumulation of H 2 O 2 and O 2 − while genotypes with only lm locus showed reduced accumulation. The microsatellite markers identified in this study may be useful for evaluating whether proposed parents with n.ormal phenotype are carriers of lesion-mimic alleles and could be of interest in breeding wheat for disease resistance.

Spot blotch disease of wheat: the current status of research on genetics and breeding

“…It has also been shown that lesion mimic loci ( Lm/lm ) that are responsible for spontaneous formation of necrotic spots on leaves, and confer resistance to rusts, promote susceptibility to spot blotch. Therefore, the presence of these Lm loci in spot blotch resistant genotypes needs to be avoided in those wheat‐growing regions of South Asia, where rust is not yet a problem (Pandey et al ., ). In other places, where rusts and spot blotch are both a problem, deployment of Lm/lm for rust resistance also needs due care.…”

“…Indeed, Pandey et al . () suggested that tissue necrosis (the result of hypersensitivity) encourages the growth and reproduction of B. sorokiniana . It has actually been shown that in addition to HR, resistance is also provided by the epidermal cell walls, electrolyte leakage from infected tissue of the host and formation of papilla‐like cell wall apposition, laid down by the host at the site of attempted penetration by the fungus (Kumar et al ., ; Ibeagha et al ., ).…”