Perspectives on the utilization of resistance mechanisms from host and nonhost plants for durable protection ofBrassicacrops against Alternaria blight

Abstract

BackgroundAlternaria brassicae, the causal organism of Alternaria blight, is a necrotroph infecting crops of theBrassicaceaefamily at all growth stages. To circumvent this problem, several disease management strategies are being used in the field, and disease-resistant varieties have also been developed. However, no strategy has proven completely successful, owing to the high variability in virulence amongA. brassicaeisolates, which causes a diverse spectrum of symptoms. Nonhost resistance (NHR) is a robust and broad-spectrum defense mechanism available in plants, and the exploitation of gene pools from plant species that are nonhost toA. brassicaecould serve as novel sources of resistance.MethodologyWe searched the literature using key words relevant to this study in various search engines, such as PubMed, Web of Science, and Google Scholar, as well as certain journal websites. The literature was retrieved, sorted, and mined to extract data pertinent to the present review.ResultsIn this review, we have comprehensively covered the recent progress made in developing Alternaria blight resistance inBrassicacrops by exploiting host germplasm. We also enumerate the potential NHR sources available forA. brassicaeand the NHR layers possibly operating against this pathogen. In addition, we propose different strategies for identifying NHR-related genes from nonhost plants and testing their relevance in imparting broad-spectrum resistance when transferred to host plants.ConclusionThis review will help broaden the current knowledge base pertaining to the resistance sources available in host germplasm, the exploitation of NHR mechanisms, and their applications in protectingBrassicacrops from Alternaria blight. The insights might also be applicable to a wider repertoire of plant pathogens.