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

Background: , the causal organism of Alternaria blight, is a necrotroph infecting crops of the family 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 among isolates, 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 to could serve as novel sources of resistance.

Methodology: We 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.

Results: In this review, we have comprehensively covered the recent progress made in developing Alternaria blight resistance in crops by exploiting host germplasm. We also enumerate the potential NHR sources available for and 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.

Conclusion: This 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 protecting crops from Alternaria blight. The insights might also be applicable to a wider repertoire of plant pathogens.