Differences in immunity between pathogen-resistant and -susceptible yam cultivars reveal insights into disease prevention underlying ethylene supplementation

Abstract

Leaf necrosis induced by fungal pathogens is one of the most devastating diseases of yam. The objectives of this study were to examine the production of defensive phytohormones and perform a comparative transcriptome analysis between two yam cultivars with different resistance levels against Botrytis cinerea inoculation. After inoculation with B. cinerea, the endogenous ethylene level was found to have accumulated to a higher level in the MH1 resistant cultivar. Meanwhile, expression profiles identified differential defense regulation of ethylene pathway in MH1 (versus susceptible cv. MH3) in response to B. cinerea. A number of ethylene-synthesis and -responsive genes were expressed at higher levels in MH1 than in MH3 after inoculation. Furthermore, ethylene supplementation in MH3 plants by ethephon spraying indeed enhanced the resistance against B. cinerea and Colletotrichum alatae, and elevated the expression of DaEIN2 and DaERF96. Our work improves understanding of defense mechanism and highlights the function of ethylene potentially utilized for yam protection against diseases.