Functional RNAi response in Colletotrichum graminicola reveals potential for host-induced gene silencing against maize anthracnose

Abstract

Colletotrichum graminicola is a filamentous fungus that causes anthracnose disease in maize, leading to yield losses of up to 35%. RNA interference (RNAi) has been successfully employed to protect crops against phytopathogenic fungi through multiple approaches, demonstrating considerable efficiency in silencing target genes. In this study, it was evaluated RNAi-mediated silencing of C. graminicola chitin synthase genes (CHSV and CHSVII), two important structural components and the phosphopantetheinyl transferase gene (PPT) involved in the melanin biosynthesis pathway and directly associated with C. graminicola pathogenicity. In this work, it was also tested siRNA and dsRNA and topical applications in culture medium and detached maize leaves. The siRNAs in culture media proved more efficient in reducing transcripts levels compared to long dsRNAs; and in detached maize leaves it was observed the opposite. No significant difference was found in the overall suppressive effect of siRNAs and dsRNAs, as both approaches inhibited fungal biomass accumulation and reduced the severity of anthracnose in maize leaves. It was also tested the effect of expression CHSVII dsRNA in transgenic maize with experimentally infected C. graminicola. The 20 maize transgenic events showed a gradient from low to high severity of anthracnose in leaves and stalk compared to the non-transgenic plants indicated that it also can be used as strategy to mitigate this disease. The RNAi strategies applied in this study to inhibit C. graminicola growth both in vitro and in vivo, as well as to protect transgenic maize plants against anthracnose, suggest this could support future technologies aimed at mitigating yield losses and reducing fungicide application used in maize fields.