Monogenic resistance to a new fungicide, JS399‐19, in Gibberella zeae

Abstract

The fungicide JS399‐19 is a novel cyanoacrylate fungicide active against Gibberella zeae, and has been marketed in China for control of fusarium head blight (FHB) on wheat. Forty‐three isolates sensitive to fungicide JS399‐19 were collected from three commercial wheat fields in China. Forty‐five isolates resistant to JS399‐19, obtained from five sensitive isolates by selection for resistance to JS399‐19, were selected. Three sensitivity levels were identified: sensitive (S), moderately resistant (MR) and highly resistant (HR) to JS399‐19, based on a previous study. Eight isolates representing the three sensitivity‐level phenotypes were randomly selected for a study on the inheritance of JS399‐19 resistance by analysing the sensitivity of hybrid F1 progeny. A nitrate‐non‐utilizing mutant (nit) was used as a genetic marker to confirm that individual perithecia were the result of outcrossing. Five crosses were assessed: S × S, S × HR, MR × HR, HR × HR and MR × S. In crosses between parents with different sensitivity levels, such as S × HR, MR × HR and MR × S, the progeny fitted a 1:1 segregation ratio of the two parental phenotypes. No segregation was observed in the crosses S × S and HR × HR. It was concluded that the MR and HR phenotypes in G. zeae were conferred by different allelic mutations within the same locus. In these isolates, resistance to JS399‐19 was not affected by modifying genes or cytoplasmic components.