Abstract: Zymoseptoria tritici is a host-specific necrotrophic pathogen, causing Septoria tritici blotch (STB) disease on wheat leaves. Although substantial efforts have been made to identify pathogenicity factors in Z. tritici, the genetic components contributing to the qualitative/quantitative virulence of Z. tritici remain largely elusive.

Within Z. tritici populations, quantitative differences in virulence among different isolates are commonly observed. Thus, we first performed an intra-specific comparative transcriptomic analysis (RNA-seq experiment) aiming to identify genes impacting the quantitative virulence traits of different Z. tritici isolates during infection on the wheat cultivar WW2449. In this experiment, we identified a multi-copy gene REP9-1 residing in a Class II transposable element, whose expression negatively impacts the asexual reproduction of Z. tritici during infection. The regulatory effect of REP9-1 is independent of the host genotype, adding to the complexity of this devastating wheat pathogen.

In addition to the RNA-seq experiment, we also attempted to identify genes impacting the qualitative virulence of Z. tritici on wheat cultivars containing specific resistant (Stb) genes via a forward genetics approach (UV-mutagenesis). In this experiment, the wildtype Z. tritici isolate WAI332 is non-pathogenic on wheat cultivars Arina and Israel_493. We generated and screened 1,000 WAI332 mutants and obtained 9 and 10 mutants that gained virulence on Arina and Isral_493, respectively. The genomes of these mutants have been sequenced and the single nucleotide polymorphisms (SNPs) within each mutant have been identified. The SNP data will contribute to the discovery of potential avirulence (Avr) genes in WAI332.

Biography -Chen is a PhD student in the Solomon lab, Division of Plant Sciences, RSB, ANU. Prior to his PhD he completed his bachelor’s degree in biotechnology at Wuhan University in 2014 and master’s degree in biological sciences at ANU in 2016.