Phenotypic and Genotypic Diversity of Puccinia sorghi in Eastern Australia: Implications for Maize Breeding Programs

Abstract

Common rust of maize (CR), caused by Puccinia sorghi Schwein., is found in all maize growing regions across the globe. In recent years, an increase in the incidence and severity of CR has been observed in Australia. The challenges posed by a diverse population of P. sorghi to maize breeding programs and the strategies required to deploy durable resistance were explored. Preliminary studies of diversity were conducted by phenotyping the five most diverse isolates against maize lines carrying no resistance genes and one to four resistance genes. The results showed that further genotyping studies were required. Short reads of 17 CR isolates were collected from an array of agroecological regions in Eastern Australia, and these were mapped back against the hybrid assembly of Isolate 1. A hybrid assembly between short (Illumina paired-end) and long (PacBio) reads was conducted in MaSuRCA of the first isolate collected. A draft genome of 145,963,792 bp was obtained after QUAST analysis, with a total length of 145,815,044 bp (when removing base pairs below ≥1,000). The prediction from the BRAKER pipeline identified 20,438 gene models. All 17 isolates sequenced represented unique genotypes, and no clones were detected. The 17 isolates grouped into three clusters. The diversity observed within the population of P. sorghi in Australia suggests that monogenic resistance might not be durable. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Keywords

• fungal pathogen diversity
• genome assembly
• hybrid assembly
• long reads
• Pucciniales
• rust