Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects

Abstract

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to Pca in Avena have been designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of Pca in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between wild oat communities and oat crops. Efforts to develop cultivars with genetic resistance to Pca began in the 1950s. Based almost solely on all all-stage resistance, this has had temporary benefits but very limited success. The inability to eradicate wild oats, and their common occurrence in many oat growing regions, means that future strategies to control Pca must be based on the assumption of a large and variable prevailing pathogen population with high evolutionary potential, even if cultivars with durable resistance are deployed and grown widely. The presence of minor gene, additive APR to Pca in hexaploid oat germplasm opens the possibility of pyramiding several such genes to give high levels of resistance. The recent availability of reference genomes for diploid and hexaploid oat will undoubtedly accelerate efforts to discover, characterise and develop high throughput diagnostic markers to introgress and pyramid resistance to Pca in high yielding adapted oat germplasm.

Genotypic and resistance profile analysis of two oat crown rust differential sets urge coordination and standardisation

“…As of today, 92 loci ( Pc1-Pc85, Pc91-Pc96, Pc98 ) associated with Pca resistance are nominated based on phenotypic data and limited genetic characterisation (Carson 2017; Nazareno et al 2018). Only a few of these have been genetically mapped in oats (Carson 2017; Park et al 2022a). Furthermore, none of the Pc genes have been cloned so far and genetically linked molecular markers have been developed for only a handful.…”

Nested Association Mapping in Oat (Avena Sativa L.) Identifies the Location of Multiple Genes Conferring Resistance to the Crown Rust Pathogen Puccinia Coronata f. sp. Avenae

“…This pathogen is distributed widely, being present in almost all regions where oat is cultivated (Simons, 1970;Nazareno et al, 2018). Populations of Pca exhibit high variability in virulence, with rapid emergence of new virulent races both in the presence and absence of sexual recombination (Park, 2008;Park et al, 2022;Nazareno et al, 2018). In seasons when environmental conditions favor pathogen development, disease severity can peak at over 90% in susceptible genotypes (Martinelli et al, 1994).…”

“…Ninety-eight alleles at 92 loci conferring resistance to Pca have been designated in the genus Avena (Park et al, 2022). Few of these loci have been mapped to a chromosome (chr.…”

“…According to Chong et al (1994), PcX could be either Pc6c or Pc9. Given that both the Pc6 and Pc9 loci comprise multiple alleles, either would add more complexity to this resistance linkage group (Park et al, 2022). The QTL mapped in the PC13, PC50, PC46, and Ensiler subpopulations suggests that the genes present in each are closely linked or allelic.…”

“…Pc55 was also reported as a dominant gene in crosses with Algerian, TAM-O-312, and several Pendek isolines carrying other genes (Brouwer, 1983), which agrees with our findings that were also based on Pc55 in a Pendek background (Table 1). Kiehn et al (1976) and suggested that Pc55 and Pc39 are either very closely linked or allelic, and several authors have reported an association between virulence for Pc39 and Pc55 (Chong and Seaman 1989;Park et al, 2022). Wight et al (2004) mapped Pc39 to a region homologous to KO group 37, while more recent studies by Sowa and Paczos-Grzeda (2020) and Zhao et al (2020) both mapped Pc39 to Mrg11, on chr4C.…”