Mapping of crown rust (Puccinia coronata f. sp. avenae) resistance gene Pc54 and a novel quantitative trait locus effective against powdery mildew (Blumeria graminis f. sp. avenae) in the oat (Avena sativa) line Pc54.

Authors: ADMASSU-YIMBER, BELANYNE - University Of Idaho; Esvelt Klos, Kathy; GRIFFITHS, IRENE - Aberystwyth University; COWAN, ALEXANDER - Aberystwyth University; HOWARTH, CATHERINE - Aberystwyth University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2021
Publication Date: 4/25/2022
Citation: Admassu-Yimber, B., Esvelt Klos, K.L., Griffiths, I., Cowan, A., Howarth, C. 2022. Mapping of crown rust (Puccinia coronata f. sp. avenae) resistance gene Pc54 and a novel quantitative trait locus effective against powdery mildew (Blumeria graminis f. sp. avenae) in the oat (Avena sativa) line Pc54.. Phytopathology. 112:1316-1322. https://doi.org/10.1094/PHYTO-10-21-0445-R.
DOI: https://doi.org/10.1094/PHYTO-10-21-0445-R

Interpretive Summary: Crown rust and powdery mildew are two of the most important diseases of oats. The annual grain yield losses from crown rust and powdery mildew infections are estimated to range from 1.7 to 20%, and 5 to 40%, respectively. The use of fungicides to manage both diseases in oats is not recommended as it is not economically justifiable or environmentally desirable and excessive use may lead to the development of fungicide resistance in the pathogen populations. The use of resistant cultivars carrying effective genes against the pathogens is generally accepted as the best alternative to control crown rust and powdery mildew diseases in oats. The present study identified the chromosomal locations of two genes conferring crown rust and powdery mildew resistance in oats. It also identified molecular markers closely associated with the two genes. The molecular markers will enable the rapid selection of oat genotypes with the resistance genes. The results of the present study will also help in understanding the molecular mechanism of resistance to crown rust and powdery mildew, thereby contributing towards durable management of crown rust and powdery mildew diseases in oats.

Technical Abstract: Crown rust and powdery mildew are two of the most important diseases of oats. The Pc54 oat line carries the crown rust resistance gene ‘Pc54’ and an unknown gene effective against powdery mildew. In this study two recombinant inbred lines (RIL) populations were developed with the objectives of identifying the genomic locations of the two genes and producing lists of molecular markers with a potential for marker assisted selection. Each mapping population contained 178 and 115 RILs. The RILs along with parents were phenotyped for crown rust and powdery mildew in a controlled environment. They were also genotyped using the 6K Illumina Infinium iSelect oat SNP chip. Multiple interval mapping placed the Pc54 gene on the linkage group Mrg02 and the novel powdery mildew QTL ‘QPm.18’ on Mrg18 using RILs from a cross between the Pc54 line and Otana. The map locations were validated using a second mapping population developed by crossing the Pc54 line with the susceptible Pc96 differential line. A total of ten and 30 significant SNP and SSR markers were identified linked with the Pc54 gene and QPm.18, respectively. Other crown rust resistance genes and QTLs were previously reported on Mrg02, but reactions to crown rust inoculations have justified separate identity of Pc54 from the other genes and QTL except for the QTL ’qPCRFd’. The powdery mildew resistance gene Pm3 was the only one mapped on Mrg18 as ‘QPm.18’. However, the pm3 differential line, Mostyn was susceptible to the oat powdery mildew race used in this study suggesting that Pm3 and QPm.18 are different genes. Determining the chromosomal locations of Pc54 and QPm.18 genes will help in understanding the molecular mechanism of resistance to crown rust and powdery mildew in oats. SNPs identified in this study that are closely linked with the genes can be used to develop further PCR based molecular markers and facilitate the utilization of these genes in oat breeding programs.