Resistance to downy mildew (Peronospora viciae) in Australian field pea germplasm (Pisum sativum)

Abstract

Downy mildew (caused by Peronospora viciae) can cause significant yield losses in field pea crops of southern Australia. When the Australian Field Pea Improvement Program released cv. Kaspa in 2001 it was resistant to the ‘Parafield’ strain of this pathogen. A population strain of P. viciae virulent on cv. Kaspa field peas was discovered in South Australia in 2007 (designated ‘Kaspa’ strain). High natural infection at a main field pea breeding nursery site in 2008 (Balaklava (SA)) opportunistically allowed screening against the Kaspa strain of P. viciae. Germplasm with relatively higher resistance was in most instances directly derived or closely related to a specific breeding line “96-286”. Glasshouse screening of the parental lines of “96-286” identified the source of resistance as an Afghanistan pea accession (PS998). PS998 has resistance to both strains of P. viciae. Glasshouse screening of advanced and released cultivars to either strain validated relative field ratings at sites Balaklava (SA) and Beulah (Vic) in 2008 where the cv. Kaspa contrasted in susceptibility. Despite drought conditions, there was still a positive regression between low disease incidence score and increased grain yield for breeding lines at Balaklava in 2008.