Field susceptibility of Japanese-type plums to Xanthomonas campestris pv. pruni

Abstract

Fifty-five cultivars and 9 breeding selections of Japanese-type plum (Prunus salicina and hybrids) were evaluated from 1985 to 1988 for their susceptibility in the field to Xanthomonas campestris pv. pruni in a cultivar screening trial at the Granite Belt Horticultural Research Station (GBHRS), Applethorpe, Queensland. Laroda, Friar and Beauty were the most susceptible cultivars and showed severe leaf shothole, summer twig cankers and twig death. October Purple, Eldorado, Santa Rosa and Blackamber were also susceptible, displaying leaf shothole and twig cankers in the worst years. The locally established cultivars Doris, Queensland Red Ace, Shiro and Santa Rosa have been considered our most susceptible cultivars but were not as susceptible as many of the recent Californian introductions. Californian cultivars were more susceptible to bacterial spot than the selections from the GBHRS plum breeding program. The incidence of bacterial spot was higher in the years of high summer rainfall. Seventeen genotypes including 5 GBHRS selections did not display symptoms of bacterial spot. Wilson (P. salicina x P. cerasifera) is considered a good source of bacterial spot resistance for use in breeding.