Turnip mosaic virus: potential for crop losses in the grain belt of New South Wales, Australia

Abstract

The potential of Turnip mosaic virus (TuMV) to infect and damage cool season crops in the grain belt of New South Wales, Australia, was investigated by serological tests on 24,689 dicot weed, grain, and forage specimens from 1999 to 2007 and infectivity/pathogenicity tests with six isolates. Natural infection by TuMV was common in Brassicaceae weeds. Infected grain crops included mustard (Brassica juncea), field pea (Pisum sativum), chickpea (Cicer arietinum), and coriander (Coriandrum sativum). Forage (turnip, Brassica rapa) was also infected. None of 9,816 canola (Brassica napus, at least 19 cultivars) or 1,967 faba bean (Vicia faba, three cultivars) plants were infected. Six isolates from weeds, mustard, and chickpea were inoculated on a range of weed and crop species including four B. napus pathotype differential lines. Inoculated Brassicaceae weeds, mustard, field pea cv. ‘Cressy Blue’, coriander, Chinese cabbage (B. rapa), and forage turnip (B. rapa) were usually infected. Field pea cv. Dundale and radishes (Raphanus sativus) were infected infrequently. Symptoms were severe in mustard, forage turnip, chickpea, and field pea. The reportedly susceptible canola cv. ‘Outback’ displayed only variable infectivity and mild symptoms for five isolates and no infectivity for one isolate. Faba bean, field pea cv. ‘Excell’, and two B. napus differentials appeared to be non-hosts. The results suggest that TuMV strains naturalised in Brassicaceae weeds in NSW in 1999–2007 could damage mustard, field pea, and forage turnip, but not canola or faba bean. These NSW strains appeared to be distinct from strains that damage canola in Europe, North America, and Asia.