Mastreviruses in chickpea (Cicer arietinum) and other dicotyledonous crops and weeds in Queensland and northern New South Wales, Australia

Natural infection by mastreviruses was investigated in chickpea (Cicer arietinum) and other dicotyledonous crops and weeds in grain production areas of Queensland and northern New South Wales, Australia, from 2000 to 2005. Altogether, 33639 plants comprising 31 species and 10 dicot families were screened for infection by a tissue-blot immunoassay that did not distinguish between mastrevirus strains or species. Nine plant species in three families were identified as natural hosts. Chickpea was infected throughout the region although infection incidence did not exceed 5%. Infection was rare in faba bean (Vicia faba), canola (Brassica napus), and mustard (B. juncea) and not detected in field pea (Pisum sativum). Infection of chickpea and turnip weed (Rapistrum rugosum) was confirmed by immunocapture polymerase chain reaction (IC-PCR) with primers generic for dicot-infecting mastreviruses, and also immunosorbent electron microscopy and graft transmission in the case of chickpea. Individual mastreviruses were identified by comparing their IC-PCR amplicons by a combination of methods. Among 42 isolates from 41 chickpea plants, one was typical Tobacco yellow dwarf virus (TYDV) and the others were three recently distinguished strains including two proposed novel species: 34 Chickpea chlorosis virus strain A, six Chickpea chlorosis virus strain B, and one Chickpea redleaf virus. All of 10 isolates from 10 turnip weed plants were TYDV-B, a strain distinct from typical TYDV. The symptoms associated with mastrevirus infection in chickpea included foliar chlorosis or reddening, stunting, and usually phloem browning. The potential for losses in winter and summer grown field crops is discussed

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

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