Cucumber mosaic cucumovirus infection of cool-season crop, annual pasture, and forage legumes: susceptibility, sensitivity, and seed transmission

Abstract

Seven field experiments were done in 19944—98 to determine the relative susceptibilities and sensitivities of a wide range of alternative crop, annual pasture, and forage legumes to infection with cucumber mosaic virus (CMV). Seed harvested from some species was tested for seed transmission of the virus. Most of the 24 genotypes of Cicer arietinum and 39 of Lens culinaris tested in 2 replicated field experiments were ranked as highly susceptible or susceptible; moderate resistance was recorded in 8Lens culinaris genotypes, the most resistant of which was ILL7163, and in C. arietinum cv. Amethyst Mutant. Sensitivity varied from low to high in different Lens culinaris genotypes, whereas in C. arietinum they were all sensitive or highly sensitive. In 4 other experiments, 12 species (49 genotypes) of other crop legumes were ranked as follows: Vicia narbonensis susceptible to moderately resistant, V. ervilia susceptible, Pisum sativum resistant, and V. faba resistant to potentially highly resistant; Lathyrus cicera,L. clymenum, L. ochrus, L. sativus, L. tingitanus, V. benghalensis, V. monantha, and V. s a t i v a were not infected. V. ervilia andV. faba were very sensitive to infection, but V. narbonensis had intermediate sensitivity and P. s a t i v u m was tolerant. When single genotypes of each of 16 pasture and forage species were tested in 2 replicated field experiments, 1 was highly susceptible, 3 were susceptible, 9 moderately resistant, 2 resistant, and 1 was potentially highly resistant. The 4 most susceptible were the sensitive species Trifolium incarnatum and T. isthmocarpum and the intermediately sensitive species T. michelianum and T. vesiculosum. T. squarrosum (intermediate sensitivity) and T. spumosum (very sensitive) were resistant and Ornithopus sativus was not infected. In sap inoculations, L. ochrus,L. sativus, and P. sativum occasionally became infected. In aphid inoculations,Lens culinaris ILL7163 and V. faba became infected only rarely and V. benghalensis cv. Popany developed a systemic hypersensitive reaction. The following were not infected in the field or glasshouse: L. cicera ATC80521, L. clymenum C7022, O. sativus cv. Cadiz, and V. sativa cv. Languedoc.Seed transmission of CMV was detected for the first time in one crop species, V. narbonensis(0.1mp;mdash;0.8%), and confirmed in C. arietinum (0.2–0.3%) and Lens culinaris (0.3%). It was also detected in T. cherleri (0.05%), T. clypeatum (0.05%), T. dasyurum (0.1%), T. incarnatum (5%), T. purpureum (0.04%), T. spumosum (0.5%), T. squarrosum (0.1%), and T. vesiculosum (1%), but not in 8 other pasture or forage species.

The high susceptibility and sensitivity to CMV of some alternative crop, annual pasture, and forage legumes is cause for concern, especially when they are intended for sowing in CMV-prone high rainfall zones. Infection of seed stocks with CMV is also of concern as it leads to inadvertent introductions of the virus.