Alfalfa mosaic and pea seed-borne mosaic viruses in cool season crop, annual pasture, and forage legumes: susceptibility, sensitivity, and seed transmission

Field experiments determined the susceptibilities and sensitivities of a wide range of crop, annual pasture, and forage legumes to infection with alfalfa mosaic (AMV) and pea seed-borne mosaic (PSbMV) viruses. Seed harvested from most of the species was tested for virus seed transmission. With AMV, all 23 Cicer arietinum genotypes tested were ranked as highly susceptible, and 9 out of 19 Lens culinaris genotypes as highly susceptible, 8 susceptible, 1 moderately resistant, and 1 resistant. Genotypes of Vicia narbonensis (5), Lathyrus cicera (5), L. sativus (5), L. ochrus (2), V. sativa (1), and V. benghalensis (1) were highly susceptible, susceptible, or moderately resistant. Genotypes of Pisum sativum (5) and V. faba (3) were susceptible, moderately resistant, or resistant but 1 genotype of V. faba was not found infected. Sensitivities ranged from low in L. ochrus to high in some genotypes of most species tested except V. benghalensis. The 20 genotypes (19 species) of pasture and forage legumes ranged from `not found infected' in Hedysarum coronarium to `highly susceptible' in Ornithopus sativus and Trifolium resupinatum. Sensitivity varied from low in T. michelianum to very high in Biserrula pelecinus and Ornithopus sativus. With PSbMV, the genotypes of P. sativum (17), V. narbonensis (5), and L. cicera (3) were ranked as highly susceptible, susceptible, or moderately resistant, while those of L. ochrus (3), V. faba (6), V. sativa (3), V. benghalensis (2) and V. ervilia (1) were either moderately resistant or resistant. The genotypes of C. arietinum (6) and Lens culinaris (6) were all resistant. With L. sativus, 2 genotypes were resistant and 1 was not found infected. Sensitivities ranged from low in some P. sativum genotypes to high in some of L. cicera and V. narbonensis. The seed coats of 9 crop legume species developed necrotic ring markings, a serious quality defect due to PSbMV infection. Of the 19 genotypes (1/species) of pasture and forage legumes, 4 were resistant with only symptomless infection developing and the remainder not found infected. In glasshouse inoculations to genotypes not found infected in the field, AMV infected V. faba cv. Ascot systemically but H. coronarium cv. Grimaldi (with AMV) and L. sativus BIO L254 (with PSbMV) only became infected in inoculated leaves, H. coronarium developing a localised hypersensitive reaction. Seed transmission of AMV was detected in L. cicera (2%), L. sativus (0.9-4%), V. benghalensis (0.9%), V. narbonensis (0.1%), and V. sativa (0.7%). It was also found in 15 pasture and forage legume species, ranging from 0.05% in T. michelianum to 7% in Trigonella balansae. Seed transmission of PSbMV was detected in L. cicera (0.4%), L. clymenum (5%), L. ochrus (0.7%), L. sativus (1%), P sativum (1-18%), V. benghalensis (0.1%), V. faba (2%), and V. sativa (0.3%). The implications of these findings and their importance to the management of these and other virus diseases are discussed.