S. Benzen, and
H.-Y. Liu, United States Department of Agriculture (USDA), Agricultural Research Service, 1636 East Alisal Street, Salinas, CA 93905
Beet necrotic yellow vein virus (BNYVV) causes one of the most economically destructive diseases of sugar beet (Beta vulgaris), rhizomania, which may reduce sugar yield by 80%. This field investigation was conducted to evaluate the interactions between spinach genotypes and different BNYVV strains, and to determine whether BNYVV is transmitted through spinach seeds. Eight commercial spinach cultivars were planted in two BNYVV-infested fields and two control fields in Salinas, CA in 2009. Spinach plants in the BNYVV-infested fields showed disease symptoms of yellow-green or light-green vein clearing, mottling, or yellow-green chlorotic lesions on younger leaves as early as 28 days after planting (four- to six-true leaf stage). Leaves may also become stiff, more crinkled, and necrotic. There was an increase of lateral roots and leaf number but a decrease in leaf weight compared to healthy plants. Infected plants often became stunted, deformed, wilted, and dead. Symptomatic leaves and roots from plants with or without leaf symptoms in BNYVV-infested fields all tested positive for BNYVV by enzyme-linked immunosorbent assay. A more aggressive (resistance-breaking) strain of BNYVV led to higher disease incidence in spinach than in the wild type. BNYVV was not transmitted through spinach seeds. There were significant differences in disease development among cultivars, with disease incidence ranging from 8 to 44%, suggesting that genetic improvement of BNYVV resistance through spinach breeding should be feasible.