Field Serological Detection of Viral Antigens Associated with Grapevine Leafroll Disease

Abstract

A polyclonal antiserum produced against closteroviruslike particles purified from leafroll-diseased grapevines in New York [USA] was used to determine the best time and tissue type for field detection of the disease. Grapevine leafroll-associated viral antigens were detected by direct enzyme-linked immunosorbent assay in 8-yr-old Pinot noir vines in a commercial vineyard in New York during the 1986 growing season. The viral antigens were detected in phloem extracts of dormant cuttings after 6 mo of storage at 6 C. Viral antigens were first detected 15 days after budbreak in flowers at the stage of inflorescence swelling. Basal leaves were not reliable for field detection until bloom. Viral antigens were evenly distributed in shoots arising at the basal, middle, and apical portions of 1-yr-old canes. Besides flower clusters and leaves, the viral antigens were also detected in roots, fruit, fruit peduncles, tendrils, and bark tissue. In fruit, the viral antigens were detected in all stages, except when they were 2-4 min in diameter. Virus was detected in symptomatic and symptomless leaves in diseased but never in healthy vines. Flower clusters and roots were the tissues from which the virus was first detected 15 days after budbreak in greenhouse-grown, diseased cuttings, whereas leaves did not became reliable virus sources until 28 days after budbreak. The rate of advance of the viral antigens in growing shoots appeared to vary according to the growth stage of the vines: 1) from budbreak to inflorescence swelling, the viral antigens were restricted to flower clusters and were not detected in leaves; 2) from inflorescence development to developing berries (25-75 days after budbreak), the viral antigens were detected in the leaves but did not reach the terminal ones; and 3) from berry touch stage until harvest, the viral antigens were detected in all leaves including the terminal leaf.