Abstract

Isolates of zucchini yellow mosaic virus (ZYMV) were obtained from six cucurbit species from four states of Australia and identified by host range, electron microscopy and serology. A survey of coastal Queensland in 1986-87 showed no ZYMV north of Townsville nor around Rockhampton, but major centres of ZYMV incidence with specific pathotypes, around Ayr, Bowen and in south-east Queensland. Pathotypes were distinguished using Cucumis melo differentials, Trichosanthes anguina and Phaseolus vulgaris. Three ZYMV isolates were compared with watermelon mosaic virus 2 and papaya ringspot virus, cucurbit strain, on 20 hosts from 5 families. The effect of ZYMV on 19 cvv. of pumpkin, squash, zucchini, cucumber, rockmelon and watermelon was examined in the field where marketable fruit production was most affected in Cucurbita maxima and C. pepo, moderately in C. melo and Citrullus lanatus and least in C. moschata and C. sativus. One instance of ZYMV seed transmission in C. pepo and transmission by Aphisgossypii was demonstrated. Resistance breeding progress with C. maxima using a C. ecuadorensis source and in C. lanatus using Citrullus sp. cv. Egusi is reported. Virus purification was achieved using carbon tetrachloride and Triton X-100 clarification with sucrose pad and gradient centrifugations. An antiserum was produced and reacted well in agarose gel-diffusion tests without prior virus particle disruption.