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Abstract
Because of the high incidence and serious effect of grapevine fanleaf and leafroll viruses on vines in New Zealand, virus-free material is needed for new plantings and replacement of existing infected vines.
Virus-free vines of a number of varieties have been introduced from California, and heat treatment has been applied to all important local varieties.
Vines of 18 varieties have been treated at 100°F for periods ranging from 56 to 141 days. Of 167 vines raised from shoot tips of heat-treated plants, 45 have been screened for virus infection. Four were found to be infected with fanleaf and 9 with leafroll virus.
Vines of the first variety from which virus was eliminated by heat treatment were released in 1968. Plants of a further 6 varieties will be released next year, and 11 varieties, stilI being indexed, should be available for release in 1972 and 1973. Eight other varieties are undergoing heat treatment.