Improved shoot growth and berry set of virus-free grapevines.
1990
Okamoto G. | Noda M.
1. One year-old virus-free grape vines, cv. 'Gros Colman', 'Muscat of Alexandria' and 'Pione', which had been propagated by tissue culture of heat-treated shoot apices, were planted on rock fiber beds and fertilized with coated fertilizer or nutrient solution. Control vines supposed to be virus-infected, were propagated by cuttings from canes collected in commercial vineyards. Shoot growth of virus-free vines of both 'Gros Colman' and 'Pione' was more vigorous than that of control vines. More active root growth was also observed on virus-free vines of 'Pione'. In 'Muscat of Alexandria', on the other hand, no obvious difference in shoot growth was observed between virus-free vines and control vines. 2. Shoot growth on control vines of 'Pione' was inhibited when they were fertilized with the weakest dilution of the nutrient solution (N; 20ppm), though the shoot of virus-free vines grew as normally as those fertilized with the stronger dilutions of nutrient solutions (N; 60,120ppm). 3. Photosynthetic activity of the mature leaves on virus-free 'Pione' vines was found to be not higher than that of control vines when measured late May and early August. 4. The growth of rooted cuttings propagated from virus-free vines in nurseries was more vigorous than that of control vines. More than 90% of the cuttings from virus-free vines of 'Pione' and 'Muscat of Alexandria' grew to marketable size. Only 61% of 'Pione' and 38% of 'Muscat of Alexandria' from control vines of these cultivars grew normally. 5. Young vines of virus-free 'Pione', growing in a heated plastic house from January or February, set more berries than control vines. No obvious difference, however, was observed in the rate of perfect ovules between virus-free vines and control vines. The number of pollen tubes growing into the style and ovary tissue also did not differ, though the rate of ovules penetrated by a pollen tube through the micropyle was higher in the ovaries of virus-free vines.
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