ISHS Acta Horticulturae 478: VI International Symposium on Plum and Prune Genetics, Breeding, Pomology
INCIDENCE OF SHARKA IN PLUM PROGENIES IN COMPARISON WITH ADULT CLONAL MATERIAL |
| Authors: | J. Blazek, R. Karešová |
| Keywords: | Breeding, resistance, virus, cultivars, seedlings, rootstocks |
| Abstract:
Plum breeding programme was started at Holovousy in 1990 with a main aim to create new superior cultivars with resistance or tolerance to sharka. Till 1994 about 50 crosses were made from which nearly 2000 seedlings were raised and preselected during growing up in a nursery. Usually after two years in the nursery these seedlings on own roots were by sequel in 1992–1996 planted into the orchard at a spacing 5 by 1 m. In the same years various clonal material, which had been mostly derived from 'Domestic Prune' budded or grafted on various rootstocks, was also planted into the orchard with only one difference using a grater distance up to 5 by 3 m. Experimental plots were located close to germplasm plum orchard where about 80 % of trees were contaminated by plum pox virus. Besides, infection pressure of PPV from surroundings was rather high according to our previous experience there. Every year twice during growing season (in June and August) all trees in the experimental orchard were carefully inspected in a search for PPV symptoms and the trees showing PPV symptoms were immediately removed by grubbing. The average rate of contamination by PPV per year in 1993–96 was 3.1 % of total number of trees in the orchard. However, with adult clonal material the average rate was only 2.2 % whereas with seedlings it was 6.6 % i.e. three times more. There was also a significant difference in the rate between seedlings from progenies of cultivars sensitive to sharka (9.2 %) and those ones from progenies of parent more or less resistant or tolerant to the disease (4.0 %). Some possible explanations of these findings are being discussed. | |
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