ISHS Acta Horticulturae 338: VI International Workshop on Fireblight
CROSS COMBINATIONS FOR FIRE BLIGHT RESISTANCE IN PEAR |
| Authors: | G.L. Bagnara, L. Rivalta, M. Laghi, R. Quarta, P. Lecomte |
| Abstract:
The objective of this paper is to estimate the heritability and to select the best parents for fire blight resistance in pear. For this purpose, about 4000 seedlings, from cross combinations of 21 parents, were tested inoculating 6 shoots per seedling. Breeding value was calculated to estimate the potential of each single parent. Heritability was also calculated by variance analysis in sib analysis (Falconer, 1989). Furthermore, the different components of phenotypic variance (variance of seedling among shoots; variance among seedling of the same cross; and variance among cross combinations) were related to the performance of each seedling to estimate their influence by a multiple regression analysis. Standard cultivars (Stark Delicious, Bella di Giugno, Nain Vert, Coscia and Max Red Bartlett), susceptible or low resistant, gave offsprings with good resistance. Resistance accounted for 50 percent of additive genetic variance, confirming the results of Bell et al. (1977). Standard parents gave the bulk of additive component, explaining the high breeding value. Environment variability, estimated by the variance within the same seedling, had on breeding value a weight as well as variability within cross combination. Variance between cross combinations was the greatest source of variability. Due to the high environmental influence and non-additive genetic effects it is necessary to estimate a parent by its breeding value. Considering the variability sources, the best selection potential is given by variance among progenies, which implies an increase of cross combination number for breeding strategy. | |
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