ISHS Acta Horticulturae 528: VII International Symposium on Grapevine Genetics and Breeding
INVESTIGATIONS ON THE INHERITANCE OF RESISTANCE FEATURES TO MILDEW DISEASES |
| Author: | R. Eibach |
| Keywords: | Vitis L., powdery mildew, downy mildew, resistance, heritability |
| Abstract:
During the years 1994 to 1997 the offsprings of 48 different cross combinations as well as their corresponding parent varieties were evaluated for their degree of infection of downy and powdery mildew on both leaf and berry. Within the investigated genetic material, the differences between the mean offspring degree of infection is rated higher for powdery mildew than for downy mildew. Extreme rates differ from 1.7 (infection of downy mildew on the berry) up to 3.5 of rating degree (infection of powdery mildew on berry). By formation of sub-groups, containing the same parental varieties, according to a diallel crossing scheme it is possible to ascertain significant differences between the parental varieties concerning the degree of infection for their offspring. Mostly the order of the parental varieties differs significantly for the characteristics of powdery mildew and downy mildew. This is even true for pure V. vinifera cultivars. The correlation coefficients within a mildew disease between leaf and berry, established from all investigated genotypes, are significantly higher compared to those between the mildew diseases (leaf, berry). Results indicate that to a great extent different genes seem to be responsible for resistance to powdery and downy mildew. Furthermore no marked coupling seems to exist between those genes, causing powdery and downy mildew resistance. The defined heritability coefficients in a narrow sense (he+2), basing upon the genetic material of the investigations, range for Oidium significantly higher (he2leaf=0,63 he2berry=0,65) than for Plasmopara (h1 leaf=0,43 he2berry=0,32). In some offsprings, considerable transgressions are noted especially for powdery mildew, pointing to a combination of different resistance mechanisms. The development of molecular markers for these different mechanisms would be tools in the field of resistance management to support effectively the endeavours of combining as many resistance mechanisms as possible. | |
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