| Abstract Detail
Breeding and Genetics Haynes, Kathleen G. [1], Christ, Barbara J. [2], Vinyard, Bryan T. [3]. When Practical Limitations in Disease Resistance Studies Meet Breeding Theory: A Different Perspective on General and Specific Combining Ability with Specific Reference to Foliar Late Blight Resistance. GENERAL combining ability (GCA) and specific combining ability (SCA) are estimates of the effect of all crosses that include a common parent and the effect of each pair of parents for a specific parental combination, respectively. In screening large populations for disease resistance over years it may be difficult or impossible to accurately estimate these effects. Once a clone has been found to be susceptible it is usually discarded, while with the chance of escapes in the field, multiple evaluations are desired before declaring a clone resistant. The purpose of this study was to derive tests for determining the importance of GCA and SCA for foliar resistance to late blight when the effects can not be estimated directly. Thirty-two families were generated from a design II mating scheme involving eight females crossed to four males, and approximately 120 progeny per family were evaluated for late blight from 2002-2004. In the first two years progeny that had > 80% late blight infected foliage were discarded; those that were saved were retested the following year. Sixty-seven (2.3%) clones had less than 50% infected foliage each year. Separate Chi-square tests with (f-1) or (m-1) degrees of freedom revealed that GCA was significant in the female (f) and male (m) parents, respectively. The proportions of resistant progeny from the female and male parents were used to calculate the expected proportion of resistant progeny from each parental combination. The probbnml function in SAS was used to calculate the probability that the actual number of resistant clones observed was as great or greater than expected: SCA was significant in ten crosses. Although this method does not give estimates of GCA or SCA, it does determine if GCA or SCA are significant and which parents or parental combinations have significant GCA or SCA, respectively.
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1 - United States Department of Agriculture/Agricultural Research Service, Vegetable Laboratory, 10300 Baltimore Ave., Beltsville, MD, 20705
2 - The Pennsylvania State University, Department of Plant Pathology, University Park, PA, 16802
3 - United States Department of Agriculture/Agricultural Research Service, Biometrical Consulting Service, Beltsville, MD, 20705
Keywords:
Phytophthora infestans
general combining ability
specific combining ability
Disease resistance
potato breeding.
Session: Poster-40
Location: Ballroom CD/Monona Terrace
Date: Tuesday, July 25th, 2006
Time: 8:00 AM
Abstract ID:362 |
