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CROP BREEDING, GENETICS & CYTOLOGY

Combining Ability for Resistance to Sclerotinia Head Rot in Sunflower

^a Dep. of Plant Sciences, North Dakota State Univ., P.O. Box 5051
^b USDA-ARS, Northern Crop Science Lab., P.O. Box 5677, Fargo, ND 58105

^* Corresponding author (millerjf{at}fargo.ars.usda.gov).

Sclerotinia head rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a major disease in sunflower (Helianthus annuus L.). The development of hybrids with adequate genetic resistance is necessary to reduce yield losses caused by this disease. The objective of this study was to estimate the general (GCA) and specific (SCA) combining ability of a set of female and male oilseed sunflower inbred lines in hybrid combinations for resistance to Sclerotinia head rot. Six female and six male lines were crossed in a factorial mating design. The hybrids were planted in three U.S. environments and in Argentina. Plants were inoculated with a suspension containing 5000 ascospores per milliliter. Sclerotinia head rot disease incidence was measured as percentage of plants attacked on a plot basis. The GCA effects accounted for a greater proportion of the treatment sum of squares than the SCA effects, suggesting that additive gene effects were relatively more important than nonadditive gene effects in the phenotypic expression of resistance to Sclerotinia head rot. The importance of additive gene effects suggests that selection could start at the inbred line development stage. However, hybrids should also be tested since nonadditive gene effects were significant in the individual environments and certain hybrid combinations showed higher or lower disease incidence than would be expected based on the average performance of their parents.

Abbreviations: GCA, general combining ability • SCA, specific combining ability

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THIS ISSUE IN CROP SCIENCE

Crop Science 2004 44: 1507-1510. [Full Text]