The genetics of resistance in sunflower capitula to Sclerotinia sclerotiorum measured by mycelium infections combined with ascospore tests |
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| Authors: | Fernando Castaño Felicity Vear Denis Tourvieille de Labrouhe |
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| Institution: | 1. Facultad de Ciencias Agrarias-UNMdP/Estación Experimental Agropecuaria-INTA, Unidad Integrada Balcarce (, CC 276, RA 7620, Balcarce, Argentina
2. I.N.R.A. Centre de Recherches Agronomiques, Domaine de Crou?lle, F 63039, Clermont Ferrand Cedex 2, France
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| Abstract: | To enhance efficiency of breeding programmes for Sclerotinia sclerotiorum resistance in sunflower capitula, two separate resistance tests have been recommended. However, the time necessary to develop
genotypes with two types of resistance makes this impractical. A strategy to combine the two tests was consequently proposed
to reduce the number of seasons per selection cycle, but genetic studies were necessary to determine if it could be applied
in breeding programmes. This was the objective of this work. Data from two genetically different sunflower inbred lines and
their F1, F2 and backcross generations were analysed in two years to determine the genetics of resistance to S. sclerotiorum in capitula measured by application on the same plants of a mycelium test combined with an ascospore test. Effects of maternal
origin were detected when the reciprocal generations were evaluated for the mycelium test. This suggests the importance of
choice of the inbred line used as female in population formation by hybridisation. Progeny subjected to the mycelium test
did not show any change in relative reactions to two S. sclerotiorum isolates suggesting that ranking genotypes according to the results of combined S. sclerotiorum tests is repeatable across Sclerotinia isolates and experimental seasons. Moderate narrow sense heritability indicated that selection of the best F2 plants should
be effective. Genetic gain from selection is possible because a reduction of lesion areas produced by the mycelium test can
be expected. Additive gene effects contribute significantly to reduction in lesion area. Consequences of results in population
improvement for S. sclerotiorum resistance in capitula are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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| Keywords: | additive gene effects breeding genetic populations Helianthus annuus maternal inheritance sunflower white rot resistance |
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