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GENETICS OF FABA BEAN RESISTANCE TO CHOCOLATE SPOT DISEASE
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Abstract: The main objective of this study was to estimate the type of gene action and the mode of inheritance of resistance to chocolate spot disease caused by Botrytis fabae in four faba bean parents and their diallel F1 and F2 generations. The investigation was carried out under the insect free cage during three successive seasons. Results showed significant differences mainly due to genetic diversity, additive, non-additive, cytoplasmic and reciprocal effects. Negative significant GCA and SCA values were regarded to determine the favorable parents combining ability and detected the good combiners. P2 (X-1786) and P4 (X-1789) seemed to be the best combiners for chocolate spot disease, especially if both parents in the same cross P2 × P4 and its reciprocal. Only one cross (P2 × P3) had negative heterosis and displayed highly resistant percentage above the mid-parent value, but some crosses had highly significant positive, indicating to high role of non-additive gene action. However, there is no useful or true heterosis above better parent for resistance to chocolate spot disease. Significant positive values of inbreeding depression in some crosses were detected. Additive component of genetic variability "D" was highly significant over generations, but dominance effect "H1" was significant in F1, however D estimates were greater than H1, suggesting that additive genetic variance is important than non-additive one and selection would be effective in early generations for resistance to chocolate spot. The covariance of additive and dominance effect "F" was significantly negative, indicating that recessive alleles were more the dominant ones. The average degrees of dominance (H1/ D)1/2 were less than one, indicating that dominance for resistance was almost partial. Overall dominance effects of heterozygous loci (h2) confirm that dominance is unidirectional positive. The KD/KR was less than one in F1and more than one in F2, indicating that there were more recessive genes in the parents than dominant ones in F1 but the opposite in F2. Narrow sense heritability ranged from 85.82% in F1 to 89.45% in F2, meaning genetic variation due to the additive effects and can improve the resistance to chocolate spot in faba bean through selection.
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| Publication year |
2012
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| Pages |
15 – 26
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| Organization Name |
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| City |
Giza
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| Author(s) from ARC |
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| Publication Type |
Journal
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