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Quantitative genetic analysis of erect glandular trichome density in diploid alfalfa

Gonzalez-Garcia, J., Ray, I.M., Henning, J.A., Murray, L.W.
Euphytica 2000 v.111 no.1 pp. 61
crossing, Medicago sativa, plant glands, trichomes, density, quantitative genetics, genetic techniques and protocols, heritability, paternal effect, maternal effect, genetic variance, gene interaction, epistasis, genotype, linkage (genetics)
The presence of glandular trichomes may protect alfalfa (Medicago sativa L.) against certain stem-, leaf-, and fruit-eating insect pests. In order to determine appropriate breeding methods to select for this trait, this study characterized quantitative genetic parameters of erect glandular trichome density in 'KS94GH6' diploid (2n=2x=16) alfalfa. Eight female and five male plants were crossed in a Design II mating to produce 40 full-sib families. Glandular trichome density was determined on these families under replicated greenhouse conditions in Las Cruces and Los Lunas, New Mexico, U.S.A. The effect of males was significant (p ltoreq 0.10) across the two environments. Variation among females was not significant within either location or across locations. The dominance genetic variance (sigmaD2 = 0.210) was greater than the additive genetic variance (sigmaA2 = 0.111). The average degree of dominance exceeded a value of '1' indicating that erect glandular trichome density in KS94GH6 may be influenced by digenic epistasis, and/or repulsion phase linkage disequilibrium. The large contribution of non-additive effects was reflected by a low narrow-sense heritability estimate (hn2 = 0.25). The results indicate that further improvements in erect glandular trichome density in KS94GH6 alfalfa will require replicated progeny testing. Approaches to introgress this trait into cultivated tetraploid alfalfa are discussed.