Genetic analysis of epicuticular wax production in alfalfa

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Abstract
Epicuticular wax production increases in drought-stressed plants and has been identified as a potential drought resistance selection criterion. The objective of the present study was to determine the genetic variances and narrow-sense heritability of epicuticular wax production in alfalfa (Medicago sativa L.). These parameters were determined from a 14 parent diallel cross that included all possible progeny combinations. Cross progenies, selfed progenies, and reciprocal crosses were grown in a space-plant nursery at Logan, Utah. Epicuticular wax was determined gravimetrically after washing 100 cm2 of leaves (2.5 g) in carbon tetrachloride. General combining ability was significant (P < 0.05), and estimated heritability was 35% from one harvest in 1985. Specific combining ability and reciprocal effects were not significant. A subset of six parents and their progenies were sampled for two harvests in 1986. The general combining ability by harvest interaction was significant (P < 0.01) for epicuticular wax production, indicating that the true narrow-sense heritability may be lower than 35%. The range in epicuticular wax production among harvests was as great as among progenies. A greater diversity of genetic material would be useful in a selection program for epicuticular wax production in alfalfa.Key words: Medicago sativa, heritability, drought resistance, genetic variability, diallel analysis.