Genetic variability and association between agronomic and quality characteristics in twenty-nine female genotypes of Humulus lupulus L. Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/tb09j8803

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  • The genetic variability in and association between 14 traits that affect maturity, yield, and chemical properties of its product. The plant characters measured were: vigor, flowering date, harvest date, yield, lateral length, nodes per lateral, cones per lateral, cones per vine, cone weight. Alpha-acid and beta-acid content of the cone, alpha:beta-acid ratio, total soft resin, and lupulin content of the cone were included in the chemical evaluation. Genetic variance, genetic coefficient of variation, broad sense heritability and expected gain were calculated for each of the traits. The degree of association between traits was determined on the basis of phenotypic, genotypic and environmental correlations. The phenotypic correlations were further analyzed by path coefficient analysis to determine the interrelationships of the traits. Highly significant differences among genotypes were shown for all characters measured. The genetic coefficients of variation, broad sense heritability, and expected gains indicated there was a large genetic potential for improvement of most traits studied. Vigor, flowering date, and harvest date appear to have the least genetic potential for improvement. Application of a five percent selection pressure should result in a 90 percent gain in number of cones per vine and yield, and a 70 percent gain in lateral length and cones per lateral. All agronomic characteristics other than cone weight were positively correlated with yield. Also, all possible combinations of harvest date, lateral length, nodes per lateral, cones per lateral, cones per vine, and yield had significant positive phenotypic correlations. With the exception of vigor, phenotypic correlations between agronomic characters and the quality traits, alpha-acid and betaacid content of the cone, were either significant in a positive direction or showed no relationship. Correlations between alpha-acid and beta-acid concentration tend to support the concept that the two compounds are genetically independent after their common biosynthetic pathways diverge. Path coefficient analyses of phenotypic correlation coefficients showed that lateral length and cones per vine have more of a direct and indirect effect on yield than does vigor, flowering date, harvest date, nodes per lateral, or cone weight. The results reported in this study are important to the hop breeder whose objective is to improve yield and quality. The results indicate: 1. There is a large genetic potential for improving most traits studied. 2. Associations between and among agronomic and quality traits show that selection can be practiced on either group separately without having a negative effect on the other. 3. Lateral length and cones per vine have a strong influence on yield. Improvement of these two traits provides a means for increasing yeild in early maturing cultivars.
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