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University of Manitoba (1995)

Genetic control of alfalfa seed quality characteristics

Gjuric, Radisa

Titre : Genetic control of alfalfa seed quality characteristics

Auteur : Gjuric, Radisa

Université de soutenance : University of Manitoba

Grade : Doctor of Philosophy (PhD) 1995

Résumé
There is limited information on the genetic control on alfalfa (Medicago sativa L.) seed quality characteristics and the effects of genotype and environment on these traits. The major objectives of this research were : i) to study the effect of cultivar and environment on alfalfa seed quality characteristics ; ii) to estimate the components of genetic variance involved in the inheritance of alfalfa seed size and to evaluate the factors affecting response to selection for seed size in alfalfa ; and iii) to determine if RAPD markers can be used to estimate outcrossing/selfing rates in autotetraploid alfalfa through a proposed method labelled ’RAPD multiplex loci analysis’. A series of field experiments were conducted in southern Manitoba during 1gg2-1gg4 to study the effect of genotype and environment on alfalfa seed quality. Plant material for the research on the genetic control of seed size and RAPD multiplex analysis was grown under controlled environmental conditions. A broad based alfalfa germplasm ’BIC-7WH’ was used as a reference population and seed size was measured both on the parental plants involved in the mating design and their progeny plants. The proposed method of RAPD multiplex loci analysis included : (i) RAPD marker selection based on the polymorphism between a given seed parent and its open pollinated progeny and (ii) screening individual open pollination progeny of that seed parent for the presence of these markers. The results from the field experiments showed that cultivar ranking for seed yield was consistent over an wide range of seed yields obtained under different environmental conditions. All seed quality characteristics were strongly influenced by the environment, and there was a cultivar response for seed weight and percentage hard seed. This research demonstrated that digital imaging of alfalfa seed has potential for developing alternative measurements of seed quality. Results from the genetic study showed that the seed parent had the greatest influence on the seed size and that the genetic expression for seed size should not be measured on the parental plants involved in a crossing design, but seed size should be measured on the progeny plants. seed size was shown to be controlled by both additive and non-additive components of genetic variance and appeared to be a highly heritable trait. RAPD multiplex loci analysis allowed accurate identification of F., and S’ progeny and estimation of outcrossing rates in autotetraploíd alfalfa. ln conclusion, this research indicates that there is a genetic effect for most of the alfalfa seed quality characteristics, but these effects are often masked by a combination of the environmental conditions and seed parent effect.

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