Document Type

Dissertation - University Access Only

Award Date

1990

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy

Abstract

The genetic variation of plant water relation traits was examined in the field and greenhouse. Two separate field experiments were conducted in five environments. The first experiment studied genotypes selected for relative water content (RWC) and the second for excised leaf water retention (ELWR). The plant water relation traits, RWC, ELWR, solute potential at full turgor (SPFT), and stomata! conductance (STCON) were examined at two growth stages. Genotype rankings in RWC and ELWR were generally consistent across environments. However, separation of genotypes by ELWR and RWC was better in stress than nonstress environments. Discriminant analysis showed that genotypes were classified into high, intermediate and low groups by their ELWR, and RWC values. A third experiment examined the combining ability of six parents for plant water relation traits. The F2 and F3 generations of the six parent diallel cross were used for combining ability analysis. Mean squares for general combining ability (GCA) and specific combining ability (SCA) were significant indicating both additive and nonadditive effects were important for RWC, ELWR, and SPFT. The GCA:SCA mean square ratio suggested that GCA predominated. A greenhouse experiment examined the root morphology of five F2 derived F3-lines and their parents. Variability for root traits were observed among the crosses and parents. Burnett had the largest root length and dry weight. Among the five crosses, Burnett X Chief had the greatest root length and dry weight. The correlation between root dry weight and length (r=0.86**) indicates that selection for high root dry weight is likely to result an increase in root length. In conclusion, there was wide variation for RWC, ELWR, SPFT, STCON, and root traits. Both additive and nonadditive genetic factors were important for RWC, ELWR and SPFT. The relative rank of genotypes in RWC and ELWR was consistent in stress environments. Therefore, RWC and ELWR could be utilized as screening techniques for water stress resistance. The results also suggested the possibility for improving root morphological characters through breeding and selection.

Format

application/pdf

Number of Pages

206

Publisher

South Dakota State University

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