To investigate the genetic influences on tall fescue’s (Lolium arundinaceum [Schreb.] Darbysh. = Schedonorus arundinaceus [Schreb.] Dumort., formerly Festuca arundinacea Schreb. var. arundinacea Schreb.) performance, a number of studies were performed utilizing a pseudo F1 tall fescue population developed by crossing a drought tolerant female (B348) to a drought susceptible male (W947). These studies were designed to investigate the genetic influences over several agronomically relevant growth traits (plant height, tiller count, leaf width, water content (WC), and dry biomass yield (DBY). To investigate genetic influences using an agronomic approach, a number of analysis of variance (ANOVA) models were constructed, each focusing on a different component of tall fescue growth. The models measured different components of the total observed variation within that specific trait in response to two water treatment conditions (irrigated and rainfed). Selection within each of these traits was carried out using Fisher’s protected least significant difference (LSD) as well as a mean-adjusted index of merit for DBY. Additionally, a product moment correlation analysis measured correlations between traits, separated by water treatment, which suggested potential options for indirect selection. Results indicated a strong potential for tall fescue cultivar improvement via breeding trials and recurrent selection. The precursors for such a breeding program are presented here in the form of significant genotype main effect, selection within desirable agronomically relevant traits, and correlation data for several phenotypic traits. To investigate performance with respect to molecular genetics, genotypes and parental linkage maps were constructed with simple sequence repeat (SSR) markers. The female map covered 1,071 cM of tall fescue genome with, on average, a marker every 6.53 cM. The male parent map spanned 1,280 cM with an average marker density of 6.85 cM per marker. The future integration of this research with the existing SSR/amplified fragment length polymorphism (AFLP) map will allow for more complete molecular maps of tall fescue’s complex genome. Using the generated linkage maps, quantitative trait loci (QTL) were identified for the agronomically relevant traits of WC, tiller count, plant height and DBY. Each trait showed QTL which increased and/or decreased respective performance. All traits showed QTL effects that varied in response to water treatment. Several of the mapped linkage groups (LG) showed overlapping confidence intervals for QTL in different traits, indicating possible pleiotropic effects. A notable example of this occurred at 32.0 to 37.1 cM on LG 3F, where primary QTLs for plant height, tiller number, and a suggestive QTL for DBY were all detected. Additionally, several primary QTL were detected in either rainfed or irrigated conditions, but lacked a corresponding QTL in the contrasting water treatment. These results may correspond with significant genotype × irrigation interaction effects observed in the agronomic study. Each parent contributed QTL with positive and negative effects on growth and performance, but some traits showed significantly more QTL inherited from one parent and not the other. This was the case in tillering and DBY, which showed considerably more QTL in the maternal and paternal maps, respectively. The collection of synthesized data presented in this study will be directly relevant to future tall fescue breeding studies. This is especially true for studies that utilize marker-assisted breeding techniques or comparative mapping.
|Advisor:||Islam, M. Anowarul|
|Commitee:||Groose, Robin W., Legg, David E., Saha, Malay C.|
|School:||University of Wyoming|
|School Location:||United States -- Wyoming|
|Source:||MAI 56/02M(E), Masters Abstracts International|
|Subjects:||Agronomy, Genetics, Plant sciences|
|Keywords:||Genetics, Mapping, Merit of index, Quantitative trait locus, Selection, Tall fescue|
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