Graduate Thesis Or Dissertation
 

Wheat genotypes selected under optimum conditions and their response to water and heat stress

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rn301354g

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  • Concerns have been expressed that wheat (Triticum aestivum L.) cultivars selected under optimum conditions may lack adequate adaptation for stress environments. Experimental populations were grown under three environmental conditions 1) optimum, 2) reduced irrigation, and 3) high temperature. Field experiments were conducted at the Center for Northwest Experimental Station (CIANO), in Cd. Obregon, Sonora, Mexico during 1992-93 and 1993-94 cropping seasons. An analysis of variance for each environment and a combined analysis over environments for a single year and for two years were calculated for 130 selected lines from six crosses. To examine the magnitude of the possible genotype x environment interaction and its implications to yield stability, three stability methods were employed. A stress index was computed to evaluate the sensitivity of the genotypes to water and heat stress. Correlations coefficients and path-coefficients were calculated for yield and selected agronomic traits to determine if specific traits were associated with stable genotypes. Single and combined analyses of variance across environments confirmed that differences existed among the genotypes in their response to changes in environments. The genotype yield performance suggested that the selection under optimum management conditions was effective in identify germplasm with relatively better grain yield under moisture and heat stress. The relative magnitude of genetic to environmental variance was found to be low for several genotypes by both the stability variance (S²) and the genotype grouping technique. Stress index values and the results of the genotype yield performance suggested that selection under optimum management conditions could lead to the selection of genotypes with tolerance to drought and heat. Correlations coefficients and path-coefficients indicated that biomass, grains m⁻², and spikes M⁻² were the most important components associated with grain yield under each environmental condition evaluated. Results of this study, confirm that most genotypes selected under optimum management conditions retain their yield potential advantage when exposed to moisture and heat stress. However, it will be necessary that genotypes selected under optimum conditions be evaluated under stress environments to identify the most promising individuals.
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