Graduate Thesis Or Dissertation

 

Methods of evaluation, effects of intermating and results of one cycle of S₁ family recurrent selection in barley Öffentlichkeit Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4b29bb02m

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  • The focus of this study was to determine if S₁ family recurrent selection might be successfully used for barley improvement. Objectives were: 1) to identify suitable methods of evaluating grain yield in small plots, 2) to study the effects of intermating on mean values and variances of selected agronomic characters, and 3) to evaluate the response to one cycle of S₁ family selection for grain yield. Genetic materials included parents, random F₃ lines from four single cross populations, and random S₁ lines from the Cycle 0 (C-0) population which was developed by intermating the four single crosses for two generations. Heading date, plant height, and grain yield were measured on F₃ and S₁ lines grown in unreplicated small (0.7 m²) two row plots in two locations in 1979. The same traits were measured on bulk progenies of F₃ and S₁ lines grown in unreplicated large (6.0 m²) plots in three locations in 1980. Moving mean technique, which uses the mean grain yield of a number of adjacent plots as a covariable in an analysis of covariance, improved the precision of yield trials. Error mean square of replicated parents was reduced between 0 and 80 percent at different experimental sites, depending on the magnitude of field variation. Comparison of grain yield of parents grown in both large and small plots in the same year-location indicated that grain yield in small plots was affected by competition effects associated with plant height. Additional evidence for the inaccuracy of small plot yield data was supplied by the higher positive correlation between grain yield and plant height in small plots as compared to large plots. Breakup of favorably interacting associations of alleles by intermating was studied by comparing the mean of the four single crosses with the mean of the C-0 population. Two generations of intermating did not affect the mean values for plant height or grain yield, however the C-0 population headed significantly earlier due to the effect of rapid generation advancement in the intermating process. Two generations of intermating increased genetic variance for heading date and plant height, but no effect could be detected for grain yield. While some of the estimates of genetic variance for grain yield were negative, most were small and non-significant. Lack of genetic variation for grain yield is believed to be due to common parentage of the genetic materials in this study. Response to selection for grain yield was evaluated with Cycle 1 (C-1) S₁ lines developed by intermating the highest yielding 10% of C-0 S₁ lines. The C-1 population was significantly higher yielding than parents and significantly taller than parents and the C-0 population. Since little genetic variation for grain yield was found in this study, the response to selection for grain yield shown in small plot tests is believed to be a manifestation of competition effects associated with the increased plant height of the C-1 population. Successful S₁ family recurrent selection in barley may require the development of populations with greater genetic variation for grain yield. If populations with more diverse parentage and greater genetic variability are developed, then S₁ family selection in concert with improved field plot techniques may result in continued grain yield improvement in barley.
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