Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

K. J. Frey

Second Advisor

A. Campbell

Abstract

Two experiments were conducted in the course of this study. In the first one 50 oat genotypes adapted to the midwestern USA were grown in a randomized complete block design to evaluate three indirect methods of measuring lodging resistance, namely lodging resistance factor (cL[subscript] r), unit straw weight (USW), and straw breaking strength (BS). Correlations among different methods of measuring lodging resistance showed inconsistency both over years and for different plot types within the same year and location. USW was significantly correlated with actual lodging and snap scoring in the two years of study. These results suggest that multilocation testing over years will be needed to determine lodging resistance of new and potential oat varieties. USW may be useful for eliminating the most lodging susceptible types in early generations of testing;In the second experiment, recurrent selection was used to improve cL[subscript] r and USW. Two line of descent (cL[subscript] r and USW) from a single base population were employed. Effects of two cycles of S0.1 recurrent selection were evaluated for each of the two lines of descent. Results of the cL[subscript] r line of descent indicated that there was an increase in the cL[subscript] r mean of 8% of the C0 mean per cycle estimated from the progeny populations and 7% of the C0 mean per cycle estimated from the parental populations. Broad-sense heritability and genotypic variances tended to decrease from C0 to C2. Most phenotypic and genotypic correlations between cL[subscript] r and other traits were nonsignificant, except for cL[subscript] r and plant height, which were negatively associated. The gain in USW per cycle of selection was 1% of the C0 mean when estimated from progenies and 5% of the C0 mean when estimated from parents. Broad-sense heritabilities were moderate and significant in all cycles. Phenotypic and genotypic correlations between USW and all other traits, except days to heading were positive and highly significant.

DOI

https://doi.org/10.31274/rtd-180813-11398

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Moh'd M.M.T. Al-Ajlouni

Language

en

Proquest ID

AAI9220966

File Format

application/pdf

File Size

108 pages

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