Date of Award

2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Enviromental and Soil Sciences

First Advisor

Stephen A. Harrison

Abstract

Waterlogging stress is one of the factors depressing wheat yield. Study of heritability for yield and yield components under waterlogging is important in determining the influence of genetic factors accounting for waterlogging tolerance as compared to environmental stress. The objectives of this study were: (1) to study the effect of waterlogging on yield and yield components of soft red winter wheat; (2) to estimate losses from waterlogging; (3) to estimate heritability of waterlogging tolerance in early generations of wheat for yield and yield components, and (4) to provide selection criteria for waterlogging tolerance in wheat breeding. Linear reduction in yield and yield components was observed as a result of 0, 10, 20, and 30 days of waterlogging treatments. Average yield losses from waterlogging, evaluated in a field experiment were 44%. This reduction was mainly due to a decrease in tiller number and kernels/head. Screening of wheat genotypes identified the potential for waterlogging tolerance in breeding material. Genotypes Terral LA 422, Shelby, and Pioneer 26R61 were the most waterlogging tolerant. Some of the high yielding genotypes under control conditions, such as Coker 9663 and FFR 502W, had low tolerance due to a large interaction with waterlogging. Restricted maximum likelihood (REML) estimation of additive and dominance variance components were obtained from 80 related F2 families. Compared to the traditional quantitative genetic designs, this method provides estimates of genetic variance components without any restriction in mating design. Narrow sense heritabilities estimated on per plot basis were high for kernel weight and chlorophyll content. Early generation selection for waterlogging tolerance for yield would not be efficient. Heritability of yield was low and its standard error was high. Strong genetic correlations were observed between yield and kernel weight, and yield with tiller number. Selection indices were constructed to make use of a strong genetic correlation of yield with some yield components with high values of heritability. A maximal improvement of 17% is expected in yield, as a result of selection based on yield-kernel weight-tiller number index. At least three cycles of selection would be needed to produce waterlogging tolerant populations by applying selection indices.

ISBN

9780493070032

Pages

119

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