Degree Type

Dissertation

Date of Award

1987

Degree Name

Doctor of Philosophy

Department

Agronomy

Abstract

The efficiency of backcrossing to transfer major genes for resistance to phytophthora stem and root rot, caused by Phytophthora megasperma f. sp. glycinea Kuan and Erwin, into susceptible soybean Glycine max (L.) Merr. cultivars is dependent on the number of backcrosses required to recover the desirable agronomic characteristics of the recurrent parent. The objective of this study was to determine in which backcross generation individual lines with Phytophthora resistance and yield equivalent to that of the recurrent parent can be selected, and in which backcross generation a group of random lines from the population have an average yield equivalent to that of the recurrent parent. The allele Rps(,1)('k), for resistance to Phytophthora, was transferred from the cultivar Williams 82 to two susceptible recurrent parents, Cumberland and A78-123018. Thirty-six random resistant lines from each of five backcross generations were evaluated individually for agronomic traits. Bulks of the 36 lines of each backcross generation also were tested. The results indicated that, if the donor and recurrent parents differ in yield by 10% or less, a single cross is sufficient to develop a population from which a homozygous resistant line with a yield equal to that of the recurrent parent can be selected. Alternatively, the recurrent parent can be replaced by a bulk of random homozygous resistant lines after one backcross.

DOI

https://doi.org/10.31274/rtd-180813-11312

Publisher

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

Copyright Owner

Verni Kitzmann Wehrmann

Language

en

Proquest ID

AAI8716836

File Format

application/pdf

File Size

167 pages

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