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Estimates of genetic homestimates of genetic homeostasis in maize^*

Roberto Valdivia-Bernal; Arnel R. Hallauer

Department of Agronomy, Iowa State University, Ames, IA, 50011 USA. Send correspondence to A.R.H

ABSTRACT

Genetic homeostasis was estimated in maize (Zea mays L.) in order to determine whether selection has affected homeostasis and to determine whether homeostasis is heritable. A group of six inbred lines released before the 1960's, and another group of six, released after the 1970's, were used to develop single cross, F2, and backcross generations. The experiments were conducted at two Iowa locations in 1985 and 1986. Individual plant measurements were taken for eight maize traits. Estimates of genetic homeostasis were obtained using a proportional measure of the environmental variance contained in the within-plot variance, the magnitude of the genotype x environment interaction, and the coefficient of variation.
Genetic homeostasis depended on the level of heterozygosity and heterogeneity of the maize genotypes and populations. The newer lines were more homeostatic than the older lines. The inbred lines were consistent for transmitting in a heritable manner the homeostatic effects, either good or bad, to their single cross, F₂ ,and backcross generations. In most instances, the eight traits measured followed the same tendency in all comparisons among generations within both groups. Kernel depth, however, did not have a regular pattern of transmission of the homeostatic effects across generations.

Keywords: Genetic homeostasis; Maize.

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* Joint contribution of the Cereal and Soybean Research Unit, USDA, Agriculture Research Service and Journal Paper No. J-13834 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA. Project. No. 2778. Part of a dissertation submitted by Roberto Valdivia-Bernal in partial fulfillment of the requirements for a Ph.D. degree.