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Selection Index Based on Genetic Correlations Among Environments

Dep. of Agronomy, Univ. of Kentucky

P. L. Cornelius

Dep. of Agronomy and Dep. of Agronomy and Dep. of Statistics, Univ. of Kentucky, Lexington, KY 40546-0091

^* Corresponding author.

Plant breeders often conduct preliminary tests of genotypes at one or two primary locations due to limited seed supply and/or limited resources. The location of these tests may be somewhat arbitrary, and in general, it is not known how performance at these locations relates to performance in a much broader target environment. The objective of this study was to develop a method for weighting performance at primary locations, based on the genetic correlations between these locations and the target environment, that would lead to greater predictive value of the primary locations. Using data from wheat (Triticum aestivum L. em. Thell) and soybean (Glycine max L.) cultivar trials in Kentucky from 1987 to 1991, we developed a selection index based on the genetic correlations of cultivar performance in the primary locations, Lexington (LEX) and Princeton (PR), and the target environment, represented by as many as seven locations from the cultivar trials (). As expected from theory, predicted response to index selection exceeded predicted response to selection at either LEX or PR, and it was superior to predicted response of selection based on the unweighted mean of LEX and PR. In all years, a lower number of statistically significant wheat genotype rank changes occurred when ranks across the primary locations were based on the index than when ranks were based on the unweighted means. For soybean, this was true in 4 of 5 years. Although the use of cultivar trial data for parameter estimation violates some of the usual assumptions of traditional quantitative genetic investigations, we suggest the potential benefits to breeding programs outweigh these concerns.

Received for publication August 14, 1992.