Comparison of discriminatory effects of corn yield test locations based on their genetic variation expression among hybrids

Authors: Ashworth, Amanda; KNAPP, VICTORIA - University Of Tennessee; FRED, ALLEN - University Of Tennessee; SAXTON, ARNOLD - University Of Tennessee

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2020
Publication Date: 9/28/2020
Citation: Ashworth, A.J., Knapp, V., Fred, A., Saxton, A. 2020. Comparison of discriminatory effects of corn yield test locations based on their genetic variation expression among hybrids. Crop Science. 60:3166–3174. https://doi.org/10.1002/csc2.20298.
DOI: https://doi.org/10.1002/csc2.20298

Interpretive Summary: Corn is one of the most important and widely produced crops in the world. Quantitative traits like corn seed yield are known to display large genotype x environment interactions (GxE) because diverse environments have differing effects on the genetic expression of genotypes (cultivars and breeding lines). Thus, variety trials and breeding line tests for yield require multi-environment trials (METs; i.e., location–year combinations) to obtain reliable estimates and rankings of yield performance of different genotypes across a targeted geographic region of production. Because yield trials are time consuming and expensive, the choice and number of selected test locations are important. It is critical that the METs discriminate among genotypes and are representative of the environments encountered in the targeted marketing region and that the locations chosen provide minimum redundancy of performance information. A team of researchers used a 14-year corn variety dataset of three relative maturity groups at five locations to compare test location redundancy using genetic variance estimates. These results indicate that for the three maturity groups, all locations were needed to provide the best yield trial information on corn cultivars. Such analyses are worthwhile for targeting yield trial locations for their discriminating ability and representativeness that are essential for a robust variety test program for a targeted region, especially considering costs associated with variety testing.

Technical Abstract: It is important for yield test sites to elicit differences among genotypes, minimize redundancy of performance information, and generate a genotype x environment interaction representative of the targeted region. The objective of this study was to utilize corn (Zea mays L.) variety trial results from three relative maturity group (MG) tests at five Tennessee locations spanning 14 years to compare test location uniqueness/redundancy via genetic variance estimates and cluster analysis. Principle components (PC) analyses allowed for location comparisons of genetic variance expression among cultivars in different MG tests. Individual location/test/year genetic variance estimates ranged from <1 to 584 (Mg ha-1)2. Years and locations affected the magnitude of genetic variance, with years largely driving genetic expression within MGs in these environments. However, the Late MG consistently had the greatest variance estimate. Across 14-years, there was minimum duplicative information provided across the five yield test sites. Consequently, all locations were needed and none could be eliminated without compromising cultivar yield trial information for the three MG tests. Correlations between mean yields and genetic variance showed a weak relationship across locations (environments), years, and MG tests (R=0.021), thus high yielding environments did not correspond with increased genetic variance expression. These types of analyses are useful for evaluating the discriminating ability and duplicative or correlated expression of genetic information across environments for robust variety trials within and across maturity groups and targeted regions.