|Peterson, C. James -|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2011
Publication Date: February 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/54068
Citation: Graybosch, R.A., Peterson, C. 2012. Specific adaptation and genetic progress for grain yield in Great Plains hard winter wheats, 1987-2010. Crop Science. 52: 631-643. Interpretive Summary: Increased food production will be necessary if the world’s population continues to grow at present levels. Increases in average grain yield of winter wheat in the bread basket of North America, the Great Plains, can be achieved either through use of more productive cultural environments, or the development of wheats with higher innate or genetic potential for grain production under current conditions of cultivation. A previous investigation determined that the annual rate of increase for wheat grain production, using region-wide averages from long-term USDA coordinated nurseries, had slowed, and little recent progress in innate genetic potential for higher grain yield could be demonstrated. The present investigation extended these observations further by evaluating this innate genetic potential for grain yield in specific production or agro-ecological zones. Using data from USDA coordinated regional trials conducted over the years 1987 – 2010, little increase in the rate of genetic improvement for wheat grain yield could be demonstrated. Levels of genetic diversity also were examined via statistical approaches. These levels have remained fairly constant over the years examined, indicating, that while grain yield potential per se has not increased, no erosion of wheat’s genetic diversity has occurred.
Technical Abstract: Meeting the food demands of a growing world population will become increasingly difficult should the rate of genetic improvement in grain yield of wheat (Triticum aestivum L.) and other grain crops decelerate. Data from USDA-ARS coordinated long-term regional performance nurseries was used to examine the rate of genetic improvement of Great Plains winter wheats in specific agro-ecological or production zones over the time period 1987-2010. The absolute grain yield of all entries, and of the top five most productive entries, did increase over this time period. The relative rate of genetic improvement, obtained by comparing grain yields to those of the long-term control cultivar Kharkof, ranged from not significantly different from zero to 1.98% year -1. This rate of change, however, was statistically significantly increased in only two of the 12 zones evaluated. Variance components identified environmental factors, either production zone, or locations within production zone, as being the largest sources of variation in grain yields. Variance due to either genotype, or genotype by environmental factors, remained both constant over the 24 year time period, and small, relative to the environmental variances. Genetic progress for enhanced wheat yield in the region might be limited by the magnitude of these environmental variances, and by constraints arising from continuous variation in pest and pathogen populations.