Abstract
Wheat accessions from the USDA-ARS National Small Grains Collection (NSGC) are a potential genetic resource for variety improvement. This study assessed the agronomic performance and drought tolerance in 198 winter wheat accessions under irrigated and terminal drought environments in the 2012–2013 season, and repeated the test under terminal drought only during the 2013–2014 season. The 198 accessions were classified into three maturity groups, early, intermediate, and late based on heading data. In all three environments, the early accessions had the best agronomic performance, produced higher grain yield, thousand-kernel weight and grain volume weight, and had earlier heading date and shorter plant height. The intermediate accessions had similar grain yield and thousand-kernel weight as the early accessions in the irrigated environment, but had lower thousand-kernel weight in the terminal drought environments. Terminal drought had significant effects on grain yield, plant height, thousand-kernel weight, and grain volume weight. The positive correlation between GY and HD suggests that the ‘late early’ types in the early maturity were the most successful. Out of 198 accessions evaluated, twenty-three had high yield stability and drought tolerance according to the drought susceptibility index and membership function value of drought tolerance. The eight of twenty-three accessions identified (four early and four intermediate) had high grain yield in three environments. Some of these accessions have been further used in bi-parental mapping studies and by breeders for grain yield and drought tolerance improvement.
Highlights
Wheat is the third largest crop in the world after maize and rice and is an important source for protein and calories in human food
Genotypic effect were significant (p < 0.001) for all traits (i.e., grain yield (GY), heading date (HD), plant height (PH), thousand-kernel weight (TKW) and grain volume weight (GVW)) evaluated in individual environments and in the combined analysis of variance across environments, and environmental effects of the all traits except HD were significant in the combined analysis (p < 0.0001)
The present study evaluated agronomic traits (GY, HD, PH, TKW and GVW) and drought tolerance for a set of 198 winter accessions from USDA-ARS National Small Grains Collection (NSGC) in one irrigated and two terminal drought conditions
Summary
Wheat is the third largest crop in the world after maize and rice and is an important source for protein and calories in human food. The yield of wheat has shown steady growth, with an average annual production from 1998 to 2002 [1] of 586 million metric tons, partly attributed from genetic improvements, development of locally adapted cultivars with resistance to diseases and abiotic stresses [2,3], and Agronomy 2017, 7, 51; doi:10.3390/agronomy7030051 www.mdpi.com/journal/agronomy. The yield growth rate in the past two decades is insufficient to meet projected future demand on the basis of the increasing human population [3,5]. Along with the population growth, global average annual temperatures have increased in the past decades [6]. Temperature increases in agricultural regions of the world [1] can result in extreme heat exposure, which can greatly reduce wheat yield if it occurs in the reproductive period of growth [7,8].
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