Increasing Hard Winter Wheat Yield Potential via Synthetic Wheat: I. Path-Coefficient Analysis of Yield and Its Components

Synthetic hexaploid wheat, created from a cross between durum [Triticum turgidum L. (syn. Triticum durum Desf.)] and Aegilops tauschii Coss., is a good source of new genes for bread wheat (Triticum aestivum L.) improvement. The purpose of this research was to evaluate the potential and performance of synthetic wheat in Texas. Ten elite primary synthetics from the International Maize and Wheat Improvement Center (CIMMYT) were backcrossed to two Texas cultivars, TAM 111 and TAM 112. Populations were bulked and modified bulked to advance generations. Yield-related agronomic traits were measured on the BCF4 and BCF5 populations across five Texas locations. Improvement was observed in South Texas and the Blacklands, which had more disease pressure and fewer intermittent dry spells than locations in the Texas Rolling and High Plains. Selected bulks were not superior to nonselected bulks. Head number per unit area had the highest correlation with yield. Similar to crosses with spring wheat, synthetics contributed to yield through an increase in seed weight. Synthetic populations that produced higher grain yield than both TAM 111 and TAM 112 maintained their large seed size and weight but had increased number of heads and grains per head. Poorer performance in environments with harsh winters could be because of a lack of winter-hardiness in the primary synthetics. Improved yield could result from selecting for increased number of heads per unit area and grains per head in lines derived from these populations.