YIELD AND STABILITY FACTORS ASSOCIATED WITH HYBRID WHEAT (REPRINTED FROM WHEAT - PROSPECTS FOR GLOBAL IMPROVEMENT, 1998)

For hybrid wheat to be accepted in the Great Plains of the USA, hybrid s must exhibit enhanced yield performance, yield responsiveness, and r easonable yield stability across a wide array of production environmen ts. Agripro has been researching hybrid wheat since 1981 and has an es tablished pureline release history since 1978. Yield data from 1991 to 1995 were examined to compare the trend performance and selection gai ns of purelines and hybrids in a large scale parallel development effo rt. This data set (13,739 points) reveals an average 0.454 t ha(-1) or 10.8% hybrid yield advantage over purelines in preliminary regional t esting. Entries selected from the preliminary trials show a greater hy brid advantage of 0.652 t ha(-1), or 13.5%. Several factors including enhanced stability over strong yearly environmental effects, improved agronomic and epidemiological expression through complementary inbred trait selection, and improved heat tolerance are likely contributors t o this significantly improved selection gain. Yield stability of hybri ds and purelines was compared in Agripro Standard Variety Trials and U SDA-ARS Southern Regional Performance Nurseries from 1990 to 1995. In addition to having higher means than purelines, hybrid yield advantage increased with improving production conditions. The enhanced responsi veness of hybrids, as indicated by higher slopes in regression analyse s, was combined with similar deviations from regression response. Hybr id wheat in the Great Plains of the USA has shown a fundamental yield, responsiveness and selection gain advantage over pureline varieties t hat could result in acceptance by producers.