Environment and Cultivar Effects on Winter Wheat Response to Ethephon Plant Growth Regulator1

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Abstract
Recent introductions of new disease resistant, higher yielding winter wheat (Triticum aestivum L.) cultivars and plant growth regulators (PGRs) to reduce lodging, coupled with a growing awareness of high wheat yields in Europe, has resulted in an increased interest in and the development of Intensive Cereal Management (ICM) systems in the USA. Increases in fertility levels and seeding rates, practices used in ICM systems, may significantly increase lodging in winter wheat. The objective of this study was to evaluate the effects of the PGR ethephon [(2‐chloroethyl) phosphonic acid] on grain yield, lodging, plant height, test weight, and moisture percentage of seven winter wheat cultivars grown in various environments. Averaged across environments and cultivars, ethephon reduced lodging and plant height, and increased grain yield an average of 0.28 Mg ha−1, of 6.4%. Average environment × PGR and cultivar × PGR interactions were nonsignificant for grain yield, plant height, lodging, and test weight, but orthogonal contrasts showed variable responses to ethephon between environments and cultivars. Lodging and grain yield were negatively correlated, while lodging and plant height were positively correlated. With the exception of the cultivar Caldwell, grain yields were not increased by PGR applications when there was no lodging.