Field evaluation of green stem disorder in soybean cultivars

Green stem is a disorder of soybean [Glycine max (L.) Merrill] that causes the stems to remain green, nonsenescent, and moist, although pods and seeds are fully ripe and dry. The disorder is a nuisance for producers because it complicates harvesting of soybeans by significantly increasing the difficulty in cutting the affected plants during harvest. The cause of the disorder is unknown; however, differences in relative sensitivity to the disorder have been observed. The primary objective of this research was to evaluate the relative sensitivity among commercial or near-commercial cultivars from private and public soybean breeding organizations in replicated variety tests in Illinois. In 31 tests at Dekalb, Monmouth, and Urbana, IL, during 2001 to 2004, 1187 different MG I (maturity group)-MG IV conventional and glyphosate[N-(phosphonomethyl)glycine]-tolerant, cultivars were visually evaluated. There were significant differences in sensitivity among cultivars in 29 of the 31 tests, indicating that genetic variability among cultivars for green stem sensitivity exists. This variability may provide a basis for breeding for low sensitivity to the green stem disorder. Total levels of green stem disorder incidence varied over years and locations. Herbicide management systems did not appear to affect the levels of green stem incidence.