Disease- and performance-related traits of ethylene-insensitive soybean

Ethylene controls many beneficial responses in plants but also promotes chlorosis, senescence, disease, and fruit over-ripening. The present study compared previously isolated ethylene-insensitive lines of soybean [Glycine max (L.) Merr.] to their isogenic, ethylene-sensitive parent with respect to disease resistance, seed yield, and other field performance traits. In laboratory tests, ethylene insensitivity reduced root colonization by soybean cyst nematode. Using healthy young plants, ethylene-insensitivity also reduced ethylene-activated leaf chlorosis and abscission. However, in the field, leaf chlorophyll and late-season senescence were not altered, suggesting that ethylene is not a main determinant of late-season senescence of soybean leaves. Field studies also revealed no changes in susceptibility to Septoria brown spot disease (caused by Septoria glycines Hemmi), flowering date, plant height, or seed total protein and oil concentration. Field studies did demonstrate elevated susceptibility to white mold disease [Sclerotinia sclerotiorum (Lib.) deBary], poor stand establishment in some but not all environments, altered plant architecture, and earlier maturity date in the ethylene-insensitive lines. Seed yield was notably undependable, being similar to the parental line in some field locations but significantly reduced in most environments. To avoid these negative impacts on overall performance, manipulation of plant ethylene responses should be targeted to specific tissues, growth stages, or growth environments.