Tolerance of transgenic soybean (Glycine max) to heat stress

摘要

Greenhouse studies were conducted to compare agronomic and physiological characteristics of selected herbicide-resistant and conventional soybean (Glycine max) varieties. Growth chamber studies were initiated to examine the effects of heat stress of soybean in a sterile environment. Twelve soybean varieties (six glyphosate-resistant, one glufosinate-resistant, one sulfonylurea-tolerant, and four conventional varieties) were examined in three temperature regimes (25/20 deg C, 35/30 deg C, 45/30 deg C). Overall, soybean growth was most vigorous at 35/30 deg C and poorest at 45/30 deg C. Glyphosate- resistant soybeans tended to be more susceptible to heat stress than glufosinate-resistant and conventional soybean varieties. The glyphosate-resistant soybean varieties tended to be shorter and lower in chlorophyll content and fresh weight than non-glyphosate- resistant soybean varieties. Base stem splitting between VI and V2 that had been reported from field observations was observed at the 45/30C regime. Glyphosate- resistant soybean varieties exhibited a higher percentage (90-100%) stem splitting than glufosinate-resistant (50%) or conventional soybean varieties (45-70%). To better understand the stem splitting effect, an acid-detergent fiber (ADF) analysis was conducted to determine lignin content of stems. At 25/20 deg C, glyphosate-resistant soybeans had elevated lignin content (12-13% w/w). At 45/30 deg C, the lignin content of conventional soybeans equaled that of the glyphosate-resistant soybean varieties. A significant correlation between lignin content at 25/20 deg C and stem splitting at 45/30 deg C was observed.