Tocopherols in Soybean Seeds: Genetic Variation and Environmental Effects in Field-Grown Crops

Controlled environment studies show a-tocopherol (aT) in soybean seeds increases several fold as a result of warmer temperature or drought during seed maturation, but total tocopherols (Ttot) stay approximately constant. To determine if natural variation in weather or climate affect T under field conditions, we analyzed soybean seeds grown at several locations in Maryland between 1999 and 2002. Weather was relatively normal during 1999–2001, whereas warmer temperatures and extreme drought were characteristic of 2002. Comparing 18 lines, there were small but significant differences in Ttot as well as 2to 3-fold differences in aT during 1999–2001. Seeds from locations on the Eastern Shore of Maryland (full season crops) had higher absolute and relative levels of aT compared to seeds from a (cooler) central Maryland location or seeds from a later planting (double crop) on the Eastern Shore. Effects of location or planting date were small compared to that of genetic line when considering the normal years 1999–2001. In 2002, however, several fold increases in aT/Ttot were observed in Maturity Group III and IV seeds, especially from full season crops grown at two locations on the Eastern Shore of Maryland. We conclude weather and climate are significant factors affecting soybean seed T content.