Changes in yield and essential amino acid composition associated with air temperature stress in Thai soybean seeds, SOR JOR 5 cultivar

Abstract

This study is aimed at assessing the impacts of high and low air temperature stress on seed yield and essential amino acids composition of Thai soybean (Glycine max (L.) Merrill) cultivars: SOR JOR 5. This study was carried out in 2013 to 2014 at Naresuan University, Phitsanulok, Thailand. Soybean were planted and covered with open top chamber (OTC) since seedling through maturing stage. The controlled air temperature in OTC were set into three temperature situations: 25.5±1.3^oC (low temperature /LT treatment), 37±3.4^oC (high temperature /HT treatment) and 35±1.9^oC (ambient temperature / CT-treatment). The results indicated that number of pod plant^-1 was not affected by temperature changes, whereas number of seed plant^-1 and 100-seed weight were negatively and significantly affected under both controlled low and high temperature. Seed yield reductions by 54% and 52 % were found under high temperature and low temperature, respectively. However, the contrast results were found in essential amino acids composition. We observed that both of low and high temperature situations induced the significance increase in 8 amino acids; histidine, arginine, isoleucine, leucine, lysine, phenylalanine , threonine and valine. The highest increase by 6.2% and 8.5% under controlled high temperature and low temperature were recorded in leucine and lysine, respectively.  To summarize, the enhanced or decreased surface air temperature situations in growing season could cause yield loss but induced the increases in essential amino acids of Thai soybean, SOR JOR 5.

Keywords: temperature stress, Thai soybean, , yield, amino acid