Soluble starch synthase activity in relation to thermal tolerance of developing wheat (Triticum aestivum, Triticum durum) and maize (Zea mays) grains

Abstract

Triticum aestivum (var HD 2987), T. durum (var HD 4719) and Zea mays (var HQPM 7) were exposed to control (C) and elevated (E) temperature (2.1-3.8°C higher) in open top chambers during post anthesis period. Soluble starch synthase (SSS) activity in the developing grains and grain yield components at maturity were determined in C and E grown plants. Excised developing grains at 20 DAA (days after anthesis) of ambient grown T. aestivum (var HD 2987), T. durum (var HD 4719) and Zea mays (var HQPM 7, HM 10 and DHM 117) were also incubated at 25, 35 and 45°C for 2 hours and then analysed for the activities of SSS. The kinetic parameters of SSS in the grains of ambient grown plants were also determined. The study revealed a higher catalytic efficiency and relatively thermostable SSS in maize grains compared to wheat. Among tested wheat varieties, aestivum wheat showed a better thermostability of SSS in vitro and in vivo than durum wheat. An association of thermostability of SSS and thermotolerance for grain growth was indicated. The above observation of a highly efficient and relatively thermostable SSS in maize grains may possibly be utilized for improving thermotolerance of SSS and grain growth in wheat. The improved thermotolerance for grain growth in wheat will go a long way in enhancing wheat productivity, which suffers heavy losses due to frequent hot winds during grain filling period.