Comparative adaptive traits in green gram (Vigna radiata L.) and soybean (Glycine max L.) as influenced by varying regimes of shade

Abstract

Study of shade adaptive traits of understorey crops is of utmost importance for their potential use in agroforestry system. The present study was conducted to decipher shade-adaptive traits through comparative changes in leaf pigments, epicuticular wax level and protein profiles in leaves of green gram and soybean grown in three different regimes of shade (33%, 50%, and 75% shade) and without shade (open sunlight). Chlorophyll a (Chl a), Chl b and total Chl progressively increased, whereas, Chl a/b ratio gradually decreased with increase in shade intensity in both the crops. Anthocyanin, wax level and soluble protein of leaves gradually decreased with increase in shade. Green gram showed higher anthocyanin than soybean in all the light environments. Wax level of leaf in green gram was higher in open than soybean, whereas, it was comparable in 33% shade in both the crops. Wax level of leaf in green gram decreased more in deep shade (50% shade and 75% shade) than soybean indicating more shade resilience of soybean. The rate of shade-induced reduction of leaf protein content in soybean was less than green gram. Protein profiling through SDS-PAGE clearly revealed degeneration of proteins in shade around ~55 kDa which indicated to the RUBISCO (Ribulose bisphosphate carboxylase-oxygenase) proteins. Both the crops revealed their shade adaptation mainly through alteration in epicuticular wax, pigments and proteins mostly associated with LHCP (Light harvesting complex protein) complex and towards RUBISCO protein which assume significance for their use in crop improvement programme in searching shade tolerant crops for agroforestry system.