Influence of exogenous application of some phytoprotectants on growth, yield and pod quality of snap bean under NaCl salinity

Snap bean is a salt sensitive plant and suffers from losses in yield and pod quality with any little increase of salt concentration in irrigation water. In order to study the effect of salicylic acid (SA), spermidine (Spd), and glycine betaine (GB) as phytoprotectants on enhancing growth, yield and pod quality of snap bean under different levels of NaCl salinity, an outdoor pot experiment was conducted in 2012 and 2013 seasons. Salinity was applied as NaCl form at 0 and 2000 ppm. The concentrations of foliar treatments were two levels for each treatment; the first level was 0 mM which served as control, and the second level was 1 mM SA, 0.5 mM Spd and 5 mM GB, in addition to their combinations. NaCl salinity at 2000 ppm reduced most of vegetative growth parameters such as plant f.w., leaf area ratio and leaf area index, which in turn reflected on the reduction of pods no./plant and yield f.w./plant and an increase in the fruit abscission percentage. Pod moisture % decreased under 2000 ppm NaCl which reduced pod f.w., and increased pod curvature %. Under 2000 ppm NaCl, GB at 5 mM and all its combinations increased membrane stability index, total soluble sugars and total soluble proteins concentration, while reducing free amino acids concentration, which were concomitant with decreasing pod curvature %. Meanwhile, application of SA at 1 mM, GB at 5 mM, and GB5 + SA1 + Spd0.5 increased leaves and pods no./plant, pod moisture %, and pod f.w., which reflected on increasing green pod yield.