Comparative response of a hulled and a free-threshing tetraploid wheat to plant growth promoting bacteria and saline irrigation water

Abstract

Given the potential of wild and semi-domesti- cated varieties of crop plants as genetic sources of stress tolerance-related traits, along with a capability of plant growth promoting rhizobacteria (PGPR) in promoting plant growth under adverse environmental conditions, response of a hulled tetraploid wheat, in comparison to a durum cultivar, to saline water at the presence of three PGPR strains was examined in a field study. Changes in some physiological attributes including chlorophyll (chl) a, b, and total chl (chl-tot), proline, soluble carbohydrates, Na ? and K ? concentrations, Na ? /K ? and grain yield and its attributes, dry mass and harvest index in ''Joneghan'' as a hulled tetraploid wheat and ''Yavaroos'' as a durum wheat cultivar were studied using a 3-replicate split-plot ran- domized complete block experiment. Irrigation water salt levels (control, 100 and 200 mM of NaCl) were chosen as main plots, and the two tetraploid wheat genotypes and three PGPR strains (550, 57, and UW3) and bacteria-free control were considered as subplots. The 200 mM salt level led to significant decreases in chl-a, chl-b, chl-tot, LAI, K ? , grain yield/m 2 , grains/spike, spikes/m 2 , grains/m 2 , 1000-grain weight, dry mass, and harvest index; however, it led to significant increases in Na ? ,N a ? /K ? , proline, and soluble carbohydrate contents of the two tetraploid wheat types. Salinity adversely affected the latter traits in the two types of tetraploid wheat in, almost, a same manner and proportion, except for dry mass and harvest index, proving that the hulled tetraploid wheat is not notably different from the durum wheat in its response to the saline water. Bacterial strains effects on the above-mentioned traits varied with salt level. Strain UW3 appeared to leave mit- igative effects at 200 mM and strain 550 did not seem potent to ameliorate the salt stress even at the 100 mM NaCl level. From the data obtained in the present study, we can conclude that the PGPR efficacy in mitigating salt stress in tetraploid wheat is salt level and bacterial strain specific. The ''Joneghan'' hulled tetraploid wheat was out- performed by the ''Yavaroos'' durum wheat, though its yield penalty due to saline water did not appear to differ from that of the latter durum genotype.