RESUMEN
Ascertaining the genetic variability and its relationships among valuable genetic resources is important for crop improvement programme. Here, we assessed the response of eleven wheat (Triticum aestivum L.) genotypes using cluster and principal component analysis (PCA) based on morphophysiological data and yield under nine different environments. Wheat genotype WH 1080 maintained higher photosynthetic efficiency under individual stress of 50% water deficit (drought) and 100 mM NaCl (salt), whereas under interactive stresses KRL 370 and KRL 283 were found to be the best genotypes. The highest value of Na+/K+ ratio in shoots was recorded for WH 1080 (1.167) and lowest in KRL 283 (0.612) under combined stresses. Proline accumulation was maximum in KRL 330 (3.17 mg g-1 FW) and minimum in KRL 283 (2.8 mg g-1 FW). Significantly higher reduction (73.4%) was observed in HD 2009 for grain weight/plant at 100 mM NaCl + 50% WD stress treatment whereas minimum reduction of 39.18% was recorded in KRL 370 in comparison to the control treatment. The PCA showed that the first three components comprising about 91% of the total variation for which the variables were analyzed. AMMI model revealed KRL 210 to be stable genotype as being close to center on biplot. E5 environment (100 mM NaCl) was most stable followed by E9 (50% WD + 100 mM NaCl). HD 2888, C-306, HD 2851 and HD 2009 were having positive interaction with E1 (Control) whereas WH 1080 had positive interaction with water deficit environments i.e. E2 and E3 (25 and 50% WD) while KRL 433 had highest positive interaction with combined water deficit and salt stress environments E6, E7, E8 and E9, followed by KRL 370. Similarly, KRL 283, KRL 330, KRL 210 and Kharchia 65 had high positive interaction with saline environments E4 and E5. Findings of the experiment would be beneficial to wheat breeders, specifically the location-specific promising genotypes could possibly be used to develop/breed MAGIC populations to tag genes/alleles conferring drought and salinity tolerance.
RESUMEN
Soil salinization and alkalinization frequently co-occur in nature, but very few studies focus on the interactive effects of mixed salt and alkali stresses on plants. Sporobolus marginatus Hochst. ex A. Rich. (perennial halophytic grass) collected from extreme saline sodic Kachchh plains, Bhuj, Gujarat was analyzed to evaluate the stress specific responses in osmoprotectants, antioxidants, ionic relations and protein profiling under saline, sodic and mixed saline-sodic soils. Osmotic adjustments in terms of total soluble sugars (TSS), glycine betaine, proline content and protein concentration exhibited differential responses to variable stress conditions. Proline content increased 4.8 folds at pH2 10.0, 5.2 folds at ECe 35 dSm-1 and 5 folds at pH2 9.0 + ECe 20 dSm-1. The greater accumulation of proline in Sporobolus, may presumably be one of the factor for tolerance to higher salt. At the same time, superoxide dismutase (SOD) activity in leaves increased with increasing sodicity i.e. 30.73 and 33.55 units g-1 FW at pH 9.5 and pH 10.0, respectively. Gradual increase in peroxidase enzyme (POX) activity was observed under all the stresses. Under control condition, POX activity was 21.67 units g-1 FW in Sporobolus, which increased to 26.56 units g-1 FW at pH 10.0, 27.89 units g-1 FW at ECe 35 dSm-1 and 27.44 units g-1 FW at pH 9.0 + ECe 20 dSm-1. The basal activity of APX increased with increasing stress conditions and was maximum (43.91 units g-1 FW) at pH 10.0. On the other hand, 2 times higher glutathione reductase (GR) activity was obtained under sodic stress of pH 9.5 and pH 10.0. SDS-PAGE revealed that five new polypeptide bands of MW 58.5, 53.7, 39.7, 31.8 and 28.3 kDa were expressed at higher saline level while one polypeptide band of 39.7 kDa disappeared at higher salinity level of 35 dSm-1 which may be due to its degradation at higher salt concentration. Synthesis of common polypeptides of MW 98.1, 69.3, 35.45, 24.89 and 23.3 kDa under all the stress conditions need special mention. Furthermore, the enhanced expression of these proteins, which also existed in the control plants, were specifically increased under stress condition which revealed that these proteins were up-regulated in specific regions of Sporobolus adapted to salt stress. Therefore, further exploration is needed to test the contribution of salt stress related proteins/genes or regulatory factors from the salt tolerant grasses (STGs) for possible utilization in cereal crop improvement.