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Heat and drought stresses have negative impacts on wheat yield and growth worldwide, causing up to 60% and 40% yield losses, respectively, but their combined effect can cause severe losses. The present study aimed to identify the high-yielding genetic resources tolerant to drought and/or heat stresses under climate change scenarios. The field trials on 42 genotypes were conducted at three locations in four environments (normal TSIR-NS, drought TSRF-DR, heat LSIR-HT, and heat and drought combined LSRF-DHT) each for two consecutive years. Yield contributing traits were recorded in all the experiments and all the locations: SI (susceptibility index) and STI (stress tolerance index) were also estimated. GY (Grain yield) was severely affected by LSRF-DHT (48.6%), followed by TSRF-DR (23.6%) and LSIR-HT (16.8%). GY had a positive correlation with BM (biomass), HI (harvest index), and TGW (1000-grain weight) under all environments and negative with DH (days to heading) (LSIR-HT and LSRF-DHT). Stepwise regression analysis revealed a higher contribution of BM and HI towards GY under all environments. GW (grain weight/spike) contributed under LSIR-HT and LSRF-DHT, and GN (grain number/spike) under TSIR-NS and TSRF-DR. GFD (grain-filling duration), TGW, and PTL (productive tillers) contributed under all conditions except LSRF-DHT. WS 2016-4 was the only genotype that yielded high under all the conditions. WS 2016-12 and CNM 16-1 were tolerant to heat and drought stresses and high yielding. HINDI 62, HTW 11, and QBP 1606 were less sensitive to all the stresses but low yielding. Overall, out of 30 tolerant genotypes (10 of each category), 19 adapted to escape mechanism which is irrespective of their yielding level. The study demonstrated the potential of identified genotypes in wheat breeding for climate resilience and the traits imparting tolerance to these genotypes. [ABSTRACT FROM AUTHOR]

Survival of living organisms depends on the availability of water resources required for agriculture. In the current scenario of limited water resources, it is our priority to maximise the yield potential of crops with a minimum supply of available water. In this study, we evaluated seven cultivated varieties of Gossypium hirsutum (FH-114, FH-152, FH-326, FH-492, FH-942, VH-327 and FH-NOOR) for their tolerance, yield potential and fibre quality under water shortages. We also studied the effect of drought stress on osmoregulation, chlorophyll content, antioxidant (peroxidase and catalase) activity, lipid peroxidation and secondary metabolite accumulation in the varieties under study. It was revealed that three varieties (FH-114, FH-152 and VH-327) exhibited a lower stress susceptibility index and more tolerance to drought stress. All the varieties demonstrated enhanced proline and malondialdehyde content, but no significant change in chlorophyll content was observed under limited water supply. Antioxidant activity offered by catalase and phenolic content was enhanced in FH-492 whilst peroxidase activity increased in FH-114 and FH-326. Phenolic content was highest in FH-942 and decreased significantly in the remaining varieties. Ginning outturn of the cotton varieties increased in VH-327 (19.8%) and FH-326 (3.7%), was not affected in FH-114 and FH-492 and was reduced in FH-152, FH-942 and FH-NOOR. All cotton varieties tested showed an increase in micronaire thickness when exposed to drought stress as early as the seedling stage. This study highlights the evaluation and screening of cotton varieties for their response to drought stress in terms of yield and fibre quality when exposed to water shortages during plant development and can help in devising irrigation plans. [ABSTRACT FROM AUTHOR]

Ninety-eight high-yielding recombinant inbred lines (RILs) of WAB638-1/PRIMAVERA rice were evaluated with the parents under reproductive stage drought stress. The study aimed at characterizing flowering time response under drought stress and consequently classifying the genetic resources for efficient use in breeding programmes. Two field trials were conducted during the 2016 and 2017 dry seasons using the randomized complete block design with two replications. In 2016, 12 RILs were evaluated with the parents for the rooting attributes under drought stress and well-watered treatments. Analysis of variance revealed a significant (P < 0.05) variation among the genotypes for the traits evaluated. Drought stress reduced most of the characters in this study, including grain yield. However, the inbred lines exhibited considerable tolerance to drought stress as indicated by yield-related stress indexes, including stress susceptibility and drought tolerance indexes. Delayed flowering (FD) was recorded in 75 genotypes (including WAB638-1), while 25 genotypes (including PRIMAVERA) had no delay under drought stress compared to the control. The genotypes were grouped into flowering delay (D) genotypes (FD > 1 d) and no delay (N) genotypes (FD < 1 d), which significantly differ (P ⩽ 0.05) for numbers of days to 50% flowering. The flowering delay genotypes may be suitable for intermittent drought, while genotypes with little or no delay may be selected for terminal drought conditions. There was a significant correlation (r > 0.5) between the root length and number of days to 50% flowering. The study indicated that root parameters, such as the root length, may contribute to the drought adaptation mechanisms of the RILs. [ABSTRACT FROM AUTHOR]

Stress susceptibility indexes ( SSI) of eight maize and eight triticale genotypes for their ability to cope with soil compaction ( SC) combined with drought (D) or waterlogging (W) were estimated through the determination of changes in dry matter of the shoot (S), root (R) and whole plant (S+R) grown at three levels of soil compaction (1.1, 1.3 and 1.6 g cm−3) and exposed to D or W stress for 7 or 14 days. The SSI values showed variation between and within maize and triticale genotypes, and it was possible to divide genotypes into groups of sensitive and resistant ones. The correlation coefficients ( r) between stress susceptibility indexes of soil compaction ( SCSI) and drought ( DSI) or waterlogging ( WSI) and between DSI and WSI were statistically significant. This indicates that genotypes resistant to soil compaction ( SC) were resistant to drought (D) or waterlogging (W) stresses and that genotypes resistant to D were also resistant to W. Seedlings grown under the stresses showed changes in S to R ratio (S/R). Sensitive genotypes had higher S/R ratio than resistant ones. Decrease of S/R ratio depends on the duration of stresses, and it may be considered an adaptation mechanism to stress. After 7 days of recovery for D and W treatments, we observed only a partial return of growth traits to the level of control plants. [ABSTRACT FROM AUTHOR]

Terminal drought stress during grain filling period has recently become more common in the semiarid Mediterranean regions, where wheat (Triticum aestivum L.) is grown as an important winter cereal crop. The objective of this experiment was to study the effect of terminal drought stress on grain yield, gas exchange variables, and some physiological traits of nine bread wheat cultivars. An experiment was carried out in a split-plot arrangement using randomized complete blocks design with three replications during the 2010-2011 season at the research farm of Razi University, Iran. Based on the results obtained, post anthesis water deficit significantly decreased grain yield, biomass, 1,000 grain weight, and harvest index of wheat cultivars. Under terminal drought stress and control treatments, there were significant differences between cultivars in terms of all traits studied. Also, terminal drought stress decreased leaf net photosynthesis rate (Pn), stomatal conductance (gs), transpiration rate, Chlorophyll a, b, and a/b, and increased leaf temperature and sub-stomatal CO2 concentration. Cultivars differed in their response to water stress. In general, tolerant cultivars showed a higher Pn and gs and leaf water content under both moisture conditions compared with susceptible ones. A greater reduction in gs and transpiration rate and smaller reduction in Pn under stress condition led to a remarkably higher photosynthetic water use efficiency of the tolerant cultivars. Finally, it can be concluded that planting wheat variety DN-11 in areas with post-anthesis water stress was recommendable for maximizing grain yield. [ABSTRACT FROM AUTHOR]

Field experiment was carried out in 2010 to evaluate the response of different genotypes of barley (Hordeum vulgare) to drought stress at the Agricultural Faculty of Azad University of Karaj, Iran. The experimental design was a randomized complete block with a split-plot arrangement and four replications. Treatments were two levels of irrigation (normal and deficit irrigation) as main plots and barley varieties at 10 levels (Valfajr, Rayhan, Kavir, Zarjo, Goharjo, Karoon, Dasht, Turkmen, Nosrat and Yousef) as sub-plots. A correlation was found between grain yield with spike weight, harvest index, biomass, peduncle length and number of spikes per unit area (at the 0.01 level) under drought stress. Data analysis also revealed that there was a significant and positive correlation between grain yield with spike weight, harvest index, biomass, number of spikes per unit area and total dry weight (at the 0.01 level) under normal stress (at the 0.01 level). Five selection indices including mean productivity index (MP), geometric mean productivity (GMP), stress tolerance index (STI), stress susceptibility index (SSI) and tolerance (TOL) were determined based on grain yield under drought-stress and non-stress conditions. The results showed that MP, GMP and STI were the best indices in identifying high yielding cultivars in both drought-stressed and normal conditions. Genotypes Nosrat, Turkmen and Youseph were the most drought tolerant and Kavir, Karoon and Zarjo were the most sensitive genotypes to drought stress. [ABSTRACT FROM AUTHOR]

To understand the physiological basis of tolerance to combined stresses to low phosphorus (P) and drought in mungbean (Vignaradiata (L.) R. Wilczek), a diverse set of 100 accessions were evaluated in hydroponics at sufficient (250 μM) and low (3 μM) P and exposed to drought (dehydration) stress. The principal component analysis and ranking of accessions based on relative values revealed that IC280489, EC397142, IC76415, IC333090, IC507340, and IC121316 performed superior while IC119005, IC73401, IC488526, and IC325853 performed poorly in all treatments. Selected accessions were evaluated in soil under control (sufficient P, irrigated), low P (without P, irrigated), drought (sufficient P, withholding irrigation), and combined stress (low P, withholding irrigation). Under combined stress, a significant reduction in gas exchange traits (photosynthesis, stomatal conductance, transpiration, instantaneous water use efficiency) and P uptake in seed and shoot was observed under combined stress as compared to individual stresses. Among accessions, IC488526 was most sensitive while IC333090 and IC507340 exhibited tolerance to individual or combined stress. The water balance and low P adaptation traits like membrane stability index, relative water content, specific leaf weight, organic acid exudation, biomass, grain yield, and P uptake can be used as physiological markers to evaluate for agronomic performance. Accessions with considerable tolerance to low P and drought stress can be either used as 'donors' in Vigna breeding program or cultivated in areas with limited P and water availability or both. [ABSTRACT FROM AUTHOR]