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Heat stress is a critical environmental factor that adversely affects crop productivity. With the increasing frequency and intensity of heat waves and extreme weather events, heat stress has become a challenge for wheat production, which is one of the most important cereal crops. To sustain wheat production under heat stress conditions, there is an urgent need to develop high-yielding, heat-tolerant wheat varieties. This requires characterizing the genetic and physiological mechanisms underlying heat tolerance, as well as developing efficient phenotyping methods to evaluate a large number of wheat genotypes under heat stress field conditions. In this study, we used 184 wheat genotypes that were sown at two times of sowing (TOS), i.e., optimal sowing as TOS1 and late sowing as TOS2, with higher temperatures faced by plants during heading and grain filling in TOS2. We used a combination of physiological traits, multispectral vegetative indices (VIs) derived from aerial imagery and machine learning approaches to effectively differentiate wheat genotypes for heat tolerance and susceptibility. The response of wheat genotypes to heat stress was delineated as being susceptible, moderate, and tolerant using the stress susceptibility index, percentage loss, and tolerance index. Different VIs varied significantly between the two TOS. The decline in VIs during anthesis and post-anthesis was minimal in heat tolerant genotypes compared to susceptible genotypes under TOS2. We classified the stress severity and yield using VIs with a machine learning approach. A model was created with a random forest classifier (RFC) trained to categorize genotypes based on the stress susceptibility index using Python libraries. The PCA was utilized to reduce dimensionality, and five principal components explaining 99 % of the variability were employed as input for developing the model. The RFC model achieved an accuracy of 64 % and excelled in recognizing crops under extreme stress, with a recall rate of 0.87 and an F1 score of 0.77 for the susceptible class. The model had high precision metrics, with values of 0.69, 0.42, and 0.80 for the susceptible, moderate, and tolerant classes, respectively. Our results suggest that multispectral-driven phenotypic traits can be used by breeders to select and develop wheat varieties tolerant to heat stress.

Temperature during flowering and seed filling is a very important indicator for estimating the yield potential of rapeseed. In order to evaluate the effect of heat stress due to delay in sowing date on agronomic characteristics of different rapeseed genotypes (including, Hyola420, Hyola50, Hyola60, SAN37, SAN34 and Dalgan) two separate experiments on two Conventional sowing date (11th Nov.) and late sowing date (16th Dec.) each in the form of a randomized complete block design with three replications was carried out in the research farm of Islamic Azad University, Ramhormoz Branch, during the growing season of 2016 and 2017. Each sowing date was considered as an environment and the data were finally analyzed by combined analysis. The results showed that with delay in sowing date and the occurrence of heat stress at flowering and seed filling stages, the number of flowers on the main raceme, ratio of siliques produced per flowers produced, number of siliques per plant, and branches per plant, number of seeds per silique, 1000-seed weight, silique length, plant height and reproductive period decreased and led to significant reduction in seed yield. Reducing silique numbers per plant had the highest contribution to reducing seed yield. In conventional sowing date, seed yield in Hyola 420 and SAN 34 was higher than other genotypes. Under heat stress conditions due to delay in sowing, seed yield in Hyola50 followed by SAN34 was higher than other genotypes and Dalgan had the lowest seed yield. The lowest percentage of reduction seed yield was belonged to Hyola50 (55%) and the amount of stress susceptibility index in this genotype indicated that it was semi-tolerant to late season heat stress. In conventional sowing date, genotypes that quickly reached to the flowering stage but had a longer flowering period, had higher yields. In late sowing date, significant negative correlation was observed between the duration of flowering with number of siliques per plant, number of seeds per silique and seed yield. SAN 34 had high yield in both conventional and late sowing dates and is suggested as a suitable genotype for achieving stable yield in Ramhormoz region.

Improving wheat's tolerance to environmental stress is of utmost importance in the current era due to climatic changes. This study was carried out to determine the relative merits of pedigree selection for grain yield per plant on old and new land. To quantify the response of selection, two cycles of pedigree selection for grain yield per plant were applied to a segregating population of bread wheat crosses (Misr 3 Line #1) in F3 and F4 generations under new land stress conditions. The F5-selected families were evaluated in both old and new land habitats after the second cycle. Under both circumstances, the genotypic variance was much less than the phenotypic variance, and it generally decreased from the F3-generation to the F5-generation. Furthermore, compared to the old land environment, broad-sense heritability estimates for grain yield plant-1 were lower in the new land environment. After Cycle 1 and Cycle 2, the realized heritability in old land was 52.03 and 84.52 percent, respectively, compared to 34.08 and 62.80 percent in new land. In both cases, the instant reaction to selection that was found on ancient soil was examined, and the results showed a significant increase in grain production from both the bulk and the best parent of 5.40 and 5.02 percent and 17.28 and 7.03 percent, respectively. Selected families for grain yield under new land that were studied under both conditions revealed negligible increases of 12.29 and 2.80 percent from the bulk and considerable increases of 28.24 and 22.34 percent from the better parent, under new and old land, respectively. The results indicate these genotypes could be used as sources of tolerance or factors contributing to general adaptation. Furthermore, selection for grain yield/plant under new land stress was superior to selection under old land stress, regardless of whether selection entries were evaluated under stress or non-stress. [ABSTRACT FROM AUTHOR]

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]

Water deficit is a limiting factor in sesame cultivars yield, thus identification of genetic mechanisms of sesame traits under water stress conditions is essential to development of water stress tolerant genotypes. Hence, the triple test cross (TTC) analysis in F2 population of the sesame cross (NA76 ​× ​NA54) was used. Since, 30 TTC families with their 13 respective parents were evaluated during the summer season 2020 under two irrigation treatments. i.e., normal irrigation with 5952.38 ​m3 ​hm−2 of applied water, and water stress with 2976.19 ​m3 ​hm−2 of applied water. This was implemented at the experimental field of Kafr El Hamam/Sharkia, Agricultural Research Station, Agricultural Research Center (ARC), Egypt. Additive (D) and dominance (H) gene actions as well as epistatic and its two components of additive ​× ​additive, additive ​× ​dominance plus dominance ​× ​dominance were involved in the inheritance of all studied traits under both irrigation treatments and their combined analysis. The degree of dominance (H/D)0.5 verified the presence of partial dominance in most cases. The correlation coefficient between sums (additive) and differences (dominance) was non-significant, showing that dominant genes between lines were ambidirectional. The moderately water stress tolerant TTC families as the best selected families were found in families 22, 25, 10, 12, and 15. Therefore, postponing selection in these selected families to later segregating generations for all studied traits would be effective to exploit the positive effects of additive ​× ​additive epistasis.

Water scarcity is one of the most significant constraints to wheat production in Egypt and around the world. Therefore, twenty genotypes and four cultivars of bread wheat were tested under normal irrigation (six irrigations including planting irrigation) and water deficit stress (two irrigations at 21 and 45 days after the planting irrigation) during the 2020/2021 and 2021/2022 growing seasons at Shandaweel Agricultural Research Station, Sohag, Egypt. Each irrigation treatment was considered a separate experiment in the randomized complete block design. The two seasons and two water treatments showed sufficient genetic variability among the studied genotypes. The number of days to heading and maturity, plant height, yield and its components traits significantly decreased under water deficit stress. The genotypes G13 and G17 significantly outperformed all studied genotypes and checked cultivars for grain yield under normal irrigation and water stress conditions. The genotypes G16, G2, G12, G9, G17, G20, G18, G8, G10 and G5 as well as cultivars Sids 14, Sokoll and Kasuko showed stress susceptibility index (SSI) <1 and they can be used as a source of water deficit tolerance in a breeding program. Genotypic main effect plus genotype by environment interaction (GGE) Biplot analysis revealed that the genotypes G13 and G17 had high yielding ability but genotype G17 showed more stability and tolerance under water stress conditions. Therefore this study concluded that the genotypes G13 and G17 were suitable genotypes to be cultivated under water shortage conditions and could be used to enhance the wheat breeding program for water deficit stress tolerance. [ABSTRACT FROM AUTHOR]

The purpose was to elucidate the hypoxia tolerance mechanism of millet species by focusing on the oxygen acquisition mechanism of adventitious roots. Brachiaria ramosa, Echinochloa utilis, Eragrostis tef, and Setaria italica were used. Thirty-day old plants were hydroponically cultivated for 28 days as the control, where aeration was continued and a hypoxia treatment was applied, where nitrogen gas was flushed to reduce the oxygen concentration. From the stress susceptibility index based on plant growth rate, it was clarified that E. utilis and E. tef had higher hypoxia tolerance than B. ramosa and S. italica. Root growth rate, nitrogen concentration of leaves and stems, and sodium concentration per plant of the higher hypoxia-tolerant species did not change with hypoxia treatment. In hypoxia-susceptible millet species, the root growth rate and nitrogen concentration in the leaf and stem decreased, and the sodium concentration in the whole plant increased. The proportion of the stele area of the adventitious root of the hypoxia-tolerant millet species was smaller than that of the hypoxia-susceptible millet species, and the lysigenous aerenchyma was constitutively developed. Furthermore, root hairs were observed near the root tip in the hypoxia-tolerant millet species. In conclusion, we deduced that the hypoxia tolerance of the millet species is mainly attributable to the supply of oxygen to the root tip via the lysigenous aerenchyma along the adventitious root. Lower oxygen consumption by a smaller proportion of the stele area might be an important genetic trait. Furthermore, root hair may contribute to nutrient absorption.

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]

The purpose was to elucidate the hypoxia tolerance mechanism of millet species by focusing on the oxygen acquisition mechanism of adventitious roots. Brachiaria ramosa, Echinochloa utilis, Eragrostis tef, and Setaria italica were used. Thirty-day old plants were hydroponically cultivated for 28 days as the control, where aeration was continued and a hypoxia treatment was applied, where nitrogen gas was flushed to reduce the oxygen concentration. From the stress susceptibility index based on plant growth rate, it was clarified that E. utilis and E. tef had higher hypoxia tolerance than B. ramosa and S. italica. Root growth rate, nitrogen concentration of leaves and stems, and sodium concentration per plant of the higher hypoxia-tolerant species did not change with hypoxia treatment. In hypoxia-susceptible millet species, the root growth rate and nitrogen concentration in the leaf and stem decreased, and the sodium concentration in the whole plant increased. The proportion of the stele area of the adventitious root of the hypoxia-tolerant millet species was smaller than that of the hypoxia-susceptible millet species, and the lysigenous aerenchyma was constitutively developed. Furthermore, root hairs were observed near the root tip in the hypoxia-tolerant millet species. In conclusion, we deduced that the hypoxia tolerance of the millet species is mainly attributable to the supply of oxygen to the root tip via the lysigenous aerenchyma along the adventitious root. Lower oxygen consumption by a smaller proportion of the stele area might be an important genetic trait. Furthermore, root hair may contribute to nutrient absorption. [ABSTRACT FROM AUTHOR]

Water deficit is a limiting factor in sesame cultivars yield, thus identification of genetic mechanisms of sesame traits under water stress conditions is essential to development of water stress tolerant genotypes. Hence, the triple test cross (TTC) analysis in F2 population of the sesame cross (NA76 x NA54) was used. Since, 30 TTC families with their 13 respective parents were evaluated during the summer season 2020 under two irrigation treatments. i.e., normal irrigation with 5952.38 m³ hm-2 of applied water, and water stress with 2976.19 m³ hm-2 of applied water. This was implemented at the experimental field of Kafr El Hamam/Sharkia, Agricultural Research Station, Agricultural Research Center (ARC), Egypt. Additive (D) and dominance (H) gene actions as well as epistatic and its two components of additive x additive, additive x dominance plus dominance x dominance were involved in the inheritance of all studied traits under both irrigation treatments and their combined analysis. The degree of dominance (H/D)0.5 verified the presence of partial dominance in most cases. The correlation coefficient between sums (additive) and differences (dominance) was non-significant, showing that dominant genes between lines were ambidirectional. The moderately water stress tolerant TTC families as the best selected families were found in families 22, 25, 10, 12, and 15. Therefore, postponing selection in these selected families to later segregating generations for all studied traits would be effective to exploit the positive effects of additive x additive epistasis. [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.

Drought is an important factor that causes a decrease in yield and quality in regions where second crop silage plants are grown. One of the biggest problems in animal husbandry is feed. Especially silage feed production tends to decrease in areas with increasing water deficit and where water needs cannot be met. The high water requirement of the corn plant requires irrigation in arid and semi-arid regions. However, in order to continue the production of silage fodder in regions where water resources are insufficient with the increase of drought, it will be necessary to grow forage plants that can be an alternative to corn plant. In previous studies, it has been discussed whether the sorghum plant is an alternative to the corn plant. The aim of this study is to determine the drought sensitivity index based on the yield values of both plants in wet and dry conditions. Thus, it will be determined whether the sorghum plant will be an alternative to the corn plant in terms of drought. The identification and selection of drought-resistant cultivars and species is possible using various indices. In this study, second crop silage maize and sorghum crops were grown in Kahramanmaraş conditions for two years (2018 and 2019), dry and irrigated. Stress sensitivity index (SSI) was used to determine the drought tolerance of silage maize and sorghum crops. 'Colonia' variety was used for silage corn and 'Es Foehn' variety was used for sorghum. When the STI values are examined, the corn and sorghum values for 2018 were 0.55 and 0.53, respectively, while the d values for 2019 were found as 0.33 in corn and 0.54 in sorghum. these values are very close to the YSI values. While the 2018 values in both indices were not determinative in terms of drought resistance, the value of sorghum in 2019 was 64% higher than corn (this value was found to be 61% for YSI). This also showed that there is a direct correlation between YSI and STI indices. [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]

Abstract Background This study was conducted to investigate the effect of heterogeneity and heterozygosity on lint yield and fiber quality of Egyptian cotton for late planting stress tolerance. Lint yield was recorded in two planting dates among four cotton population types which included homozygous lines grown in pure stands, hybrids grown in pure stands, homozygous lines in blended stands, and hybrids grown in blended stands. Comparisons were made using trait means, blend response, and heterotic response. Stress susceptibility index (SSI) was calculated over planting dates. Results In normal planting date, the results showed that means of lint yield for homozygous entries (population I and II) were greater than mean yields of heterozygous entries (population III and IV). In late planting date, the results showed that mean of lint yield for some homozygous entries was equal mean yields of heterozygous entries. Regarding the yield, there was no significant difference between inbreds and blend of hybrids. However, the heterozygous populations had a lower (SSI) and more tolerance for late planting than homozygous populations. In late planting date, the two parents G.90 × CB.58 and G.95 had lint yield equal to or greater than means of blends (heterozygous populations). Adding to the two blends of inbreds, [((G.91 × G.90) × G.80)] + [G.90 × CB.58] and [((G.83 × G.80) × G.89) × (G.83 × Deltabine 703)] + [G.90 × CB.58] had the highest lint yield included the best inbred (G.90 × CB.58) suggesting that blend performance was determined by inbred performance. Conclusions Cotton blends may not provide buffering against late planting date. Blend response or heterotic response increased with late planting. However, cotton yields can sometimes be increased through the blends. Blends were not better than inbreds, and blend response was not consistent among the blends. Using blends is not recommended to increase yields or tolerance for late planting, and homozygous population’s cultivars could result in increased yields relative to blends. Assuming an efficient method for producing homozygous population’s cultivars was available, homozygous populations should be a viable option for commercial production to decrease observed losses in late planting date conditions.

Intraspecific variations in wheat growth responses to elevated CO2 was evaluated using 20 Iranian bread wheat (Triticum aestivum L.) cultivars. The plants were grown in the modified Hoagland nutrient solution at a greenhouse until 35 days of age using two levels of CO2 (~380 and 700 µmol mol–1). The shoot and root dry weights of the wheat cultivars exhibited average enhancements of 17% and 36%, respectively, under elevated CO2. This increase was associated with higher levels of chlorophyll a (25%), chlorophyll b (21%), carotenoid (30%), leaf area (54%) and plant height (49.9%). The leaf area (r = 0.69**), shoot N content (r = 0.62**), plant height (r = 0.60**) and root volume (r = 0.53*) were found to have important roles in dry matter accumulation of tested wheat cultivars under elevated CO2 concentration. However, responses to elevated CO2 were considerably cultivar-dependent. Based on the stress susceptibility index (SSI) and stress tolerance index (STI), the wheat cultivars exhibiting the best response to elevated CO2 content were ‘Sistan’, ‘Navid’, ‘Shiraz’, ‘Sepahan’ and ‘Bahar’, while the ones with poor responses were ‘Omid’, ‘Marun’, ‘Sorkhtokhm’ and ‘Tajan’. The findings from the present experiment showed significant variation among the Iranian wheat cultivars in terms of their responses to elevated air CO2, providing the opportunity to select the most efficient ones for breeding purposes.

Drought stress is one of the environmental factors influencing crops growth, development, and production. Two field experiments were performed in Karaj, Iran, to evaluate the drought tolerance indices of 17 winter rapeseed genotypes in 2015-2016 and 2016-2017 growing seasons. The factorial arrangement of treatments was set up as RCBD with three replications. To identify drought tolerant genotypes, several indices were used based on grain yield under normal and deficit irrigation conditions. Yield results showed that cultivars Artist (504.325 g m-2) and L72 (391.525 g m-2) were the superior treatments under normal and deficit irrigation conditions, respectively. According to correlation results, 3-D graphs were drawn based on Geometric Mean Productivity (GMP) and grain yield under normal irrigation and deficit irrigation to categorize the winter rapeseed genotypes in both years. In the first year, Zorica and Lauren were in group A, while in the second year; Mercure, SW102, L72, and HL3721 were in group A. Therefore, they had superior performance and stable grain yield under both irrigation conditions. Biplot diagram showed Lauren (first year) and Mercure (second year) were superior regardless of stress conditions. Altogether, under normal irrigation, Artist genotype, and under stress condition, Mercure, L72 and HL3721 genotypes could be used for cultivation. [ABSTRACT FROM AUTHOR]

Drought has negative effects on sweetpotato production. Two experiments with two watering treatments (irrigated and water-stressed) were conducted at Umbeluzi Research Station in 2015. The objectives were to (i) determine response of 48 sweetpotato germplasms to mid-season drought, (ii) determine best traits for improvement of storage root yield under mid-season drought and (iii) assess the selection criteria for identifying drought tolerance in sweetpotato germplasms. The irrigated and water- stressed trials received 640 and 400 mm of water, respectively, throughout the season. Water stress was imposed from 30 to 70 days after planting. Each treatment had two replicates arranged in a randomized complete block design. Data collected on storage root and vine yield and derived drought tolerance indices including harvest index were subjected to analysis of variance in R. Sweetpotato germplasms with high storage root yield under mid-season drought were associated with a high harvest index. Harvest index stability and the geometric mean are key to identifying cultivars with high and stable storage root yield under both treatments. MUSGP0646-126, Irene and Ivone combined both low TOL, SSI, HI and high yield storage root yield across the treatments and over seasons. The use of drought and harvest indices is encouraged for selecting improved cultivars for varied production environments and their regular use in accelerated breeding schemes is suggested.

Delaying leaf senescence in plants, especially under water stress conditions, can help to maintain the remobilization of stored nutrients in source–sink relationships, thus leading to improved crop yields. Leaf senescence can be delayed by plant hormones such as cytokinin. Here, the Isopentenyl transferase (IPT) gene, encoding a cytokinin biosynthesis enzyme, driven by a modified AtMYB32xs promoter was transformed into wheat. Transgenic wheat plants exhibited delayed leaf senescence, retaining chlorophyll for longer under controlled environment conditions. Selected independent transgenic events and their corresponding nulls were grown under field conditions for two consecutive years under well-watered and water stress treatments using automated rainout shelters. Three independent transgenic events had improved canopy green cover, lower canopy temperatures, and higher leaf water potential than their respective non-transgenic nulls, with no abnormality in morphology and phenology. Increased grain yield was observed in transgenic events under both water treatments, with the yield increase more pronounced under water stress (26–42%). These results have shown that delayed leaf senescence using the chimeric transgene AtMYB32xs-p::IPT can be a useful strategy to achieve grain yield gains in wheat and potentially other crops for sustainable food production.

Drought is one of the main environmental factors affecting grain yield and plant architecture in durum wheat. The present work was conducted to evaluate the contribution of morphological traits above flag leaf node on grain yield of six Moroccan durum wheat varieties released between 1984 and 2007 and grown under two water regimes (irrigated and rainfed) during the 2015–2016 crop season. The following morphological traits were measured at anthesis: Flag leaf length (FLL), flag leaf area (FLA), peduncle length (PL), spike length (SL), spike area (SA), and green leaf area (GLA). Days from sowing to anthesis (DSA) and grain-filling period (GFP) were recorded. In addition, grain yield per plant (GYP) was evaluated at maturity. Analysis of variance showed the greater effect of water stress in explaining total variability of the studied traits. Mean comparisons indicated that water deficit significantly affected GYP and all morphological traits; it shortened DSA and GFP by 4 and 7 days, respectively. Moreover, GYP, DSA, and GFP increased in modern varieties. In contrast, FLL, FLA, and PL were reduced from old to modern varieties. Under irrigated conditions, correlation studies revealed that GYP was positively associated to GLA. Regarding the rainfed trial, GYP was positively correlated to FLL. Additionally, negative relationships were found between GYP and DSA in both water regimes. Stepwise regression highlighted the relative importance of each morphological traits on the stress susceptibility index, FLL was the most consistent trait entered the model followed by PL and FLA. In this study, some morphological traits above flag leaf node proved to be useful tools to select for grain yield in water-limited environments. [ABSTRACT FROM AUTHOR]

Delaying leaf senescence in plants, especially under water stress conditions, can help to maintain the remobilization of stored nutrients in source–sink relationships, thus leading to improved crop yields. Leaf senescence can be delayed by plant hormones such as cytokinin. Here, the Isopentenyl transferase (IPT) gene, encoding a cytokinin biosynthesis enzyme, driven by a modified AtMYB32xs promoter was transformed into wheat. Transgenic wheat plants exhibited delayed leaf senescence, retaining chlorophyll for longer under controlled environment conditions. Selected independent transgenic events and their corresponding nulls were grown under field conditions for two consecutive years under well-watered and water stress treatments using automated rainout shelters. Three independent transgenic events had improved canopy green cover, lower canopy temperatures, and higher leaf water potential than their respective non-transgenic nulls, with no abnormality in morphology and phenology. Increased grain yield was observed in transgenic events under both water treatments, with the yield increase more pronounced under water stress (26–42%). These results have shown that delayed leaf senescence using the chimeric transgene AtMYB32xs-p::IPT can be a useful strategy to achieve grain yield gains in wheat and potentially other crops for sustainable food production. [ABSTRACT FROM AUTHOR]

Late sown irrigated wheat crop under Maharashtra condition always adversely affected by terminal heat during flowering and grain filling stage which results in reduced grain yield. A study was undertaken to identify terminal heat tolerant bread wheat genotypes on the basis of different stress indices. Material under study comprised of newly developed nineteen bread wheat genotypes and three recommended varieties as check. Two separate experiments were conducted at Niphad under timely and late sown conditions during rabi 2013-14. Yield trait was recorded and per cent yield reduction under late sown condition as compared to timely sown condition was estimated. On the basis of yield trait different stress susceptibility and tolerance indices were estimated. Among the new genotypes studied, NIAW 2972 had highest yield potential under both, timely (48.66 q/ha) and late sown condition (46.99 q/ha) with minimum yield reduction (3.43 %) under late sown condition except the check variety NIAW 34 (1.75 % yield reduction). On the basis of combined analysis of performance of wheat genotypes under both the sowing conditions, per cent yield reduction under late sown condition and estimates of different stress indices, variety NIAW 34 was found to be most terminal heat tolerant which was closely followed by the genotype NIAW 2972. NIAW 34 (SSI=0.17) possessed highest level of terminal heat tolerance followed by NIAW 2972 (SSI=0.34) and HI 977 (SSI=0.39). Correlation analysis indicated that yield under stress environment had significant (p

Salinity resistance level on soybean which influenced by its genotype is important to be explored.One of the important factors which determine the success of soybean cultivation on saline soil or salt-affected soil is salinity resistance level. Eleven variants or genotypes of soybean were collected from Indonesian Legumes and Tuber Crops Research Institute and were tested on four different electrical conductivity level of soil (0.5 dS/; 5.8 dS/m; 8.4 dS/m; and 12.2 dS/m). Soybeans were planted on pot in green house. Salinity stress will started when plants were on 21 days after planting (DAP). The treatment was watering using some different concentration of sea water for 30 days. Three methodswhich used to determine salinity resistance level of soybean were seed yield reduction level, stress susceptibility index (SSI), and leaf scorch score. Soybean will classified into salinity tolerant genotype group when weight reduction of seed was

دستیابی به ارقام جو که با حداقل آبیاری دربهار بتوانند عملکرد دانه قابل قبولی تولیدکرده و دارای عملکرد بالا و پایدار در محیط­های متفاوت باشند از جایگاه ویژه­ای در برنامه­های به نژادی برخورداراست. به منظور تعیین مناسب­ترین شاخص­های تحمل به تنش خشکی و شناسائی ژنوتیپ­های مقاوم به خشکی، تعداد171 ژنوتیب بین المللی جو دریافتی از ایکاردا به همراه شاهد ریحان03 در دو شرایط تنش خشکی (قطع آبیاری از مرحله گلدهی) و بدون تنش درسال زراعی 1385-1384 درایستگاه­های تحقیقاتی کرج و مشهد کشت و ارزیابی ژنوتیپ­ها از نظر تحمل به خشکی با استفاده از شاخص­های تحمل به تنش(STI)، حساسیت به تنش (SSI)، تحمل (TOL)، میانگین بهره­وری (MP) و میانگین هندسی (GMP) انجام گردید. بطور کلی براساس نتایج ایستگاه­های کرج و مشهد و درنظر گرفتن تمام شاخص­های حساسیت و تحمل به خشکی و همچنین عملکرد در دو شرایط نرمال وخشکی لاین­های شماره 159، 160، 162، 116، 104 و 106 به عنوان لاین­های برتر و متحمل به تنش خشکی و ژنوتیپ­های 131، 64، 24، 26، 130، 63، 30 و 118 به عنوان ژنوتیپ­های حساس به خشکی شناسایی و جهت استفاده در برنامه­های به­نژادی جو و آزمایشات مقایسه عملکرد یکنواخت سراسری در نظر گرفته شدند. برای تعیین روابط بین عملکرد دانه و شاخص­ها از ضریب همبستگی پیرسون استفاده گردید و مشخص شد که شاخص­های STI ، GMP و MP در هر دو شرایط دارای همبستگی مثبت و معنی­داری با عملکرد دانه می­باشند و می­توانند جهت شناسایی ژنوتیپ­های متحمل به خشکی و پر محصول در هر دو شرایط محیطی بکار روند.

Perennial rhizomatous grasses are regarded as leading energy crops due to their environmental benefits and their suitability to regions with adverse conditions. In this paper, two different experiments were carried out in order to study the salinity ( S) and water stress ( WS) effects on biomass production in giant reed ( Arundo donax L.). In Experiment 1, eight clones of giant reed were subjected to four salinity ( S) and water stress ( WS) treatments: (1) well watered with non-saline solution, (2) water stress with non-saline solution, (3) well watered with saline solution and 4) water stress with saline solution. In Experiment 2, five clones of giant reed were subjected to increasing S levels in two locations: University of Catania (UNICT-Italy) (1) well watered with non-saline solution and (2) well watered with mild saline solution; and University of Barcelona (UB-Spain) (3) well watered with non-saline solution and (4) well watered with severe saline solution. Photosynthetic and physiological parameters as well as biomass production were measured in these plants. According to our data, giant reed seems to be more tolerant to S than WS. Both stresses mainly affected stomatal closure to prevent dehydration of the plant, eventually decreasing the photosynthetic rate. The differential performance of the giant reed clones was ranked according to their tolerance to S and WS by using the Stress Susceptibility Index. 'Agrigento' was the most WS resistant clone and 'Martinensis' was the most S resistant. 'Martinensis' and 'Piccoplant' were found to be the most suitable clones for growing under both stress conditions. Moreover, 'Fondachello', 'Cefalú' and 'Licata' were the most resistant clones to increasing S levels. [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]

Investigation comprised 41 tomato genotypes originating from the population of domestic and domesticated genotypes collected in Serbia and belonging to the tomato collection of the Institute of Vegetable Crop Science, Smederevska Palanka. The aim of collection screening was to choose the genotypes tolerant to drought during plant intensive growth stage, whereby the process of selection would set out to obtain the recombinant genotypes for this abiotic factor. The screening criteria were established for genotype divergence in plant height and shoot-root ratio under conditions of optimal irrigation regime and drought. Divergence was estimated using cluster analysis with Euclidean distance as a measure of distance, with a complete gene attachment to grouping. Drought tolerance is expressed by the stress susceptibility index (SSI). Various results were obtained based on the screening of genotypes grown under optimal and dry conditions. As a measure of stress susceptibility, based on SSI, genotypes having different drought tolerance level were determined. On the grounds of the analyses carried out, 10 genotypes were segregated (G102, G104, G107, G109, G110, G119, G125, G126, G128 and G141) to represent a basis to obtain the recombinant genotypes and to initiate the selection for drought resistance. [ABSTRACT FROM AUTHOR]

Water deficit stress considered as one of the most important limiting factors for oil seed canola (Brassica napus L.) growth and productivity in Iran. To evaluate the effects of water deficit stress on some qualitative and quantitative characteristics of canola cultivars, this experiment in a greenhouse trial carried out as factorial based on completely randomized design with three replications in Shahid Chamran University of Ahwaz (Iran). Canola cultivars, including 'Hyola 308', 'Hyola 401' and 'RGS 003' as first factor, and the second one was three levels of water deficit stress, including stress at early stem elongation stage to early flowering (D1), early flowering stage to early emergence of sacs (D2), beginning of stem elongation stage to early emergence of sacs (D3) and normal irrigation (C, as check). Results showed that the interaction between water deficit stress and cultivars affected biological yield, seed oil yields and harvest index (p⩽0.01), dry matter and economic yield (p⩽0.05). Water deficit stress reduced grain oil yields. 'Hyola 308' under stress at beginning stem elongation stage to early flowering had the lowest oil yields (1.1 g plants-1) and 'Hyola 401' under non-stress conditions showed highest oil yields (4.3 g plants-1). The decrease of oil yields at the flowering stage to stem elongation stage was more than the other stages. In addition, water deficit stress reduced harvest index in the three stress levels due to reduced economic yield and reduced biological yield. Stress susceptibility index for 'Hyola 401' at the beginning of stem elongation stage to early emergence of sacs was 0.914 and the 'Hyola 308' showed 1.12 at the beginning of stem elongation stage to early emergence of sacs respectively, which it can implies that 'Hyola 308' is more sensitive than 'Hyola 401' to water deficit 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]

Background: This study was conducted to investigate the effect of heterogeneity and heterozygosity on lint yield and fiber quality of Egyptian cotton for late planting stress tolerance. Lint yield was recorded in two planting dates among four cotton population types which included homozygous lines grown in pure stands, hybrids grown in pure stands, homozygous lines in blended stands, and hybrids grown in blended stands. Comparisons were made using trait means, blend response, and heterotic response. Stress susceptibility index (SSI) was calculated over planting dates. Results: In normal planting date, the results showed that means of lint yield for homozygous entries (population I and II) were greater than mean yields of heterozygous entries (population III and IV). In late planting date, the results showed that mean of lint yield for some homozygous entries was equal mean yields of heterozygous entries. Regarding the yield, there was no significant difference between inbreds and blend of hybrids. However, the heterozygous populations had a lower (SSI) and more tolerance for late planting than homozygous populations. In late planting date, the two parents G.90 × CB.58 and G.95 had lint yield equal to or greater than means of blends (heterozygous populations). Adding to the two blends of inbreds, [((G.91 × G.90) × G.80)] + [G.90 × CB.58] and [((G.83 × G.80) × G.89) × (G.83 × Deltabine 703)] + [G.90 × CB.58] had the highest lint yield included the best inbred (G.90 × CB.58) suggesting that blend performance was determined by inbred performance. Conclusions: Cotton blends may not provide buffering against late planting date. Blend response or heterotic response increased with late planting. However, cotton yields can sometimes be increased through the blends. Blends were not better than inbreds, and blend response was not consistent among the blends. Using blends is not recommended to increase yields or tolerance for late planting, and homozygous population's cultivars could result in increased yields relative to blends. Assuming an efficient method for producing homozygous population's cultivars was available, homozygous populations should be a viable option for commercial production to decrease observed losses in late planting date conditions. [ABSTRACT FROM AUTHOR]

Taro ( Colocasia esculenta (L.) Schott) is a vegetative propagated tropical root occupying the 9th position among world food crops. Taro is an important staple food for many local populations of Asia and Africa. The crop is dependent of wet and highly irrigated growth conditions. Under the scenario of undergoing climatic changes, is estimated that taro production could decrease in the next 30 years as result of drought constraints. The project EU Aid Taro, DCI-Food/2009/45 “adapting propagated crops to climatic and commercial changes” aims to study ways to adapt this clonally propagated root to these climatic changes. A set of drought stress assays were realized at ISOPlexis Genebank (Madeira University), using local taro cultivars (Macaronesian taro genepool) and elite cultivars and seedlings provided by the Secretariat of the Pacific Community (SPC). The 1st pilot assay was realized in a small greenhouse, included 3 local cultivars and aimed to modelate the wattering regimes and their influence on crop growth. The 2nd full assay was realized in two greenhouses, during a full plant growth cycle. Thirty four taro cultivars, 15 elite lines provided by SPC, and 19 local cultivars, from Madeira (10), Canary Islands (6), Azores (2), and Cyprus (1) were screened. Plants were individually cultivated in pots under 2 contrasting wattering regimes, high (0,36 liters/day) and low (0,18 liters/day). Data for 14 morpho-agronomic traits, biomass and yield parameters were collected from 5 plants for each cultivar, per treatment. Preliminary results show significant differences in the ability to cope with drought stress among elite and local varieties. A classification of cultivars according to their relative drougth tolerance was made. The most resilient of these varieties will be subject to a new complete assay, in order to better assess their level of tolerance and recommend for breeding programs in Asian countries. [ABSTRACT FROM AUTHOR]

The development of triticale (X Triticosecale Wittmack) cultivars which are tolerant to drought and heat stress is an objective in many breeding programmes, but so far success has been limited. This study was conducted to determine the susceptibility index (S) of triticale under stress conditions. Twenty genotypes were grown in replicated trials and evaluated for heat and drought tolerance under natural conditions at Adana, Turkey, from 1992 to 1996. Among the advanced lines of triticale, genetic variation for adaptation to heat and drought conditions — typical features of the Mediterranean environment — was determined. The best yielding lines under stress, hence having a low susceptibility index, were Lynx/Yogui and Zebra 31. The implications of these findings for triticale breeding in stress environments are discussed. [ABSTRACT FROM AUTHOR]