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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]