Drought-tolerant Cultivars Research Articles

Principal Component Analysis of Early Generation Drought Tolerant Tef Genotypes for Yield-contributing Traits

The present investigation was carried out to determine the relationship and genetic variability among 49 tef inbred line using principal component analysis for drought prone areas. To improve tef productivity, farmers need high-yielding and drought tolerant tef cultivars. The objective of this research is to evaluate genetic diversity among drought tolerant tef inbred lines for yield, yield-contributing traits. In this study, Component I had the contribution from the traits <i>viz.</i>, days to heading, days to physiological maturity, plant height, panicle length, culm length, number of spikelets per panicle, number of primary panicle branches per main shoot, lodging index, above-ground biomass and harvest index which accounted 40% to the total variability. Grain filling period, number of total tillers per plant, number of fertile tillers per plant, days to mature, peduncle length, number of florets per spikelet and thousand-seed weight has contributed 14% to the total variability in component II. The remaining variability of 13%, 7% and 6% was consolidated in component III, component IV and component V by various traits like days to seedling emergence, culm length, peduncle length, lodging index, above-ground biomass yield, grain yield, harvest index, number of total and fertile tillers per plant. The cumulative variance of 79% of total variation among 18 characters was explained by the first five axes. Thus, the results of principal component analysis revealed, wide genetic variability exists in this drought tolerant tef inbred lines. Drought tolerant traits with high genetic variability are expected to provide high level of gene transfer during breeding programs.

Understanding Transcription Factors in Plant Response to Drought Stress

Increasing sensitivity of plants to abiotic and biotic stress such as drought, salt and extreme temperatures poses a worldwide peril to sustained growth and productivity of crops. Decrease in crop produce corresponds to increase in food prices and lower monetary return for farmers. In view of this, developing drought tolerance cultivars arises as the most viable solution toward enhancing crop productivity in adverse environment conditions. Therefore, it is imperative to identify the key regulators of water stress in plants and develop new varieties with improved drought stress tolerance. Drought tolerance is now well understood to be regulated by multiple genes, including transcription factors (TFs) that enable plants to tolerate harsh conditions and these genes remain viable genetic options for crop breeding. Plants have evolved various mechanisms to respond to various stressors which involve many transcription factors (TFs) like WRKY, TCP, DOF, HSF and NF-Ys. They participate in activation of various signalling pathways that protect cells against the damages caused by both abiotic and biotic stress. This review summarizes the role of such TF families in drought stress and provides insights for development of stress-tolerance in plants.

A short review: Comparisons of high-throughput phenotyping methods for detecting drought tolerance

Drought is a major threat worldwide for crop production, especially due to the rapid climate changes. Current drought solutions involve improving irrigation system, rainwater harvesting, damming, cloud seeding, and changes of cultivation methods. Despite effective, each solution has economic, environmental, and temporal drawbacks. Among all solutions, the most effective, inexpensive and manageable method is the use of drought-tolerant cultivars via plant breeding. However, conventional plant breeding is a time-consuming and laborious task, especially for phenotypic data acquisition of target traits of numerous progenies. High-throughput phenotyping (HTP) is a recently developed method and has potential to overcome the mentioned issues. HTP offers massive, accurate, rapid, and automatic data acquisition in the breeding procedure and can be a breakthrough for developing drought resistant/tolerant cultivars. This study introduces various methods of HTP to detect drought stress, which can accelerate the breeding processes of drought-tolerant cultivars to provide helpful guidelines for breeders and researchers to choose appropriate methods.

DROUGHT TOLERANT INDICES OF LOWLAND TOMATO CULTIVARS

&lt;p&gt;The released lowland tomato cultivars are known for their resistance to plant diseases and high temperatures. The study aimed to identify the drought tolerance of lowland tomato cultivars based on the drought tolerant indices. The study was arranged in a split plot design, using seven lowland tomato cultivars (Zamrud, Permata F1, Ratna, Mirah, Tombatu F1, Tyrana F1, and Tymoti F1) as the main plot and watering (standard conditions and once every eight days as the drought conditions) as the subplot. Parameters observed were morpho physiological characters (plant height, leaf area, biomass, root length, root surface area, shoot root ratio, relative moisture content, membrane stability index, chlorophyll levels, and proline levels). The parameters observed in each character included the sensitivity stress index (SSI), stress tolerance index (STI), and yield stability index (YSI). Results showed that four cultivars (Tyrana F1, Tymoty F1, Mirah, and Tombatu F1) were drought tolerance, and three cultivars (Ratna, Permata F1, and Zamrud F1) were susceptible. The water stress decreased agronomic and physiological traits performance, but the drought-tolerant cultivars were less affected to the stress and produced higher fruit weight. The study implies that the drought-tolerant cultivars could be used as a promising source for drought tolerant genotypes.&lt;/p&gt;

Effect of Seasonal Drought on the Agronomic Performance of Four Banana Genotypes (Musa spp.) in the East African Highlands

Banana (Musa spp.), a perennial (sub-)tropical crop, suffers from seasonal droughts, which are typical of rain-fed agriculture. This study aimed at understanding the effect of seasonal drought on early growth, flowering and yield traits in bananas grown in the East African highlands. A field experiment was set up in North Tanzania using four genotypes from different geographical origins and two different ploidy levels. The treatments considered were exclusively rain-fed versus rain supplemented with irrigation. Growth in plant girth and leaf area were promising traits to detect the early effect of water deficit. Seasonal drought slowed down vegetative growth, thus significantly decreasing plant girth, plant height and the number of suckers produced when compared to irrigated plants. It also delayed flowering time and bunch maturity and had a negative effect on yield traits. However, the results depended on the genotype and crop cycle and their interaction with the treatments. “Nakitengwa”, an East African highland banana (EAHB; AAA genome group), which is adapted to the region, showed sensitivity to drought in terms of reduced bunch weight and expected yield, while “Cachaco” (ABB genome group) showed less sensitivity to drought but had a poorer yield than “Nakitengwa”. Our study confirms that seasonal drought has a negative impact on banana production in East Africa, where EAHBs are the most predominant type of bananas grown in the region. We also show that a drought-tolerant cultivar not adapted to the East African highlands had a low performance in terms of yield. We recommend a large-scale screening of diploid bananas to identify drought-tolerant genotypes to be used in the improvement of locally adapted and accepted varieties.

Leaf physiological and anatomical characters contribute to drought tolerance of Nusa Tenggara Timur local rice cultivars

Morpho-anatomical characters supporting the resilience of a plant under certain environmental conditions cannot be interpreted individually but thoroughly along with the physiological factors to determine the ability of plants to survive in the drought environment. In this study, we conducted a selection of Nusa Tenggara Timur (NTT) local drought-tolerant rice through the assessment of leaf anatomical characters and their correlation with physiological mechanisms. Materials used in this study were 18 local rice cultivars and 2 control cultivars. The characters of leaf includes epidermal thickness, stomatal density and size, bundle-sheath size, vascular-bundle size and bulliform-cell size were found to be negatively correlated with the changes of chlorophyll, carotenoid, and anthocyanin contents. Moreover the change in anatomical characters is positively correlated with relative water content and cell membrane stability index based on two-way ANOVA test with 95% confidence level. Although most of the cultivars undergo decreasing in all characters measured, several cultivars includes Boawae 100-Malam, Gogo Sikka, Gogo Jak, Hare Tora, Pak Mutin and Gogo Fatuhao showed high potential to be drought tolerant cultivars as found with low reduction percentage of parameters measured.

Root‐omics for drought tolerance in cool‐season grain legumes

Root traits can be exploited to increase the physiological efficiency of crop water use under drought. Root length, root hairs, root branching, root diameter, and root proliferation rate are genetically defined traits that can help to improve the water productivity potential of crops. Recently, high-throughput phenotyping techniques/platforms have been used to screen the germplasm of major cool-season grain legumes for root traits and their impact on different physiological processes, including nutrient uptake and yield potential. Advances in omics approaches have led to the dissection of genomic, proteomic, and metabolomic structures of these traits. This knowledge facilitates breeders to improve the water productivity and nutrient uptake of cultivars under limited soil moisture conditions in major cool-season grain legumes that usually face terminal drought. This review discusses the advances in root traits and their potential for developing drought-tolerant cultivars in cool-season grain legumes.

Comparative metabolomic analysis of the metabolism pathways under drought stress in alfalfa leaves

Alfalfa (Medicago sativa L.) is a very important forage that is severely threatened by water deficiency. Metabolomic changes under drought stress conditions are largely unknown in alfalfa. Therefore, two alfalfa (Medicago sativa L.) cultivars with contrasting tolerance to drought, namely the drought-tolerant Dryland “DT” and drought-sensitive WL343HQ “DS”, were investigated to identify metabolic responses to drought stress. Both the tolerant and sensitive alfalfa showed significant differences in physiological levels under water-limiting conditions. The drought-tolerant cultivar DT sustained growth despite reduced water potential and photosynthesis, suggesting that the functioning of distinct metabolic pathways contributed to enhance tolerance. There were more differentially expressed metabolites produced by DT compared to DS under drought conditions. In addition, the drought-tolerant DT cultivar accumulated more tryptophanol, homocarnosine, S-adenosylhomocysteine, cytidine and clairol, which may be important metabolites for alfalfa drought tolerance. In addition, 17-Hydroxymethylethisterone with unknown function was a candidate tolerance metabolite, whereas the drought-sensitive cultivar DS produced reduced levels of lipid metabolites and increased levels of biosynthesis of amino acids. Among them, the up-regulated l-Proline, l-Arginine and l-Leucine were evident, supporting the conclusion that DS suffered more severe drought stress. This study provided new insights into the metabolic changes of alfalfa in drought stress conditions.

Physiological Divergence in Green Gram [Vigna radiata (L.) Wilczek] Genotypes for Drought and High Temperature Stress Tolerance During Flowering Phase

Background: Drought and high temperature stress limits the crop production. Development of drought and high temperature tolerant cultivars that can withstand and yield better under adverse conditions is very much important to ensure the food and nutritional security. Green gram is one of the important pulse crops with high nutritional and economic value. Among the various stages of plant growth and development, reproductive stage is highly sensitive to drought and high temperature stress across all species. The main objective of this study was to evaluate green gram germplasm collection and identification of elite greengram genotypes that can withstand drought and high temperature stresses at reproductive stage. Methods: The experiment was conducted during March-April, 2019, at National Pulses Research Centre, Vamban, Pudukottai district, Tamil Nadu. To study the influence of combined drought and high temperature stress during reproductive stage, the green gram genotypes were sown in pots. Six pots were maintained for each genotype of which three were maintained at 100% field capacity (control) and for another three; drought stress (50% field capacity for 5 days) was imposed combined with high temperature stress (36 ± 2°C) during reproductive phase (35 Days after sowing). At the end of stress period, physiological and biochemical analysis were carried out to identify the tolerant green gram genotypes against drought and high temperature stresses.Result: In the present study, drought and high temperature stress has negative impact on green gram physiology. Among the genotypes screened for their tolerance at reproductive stage, the following green gram genotypes viz., TARM 1, VGG 15029, VGG 17003, VGG 17004, VGG 17006, VGG 17010 and VGG 17019 were found to withstand drought and high temperature stress and maintain high total chlorophyll content, relative water content and chlorophyll stability index. These green gram gramplasm can be used in pulse breeding program to evolve resilient green gram varieties. Screening of 29 green gram genotypes for drought and high temperature stress during reproductive stage were carried out by maintaining the drought stress (50% field capacity for 5 days) combined with high temperature stress (36 ± 2°C) during reproductive stage (35 days after sowing) by pot culture experiment. Total chlorophyll, relative water content, chlorophyll stability index (CSI), oxidants and antioxidant activity were quantified to identify the tolerant green gram genotypes against drought and high temperature stresses. Based on physiological and biochemical parameters, the following green gram genotypes viz., TARM 1, VGG 15029, VGG 17003, VGG 17004, VGG 17006, VGG 17010 and VGG 17019 were found to withstand and tolerate combined drought and high temperature stresses at flowering stage.

Morpho-physiological and molecular characterization of drought tolerance traits in Gossypium hirsutum genotypes under drought stress.

Drought stress is one of the major abiotic stresses affecting lint yield and fibre quality in cotton. With increase in population, degrading natural resources and frequent drought occurrences, development of high yielding, drought tolerant cotton cultivars is critical for sustainable cotton production across countries. Six Gossypium hirsutum genotypes identified for drought tolerance, wider adaptability and better fibre quality traits were characterized for various morpho-physiological and biochemical characters and their molecular basis was investigated under drought stress. Under drought conditions, genotypes revealed statistically significant differences for all the morpho-physiological and biochemical traits. The interaction (genotype × treatment) effects were highly significant for root length, excised leaf water loss and cell membrane thermostability indicating differential interaction of genotypes under control and stress conditions. Correlation studies revealed that under drought stress, relative water content had significant positive correlation with root length and root-to-shoot ratio while it had significant negative correlation with excised leaf water loss, epicuticular wax, proline, potassium and total soluble sugar content. Analysis of expression of fourteen drought stress related genes under water stress indicated that both ABA dependent and ABA independent mechanisms of drought tolerance might be operating differentially in the studied genotypes. IC325280 and LRA5166 exhibited ABA mediated expression of stress responsive genes and traits. Molecular basis of drought tolerance in IC357406, Suraj, IC259637 and CNH 28I genotypes could be attributed to ABA independent pathway. Based on physiological phenotyping, the genotypes IC325280 and IC357406 were identified to possess better root traits and LRA5166 was found to have enhanced cellular level tolerance. Variety Suraj exhibited good osmotic adjustment and better root traits to withstand water stress. The identified drought component trait(s) in specific genotypes would pave way for their pyramiding through marker assisted cotton breeding.

Combining Ability of Some Bread Wheat Genotypes for yield and its Components under Normal Watering and Water-Stress Conditions

A diallel cross set was carried out at the Experimental Farm of Gemmeiza Agriculture Research Station, Agriculture Research Center, (ARC), Egypt, during the two winter seasons of 2017/2018 and 2018/2019 to assess the variations among six wheat genotypes and their new combinations to estimate heterosis, general and specific combining abilities to determine suitable measurements for drought tolerance in wheat genotypes. Genotypes and the resulted crosses mean squares were found to be either significant or highly significant for all the studied traits under normal and stress environments as well as the combined analysis, except for chlorophyll-a under drought. General combining ability and specific combining ability were found to be significant for all the studied characters under both conditions, except plant height for (SCA) under normal condition, chlorophyll-a for GCA under normal and drought as well as combined analysis and SCA under water-stress condition. The GCA/SCA ratios were found to be greater than unity, suggesting that, additive was much larger and more important than non-additive gene effects in the inheritance of these traits. The two parents Line 1 and Line 3 could be considered as excellent parents in breeding programs aimed to release drought tolerance cultivars. P1, P3, P4, P5 and P6 had the lowest drought susceptibility index value and F1 crosses P1xP2, P1xP3, P1xP4, P1xP5, P2xP6and P3xP5would be classified as drought tolerance due to the least reduction in yield under water stress compared to normal condition, such results might be useful for improving drought tolerance in wheat breeding program.

Fertilizer responsiveness of high-yielding drought-tolerant rice in rainfed lowlands

ABSTRACT Recent advances in rice breeding in tropical Asia led to the release of high-yielding drought-tolerant cultivars. Together with the use of these cultivars, improved nutrient management under drought should further increase rice productivity in rainfed lowland ecosystems. The objectives of this study were to evaluate cultivar differences in the responses of plant growth and grain yield to fertilizer application regimes. We compared 13 drought-tolerant rice cultivars with two irrigated rice cultivars under three nutrient management conditions in irrigated and rainfed lowlands in the Philippines during the wet seasons of 2014 and 2015. Drought stress was mild in both years, with a yield reduction of 11 to 12%, and there was no significant cultivar × nutrient management interaction in yield. The drought-tolerant cultivar NSIC Rc282 proved fertilizer-responsive, and had similar yield to those of the popular high-yielding cultivar NSIC Rc222 under all conditions. An ancillary experiment in 2016 confirmed that NSIC Rc282 was more drought-adapted than NSIC Rc222, with 11% to 37% higher yield under stress. In order to maximize the yield, NSIC Rc282 required N application only when the drought ended, whereas NSIC Rc222 required additional N during the drought. This shows that the details of drought-adaptive nutrient management differ between irrigated and drought-tolerant rice cultivars. We suggest that the introduction of high-yielding drought-tolerant rice cultivars will both improve productivity and increase the nutrient-use efficiency in rainfed environments.

Genome-wide transcriptional changes triggered by water deficit on a drought-tolerant common bean cultivar

BackgroundCommon bean (Phaseolus vulgaris L.) is a relevant crop cultivated over the world, largely in water insufficiency vulnerable areas. Since drought is the main environmental factor restraining worldwide crop production, efforts have been invested to amend drought tolerance in commercial common bean varieties. However, scarce molecular data are available for those cultivars of P. vulgaris with drought tolerance attributes.ResultsAs a first approach, Pinto Saltillo (PS), Azufrado Higuera (AH), and Negro Jamapa Plus (NP) were assessed phenotypically and physiologically to determine the outcome in response to drought on these common bean cultivars. Based on this, a Next-generation sequencing approach was applied to PS, which was the most drought-tolerant cultivar to determine the molecular changes at the transcriptional level. The RNA-Seq analysis revealed that numerous PS genes are dynamically modulated by drought. In brief, 1005 differentially expressed genes (DEGs) were identified, from which 645 genes were up-regulated by drought stress, whereas 360 genes were down-regulated. Further analysis showed that the enriched categories of the up-regulated genes in response to drought fit to processes related to carbohydrate metabolism (polysaccharide metabolic processes), particularly genes encoding proteins located within the cell periphery (cell wall dynamics). In the case of down-regulated genes, heat shock-responsive genes, mainly associated with protein folding, chloroplast, and oxidation-reduction processes were identified.ConclusionsOur findings suggest that secondary cell wall (SCW) properties contribute to P. vulgaris L. drought tolerance through alleviation or mitigation of drought-induced osmotic disturbances, making cultivars more adaptable to such stress. Altogether, the knowledge derived from this study is significant for a forthcoming understanding of the molecular mechanisms involved in drought tolerance on common bean, especially for drought-tolerant cultivars such as PS.

Physiological and biochemical parameters of apricot cultivars under drought conditions on the Southern Coast of the Crimea

In order to determine special features of the photosynthetic apparatus activity and the content of thread compounds in various apricot cultivars during the period of maximum drought probability on the Southern Coast of the Crimea, we studied the concentration of proline, phenolic compounds and chlorophylls, as well as the parameters of chlorophyll fluorescence induction (CFI) in some apricot cultivars ( Prunus armeniaca Lam.), characterized by various degree of drought tolerance (‘Alupkinsky’, ‘Krymskiy Amur’) are weakly resistant; Khurmai cultivar is characterized by labile resistance, and the cultivars Kazachok, Professor Smykov, Nagycorosi Orias are drought tolerant cultivars). It has been found out that drought-resistant cultivars are characterized by a relatively low content of proline in their leaves. It is supposed that this amino acid is involved in the protective reactions of apricot plants under water stress. The results of the photosynthetic apparatus studies in the presented cultivars demonstrated that in leaves, water loss less than 20% caused reversible changes in the parameters of CFI. An increase in the water deficit up to 25-30% caused the destruction of PS2 in weakly drought-resistant cultivars. The most stable photosynthetic apparatus activity was noticed in the cultivar Nagycorosi Orias. Deviations in photosynthesis processes were most pronounced during the period of water restoration in leaves.

Harnessing High-throughput Phenotyping and Genotyping for Enhanced Drought Tolerance in Crop Plants

Development of drought-tolerant cultivars is one of the challenging tasks for the plant breeders due to its complex inheritance and polygenic regulation. Evaluating genetic material for drought tolerance is a complex process due to its spatiotemporal interactions with environmental factors. The conventional breeding approaches are costly, lengthy, and inefficient to achieve the expected gain in drought tolerance. In this regard, genomics-assisted breeding (GAB) offers promise to develop cultivars with improved drought tolerance in a more efficient, quicker, and cost-effective manner. The success of GAB depends upon the precision in marker-trait association and estimation of genomic estimated breeding values (GEBVs), which mostly depends on coverage and precision of genotyping and phenotyping. A wide gap between the discovery and practical use of quantitative trait loci (QTL) for crop improvement has been observed for many important agronomical traits. Such a limitation could be due to the low accuracy in QTL detection, mainly resulting from low marker density and manually collected phenotypes of complex agronomic traits. Increasing marker density using the high-throughput genotyping (HTG), and accurate and precise phenotyping using high-throughput digital phenotyping (HTP) platforms can improve the precision and power of QTL detection. Therefore, both HTG and HTP can enhance the practical utility of GAB along with a faster characterization of germplasm and breeding material. In the present review, we discussed how the recent innovations in HTG and HTP would assist in the breeding of improved drought-tolerant varieties. We have also discussed strategies, tools, and analytical advances made on the HTG and HTP along with their pros and cons.

Physio-morphological, biochemical, and anatomical traits of drought-tolerant and susceptible sorghum cultivars under pre- and post-anthesis drought.

Understanding the physiological mechanisms that control drought tolerance in crop plants is vital for effective breeding. In this study, we characterized drought stress responses in four sorghum cultivars exhibiting differential levels of drought tolerance at pre- and post-anthesis. Greenhouse-grown plants were subjected to two types of drought treatment, water stress (WS) and desiccant-induced water stress (DA), timed to occur at pre- and post-anthesis. Multiple physiological measurements were then made revealing varying responses among the experimental cultivars. The pre- and post-flowering drought-tolerant cultivar P898012 showed a significantly higher net photosynthetic rate, higher transpiration rate, and greater stomatal conductance compared to the drought-susceptible cultivars at both pre- and post-anthesis. A significantly greater stomatal size was also detected in P898012, while the highest stomatal density was found in the drought-susceptible cultivar P721Q. Meanwhile, the two post-flowering drought-tolerant cultivars P898082 and B35 had a higher starch content and exhibited greater osmotic potential under post-anthesis water stress. Compared to WS and well-watered control plants, a greater increase in root biomass was observed in P898012 under DA at pre-anthesis. This finding suggests that plants invested more assimilates into the roots under severe DA at pre-anthesis. Overall, our results show good conformity between drought tolerance in sorghum and key physiological mechanisms of stomatal conductance, root growth patterns, and starch accumulation, all of which act as coping mechanisms during critical drought-sensitive growth stages.

Minimal irrigation requirements of Kentucky bluegrass and tall fescue blends in the northern transition zone

AbstractLawns in the cool‐humid region typically consist of mixtures or blends of cool‐season turfgrass species and cultivars. To maintain a desirable aesthetic appearance and maximize seasonal greenness, many lawns receive supplemental irrigation. Turfgrass breeders have developed superior cultivars with reduced water needs, but the exact proportion of these grasses to include in lawn seed blends to reduce irrigation needs has not been well documented. A field study was conducted to determine the irrigation requirements of various blend ratios (0, 25, 50, 75, and 100%, w/w) of drought‐tolerant (DT) and drought‐susceptible (DS) Kentucky bluegrass (Poa pratensis L., KBG) and turf‐type tall fescue [Schedonorus arundinaceus (Schreb.) Durmort., syn. Festuca arundinacea Schreb.; TF] cultivars at two mowing heights (5.1 or 8.9 cm). Supplemental irrigation requirements were determined over a 74‐d deficit irrigation period using a 70% green coverage threshold (GCT70) approach, where 12.7 mm of supplemental irrigation was applied if an individual plot fell below GCT70 using digital image analysis. Total irrigation needs ranged from 66.7 to 176.9 mm, and TF generally required the least irrigation. For KBG, a blend containing ≥75% DT cultivar required the longest time to reach GCT70 (25–33 d), the least irrigation (94–110 mm), and provided the highest overall visual quality. The TF responses were more variable, and the magnitude of differences among cultivar blends was less compared with KBG. These results indicate that where blending of cultivars is desired, the inclusion of cultivars with demonstrated drought tolerance in blends is important for reducing lawn irrigation needs.

Yield Performance and Response to High Plant Densities of Dry Bean (Phaseolus vulgaris L.) Cultivars under Semi-Arid Conditions

To identify eco-efficient bean cultivars that can be planted at high densities for sustainable bean production under climate change, this study analyzed the performance of ten dry bean (Phaseolus vulgaris L.) cultivars grown at 90,000, 145,000 and 260,000 plants ha−1 under rainfed semi-arid conditions in Mexico. The study compared the yield and yield components (leaf area index (LAI), pods per plant, and hundred seed weight) of the cultivars. We also analyzed the dry matter distribution (DMD), growth rate (GR), radiation use efficiency (RUE), and harvest index (HI) of the best performing cultivars to determine how they respond to higher densities. The cultivars were established under similar planting and management conditions during two growing seasons. The precipitation for the first and second seasons were 175 and 492 mm, respectively, representing 57% and 160% of the mean precipitation in the area during the July–October growing period. Pinto Saltillo, a drought-tolerant indeterminate semi-prostrate cultivar, and Azufrado 2, a determinate shrub cultivar, performed best at high densities under low-precipitation conditions (175 mm). Both cultivars responded to the highest density (260,000 plants ha−1) with increases of 54% to 69% (0.7 to 1.1) in LAI and 21% to 86% (0.32–0.81 Mg ha−1) in yield. The two cultivars responded to increasing plant density with a modification in their fraction of DMD over plant parts and a change in their GR from 0.23–0.25 at low density to 0.96–1.74 gr m−2 day−1 at high density. The two cultivars had an RUE of 3.8 to 4.4 g MJ−1 and HI of 0.31 to 0.36 at high planting density. Farmers’ use of these commercially available cultivars proven to have high yields and the ability to respond favorably to high densities under rainfed conditions can be a viable short-term strategy to increase dry bean production for sustainable agriculture in semi-arid temperate regions.

Correlation between expression and activity of ADP glucose pyrophosphorylase and starch synthase and their role in starch accumulation during grain filling under drought stress in rice

ADP glucose pyrophosphorylase (AGPase, EC 2.7.7.27) and starch synthase (SS, EC 2.4.1.21) are key regulatory enzymes involved in the starch biosynthesis. Comprehensive analysis of transcription levels of ADP-glucose pyrophosphorylase and starch synthase genes was performed in leaves, roots, and developing grains of drought susceptible (IR64) and drought-tolerant (N22) cultivars under applied water deficit stress (WDS). AGPase and SS genes are differentially regulated in leaves, roots, and grains under the drought stress. The expression pattern of SS and AGPase genes was correlated with the activity of both AGPase, SS, and starch content of developing grains under the drought. Drought stress reduced transitory starch in leaves and enhanced storage starch in developing grains. An increase in the activity of AGPase in developing grains was due to induced expression of ADP glucose pyrophosphorylase large subunit 3 (AGPL3) in N22 and both ADP glucose pyrophosphorylase small subunit 2 (AGPS2) & ADP glucose pyrophosphorylase large subunit 3 (AGPL3) in IR64 and a positive correlation was established with starch content. Similarly, an increase in the SS activity in developing grains was due to induced expression of soluble starch synthase (SSIIB, SSIVA, and SSIVB) in N22 and SSIVB in IR64.

Effect of Irrigation Scheduling on some Agronomic and Physiological Traits of some Wheat Cultivars تأثیر جدولة الری على بعض الصفات المحصولیة والفسیولوجیة لبعض أصناف القمح

Field experiments were conducted at Shandaweel Agric. Res. Station, Sohag, Egypt, during the two growing seasons 2018/2019 and 2019/2020 to study the effect of six irrigation regimes, i.e. I1 (irrigation at tillering and elongation stage), I2 ( irrigation at tillering and flowering stage), I3 (irrigation at tillering, elongation and flowering stage), I4 (irrigation at tillering, booting and grain filling stage), I5 (irrigation at tillering, elongation, booting and flowering stage) and I6 (irrigation at tillering, elongation, booting, flowering and grain filling stage) on some agronomic and physiological traits of four wheat cultivars, i.e.Shandaweel1, Sids 14, Sohag 4 and Sohag 5. Results showed that decreasing number of irrigations and amount of applied water at different growth stages significantly decreased all studied traits. The highest reduction was recorded under I1 (1432 m-3 ha-1) for all studied traits, except days to heading and number of spikes m-2. Meanwhile, the lowest reduction was observed under I5 (3088 m-3 ha-1) for all studied traits as compared to I6 (3965 m-3 ha-1 of applied water). Irrigation at both booting and flowering are essential to reduce loss in grain yield. Moreover, Sids 14 exhibited lower yield reduction under different irrigation regimes, while sohag 4 and Sohag 5 exhibited the highest yield reduction. Therefore, Sids 14 proved to be drought tolerant cultivar, while Sohag 4 and Sohag 5 were drought sensitive. Planting Sids 14 cultivar with irrigation at tillering, booting, grain filling stages (I4) are useful to save about (36.97%) of applied water without significant decrease in grain yield.