Drought Resistance Index Research Articles

Grain yield, anthesis-silking interval and drought tolerance indices of tropical maize hybrids

Abstract Water deficit stress is the abiotic factor with the highest impact on crop yield. The objective of this study was to evaluate grain yield (GY), the anthesis-silking interval (ASI) and drought tolerance indices in maize hybrids. We evaluated GY and the ASI of 86 hybrids under two moisture levels (normal irrigation and water stress) for three consecutive years. The stress susceptibility index, water stress tolerance, drought resistance coefficient, drought resistance index, stress tolerance index and harmonic mean were evaluated. There were significant hybrid x environment interactions for GY and the ASI. Differences in the ASI among environments ranged from 0 to 5 days. The hybrids P3862, 1I873, 1I923, 1I862 and 1J1211 showed high GY, associated with the highest drought tolerance indices. The stress tolerance index and harmonic mean indices can be used to identify higher-yielding maize hybrids in environments with and without water restriction.

Effect of barassinolide on growth characteristics of wheat (Triticum aestivum L.) under water stress

This experiment was conducted in the laboratories of the Seed Testing and Certification Division-Babylon province in 2018 in a completely randomized design (CRD) with four replicates and two factors. The first factor included the addition of polyethylene glycol 6000 (PEG 6000) with three levels of water stress of 0 bar, -6 bar, and -9 bar which are herein denoted by S1, S2, and S3, respectively. The second factor included three stimulation treatments of wheat seeds by soaking the seeds in the plant hormone, Brassinolide for 24 hours with concentrations of 0 mg liter-1, 2 mg liter -1, and 4 mg liter-1 which are denoted by B0, B1, and B2, respectively. The results showed that water stress adversely affected wheat seedling characteristics. With the water stress level S2, the lowest average period of germination initiation was 3.33 days, germination period was 3.38 days, drought resistance index at germination reached 1.01, total chlorophyll content was 27.91 mg/100 g fresh weight, and gibberellin content was 29.8 micromolar. The treatments with Brassinolide achieved a significant improvement in plant characteristics where B2 treatment realized the lowest average period of germination initiation of 2.58 days and drought resistance index during germination of 1.11. B2 treatment also achieved 22.13% increase in total chlorophyll content, 66.53% increase in gibberellin content, and 43.81% increase in Indole-3-acetic acid (IAA) compared to the control treatment B0 without Brassinolide.

Overexpression of OsHox-6 Gene Enhanced Tiller Number in Rice But Induced Yield Penalty

OsHox-6, belongs to the transcription factor homeodomain leucine zipper (HD-Zip) protein sub-family I, has unknown function. This study was aimed to characterize the phenotypes of two homozygous transgenic rice lines (S29-62-2 and S.40.4-158-1) containing an extra copy of OsHox-6 gene under the control of a rice constitutive promoter, OsLEA3, and to evaluate their tolerance to water stress. A real-time quantitative PCR (qRT-PCR) showed that the transcript expression of OsHox-6 gene in the transgenic lines increased 5-10 folds under a normal irrigation and 10-20 folds after exposure to water stress conditions as compared to its wild type control. Transgenic plants overexpressing OsHox-6 exhibited phenotypic alteration at the normal irrigation by inducing tiller formation, suggesting a decrease in the apical dominance. Transgenic plants also showed significant enhancement in the total grain number, however, the number of empty grains also increased significantly (~16-22%). After imposed to the water stress, the number of empty grains in the transgenic lines was even higher (up to 83% in average). Furthermore, observations on the water loss rates, relative water contents and drought resistance indices (DRI) suggested that the overexpression of OsHox-6 did not significantly increase tolerance to water stress. Further research is required to reveal the detailed mechanisms of OsHox-6 in response to water and other abiotic stresses.

A drought resistance index to select drought resistant plant species based on leaf water potential measurements

The water deficit in arid and semi-arid regions is the primary limiting factor for the development of urban greenery and forestation. In addition, planting the species that consume low levels of water is useful in arid and semi-arid regions that have poor water management measures. Leaf water potential (Ψ) is a physiological parameter that can be used to identify drought resistance in various species. Indeed, Ψ is one of the most important properties of a plant that can be measured using a pressure chamber. Drought avoiding or drought resistant species have a lower Ψ than plants that use normal or high levels of water. To determine drought resistance of species that are suitable for afforestation in arid urban regions, we evaluated twenty woody species in the Isfahan City, central Iran. The experimental design was random split-split plots with five replications. The species were planted outdoor in plastic pots and then subjected to treatments that consisted of two soil types and five drip irrigation regimes. To evaluate the resistance of each species to drought, we used the Ψ and the number of survived plants to obtain the drought resistance index (DRI). Then, cluster analysis, dendrogram, and similarity index were used to group the species using DRI. Result indicates that the evaluated species were classified into five groups: (1) high water consuming species (DRI>–60 MPa); (2) above normal water consuming species (–60 MPa≥DRI>–90 MPa); (3) normal water consuming species (–90 MPa≥DRI>–120 MPa); (4) semi-drought resistant species (–120 MPa≥DRI>–150 MPa); and (5) drought resistant species (DRI≤–150 MPa). According to the DRI, Salix babylonica L., Populus alba L., and P. nigra L. are high water consuming species, Platanus orientalis L. and Albizia julibrissin Benth are normal water consuming species, and Quercus infectoria Oliv. and Olea europaea L. can be considered as drought resistant species.

THE SELECTION OF THE INITIAL MATERIAL FOR VARIOUS DIRECTIONS OF MAIZE BREEDING ON THE BASIS OF MULTI-CRITERIA ESTIMATION

The purpose of the study is the application of the method of multi-criteria estimation to select the initial material of various direction of maize breeding. The studies were performed in the year of 2017–2018 in two different regions of trials, in the arid area of the ARC “Donskoy” (Zernograd) and in the moisture area of the All-Russian Research Institute of Maize (Pyatigorsk). 10 parental forms of maize hybrids ‘Alpha M’, ‘Almaz M’, ‘Avrora S’, ‘Milena M’, ‘Istok S’, ‘Mirt M’, ‘Malvina S’, Raduga S’, Maya M’, ‘Prestizh M’ used as testers in breeding programs were taken as initial material. The studied forms were characterized by a diversity in the value of their main economically valuable traits. Significant variability was identified in infertility of plants (V = 56.0%), smut infection (V = 46.4%) and fragility of a stem below a cob (V = 43.4%). Average variability was identified in grain productivity (V = 14.8–18.2%), drought resistance index (V = 10.5%), harvesting moisture of grain (V = 18.6%). The use of the complex of main economically valuable traits for the integrated assessment (SD), taking into account the specified contributions (Rk) and weight coefficients (Wi), made it possible to rank the initial material according to its value for various areas of selection. There have been identified the testers ‘Mirt M’, Maya M, ‘Istok S’ with the best integral values (SD = 2.63–5.65) for breeding on drought tolerance. ‘Istok S’, ‘Milena M’, ‘Avrora S’ (SD = 2.14–4.07) have been recommended as the testers in breeding programs to breed the varieties with low harvesting moisture of grain. There has been identified a universal tester ‘Istok S’ which is suitable for various directions of maize breeding. Thus, the multi-criteria estimation can be used in the breeding process to select initial material that meets the requirements of the planned breeding directions.

Assessment of Variability for Drought Tolerance Indices in Some Wheat ( Triticum aestivum L.) Genotypes

Estimation of nine yield-based drought tolerance indices was studied in ten wheat genotypes and identification of best index and best drought tolerant genotype. Nine drought tolerance indices comprising stress tolerance index (STI), tolerance index (TOL), stress susceptibility index (SSI), geometric mean productivity (GMP), mean productivity (MP),harmonic mean (HAM), yield index (YI), yield stability index (YSI) and drought resistance index (DRI) were each estimated based on yield under non-stress (Yp) and stress condition (Ys). The results of the genetic analysis for all drought tolerance indices studied demonstrated that GMP, MP and HAM had less variation between phenotypic coefficients of variability and genotypic coefficient of variability corresponded to high heritability. GMP, MP and HAM werenominated as the best useful indices that looking for drought tolerant genotypes. Also, they had positive correlation with Yp and Ys. The genotypes 1, 6 and 10 were considered drought tolerant while genotypes 3, 4, 5, 7 and 9 as drought susceptible. Genotype 8 was identified as highly drought susceptible. The studied genotypes showed considerable variation in performance and tolerated various drought conditions that could be exploited in further investigation.

Uni- and Multi-Variate Assessment of Drought Response Yield Indices in 10 Wheat Cultivars

Wheat (Triticum aestivum L.) is a major cereal with its productivity being highly affected by drought. In the current study, 10 wheat cultivars were evaluated for their grain yield under well-watered (Yp) and drought (Ys) conditions. Various drought response indices (mean productivity (MP), geometric productivity (GMP), tolerance index (TOL), stress susceptibility index (SSI), stress tolerance index (STI), harmonic mean of yield (HARM), yield stability index (YSI), relative drought index (RDI), two drought resistance indices (DRI1 and DRI2), yield reduction ratio (YRR) and yield index (YI)) were determined to identify high-yielding and drought tolerant cultivars. Spearman’s correlation coefficient among the estimated indices, hierarchical clustering of the concerned cultivars as well as principle component analysis (PCA) of both the indices and cultivars were employed. Wheat cultivars Sids 13 and Gemmeiza 11 were superior while Sakha 94 and Shandaweel 1 were inferior depending upon their Yp, Ys and drought response indices. Also, a non-significant positive correlation was recorded between Yp and Ys of the studied cultivars with GMP, STI and HARM being significantly correlated with both Yp and Ys. Based on PCA, Yp and Ys explained 61.6 and 38.1% of the total variation; respectively. Furthermore, cluster analysis sequestered the concerned cultivars into drought susceptible cultivars (Shandaweel 1, Giza 168 and Gemmeiza 11), drought moderate ones (Misr 2, Sakha 93 and Sakha 94) and drought tolerant ones (Misr 1, Sids 13, Gemmeiza 9 and Sids 12) based on the mean values of YSI, RDI, TOL, SSI and YRR within each group.

Multivariate analysis based on drought tolerance indices for screening drought tolerance in common bean (Phaseolus vulgaris L.)

Twenty common bean (Phaseolus vulgaris L.) genotypes were evaluated based on drought tolerance indices through principal component analysis. All the indices were positively correlated with each other with the exception of drought susceptibility index, which was negatively correlated with all other indices used in the study. The first PC that accounted for 73.01 % of variation, and indices such as yield (non-stress), yield (stress), geometric mean (GM), harmonic mean (HM), drought resistance index(DRI), coefficient of drought resistance (CDR), drought tolerance index (DTI) and relative drought index (RDI) were related to toleranceand percent reduction and DSI were related to susceptibility. The genotypes with higher component scores of PC1 viz., WB-1634 (1.97), WB-341 (1.371), WB-185 (1.268) and WB-451 (1.253) are also tolerant to drought. The Biplot of PC1 and PC2 also revealed WB-1634 as tolerant, whereas genotypes WB-6, WB-1587 and SR-1 as susceptible to drought.

Comprehensive evaluation and construction of drought resistance index system in Hydrangea macrophylla.

With the continuous drought stress treatment to five Hydrangea macrophylla varieties of different abilities of drought resistance, twenty-five physiological-biochemical indices were mea-sured. We evaluated the drought resistance of different varieties and established the mathematic model. The results showed that leaf mass per area, cell membrane permeability (CMP), the content of malonaldehyde (MDA), the activity of superoxide dismutase (SOD), soluble sugar content, proline content, intercellular carbon dioxide and non-photochemical quenching coefficient were significantly increased under drought stress for twenty days. In contrast, relative water content, net photosynthetic rate, stomatal conductance, transpiration rate, actual photochemical efficiency of PS2 and electron transport rate (ETR) were significantly decreased. The principal component analysis classified those indices into three independent comprehensive indices (accumulative contribution of 87.1%). The principal component 1 mainly reflected the information of photosynthetic and fluorescence. The principal component 2 mainly reflected the information of plant vigor. The principal component 3 mainly reflected the information of membrane system and osmotic adjust system. Five H. macrophylla varieties were divided into three categories by clustering analysis: drought-tolerant type (including H. macrophylla 'Lavblaa') and H. macrophylla 'Taube'), intermediate type (H. macrophylla 'You and me romance'), and drought-intolerant type (including H. macrophylla cv. Endless summer bride and H. macrophylla 'Tricolor'). Comprehensive evaluation of drought resis-tance (D value) showed that the ability of drought resistance decreased in order of H. macrophylla 'Lavblaa' > H. macrophylla 'Taube'> H. macrophylla 'You and me romance'> H. macrophylla cv. Endless summer bride > H. macrophylla 'Tricolor'. Four influential indices for drought resis-tance including CMP, the activity of peroxidase (POD), soluble protein contents (SP) and ETR was screened by stepwise regression analysis, which could be used for the rapid identification of drought resistance of H. macrophylla.

Characterization of TaDREB1 in wheat genotypes with different seed germination under osmotic stress

BackgroundThe cis-acting element DRE/CRT plays an important role in activating gene expression responsive to osmotic stress, low temperature and high-salinity. DREB1/CBF genes encode DRE-binding proteins with the function as transcript activators. TaDREB1 was also found to be induced by osmotic stress.MethodsThe dates of osmotic stress was assessed by seed germination drought resistance index; the full-length cDNA sequences of TaDREB1 gene were downloaded from NCBI datebase; identification of allelic variation and transcript expression were assessed by PCR and semi-quantitive RT-PCR analysis, respectively.ResultsTotal 13 new allele variations of TaDREB1 were identified in the germplasms tested in the paper, including 5 TaDREB1-A on chromosome 3AL, 4 TaDREB1-B on chromosome 3BL and 4 TaDREB1-D on chromosome 3DL. In each variety, there existed two loci of TaDREB1-D genes, named TaDREB1-D1 and TaDREB1-D2, both of which had the similar nucleotide sequence except an 11 bp insertion in the former. In wheat seeds under osmotic stress, we did not detect the transcript expression level of TaDREB1-A and TaDREB1-B, but that of TaDREB1-D.ConclusionsThe capacity of osmotic stress tolerance was closely correlated with the expression level and tendency of TaDREB1-D.

Evaluation of drought stress tolerance in promising lines of chickpea (Cicer arietinum L.) using drought resistance indices.

با توجه به سطح زیر کشت دیم نخود، خشکی ازجمله عواملی است که به‌طورجدی تولید و کیفیت نخود را تحت تأثیر قرار می­دهد؛ بنابراین رسیدن به ژنوتیپ­ های متحمل خشکی موردتوجه محققین است. به‌منظور بررسی تنوع ژنتیکی و تحمل به خشکی لاین‌های پیشرفته نخود، تعداد 64 ژنوتیپ نخود در قالب طرح لاتیس ساده با دو تکرار در شرایط تنش و عدم تنش رطوبتی در معاونت مؤسسه تحقیقات کشاورزی دیم سرارود کرمانشاه درسال زراعی 93-1392 مورد آزمایش قرار گرفتند. شاخص­های تحمل تنش (STI)، شاخص میانگین بهره­ وری (MP)، میانگین هندسی بهره­ وری (GMP)، حساسیت به تنش (SSI)، میانگین هارمونیک (HAM)، شاخص عملکرد (YI) و شاخص تحمل تنش تغییریافته (K1, K2) بر اساس عملکرد دانه در هر دو شرایط محاسبه گردید. همچنین از روش امتیازدهی تحمل تنش (STS) به‌منظور گزینش ژنوتیپ­ها بر مبنای کلیه شاخص­ها استفاده شد. مطالعه همبستگی ساده بین عملکرد در شرایط تنش، عدم تنش و شاخص­های مقاومت نشان داد که عملکرد در دو شرایط با شاخص­های تحمل تنش، میانگین هندسی بهره­ وری، میانگین هارمونیک، شاخص عملکرد و تحمل تنش تغییریافته همبستگی مثبت و معنی­داری داشتند. بنابراین این شاخص­ها برای شناسایی ژنوتیپ­های با عملکرد بالا مناسب می‌باشند که از بین آن‌ها STI به­ عنوان مناسب‌ترین شاخص جهت ترسیم نمودار سه‌بعدی در نظر گرفته شد. روش ترسیمی سه‌بعدی و بای ­پلات باعث گروه­ بندی ژنوتیپ های متحمل و غیر متحمل گردید به‌طوری‌که ژنوتیپ­های FLIP 08-42C، عادل، آزاد و FLIP 08-35C با قرار گرفتن در مجاورت بردارهای مربوط به شاخص ­های مهم مقاومت (STI, MP, GMP) و قرار گرفتن در گروه A از پتانسیل تولید بالا و حساسیت پائین به خشکی برخوردار بودند. همچنین با توجه به نتایج روش امتیازدهی تحمل تنش (STS) ژنوتیپ ‏های فوق نسبت به سایر ژنوتیپ ­ها دارای تحمل بیشتری به تنش خشکی بودند. در تجزیه به مؤلفه ­های اصلی، دو مؤلفه اصلی اول 98.437 درصد از کل واریانس را توجیه نمودند. درنهایت با توجه به وجود تنوع ژنتیکی بین ژنوتیپ­های موردبررسی ازنظر تحمل به تنش خشکی، می­توان از آن‌ها در برنامه­ های اصلاحی استفاده نمود.

Identification of Drought Tolerant and Sensitive Species of Thyme through Some Physiological Criteria

Drought as the most important abiotic stress has deleterious effects on plants. Developing drought tolerant varieties can help produce plants in a sustainable way. This study was conducted to identify drought tolerant and drought sensitive thyme species including Thymus vulgaris, T. vulgaris (origin: Spain), T. carmanicus, T. daenensis and T. kotschyanus and to study the mechanism used by them to cope with drought stress. For this purpose, relative water content, water use efficiency, soil water depilation rate, root:shoot ratio, drought resistance index and a new criterion ceased were used. T. carmanicus and T. daenensis had the lowest and the highest reduction on relative water content, respectively. In terms of water use efficiency and soil water depletion curve, the highest and the lowest values were detected for T. daenensis and T. carmanicus, respectively. The most and the least root:shoot ratios were recorded for T. daenensis and T. vulgaris (origin: Spain), respectively. Analyses by drought resistance index and PCA revealed that T. carmanicus is drought susceptible, T. kotschyanus and T. vulgaris are semi-drought susceptible, and T. daenensis and T. vulgaris (origin: Spain) are semi-drought tolerant species. FC ceased growth analysis showed that T. carmanicus stopped its growth at higher FC, while T. kotschyanus stopped it at lower FC. Therefore, based on this criterion and considering the sustainability of growth under drought condition, T. carmanicus and T. kotschyanus are the least and the most drought tolerant Thymus species.

Characterization of the Symbiotic Nitrogen-Fixing Common Bean Low Phytic Acid (lpa1) Mutant Response to Water Stress.

The common bean (Phaseolus vulgaris L.) low phytic acid (lpa1) biofortified genotype produces seeds with improved nutritional characteristics and does not display negative pleiotropic effects. Here we demonstrated that lpa1 plants establish an efficient nitrogen-fixing symbiosis with Rhizobium etli CE3. The lpa1 nodules showed a higher expression of nodule-function related genes than the nodules of the parental wild type genotype (BAT 93). We analyzed the response to water stress of lpa1 vs. BAT 93 plants grown under fertilized or under symbiotic N2-fixation conditions. Water stress was induced by water withholding (up to 14% soil moisture) to fertilized or R. etli nodulated plants previously grown with normal irrigation. The fertilized lpa1 plants showed milder water stress symptoms during the water deployment period and after the rehydration recovery period when lpa1 plants showed less biomass reduction. The symbiotic water-stressed lpa1 plants showed decreased nitrogenase activity that coincides with decreased sucrose synthase gene expression in nodules; lower turgor weight to dry weight (DW) ratio, which has been associated with higher drought resistance index; downregulation of carbon/nitrogen (C/N)-related and upregulation of stress-related genes. Higher expression of stress-related genes was also observed in bacteroids of stressed lpa1 plants that also displayed very high expression of the symbiotic cbb3 oxidase (fixNd).

Response of Main Maize Varieties to Water Stress and Comprehensive Evaluation in Hebei Province

Drought is a serious threat to maize production in Hebei province. Planting drought resistant maize varieties is an effective measure to solve drought in arid and less rain areas. Drought resistance in maize is controlled by many genes, and multiple indexes should be used for comprehensive evaluation (Campos H et al.2004). In the arid rain shed, using 34 maize varieties to promote crop production compared to the drought resistance test. The experiment was conducted with two treatments of drought stress (irrigation only at seedling stage) and normal irrigation, and 12 agronomic traits related to drought resistance of maize were determined. The results showed that drought had significant effects on maize yield and main agronomic characters. Under drought stress, plant height, ear length, bare tip, ear row number, row grains, 1000-kernel weight, ASI index can be used as identification index of drought resistance of maize in different period. The results indicated that the variety with strong drought resistance is Zhongdi175, the worst drought resistance is Woyu964.

High‐productivity vegetation is important for lessening bird declines during prolonged drought

Abstract Locations in which ecological assemblages show high resistance to climate pressures, such as drought, are likely to be important refuges for biota in changing climates. We asked whether environmental characteristics of locations were associated with the capacity of bird assemblages to withstand prolonged drought. We used a multispecies index to quantify trends in bird assemblages during a 13‐year drought at >500 locations (>18,000 surveys) in the Murray–Darling Basin, south‐eastern Australia, using data from the Atlas of Australian Birds. We investigated whether the resistance of bird assemblages was associated with (1) vegetation structure; (2) vegetation productivity (vegetation greenness); (3) landscape context (patch size, landscape vegetation cover); or (4) physical environment (elevation, terrain, topography, availability of surface water). Vegetation productivity, measured by vegetation greenness (Normalized Difference Vegetation Index), was the only potential predictor with strong evidence of an effect, and was positively associated with the index of drought resistance. There was little evidence that variables characterizing landscape context, vegetation structure or the physical environment of sites were associated with drought resistance of bird communities. Synthesis and applications. Bird assemblages in locations with high vegetation greenness are more resistant to severe drought. Prioritizing conservation investments in areas with locally high vegetation productivity is likely to be an effective strategy for increasing the resistance of bird assemblages to extreme drought, especially in areas where mean productivity is relatively low, such as arid and semi‐arid regions. Remotely sensed vegetation greenness may be a promising source of information for identifying drought refuges for birds and possibly other biota.

Utilización de los índices de selección en la identificación de genotipos de arroz (Oryza sativa L.) tolerantes a sequía

Doce genotipos de arroz fueron estudiados en condiciones de campo, en condiciones inundadas y en ambientes de sequía moderada y severa. Se utilizó el diseño de parcelas divididas con dos repeticiones, ubicando en parcelas los tratamientos de manejo de riego (tres) y en sub-parcelas los genotipos (12), con una separación de diez metros para controlar la filtración lateral.La siembra directa se realizó en hileras, utilizando una densidad de 80 Kg ha-1. El rendimiento en grano se ajustó a 14 % de humedad. Para cada genotipo se determinó la tolerancia a sequía utilizando los siguientes índices de selección: Índice de Susceptibilidad al Estrés (ISE), Productividad Media Geométrica (PMG), Productividad Media (PM), Media Armónica (MA), Índice de Tolerancia al Estrés (ITE), Índice de Rendimiento (IR), Índice de Estabilidad de Rendimiento (IER) e Índice de Resistencia a Sequía (IRS).Se observaron diferencias significativas entre rendimientos en condiciones de inundación y estrés en los índices Productividad Media Geométrica (PMG), Media Armónica (MA) y Productividad Media (PM). Los coeficientes de correlación indican que estos índices podrían ser utilizados para la identificación de genotipos de arroz tolerantes a sequía. Los análisis de los gráficos tridimensionales indican que IR71706 es el genotipo más tolerante a sequía y puede sembrarse en condiciones de riego y aridez.Producción Agropecuaria y Desarrollo Sostenible, Vol. 2, 2014: 11-31

Drought resistance of new synthetic hexaploid wheat accessions evaluated by multiple traits and antioxidant enzyme activity

Drought is a severe threat to wheat production. Synthetic hexaploid wheat (SHW, AABBDD) has great potential for improving resistance to various stresses of bread wheat. The drought resistance of thirty-four new SHWs and a control (bread wheat cultivar Jinmai47) were evaluated under two water regimes, i.e., well watered (WW) and water stressed (WS), in two consecutive years. Compared with the cultivar Jinmai47 under WW conditions, SHWs displayed increased plant height (PH), larger flag leaf area (FLA), longer spikes (SL) and more biomass plant−1 (BMPP), but SHWs displayed fewer grains spike−1 (GNPS) and less thousand-grain weight (TGW), resulting in lower grain yield plant−1 (GYPP) and a lower harvest index (HI). The membership function value of drought resistance (MFVD) analysis and drought resistance index (DI) under the two water regimes revealed six SHW lines (SHW1, SHW3, SHW10, SHW16, SHW21 and SHW34) identified with higher drought resistance. Our results also showed higher activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT), in WS plots than in WW plots. SHWs with higher drought resistance exhibited higher activities of antioxidant enzymes (SOD, POX and CAT) in both WW and WS plots. SHWs exhibiting excellent agronomic traits and increased drought resistance could further be applied to stress resistance studies and wheat breeding programmes.

Evaluation desertification state in East Al-Haffar project

A study was carried out and included ninety two soil series in east of Al-Haffar project and were distributed within sub-physiographic: Levee – basin – depression. Semi soil survey maps with scale of 1:50000 were used to cover an area of 50000 ha. The aim of this study was to use quantitative analysis methods for information through the linkage between the curves of geographical–geological- pedological and through depending on some pedo-geo-morphological indices which include (parent material; slope gradient; soil depth and soil texture, all these indices represent soil quality index (SQI) in addition to the index of vegetation cover; index of erosion protection and index of drought resistance which represent vegetation quality index (VQI); and salinity of irrigation water; soluble chloride ion ratio and sodium exchange ratio, which represent irrigation water quality index (IWQI). All these indices used to characterize and evaluate the environmental sensitivity to desertification. All indices were calculated by used specific mathematical equations according to the European commission system were used for rating and classification sensitivity for environmental desertification based on multiplying method between measured indices values and the maps were made for it. Results showed varied erodibility factors of wind which distributed in range of 0.09-0.37; water erodibility factor in range of 0.45 - 0.52 and soil crust factor in range of 0.08-0.73. Soil quality index varied and distributed in a range of 1.35-1.70. The areas of study were classified into three degrees and distributed from high quality to low quality. As well as vegetation quality index varied and distributed in a range of 0.07-0.26 and the location of the study was classified into four degrees, described between very low to good quality, water irrigation quality index is value of 3.35 mm and did not vary because there is only one sources of water Irrigation within the study area. In addition, the results also showed restricted three main location varied to desertification sensitivity which are classified between very low sensitive to medium sensitive.

Evaluation of Spring Wheat Cultivars Based on Drought Resistance Indices

Evaluation of Spring Wheat Cultivars Based on Drought Resistance Indices

Selection indices to identify maize (Zea mays L.) hybrids adapted under drought-stress and drought-free conditions in a tropical climate

Drought stress is the most important production constraint in maize (Zea mays L.), especially in rainfed agriculture. To improve productivity of rainfed maize, the development of hybrids with tolerance to drought stress is an important objective in maize breeding programs. The present study was undertaken to identify maize hybrids that perform better under drought-stress and drought-free conditions by using various selection indices. These selection indices were calculated on the basis of yield (t ha–1) performance of hybrids measured under drought stress and optimum environments. A set of 38 cultivars was evaluated at 10 environments (representing five each of drought stress and optimum growing conditions). The average reduction in grain yield due to drought stress was 52%. Effects of genotype, environment and their interaction were significant sources of variation in determining grain yield, respectively explaining 5.0–7.4%, 55.0–60.2% and 12.0–15.0% of total variation in yield under drought-stress and drought-free conditions. Of eight selection indices considered for study, three indices such as harmonic mean, geometric mean, and stress tolerance index were identified as suitable for selection of genotypes capable of performing well both under drought-stress and drought-free environments. Drought response index and drought resistance index were found useful in identifying hybrids that performed better under drought stress. Stress susceptibility index was negatively correlated with yield measured under drought stress. Stress susceptibility index could be used as selection index but only in combination with yield performance data under water-deficit conditions in order to identify drought-tolerant hybrids with reasonable productivity. Test weight, shelling percentage, days to maturity, and ear girth were found to be useful traits for improving yield performance across diverse environments. Cultivation of identified drought-tolerant hybrids would be useful to enhance maize productivity in drought-stress environments.