Drought Tolerance Indices Research Articles

Caracterización de la respuesta a la sequía de líneas segregantes de maíz

El estrés por sequía es una de las principales causas de la reducción del rendimiento del maíz en los trópicos, principalmente en la agricultura que depende de lluvias, por lo que se requiere generar genotipos con tolerancia a sequía. Los objetivos de la investigación fueron cuantificar la respuesta agronómica de un grupo de líneas S2 segregantes de maíz en ambientes de riego y sequía, así como seleccionar líneas con tolerancia al déficit hídrico, con base en dos índices y al promedio de rendimiento de ambos ambientes. Los genotipos de estudio fueron 96 líneas S2 segregantes, dos líneas testigo y dos líneas no seleccionadas para sequía. Las líneas se evaluaron bajo riego y sequía inducida usando un diseño Látice Alfa con cuatro repeticiones, en Ayala, Morelos, México. Se midieron 10 variables morfológicas y se estimaron los índices de susceptibilidad a la sequía (ISS) y el índice de tolerancia (IT). Con base en el rendimiento de grano en riego (3.14 t ha-1), se observó una reducción de 77.7% del rendimiento en sequía (0.7 t ha-1). Los índices ISS e IT identificaron a las líneas LUM69, LUM82 y LUM30 como tolerantes a sequía, solo LUM69 mostró un rendimiento competitivo en ambos ambientes. Los índices de ISS e IT como criterio para identificar genotipos tolerantes, no seleccionaron a las líneas con mejor rendimiento de grano bajo condiciones de riego, por lo que se debe incluir en los criterios de selección al promedio de rendimiento a través de los ambientes de humedad.

Evaluation of durum wheat lines derived from interspecific crosses under drought and heat stress

AbstractThe productivity of durum wheat [Triticum turgidum subsp. durum (Desf.) van Slageren] is affected by drought and/or high temperatures, challenges to be amplified by climate change. Pre‐breeding using wild relatives can supply useful traits for durum wheat improvement to adapt to major abiotic and biotic stresses. Sixty‐seven lines issued from backcrosses of Cham5 and Haurani durum wheat varieties with accessions of Triticum aegilopoides (Link) Bal. ex Koern., T. dicoccoides Koern. ex Schweinf., T. urartu Thumanian ex Gandilyan, and Aegilops speltoides Tausch were evaluated for drought and heat tolerance. The trials were conducted during two seasons (2016−2017 and 2017–2018) at Tessaout, Morocco, under full irrigation (optimal conditions) and rainfed conditions (drought stressed) and at Wed Medani, Sudan, under full irrigation combined with heat stress. The recurrent parents, along with eight best cultivars and elite breeding lines, were used as checks. Drought reduced the grain yield by 62%. Grain yield and drought tolerance index were used to identify lines to be used by breeding programs to enhance drought and heat tolerance. The derivatives lines 142014 (Cham5*3/T. aegilopoides), 142074 (Cham5*3/T. dicoccoides), and 142015 along with the checks Icarachaz and Gidara 2 ranked among the best under heat stress. Under drought stress, the lines 141972 (Haurani*2/T. urartu) and 141973 (Cham5*2/T. dicoccoides) yielded 196 and 142% of their recurrent parents’ yield, respectively. High variation was found for agronomic and phenology traits, with heading time explaining 16% of grain yield under drought, while thousand kernel weight accounted for 18% of the yield under heat. We conclude that gene introgression from wild relatives pays off and can increase wheat resilience to cope with climate change effects.

Loci harboring genes with important role in drought and related abiotic stress responses in flax revealed by multiple GWAS models

QTNs associated with drought tolerance traits and indices were identified in a flax mini-core collection through multiple GWAS models and phenotyping at multiple locations under irrigated and non-irrigated field conditions. Drought is a critical phenomenon challenging today's agricultural sector. Crop varieties adapted to moisture deficit are becoming vital. Flax can be greatly affected by limiting moisture conditions, especially during the early development and reproductive stages. Here, a mini-core collection comprising genotypes from more than 20 major growing countries was evaluated for 11 drought-related traits in irrigated and non-irrigated fields for 3years. Heritability of the traits ranged from 44.7 to 86%. Six of the 11 traits showed significant phenotypic difference between irrigated and non-irrigated conditions. A genome-wide association study (GWAS) was performed for these six traits and their corresponding stress indices based on 106 genotypes and 12,316 single nucleotide polymorphisms (SNPs) using six multi-locus and one single-locus models. The SNPs were then assigned to 8050 linkage disequilibrium (LD) blocks to which a restricted two-stage multi-locus multi-allele GWAS was applied. A total of 144 quantitative trait nucleotides (QTNs) and 13 LD blocks were associated with at least one trait or stress index. Of these, 16 explained more than 15% of the genetic variance. Most large-effect QTN loci harbored gene(s) previously predicted to play role(s) in the associated traits. Genes mediating responses to abiotic stresses resided at loci associated with stress indices. Flax genes Lus10009480 and Lus10030150 that are predicted to encode WAX INDUCER1 and STRESS-ASSOCIATED PROTEIN (SAP), respectively, are among the important candidates detected. Accessions with multiple favorable alleles outperformed others for grain yield, thousand seed weight and fiber/biomass in non-irrigated conditions, suggesting their potential usefulness in breeding and genomic selection.

Evaluation of Drought Tolerance Indices for Screening Some of Super Sweet Maize (Zea mays L. var. saccharata) Inbred Lines

Drought is the most common cause of severe crop production shortage in developing countries, and global warming is predicted to further exacerbate drought’s impact. The present study investigates the efficiency of drought tolerance indices in classifying 24 super sweet maize inbred lines with the highest yield potential and drought tolerance performance. The experiment was conducted as a completely randomized block design with 4 replications. Twenty indices were compared based on grain yield, under two environments (Non-Stressed and Drought-Stress condition) during the 2018 growing season. All drought indices revealed significant differences among inbred lines, except GM. Results in ranking method, indicate that STI, GMP, MP, HARM, MRP, REI and RDY are suitable indicators because of positive correlations among each other and also the highest correlation with grain yield (GY) in both environments. Cluster analysis and threedimensional plots, showed inbred lines with the highest tolerance to drought, in both conditions. The first three principle components (PCs) explained 96.34% of total variation and the PC1 can be nominated as a potentially stable yield. The Biplot diagram based on PCs, and drought tolerance indices showed that MP, GMP, STI, HARM, MRP, REI, MSTIK1, MSTIK2 and YI were the best indices for screening tolerant inbred lines such as MCH87002/19-1, MPA90010/51-1 and MSH90011/82-1.

Evaluation of drought tolerance indices for identification of drought tolerant and susceptible genotypes in wheat (Triticum aestivum L.)

This experiment was designed to identify the drought tolerant and susceptible genotypes in wheat genotypes collected from different wheat breeding centre of India. The experiment was conducted in alpha lattice design under stress and non-stress conditions to estimate the drought tolerance indices. Nine drought tolerance viz., Tolerance index (TOL), Mean productivity (MP), Harmonic mean (HM), Stress susceptibility index (SSI), Yield index (YI), Relative drought index (RDI), Grain yield per plant under potential condition (Yp ), Grain yield per plant under stress condition (Ys) were calculated. The indices were estimated based on grain yield under stress condition (Ys) and non-stress condition (Yp). These indices were subjected for analysis of variance, correlation coefficient analysis, cluster analysis. SSI is suggested as useful indicator for wheat breeding where the stress is severe; while MP, TOL and HM are suggested if the stress is less severe. Based on grain yield per plant twenty-one tolerant genotypes and eleven susceptible genotypes were identified. Identified tolerant and susceptible genotypes can be used for the development of mapping populations to identify QTLs for drought tolerance in wheat (Triticum aestivum L.).

Effect of Exogenously Applied Jasmonic Acid and Kinetin on Drought Tolerance of Wheat Cultivars Based on Morpho-Physiological Evaluation

The population acceleration and better lifestyle submit new challenges for wheat researchers to breed wheat (Triticum sativum) cultivars with upgraded yield, quality, and resistance against abiotic stresses such as drought, so exploiting all available natural relatives of cultivated wheat and introducing even sensitive ones may be a useful approach to save time and efforts. Normally, the seedling stage is highly drought vulnerable, but for sensitive cultivars, the situation is more frustrating. We examine the potentiality of two regulating hormones in the upregulation of two wheat cultivars varying in their drought susceptibility at the seedling stage comparatively evaluated by morpho-physiological traits as indicators of drought tolerance. All the studied traits revealed cultivar-dependent variation in response to water deficit where cv. Sids 1 was tolerant and cv. Beni-suef 5 was sensitive. Shoot/root ratio, total water content, total dry weight, chlorophyll stability, total osmotic potential, osmoregulatory components, viz., soluble carbohydrates, soluble proteins and proline, membrane damage trait in terms of LOX, antioxidant defense system enzymatically in terms of APX, CAT, POD, SOD, and total antioxidant as drought tolerance indicators were the troubling shot due to water shortage in both cultivars. The damaging impacts of water deficit on these traits were conceived for sensitive cultivar compared with the tolerant one. Exogenous application of jasmonic acid (JA) or kinetin (K) efficiently conferred drought tolerance to sensitive cultivar to withstand harsh conditions in earlier stages and to perform comparably with tolerant ones. Applied hormones prompted unequivocal inversion from a state of downregulation to upregulation regarding all drought tolerance traits via reallocation of photoassimilates to vegetative sinks, thus promoting growth, increasing the accumulation of some osmoregulation compounds and thus increased tissue vigor and regulated the activity of antioxidant enzymes as well as morphological modulation attained by the restoration of shoot/root ratio. The results would promisingly be supportive of research programs seeking to develop anti-drought stress practices for sensitive wheat cultivars.

How does water and salt stress affect the germination and initial growth of Brazilian soya bean cultivars?

AbstractThe effects of water and salt stress on rate of germination and seedling growth were investigated under laboratory conditions in 46 soya bean genotypes from Central‐West region of Brazil to verify how these stresses may limit crop establishment during the initial growth stage and also to identify the most tolerant genotypes to drought and salinity. Mild water and salt stresses were imposed by seed exposure to –0.20 MPa iso‐osmotic solutions with polyethylene glycol—PEG 6000 (119.57 g/L) or NaCl (2.357 g/L) for 12 days at 25°C. The germination percentage, seedling length and seedling dry matter were measured, and then, salt or drought tolerance indexes were calculated. The “NS 5909 RG,” “NS 7000 IPRO,” “NS 7338IPRO,” “FPS Solimões RR,” “NS 5151 IPRO,” “SYN 13610 IPRO,” “LG 60177 IPRO,” “NS 6909 IPRO” and “BMX Desafio RR” were identified as the most drought‐tolerant genotypes, whereas under salinity conditions, the genotypes “5D 615 RR,” “BMX Desafio RR,” “5D 6215 IPRO” and “BMX Ponta IPRO” were identified as tolerant. The “BMX Desafio RR” is the genotype most adapted to both stress conditions and, therefore, should be used under conditions of water shortage and excess salt in the soil at sowing time.

Assessment of leaf rolling role in maintaining agrophysiological performances of Moroccan durum wheat cultivars under water deficit conditions

Water deficit is the most severe abiotic stress that wheat crop endures in arid and semi-arid areas. Some cereal genotypes use leaf rolling as an avoidance strategy to water stress. This ability allows the plant to limit both the amount of light energy received and water losses. The objective of this study is to study the use of leaf rolling in wheat as an indicator of drought tolerance. Eleven durum wheat (Triticum durum Desf.) varieties were grown in the field and evaluated for grain yield (GY), stomatal conductance (gs), chlorophyll fluorescence (Fv/Fm) and leaf-rolling capacity under drought. Results showed significant differences between all of the studied varieties for their ability to adapt to drought. High-leaf rolling varieties (2777 and Irden) showed better performances under water deficit by expressing high values of Fv/Fm (0.791 and 0.731) and GY (30.1 and 30.5 g per plant) respectively. Varieties exhibiting a weak leaf rolling showed the highest reductions indicating strong sensitivity to water stress. Significant positive correlations have been brought out between leaf rolling and Fv/Fm and GY. A significant negative correlation has also been noted between leaf rolling and SC. These findings confirm that leaf rolling may be considered as a good morphological indicator for drought tolerance in durum wheat.

Characterization of the Role of SPL9 in Drought Stress Tolerance in Medicago sativa

Extreme environmental conditions, such as drought, are expected to increase in frequency and severity due to climate change, leading to substantial deficiencies in crop yield and quality. Medicago sativa (alfalfa) is an important crop that is relied upon as a staple source of forage in ruminant feed. Despite its economic importance, alfalfa production is constrained by abiotic stress, including drought. In this report, we investigate the role of Squamosa Promoter Binding Protein-Like 9 (SPL9), a target of miR156, in drought tolerance. Transgenic alfalfa plants with RNAi-silenced MsSPL9 (SPL9-RNAi) were compared to wild-type (WT) alfalfa for phenotypic changes and drought tolerance indicators. In SPL9-RNAi plants, both stem thickness and plant height were reduced in two- and six-month-old alfalfa, respectively; however, yield was unaffected. SPL9-RNAi plants showed less leaf senescence and had augmented relative water content under drought conditions, indicating that SPL9-RNAi plants had greater drought tolerance potential than WT plants. Interestingly, SPL9-RNAi plants accumulated more stress-alleviating anthocyanin compared to WT under both drought and well-watered control conditions, suggesting that MsSPL9 may contribute to drought tolerance in alfalfa, at least in part, by regulating anthocyanin biosynthesis. The results suggest that targeting MsSPL9 is a suitable means for improving alfalfa resilience towards drought conditions.

Evaluation of drought tolerance indices for barley landraces under irrigated and dry conditions

Barley cultivation for drought areas requires reliable assessment of drought tolerance variability among the breeding germplasms. Hence, 121 barley landraces, advanced breeding lines and varieties were evaluated under both moisture non-stress and stress field conditions using a lattice square (11×11) design with two replications for each set of trials. Twelve drought tolerance indices (SSI, TOL, MP, GMP, STI, YI, YSI, HM, SDI, DI, RDI and SSPI) were used based on grain yield under normal (Yp) and drought (Ys) conditions. Analysis of variance showed a significant genetic variation among genotypes for all indices with the exception of TOL and SSPI indices. Yp had a very strong association with Ys (r=0.92**) that indicates high yield potential under non-stress can predict better yield under stress conditions. Yp and Ys were positively and significantly correlated with MP, GMP, STI, YI, HM and DI indices, whereas they were negatively correlated with SSI and SDI. In principal component analysis (PCA), the first PC explained 64% of total variation with Yp, Ys, MP, GMP, STI, YI, HM and DI. The second PC explained 35.6% of the total variation and had positive correlation with SSI, TOL, SDI and SSPI. It can be concluded that MP, GMP, STI, YI, HM and DI indices with the most positive and significant correlation with yield at both non-stress and stress environments would be better indices to screen barley genotypes, although none of the indices could undoubtedly identify high yield genotypes under both conditions.

English

Drought stress is among the most important abiotic factors that contribute to the significant yield reduction of common bean (Phaseolus vulgaris L.). Due to unreliable and poor distribution of rainfall, drought tolerance has become the important train in common bean in bean growing areas. The objective of this study was to evaluate 16 common bean genotypes for drought tolerance under three moisture regimes and identify genotypes with specific traits that improved tolerance to drought that could be recommended for released and become useful parents in the breeding programs. The experiment was conducted in Maruku, Bukoba under screen- house. Based on the drought stress indices which includes drought tolerance index (DTI), Harvest Index (HI) SMC 162, DAB 602, SSIN 1128, DAB 378, DAB 362 and SMR 101 had performed better than other tested genotypes. Also, the results showed that genotypes DAB 582, SRC 59, DAB 602, SSIN 1240, SMC 24, SMR 101 and DAB 362 were drought tolerant with lower and high value of the DSI and YSI respectively. Therefore, the later genotypes can be used in the future breeding programs as the parent for drought tolerance and also can used as a new varieties by farmers. Key words: Moisture stress, common bean, seed yield, drought.  

Drought tolerance increases with seed size in a semiarid grassland from southern Mexico

Due to increased reserves available to face adverse conditions, drought tolerance should increase with seed size. This has been confirmed in the laboratory, but under field conditions the pattern has not yet been found. We tested whether drought tolerance increases with seed size under field conditions in a semiarid grassland. We recorded the performance (germination, survival, and growth) of 12 species with different-sized seeds sown under conditions associated with hydric stress: along a natural stress gradient related to soil depth, and under experimentally manipulated irradiance levels that affected evaporation and thus soil humidity. We estimated drought tolerance indices for each performance metric, as well as a multivariate tolerance index that integrated the different components of performance. Each index was regressed on seed size accounting for phylogenetic effects. Seed size had little effect on individual metrics, but the joint evidence from all tests revealed a clear positive correlation with seed size. The multivariate tolerance index also increased with seed size, confirming the expected relationship. This suggests that comprehensive measures encompassing the whole life cycle may be required to characterize drought tolerance properly and may explain why this pattern has remained elusive in most studies. Also, we used a narrow range of seed sizes, so there is the possibility that the relationship between seed size and tolerance holds only for small-seeded species.

Evaluation of Drought Tolerance Indices for Selection of Superior Genotypes in Black Cumin (Nigella sativa L.)

Evaluation of Drought Tolerance Indices for Selection of Superior Genotypes in Black Cumin (Nigella sativa L.)

Selection of drought tolerant genotypes in groundnut (Arachis hypogaea L.) using indices

A study was carried out to evaluate the effect of drought stress on pod yield and other traits of groundnut genotypes to select the ten best performing genotypes using indices. Ninety six genotypes including 90 F2:3 progenies, 4 parents and 2 checks were planted under well-watered (WW) and water-stressed (WS) conditions at the International Crops Research Institute for the Semi-Arid Tropics ICRISAT, Mali. Six selection indices including mean productivity (MP), tolerance (TOL), geometric mean productivity (GMP), stress tolerance index (STI), drought tolerance index (DTI) and reduction (%) (RED) were used. The indices were adjusted based on pod yield under WW and WS conditions. High DTI, STI, MP, and GMP values under both well-watered and water-stressed conditions were more effective in identifying high yielding cultivars under water limited conditions. Based on these indices, the F2:3 progenies ICGV-IS 13012F2-B1-297, ICGV-IS 13012F2-B1-40, ICGV-IS 13005F2-B1-46, ICGV-IS 13005F2-B1-252, ICGV-IS 13012F2-B1-29, ICGV-IS 13005F2-B1-205, ICGV-IS 13005F2-B1-287, ICGV-IS 13012F2-B1-525, ICGV-IS 13012F2-B1-576 and ICGV-IS 13005F2-B1-91 were identified as the most drought tolerant genotypes with high yield stability in the well-watered and drought stress conditions. The indices STI, MP and GMP were positively correlated with pod yield under WW and WS conditions and breeding for drought tolerance. Key words: Groundnut, breeding, selection indices, drought stress.

Grain yield and drought tolerance indices of maize hybrids

Drought is one of the major abiotic stress factors limiting crops production in Oltenia area, Romania. In order to study the response of six maize hybrids to drought stress, the trials were conducted in research field of ARDS Simnic – Craiova, during 2017-2018 (non-stressed conditions) and 2018-2019 (drought stress). Six tolerance indices including: abiotic tolerance index (ATI), stress susceptibility percentage index (SSPI), Stress tolerance index (STI), mean productivity (MP), relative drought index (RDI) and golden mean (GM), were utilized on the basis of grain yield. Results from analysis of variance showed that there is a significant difference in 1% of probability level among hybrids in terms of grain yield and tolerance indices. The yield in non-stress conditions (Yp) showed significant positive correlations with ATI, SSPI, STI and MP, and negative correlation with RDI and GM. The yield in drought conditions (Ys) showed significant positive correlation with RDI and GM, and negative correlation with ATI and SSPI. None of the tolerance indices used could identify the high yielding hybrids under drought and non-stress conditions. Based on the ranking method, the hybrids ‘Felix’ and ‘P 9903’ were the most droughts tolerant. Therefore, they hybrids are recommended to be grown under drought prone areas and to be used as parents for breeding of drought tolerance in other cultivars.

Metal-Based Nanoparticles Enhance Drought Tolerance in Soybean

Drought is a major abiotic stress that negatively impacts plant growth and crop production. Among various techniques used to alleviate drought stress in plants, nanoparticle application is considered to be effective and promising. In this study, the responses of plants treated with iron, copper, cobalt, and zinc oxide nanoparticles (NPs) were analyzed in soybean under drought-induced conditions. The obtained results indicated that these metal-based NPs supported the drought tolerance of NP-treated plants. The desired physiological traits, viz., relative water content, drought tolerance index, and biomass reduction rate, were significantly improved, especially in iron NP-treated plants. At the molecular level, quantitative PCR analysis of several drought-responsive genes revealed a gene-, tissue-, and NP-dependent upregulation of gene expression. Iron NP treatment promoted the expression of all tested genes in roots; additionally, the expression of three drought-responsive genes increased in leaves of all NP-treated plants, while the expression of GmERD1 (Early Responsive to Dehydration 1) was induced in both roots and shoots under the four NP treatments tested. Our findings suggest that NP application can improve drought tolerance of soybean plants by triggering drought-associated gene expression.

QTL mapping of drought tolerance traits in soybean with SLAF sequencing

Drought stress is an important factor affecting soybean yield. Improving drought tolerance of soybean varieties can increase yield and yield stability when the stress occurs. Identifying QTL related to drought tolerance using molecular marker-assisted selection is able to facilitate the development of drought-tolerant soybean varieties. In this study, we used a high-yielding and drought-sensitive cultivar ‘Zhonghuang 35’ and a drought-tolerant cultivar ‘Jindou 21’ to establish F6:9 recombinant inbred lines. We constructed a high-density genetic map using specific locus amplified fragment sequencing (SLAF-Seq) technology. The genetic map contained 8078 SLAF markers distributing across 20 soybean chromosomes with a total genetic distance of 3780.98 cM and an average genetic distance of 0.59 cM between adjacent markers. Two treatments (irrigation and drought) were used in the field tests, the Additive-Inclusive Composite Interval Mapping (ICIM-ADD) was used to call QTL, and plant height and seed weight per plant were used as the indicators of drought tolerance. We identified a total of 23 QTL related to drought tolerance. Among them, seven QTL (qPH2, qPH6, qPH7, qPH17, qPH19-1, qPH19-2, and qPH19-3) on chromosomes 2, 6, 7, 17, and 19 were related to plant height, and five QTL (qSWPP2, qSWPP6, qSWPP13, qSWPP17, and qSWPP19) on chromosomes 2, 6, 13, 17, and 19 were related to seed weight and could be considered as the major QTL. In addition, three common QTL (qPH6/qSWPP6, qPH17/qSWPP17, and qPH19-3/qSWPP19) for both plant height and seed weight per plant were located in the same genomic regions on the same chromosomes. Three (qPH2, qPH17, and qPH19-2) and four novel QTL (qSWPP2, qSWPP13, qSWPP17, and qSWPP19) were identified for plant height and seed weight per plant, respectively. Two pairs of QTL (qPH2/qSWPP2 and qPH17/qSWPP17) were also common for both plant height and seed weight per plant. These QTL and closely linked SLAF markers could be used to accelerate breeding for drought tolerant cultivars via MAS.

Evaluation of bread wheat (Triticum aestivum L.) genotypes for yield and related traits under drought stress conditions

ABSTRACT Drought is a major factor threatening crop production worldwide. Developing wheat varieties that are adapted to drought prone environments is a sustainable strategy to improve wheat production and productivity. The aim of this study was to evaluate and select bread wheat genotypes for yield and yield components, and for stability under drought stress and non-stress conditions. One hundred and twenty genotypes were evaluated at five test sites in the 2018/19 cropping season using a 10 x 12 alpha lattice design with two replicates. The level of drought stress was imposed using different sowing dates (early planting representing non-stressed, while late planting as drought stressed conditions) following the onset of the main rain at each site. Grain yield and yield components were recorded, and drought indices were calculated for each genotype. Among the drought tolerance indices, GMP, MP, HM, STI and YI were found to be the most suitable for predicting drought tolerance because they had significant and positive correlations with yield under drought stress and non-stress conditions. Rank sum analysis identified the most drought tolerant genotypes as ‘YS-34', ‘YS-85' and ‘YS-82’. The selected wheat genotypes are useful genetic resources for future drought tolerance breeding programmes in Ethiopia or similar agro-ecologies.

Índices de seleção para identificar cultivares de soja tolerantes à seca

A ocorrência de deficiência hídrica é um dos estresses ambientais que mais limitam a produtividade da cultura da soja. Estudos que buscam identificar cultivares de soja com maior tolerância à seca são importantes para a produção agrícola. Este estudo foi realizado com a propósito de avaliar a resposta de 22 cultivares de soja cultivados em condições ambientais adversas (sistema irrigado e sequeiro), visando determinar os melhores índices de seleção para identificar os cultivares de soja tolerantes à seca. Foram conduzidos dois experimentos em condições de campo no município de Cassilândia (MS) durante a safra de 2018/2019, um em condições de sequeiro com ocorrência de deficiência hídrica e outro em sistema de irrigação com pivô central. Utilizou-se o delineamento experimental de blocos casualizados, em esquema fatorial 2 × 22 com três repetições. Os tratamentos foram constituídos por duas condições de cultivo (sistema irrigado e sequeiro) e por 22 cultivares de soja. A partir dos dados da produtividade de grãos nos sistemas de cultivo irrigado e de sequeiro, foram estimados 12 índices de tolerância à seca. A identificação dos cultivares de soja tolerantes e/ou suscetíveis à restrição hídrica foi realizada utilizando-se diferentes métodos de análises multivariadas (método do ranqueamento, análise de agrupamentos hierárquico e análise de componentes principais). Os cultivares de soja 98R35 IRPO, RK 8317 IPRO e RK 8115 IPRO foram classificados com maior tolerância à seca, e por isso são os cultivares mais indicados para serem cultivadas em regiões do Cerrado com ocorrência de restrição hídrica. Por outro lado, os cultivares TMG 7067 IPRO, M 5917 IPR, RK 6719 IPRO foram classificados com maior susceptibilidade à restrição hídrica, e não devem ser recomendados para o cultivo na região de Cassilândia (MS) em condições de sequeiro em época com alta probabilidade de ocorrência de deficiência hídrica. Os índices de tolerância MP, STI, GMP e HM foram os mais indicados para identificar os cultivares de soja com maior tolerância à seca e com alto potencial de rendimento de grãos em sistemas de cultivo irrigado e de sequeiro na região de Cassilândia, Estado de Mato Grosso do Sul.

Screening for Drought Tolerance in Maize (Zea mays L.) Germplasm Using Germination and Seedling Traits under Simulated Drought Conditions.

Maize is known to be susceptible to drought stress, which negatively affects vegetative growth and biomass production, as well as the formation of reproductive organs and yield parameters. In this study, 27 responsive traits of germination (G) and seedlings growth were evaluated for 40 accessions of the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) germplasm collection, under no stress and simulated drought stress treatments by 10%, 15%, and 20% of polyethylene glycol (PEG). The three treatments significantly reduced G% and retarded seedlings growth, particularly the 15% and 20% PEG treatments; these two treatments also resulted in a significant increase of abnormal seedlings (AS). The heritability (H2) and correlations of the traits were estimated, and drought tolerance indices (DTIs) were calculated for traits and accessions. The H2 of G% values were reduced, and H2 for AS% increased as the PEG stress increased. Positive correlations were found between most trait pairs, particularly shoot and root traits, with 48 highly significant correlations under no stress and 25 highly significant correlations under the 10% PEG treatments, particularly for shoot and root traits. The medium to high heritability of shoot and root seedling traits provides a sound basis for further genetic analyses. PCA analysis clearly grouped accessions with high DTIs together and the accessions with low DTIs together, indicating that the DTI indicates the stress tolerance level of maize germplasm. However, the resemblance in DTI values does not clearly reflect the origin or taxonomic assignments to subspecies and varieties of the examined accessions.