Drought Tolerant Bread Wheat Genotypes Research Articles

Screening drought-tolerant bread wheat genotypes using yield-based stress indices

Screening drought-tolerant bread wheat genotypes using yield-based stress indices

Evaluation of bread wheat (Triticum aestivum L.) genotypes for drought tolerance using morpho-physiological traits under drought-stressed and well-watered conditions.

Increasing frequency of drought spells occasioned by changing climatic conditions, coupled with rise in demand for bread wheat, calls for the development of high yielding drought resilient genotypes to enhance bread wheat production in areas with moisture deficit. This study was designed to identify and select drought-tolerant bread wheat genotypes using morpho-physiological traits. One hundred and ninety-six bread wheat genotypes were evaluated in greenhouse and field experiments, under well-watered (80% of field capacity) and drought-stressed (35% of field capacity) conditions, for two years. Data were collected on five morphological traits (flag leaf size, flag leaf angle, flag leaf rolling, leaf waxiness and resistance to diseases) and 14 physiological traits. Relative water content (RWC), Excised leaf water retention (ELWR), Relative water loss (RWL), Leaf membrane stability index (LMSI), as well as Canopy temperature depression (CTD) at heading (CTDH), anthesis (CTDA), milking (CTDM), dough stage (CTDD) and ripening (CTDR) were estimated. Similarly, leaf chlorophyll content (SPAD reading) was recorded at heading (SPADH), anthesis (SPADA), milking (SPADM), dough stage (SPADD), and ripening (SPADR). Significant (p<0.01) genotypic differences were found for the traits under both well-watered and drought-stressed conditions. Associations of RWL with SPADH, SPADA, SPADM, SPADD and SPADR were significant (p<0.01) and negative under both watering regimes. The first three principal components accounted for 92.0% and 88.4% of the total variation under well-watered and drought-stressed conditions, respectively and comprised all the traits. The traits CTDD, CTDM, CTDR, SPADH, SPADA, SPADM, SPADD and SPADR with genotypes Alidoro, ET-13A2, Kingbird, Tsehay, ETBW 8816, ETBW 9027, ETBW9402, ETBW 8394 and ETBW 8725 were associated under both conditions. Genotypes with narrow flag leaves, erect flag leaf angles, fully rolled flag leaves, heavily waxed leaves, and resistant to disease manifested tolerance to drought stress. The identified traits and genotypes could be exploited in future breeding programmes for the development of bread wheat genotypes with tolerance to drought.

Combining Ability of Drought-Tolerant Bread Wheat Genotypes for Agronomic and Physiological Traits

A combining-ability analysis is key to select desirable parents and progenies with enhanced response to selection under water-limited environments. The objective of this study was to determine combining ability for agronomic and physiological traits among distantly related drought-tolerant bread wheat (Triticum aestivum L.) genotypes under well-watered (WW) and terminal-drought (TD) conditions to determine their genetic merit for breeding. Ten heat- and drought-tolerant wheat genotypes were crossed in a half-diallel mating design to generate 45 F1s, which were evaluated under WW and TD moisture regimes in rainout shelter (RS) and greenhouse (GH) environments. The following agronomic traits were assessed: days to 50% maturity (DTM), plant height (PH), spike length (SL), number of productive tillers (TN), spikelets number per spike (SPS), number of grains per spike (GPS), grain yield (GY) and thousand-kernel weight (TKW); and physiological traits (stomatal conductance (SC) and chlorophyll content index (CCI)). Variances attributable to general combining ability (GCA) and specific combining ability (SCA) were significant (p &lt; 0.05) for GY, DTM, PH, SL, SPS, GPS, TKW and CCI. The parental genotypes LM72, LM81 and LM95 with positive and significant GCA effects on GY were selected to make crosses to develop high-yielding wheat genotypes for water-limited environments. Crosses LM71 × LM02, LM71 × LM81, LM82 × LM02, LM82 × LM81, LM22 × LM100, LM22 × LM81 and LM95 × LM22 were selected with positive and significant SCA effects for GY. The selected parents and crosses are valuable genetic resources for breeding and genetic advancement.

Assessment of Genetic Diversity in Durum and Bread Wheat Genotypes Based on Drought Tolerance and SSR Markers

Six durum and twelve bread wheat genotypes were evaluated under favorable and drought-stressed field conditions, and screened with thirty simple sequence repeats (SSR) markers. The traits studied were stomata frequency (STF), relative water content (RWC), flag leaf area (FLA), flag leaf weight (FLW), flag leaf dry matter content (FLD), chlorophyll a content (Chl.a), chlorophyll b content (Chl.b), grain yield/plant (GYP) and 1000-kerenl weight (TKW). Highly significant differences were observed among wheat genotypes for all the traits, indicating considerable genetic variation. Moderate to high broad-sense heritability estimates were observed for the studied traits. Under drought stress, GYP was positively correlated with RWC, FLA, FLW and TKW, whereas negatively correlated with STF. G3 (Svevo) and G6 (WK-12-1) were the most drought-tolerant durum wheat, whereas G11 (L.S-15) and G16 (SIDS-1) were the most drought-tolerant bread wheat genotypes. SSR markers analysis indicated considerable genetic variation between and within durum and bread wheat genotypes. The percentage of polymorphism ranged from 14.3% (Xgwm174-5D) to 100% (Xgwm294-2A and Xgwm573-7B), with an average of 61.4%. The polymorphism information content (PIC) ranged from 0.20 (Xwmc596-7A) to 0.48 (Xgwm294-2A), with an average of 0.33.The highest polymorphism (77.1%) was observed in the B genome followed by A (57.8%) and D (50.0%) genomes. Cluster analysis based on phenotypic data distinguished the most drought-tolerant genotypes (G6 and G11) from the remaining genotypes. Cluster analysis based on SSR markers distinguished durum from bread wheat genotypes. The study indicated that phenotypic data and SSR markers were effective in assessing the genetic diversity in the studied genotypes.

Genetic relationship among selected heat and drought tolerant bread wheat genotypes using SSR markers, agronomic traits and grain protein content

ABSTRACT Assessing the genetic variation and relationships present in crop germplasm is a pre-requisite for parental selection and breeding. The objective of this study was to determine the genetic relationships present among selected heat and drought tolerant wheat genotypes using simple sequence repeat (SSR) markers, agronomic traits and grain quality parameters to select desirable parents for breeding. Twenty-four agronomically selected wheat genotypes sourced from the International Maize and Wheat Improvement Centre (CIMMYT)’s heat and drought tolerance nursery and four local check varieties were genotyped using 12 selected polymorphic SSR markers. The test genotypes were phenotyped using yield and yield-component traits, and grain protein content (GPC) under non-stressed (NS) and drought-stressed (DS) conditions. Expected heterozygosity mean value of 0.58 indicated moderate genetic diversity for breeding. The studied wheat genotypes were delineated into six genetic groups using cluster analysis. Significant genotypic differences were observed for agronomic traits and GPC under NS and DS conditions. Genetically unrelated breeding parents including LM02, LM13, LM23, LM41, LM44, LM71, LM73 and LM75 were selected for population development and breeding for enhanced grain yield and protein content under heat and drought-stressed environments.

Screening of bread wheat (Triticum aestivum L.) genotypes under drought stress conditions using multivariate analysis

Drought is a serious global problem of agriculture. For this, an investigation was carried out with 25 wheat genotypes composed of cultivars and advanced lines to screen drought-tolerant bread wheat genotypes using multivariate analysis. The experiment was conducted in a split plot design with three replications and two treatments control and drought. The analysis of variance revealed significant differences among the genotypes and treatments for all the characters studied, viz. plant height, flag leaf collar height, flag leaf length, flag leaf breadth, chlorophyll a, chlorophyll b, proline content, number of tillers per plant, root fresh weight, shoot fresh weight and root–shoot ratio. High heritability was observed for all the traits except flag leaf length, flag leaf breadth and number of tillers per plant. Based on the genetic distances, all the 25 genotypes were grouped into three different clusters. In control conditions, cluster number I contained most tolerant genotypes and under drought conditions, cluster number III contained most drought-tolerant genotypes. In biplot, the genotypes SATYN-24, BARI Gom-24 and SATYN-2 contributed positively and correlated with number of tillers per plant, shoot fresh weight, flag leaf breadth, proline content and plant height under drought conditions. The drought susceptibility index (DSI) indicated that the genotypes BARI Gom-24 and SATYN-9 exhibited a highly drought-tolerant genotype in the present investigation. These genotypes might carry genes for drought tolerance and may be useful for further drought tolerance breeding.

Genotype-by-environment effects on grain quality among heat and drought tolerant bread wheat (Triticum aestivum L.) genotypes

ABSTRACT This study determined genotype-by-environment effect on grain quality among heat and drought tolerant bread wheat genotypes to select ideal genotypes for grain quality improvement. Gliadin (Gli), gluten (Glu), glutenin (Glut), gliadin: glutenin ratio (Gli: Glut ratio) and total protein content (TPC) were determined among 28 elite bread wheat genotypes under non-stressed and drought-stressed conditions. Additive main effect and multiplicative interaction and genotype and genotype-by-environment biplot were used for data analyses. Large genotypic effects were observed for Gli (55.42%), TPC (67.78%) and Gli: Glu ratio (49.77%), suggesting genotypic variation for these traits. High environmental influence of 89.65 and 89.06% were observed for Glu and Glut. Wheat genotypes LM03, LM22, LM23, LM41, LM44, LM60, LM62, LM71, LM73, LM71, LM85, LM90 and LM95 with high protein and protein-fractions and high levels of abiotic stress tolerance (i.e. heat and drought) were selected for breeding for high grain quality.

Grain quality of elite bread wheat genotypes under non-stress and drought-stress conditions

ABSTRACTGrain quality, including protein content, is a key determinant of marketability and end-user acceptance of bread wheat (Triticum aestivum L.). This study determined the grain quality of bread wheat genotypes under simulated terminal drought (TD) and well-watered (WW) conditions for selecting suitable genotypes for breeding. The amount of gliadin (Gli), gluten (Glu), glutenin (Glut), gliadin: glutenin ratio (Gli: Glut ratio) and total protein content (TPC) were determined in 24 elite heat- and drought-tolerant bread wheat genotypes sourced from the International Maize and Wheat Improvement Center (CIMMYT). The experiment was conducted under rainout shelter (RS) and glasshouse (GH) environments. Genotype-by-environment interaction was significant (p ≤ 0.001) for grain quality traits. Positive correlations were observed between Gli and Gli : Glut ratio (r = 0.97), and Glut and Glu (r = 0.97). The correlation between Glut and Gli : Glut ratio was negative (r = -0.58) under TD condition. Under TD condition and in RS, positive but relatively small correlations were found between TPC and Gli (r = 0.19), Glut (r = 0.16), Gli: Glu ratio (r = 0.04) and Glu (r = 0.22). The trend was similar under GH condition in TD where positive and low correlation values were detected between TPC and Gli (r = 0.19), Glut (r = 0.29), Gli: Glu ratio (r = 0.14) and Glu (r = 0.33). This suggested selection for higher TPC may result in limited improvement of protein-fractions. Heat- and drought-tolerant wheat genotypes, such as LM95, LM90, LM85, LM82, LM73, LM71, LM62, LM60, LM55, LM44, and LM41, with improved quality attributes, were identified for breeding and production.

Evaluation of Bread Wheat (&lt;i&gt;Triticum aestivum&lt;/i&gt; L.) Genotypes for Drought Tolerance through Selection Indices

The current study was planned to identify drought tolerant bread wheat genotypes based on physiological and yield traits. In this context, a set of 12 genotypes (Sarsabz, NIA-Sundar, NIA-Amber, Sassui, Khirman, Marvi-2000, NIA-Sarang, Kiran-95, NIA-Sunheri, Bhittai, Bathoor-08 and Tatara) were evaluated under normal and water stress conditions. Mean squares from analysis of variance exhibited that genotypes, treatments and genotype x treatment interaction showed significant differences (P&lt;0.05) for majority of the studied traits, indicating that there is significant variations are existed for physio-yield traits; therefore these genotypes may be preferred for further breeding programs in respect to drought stress. Regarding reduction percentage of genotypes under drought stress against normal water conditions, the minimum reduction was observed in Bathoor-08 for spike length and flag leaf area, Kiran-95 for grain yield plant, NIA-Sundar for seed index, Marvi-2000 for relative water content, Sarsabz for grains spike, whereas maximum but desirable reduction of stomatal dimension and density was displayed by Sarsabz and Tatara under water stress conditions, respectively. On the basis of drought tolerant indices, the genotypes Kiran-95, NIA-Sundar and Sarsabz showed lower values for tolerance index (TOL), trait stability index (TSI) and stress susceptibility (SSI), nevertheless it is believed that lower values of these indices show the less reduction in yield and its related traits due to water stress conditions hence can be tagged as tolerant genotypes for drought. Correlation results revealed that MP, SSI, TOL and TSI indices were correlated with grain yield under two conditions and they can be the appropriate indices for screening wheat genotypes.

Genotype-by-environment interaction of elite heat and drought tolerant bread wheat (Triticum aestivum L.) genotypes under non-stressed and drought-stressed conditions

ABSTRACTThe selection of relatively high and stable yielding genotypes is key in wheat breeding programs to improve yield performance under heat and drought-stressed environments. This study determined grain yield response and stability among elite heat and drought tolerant bread wheat genotypes under simulated drought-stressed (DS) and non-stressed (NS) environments to select promising parents for breeding. Twenty-four elite bread wheat genotypes selected from the International Maize and Wheat Improvement Centre (CIMMYT) drought and heat tolerant nursery were assessed under NS and DS conditions using a 7 × 4 alpha-lattice design under rainout shelter (RS) and glasshouse (GH) environments. Grain yield data was subjected to analysis of variance (ANOVA), the additive main effect and multiplicative interaction (AMMI) and genotype and genotype-by-environment (GGE) biplot analyses. ANOVA and AMMI revealed highly significant (p ≤ 0.001) differences among test genotypes (G), environments (E) and G × E interaction effects suggesting differential responses for selection. The GGE biplot explained 83.76% of total variation and aided in selection of high-yielding and stable heat and drought tolerant wheat genotypes such as LM13, LM22, LM95 and LM100. These selections are recommended for breeding for yield gains under heat and drought-stressed environments.

Selection Criteria for Drought-Tolerant Bread Wheat Genotypes at Seedling Stage

Diminishing water resources as a result of excessive use of water for irrigation and climate change posture a severe global threat to food security. Herein, an experiment was conducted to determine the selection criteria for drought-tolerant bread wheat genotypes at the seedling stage using morphological and photosynthetic pigmentation-related traits. A panel of 105 wheat landraces, historical Pakistani varieties, and advance breeding lines were evaluated under normal and drought stress using factorial completely randomized design. The root length, fresh weight, dry weight, cell membrane thermo-stability, and chlorophyll b were positively correlated among themselves under both normal and stress conditions. Hence, selection of any one of these traits enhances the performance of other traits. The shoot length was non-significant and negatively associated with all other studied characters except relative water content. The results suggested that selection for shoot length could not improve genetic gain for drought tolerance. Out of 10 principal components (PCs), the first three PCs were showed significant genetic variation under both conditions. The first three PCs showed 74.6% and 76% cumulative genetic variation under normal and drought conditions, respectively. Based on PCA, 10 drought-tolerant and five drought-susceptible genotypes were identified. Overall results suggested that selection for root length, fresh weight, dry weight, cell membrane thermo-stability, and chlorophyll b at the seedling stage would improve genetic gain for drought tolerance. The outperforming genotypes under drought stress conditions can be useful in future wheat breeding programs, and early selection for the traits recommended in this study will be effective for developing high-yielding and drought-tolerant wheat varieties.

Assessment of agro-physiological traits for salt tolerance in drought-tolerant wheat genotypes

Salt stress is one of the major constraints for wheat cultivation in Iran and leads to a considerable loss in crop yield each year. In high salinity soils, the reduced osmotic potential of soil solutes may cause physiological drought. In this study the salt tolerance of different drought-tolerant bread wheat genotypes were studied by examining various agronomic and physiological traits, including Na + and K + concentrations, the Na + /K + ratio in leaf and spike, shoot dry weight, leaf greenness, stomatal conductance, leaf area, osmotic potential, relative water content (RWC) and grain yield. Two pot experiments were conducted using a completely randomized design with three replications. Wheat genotypes were grown in pots and irrigated either with tap water (EC=0.5 dSm -1 ) or saline water (EC≈18 dsm -1 ) as control and salt stress treatments, respectively. Significant differences were observed in all measured traits between control and stress treatments except for the spike potassium concentration. Differences between genotypes were significant for all traits except for RWC and osmotic potential. Among the different genotypes, one drought-tolerant genotype appeared salt tolerant, three were semi-salt-tolerant, one drought-sensitive genotype appeared semi-salt-sensitive, and two drought-tolerant genotypes appeared salt-sensitive and semi-salt-sensitive. This study shows that drought tolerance does not necessarily lead to salt tolerance. Some physiological traits including Na + content, leaf area, SPAD number, stomatal conductance and shoot dry weight, which are significantly correlated with grain yield and show remarkable variations among wheat genotypes, may be useful parameters for measuring the responses of other wheat genotypes to high-salinity soils in the field.

Evaluation of some physiological traits as indicators of drought tolerance in bread wheat genotypes

The objective of this work was to evaluate the ability of some physiological traits to identify drought-tolerant bread wheat genotypes. To this end, twenty bread wheat genotypes were assessed under post anthesis drought stress (rain-fed) and irrigated conditions. The Stress Tolerance Index (STI) was used as a measure of drought tolerance. Relationships between STI and Cell Membrane Stability (CMS), Proline Concentration (PC), Relative Water Content (RWC), Chlorophyll a/b Ratio (Chl a/b), Relative Chlorophyll Content (RCC), Excised Leaf Water Retention (ELWR), and Relative Water Loss (RWL) were determined in order to find out whether these physiological traits could be used as the indicators of drought tolerance. The results showed that ELWR, RWL, and CMS could be considered as reliable indicators in screening wheat genotypes for drought tolerance.

Selection of Drought Tolerant Bread Wheat Genotypes using Root Characteristics at Seedling Stage

The following study was carried out to determine the suitability of the box technique for screening wheat for drought tolerance and the general characteristics of wheat seedlings related to resistance to drought. Three commercial wheat varieties, Duma, Kenya Mbweha and Mbuni which are tolerant, moderately tolerant, and susceptible respectively, were screened together with 3 lines R830, R831 and R748 which have been identified to show drought tolerance characters. The 6 were planted in boxes measuring 0.03m x 1m x 0.3m after this being determined as the best size for screening wheat seedlings. The rooting pattern of these genotypes was studied. Generally, drought resistant genotypes had more roots in the crown region with nodal and seminal roots concentrated between the soil surface and 70 cm deep. Susceptible genotypes had fewer roots in the crown region. Drought tolerant varieties were not necessarily deep rooted. Drought resistant genotypes had high absorptive surface area of up to 9.6 mm 3 while susceptible ones had as low as 3.5 mm 3 . Root depth, total root length, relative absorptive surface area, number of roots, root spread, length of the longest root and root concentration were significantly different (P Int. J. Agric. Rural Dev. , 2003, 4: 9-15