Selection Criteria For Drought Tolerance Research Articles

Determination of Morpho-Physiological Traits for Assessing Drought Tolerance in Sugarcane.

Drought is a significant constraint to sugarcane productivity. Therefore, understanding how different varieties of sugarcane respond to drought stress can facilitate breeding programs and set up criteria for selecting drought-tolerant varieties. In the present study, we examined eight morpho-physiological traits to distinguish 40 sugarcane genotypes categorized into four groups based on significant differences in cane yield under non-stressed conditions and reduction of cane yield under drought-stressed conditions. The study was conducted during the formative stage in a greenhouse, encompassing both control and drought conditions. Drought treatments resulted in significant changes and differences in the mean values of various morpho-physiological traits. The hierarchical clustering analysis, utilizing stay-green traits such as higher chlorophyll fluorescence ratio (Fv/Fm), leaf chlorophyll content (SPAD), leaf relative water content (RWC), and lower leaf rolling score (LR), leaf drying score (LD), and drought recovery score (DR), successfully grouped 40 sugarcane genotypes into four major clusters, similar to the previously categorized groups. Correlation analysis showed significant relationships among cane yield, reduction of cane yield under drought conditions, and the stay-green traits. Our results demonstrated that morpho-physiological traits contributing to the "stay-green" phenotypes could be useful as selection criteria for drought tolerance in sugarcane.

Genetic Variability Studies on Drought Tolerance using Agro-Morphological and Yield Contributing Traits in Rapeseed-Mustard

A study was conducted during rabi season (October-May), 2018−2019 at the Experimental Farm of Department of Genetics and Plant Breeding, CSK HPKV, Palampur (HP), India to develop reliable selection criteria for drought tolerance. 25 advanced breeding lines of different Brassica species were used to determine their mean performance, components of variability, heritability and genetic advance under moisture stress conditions created at rosette stage, flower initiation stage and siliqua formation stage using various agro-morphological and yield contributing traits. Sufficient genetic variability was found for almost all the characters except for 1000-seed weight under non-stress stage conditions. Estimates of parameters of variability revealed that phenotypic coefficients of variation were higher than their respective genotypic coefficients of variation. Under moisture stress conditions, high heritability coupled with high genetic advance was observed for number of secondary branches plant-1 in non-stress and all the moisture-stress stages. Siliqua formation stage was found most susceptible to moisture stress conditions which also led to maximum reduction in seed yield. Using drought susceptibility index, the genotypes HPBS-1 followed by HPKM-04-1 were found to be moderately drought tolerant as these exhibited the lowest drought susceptibility index value in Stage-I and Stage-III while in Stage-II, RCC-4×Varuna followed by HPBS-1 exhibited lowest drought susceptibility index value. Therefore, systematic characterization of differences in physiological responses to drought stress among elite lines is helpful in understanding mechanisms of drought resistance. Hence, traits like primary branches plant-1, secondary branches plant-1, siliquae plant-1, seeds siliqua-1, seed yield plant-1 and 1000-seed weight can be further used in selection criteria for future breeding programme aimed for enhancing drought tolerance.

Increased significance of chickpea (Cicer arietinum L.) senescence trait under water-deficit environment

Characterizing stress–inducing trait(s) and deploying their genetic diversity are crucial for developing stress–tolerant cultivar(s). The study aimed to investigate the genotypic variations in chickpea senescence traits and their significance in yield sustainability under water–deficit stress conditions. Therefore, a panel of eighty–eight chickpea that differ in maturity duration [early–maturing (≤ 100 days) and late–maturing (> 110 days)], were grown under soil water deficit conditions. The parameters viz. days to onset of senescence (DTSI), senescence duration (SD), days to flowering (DF), reproductive period (RP), and days to maturity (DM) were recorded for each genotype and their relations with grain yield were evaluated. The parameter DTSI defines the earliness or delay in the onset of senescence; while SD represents the pace of senescence. Temporal dynamics of senescence were visually scored following a 0–10 scale. The trait senescence duration (SD) exhibited negative correlation with yield, being higher in the late maturing genotypes over the early maturing genotypes. The senescence index [SD/RP], which exhibited a higher genotypic variability over the parameter SD, was found to have a significant negative association with yield. While the index [DTSI/DM] exhibited a strong positive correlation with yield (p < 0.01) in both early and late maturing groups (p < 0.01). Multivariate regression analysis demonstrated that SD and cumulative degree–days of senescence period had a strong negative influence on chickpea yield under water–deficit conditions. Hence, the study suggested that delayed and faster senescence could serve as the selection criterion for drought tolerance in chickpea. The findings suggested that the indices [SD/RP] and [DTSI/DM] could be more realistic indicators when characterizing senescence of chickpea under water–deficit environments.

English

Durum wheat is an important staple food in Morocco. Wheat and barley are mostly grown in drought prone areas in this country. Drought is the most limiting factor under Mediterranean climate. Leaf rolling ability has been identified as a potential selection criterion for drought tolerance in cereals. The objective of this study is to test this hypothesis. The role of leaf rolling in water stress tolerance was assessed in eleven Moroccan wheat cultivars. Trials were conducted under greenhouse conditions and three watering regimes simulating different drought levels were applied. Leaf rolling, leaf area, leaf specific weight and relative water content were recorded. The results indicated that the studied cultivars have shown significant differences in their leaf rolling (LR) under water deficit. The varieties 2777 and Irden showed the highest LR scored under these constraints. The variety Marjana showed the lowest LR score and expressed no LR ability under non limited irrigation treatment. Strong correlation have been observed between LR and relative water content (RWC) (r=0.923), and negative correlation was observed between LR and leaf area (LA, r=-0.783). Cultivars with high LR scores showed their capacity to control the negative impacts of water stress by keeping their physiological traits to adequate levels in order to maintain the main physiological activities of the plants. This result showed the important role of LR in water stress tolerance in the studied durum wheat cultivars. Key words: Water stress, agro physiological traits, drought tolerance, leaf rolling, Morocco. &nbsp;

Screening of Worldwide Barley Collection for Drought Tolerance: The Assessment of Various Physiological Measures as the Selection Criteria.

Drought is a devastating environmental constraint affecting the agronomic production of barley. To facilitate the breeding process, abundant germplasm resources and reliable evaluation systems to identify the true drought-tolerant barley genotypes are needed. In this study, 237 cultivated and 190 wild barley genotypes, originating from 28 countries, were screened for drought tolerance under the conditions of both water deficit and polyethylene glycol (PEG)-simulated drought at seedling stage. Drought stress significantly reduced the plant growth of all barley genotypes, but no significant difference in drought-induced reduction in the performance of barley seedlings was observed under these two drought conditions. Both cultivated and wild barley subspecies displayed considerable genotypic variability in drought tolerance, which underpinned the identification of 18 genotypes contrasting in drought tolerance. A comparative analysis of drought effects on biomass, water relation, photosynthesis, and osmotic adjustment was undertaken using these contrasting barley genotypes, in order to verify the reliability of the screening and to obtain the credible traits as screening criteria of drought tolerance in barley. As expected, the selected drought-tolerant genotypes showed much less reduction in shoot biomass than drought-sensitive ones under water deficit, which was significantly positively correlated with the results of large-scale screening, confirming the reliability of the screening for drought tolerance under two drought conditions in this study. Likewise, the traits of water relation, photosynthetic activity, and osmotic adjustment differed greatly between the contrasting genotypes under water deficit stress, and they were highly correlated to the growth of barley seedlings, suggesting the potential of them to be the selection criteria for drought tolerance. The analysis of the variable importance of these traits in drought tolerance indicated that sap osmolality and relative water content in the youngest fully-expanded leaf are the suitable selection criteria of screening for drought tolerance in barley at seedling stage.

Selection Criteria and Selection Environment for Drought Tolerance of Egyptian Wheat (Triticum aestivum L.) Landraces

Strong correlations between wheat traits and drought tolerance (DT) associated with high heritability and high genetic advance from selection would allow plant breeder to use such traits as selection criteria. The objective of the present investigation was to determine the optimum selection criteria and selection environment for drought tolerance via estimation of correlation coefficients (r) among 13 agronomic, grain yield and quality traits and DT of 20 wheat landraces, broad-sense heritability (h2b) and genetic advance (GA) from selection for such traits under well-watered (WW) and water stressed (WS) environments. A two-year experiment was carried out using a split-plot design with four replications. Results concluded that the best selection criterion for drought tolerance in our study was grain yield/plant (GYPP), followed by a number of grains/spike (GPS), grain filling period (GFP), grain starch (GSC) and protein (GPC) content, plant height (PH) and days to maturity (DTM), since they showed high (r), high h2b and high GA estimates. The best selection environment was WW for days to anthesis, PH, spikes/plant, GPS, spikelets/spike, GYPP, GPC and WS for DTM, GFP, GSC and thousand-grain weight traits. This information could help future breeding programs in selection for improving drought tolerance of wheat.

Effect of PEG-induced drought stress on germination of ten chickpea (Cicer arietinum L.) genotypes

Chickpea (Cicer arietinum L.) is one of the most important legume crops worldwide, with its importance mainly relying on its high protein content. Chickpea productivity is strictly threatened by abiotic stresses, of which drought exerts the most crucial role in terms of growth inhibition and yield losses encountered. Given that germination is a critical stage that is negatively affected by drought, the aim of this study was to estimate the genotypic variability among ten chickpea genotypes and to determine the seed germination and seedling growth ability under drought stress conditions. Seeds were subjected to water stress by polyethylene glycol (PEG-6000) at five stress levels (0, 5, 10, 20, 30 and 50% PEG). Germination percentage, seed water content, seed water absorbance, root and shoot development and seedling vigour index were evaluated. The analyses revealed significant genetic variability in relation to genotypic performance under drought stress. Drought significantly affected germination as well as all other associated traits, with the effects of stress being analogous to the stress level applied. Findings point to the fact that seedling vigour index is a suitable selection criterion for drought tolerance as it allowed the classification of genotypes as tolerant, moderately tolerant, moderately susceptible and susceptible. Taken together, the commercial varieties ‘Thiva’, ‘Keryneia’ and ‘Gavdos’ as well as the landrace ‘Lemnos’ showed an increased drought tolerance at high stress level, indicating their possible exploitation as valuable genetic material for breeding programs or for commercial use.

Evaluation of physiological markers for assessing drought tolerance and yield potential in bread wheat.

Carbon isotope discrimination (Δ) has been recognized as a valuable phenotyping tool in wheat breeding. However, technical expertise and analysis cost restrict its large-scale use. We examined the associations of ash content (AC), minerals content (Ca, K, Mg, Fe and Mn) and leaf chlorophyll content (Chl) with grain Δ and grain yield (GY) to assess their potential as substitute to grain Δ. We evaluated 49 wheat genotypes under two water deficit regimes (W120 and W200) in a rain-out shelter. Leaf chlorophyll content (Chl) was strongly correlated with grain Δ and GY under moderate water deficit regime (W200). Significant and negative correlations (P < 0.01) of AC and potassium concentration (K) with grain Δ, and between AC and GY was observedunder both water regimes, while manganese concentration (Mn) was negatively correlated with grain Δ under W120 regime only and magnesium concentration (Mg) correlated negatively under the W200 regime only. Grain Δ was correlated (P < 0.01) positively with photosynthesis rate (A), stomatal conductance (gs) and GY, while correlated negatively (P < 0.01) with intrinsic water use efficiency (iWUE) under both water regimes. Results confirm the role of grain Δ as an indirect selection criterion for drought tolerance under a wide range of drought conditions. Additionally, Chl is the most suitable trait to predict yield under moderate water deficit conditions. AC and K concentration in grain proved potentially useful and economical alternative criterion to grain Δ in the evaluation of differences in yield potential and drought tolerance in wheat under drought.

Heritability and Correlations for Agronomic and Physiologic Traits of Maize under Deficit Irrigation at Two Growth Stages

Strong associations between agronomic and physiologic traits and drought tolerance, high heritability and high genetic advance for such traits would allow plant breeder to use such traits as selection criteria for selecting drought tolerant genotypes. The objectives of the present investigation were: (i) to explain the relationships between the drought tolerance index (DTI) and 14 agronomic and physiologic traits of 22 maize genotypes and (ii) to estimate the broad-sense heritability (h2b) and genetic advance (GA) from selection for such traits, in order to determine the selection criteria for DTI. A two-year experiment was carried out using a split plot experiment with three replications. The main plots were devoted to irrigation regimes, i.e. well watering (WW), water stress at flowering (WSF) and at grain filling (WSG), and sub plots to maize genotypes. It is evident from results that the best selection criteria for drought tolerance in our study were: 100-kernel weight (100KW) and chlorophyll concentration index (CCI) under WSF and WSG, anthesis-silking interval (ASI), upper stem diameter (SDU) and lower stem diameter (SDL) under WSF and kernels/row (KPR) and ear leaf area (ELA) under WSG, since they show high correlation (r) values with grain yield/plant (GYPP), high h2b and high GA estimates under the respective environments. Under well watering conditions, KPR, 100KW, CCI, and SDL traits showed high (r) values, high h2b and high GA estimates and therefore could be considered selection criteria for GYPP under non-stressed environment. The results concluded that predicted selection gain would be higher if selection was practiced under WW for lower values of days to silking and higher values of ears/plant, rows/ear, KPR, 100KW, SDU and SDL, under WSF for lower values of ASI and higher values of GYPP and under WSG for lower values of plant height, ear height, and barren stalks, and higher values of CCI and ELA.

Effect of moisture stress on growth and yield of cucumber genotypes

The experiment was conducted during spring-summer season with twenty five cucumber genotypessubjected to four levels of drought stress (control, 75%, 50% and 25% of recommended irrigation) in the openfield experiment using completely randomized design with three replications to assess the effects of droughton vegetative growth and fruit yield. Star flow meter instrument used to measure the amount of irrigation wateras calculated to induce an artificial drought stress levels on the plants. ANOVA revealed significant differences amongst genotypes and genotype × drought stress level interaction for all the traits indicating differential response of the genotypes. Decreased amount of water levels resulted in progressive reduction in number ofleaves (19.7, 15.3, 12.4 and 9.0), vine length (55.8, 55.4, 46.7 and 41.3 cm) and fruit yield per vine (0.982, 0.645, 0.546 and 0.487 kg), while increased in affected leaves at 18.8, 58.8, 67.2 and 84.6%, respectively in control(100%), 75%, 50% and 25% of recommended irrigation. Thus, these above phenotypic traits appeared to bepromising as selection criteria for drought tolerance at morphological level. As a result, the genotypes DGC-1and WBC-13 observed drought tolerant, whereas DGC-8 and GS-3 were drought susceptible.

Impact of Antioxidant Enzymes and Physiological Indices as Selection Criteria for Drought Tolerance in Sesame Populations

Impact of Antioxidant Enzymes and Physiological Indices as Selection Criteria for Drought Tolerance in Sesame Populations

Integrated selection criteria for drought tolerance in wheat (Triticum aestivum L.) breeding programs using discriminant analysis

Secondary traits are critical in determining the production of bread wheat in drought prone environments. This study was conducted to assess the effect of 25 morpho-physiological secondary traits on grain yield of 40 bread wheat genotypes under drought stress condition. The field and glasshouse experiments were carried out during 2009–2010 and 2010–2011. Considerable genetic variation was observed for all traits. Low genetic variance (0.10) and high genetic×environment interaction (0.31) resulted in moderate heritability (0.45) for grain yield. The average broad sense heritability for secondary traits (0.65) was significantly higher than for grain yield. In this research, ten secondary traits including water use, relative ionic leakage, leaf length, root length, grain number, awn length, above ground biomass, yield potential, days to flowering, and grain filling period could significantly discriminate high and low yield genotypes under drought stress condition. This showed the importance of these ten traits in breeding program for drought tolerance. Discriminant function of these ten traits was used as a comprehensive index for selection of high yield genotypes (Eq. (11)). This index could explain 76% of grain yield variation, and had significant positive correlation with grain yield under drought stress condition in the first (r=0.88**) and second year (r=0.53**). Consequently, this criterion was proposed for integrated selection in future breeding programs. Discriminant function showed that the relative ionic leakage and root length were the most important traits, followed by water use and grain filling period. Due to high heritability of secondary traits and their correlation with grain yield, selection based on these traits could improve genetic gain for grain yield in drought prone environments.

Suitability of carbon isotope discrimination, ash content and single mineral concentration for the selection of drought‐tolerant winter rye

AbstractCarbon isotope discrimination (∆) has been proposed as selection criterion for grain yield under dry conditions, and ash content (ma) and mineral concentration were suggested as surrogates for ∆. In this study, the relationship between grain yield, ∆, ma and mineral concentration (Si, Ca, K, Mg) was examined in 2011 and 2012 on 16 winter rye genotypes grown under severe drought, mild drought (2012 only) and well‐watered conditions. Analyses were performed on mature flag leaves and grains. Highly significant differences between water regimes occurred for all measured traits. ∆, ma and mineral concentrations were significantly correlated with grain yield under severe drought in 2011, but not in 2012 except for ∆ in flag leaf. ∆ was related to ma and mineral concentrations. Although the correlations were quite inconsistent, the results indicate that the measured traits can potentially be used as selection criterion for drought tolerance in rye. For a final statement about the suitability of these traits in rye breeding, the results should be secured with a larger and more diverse set of genotypes.

Glycine betaine application modifies biochemical attributes of osmotic adjustment in drought stressed wheat

Nineteen wheat genotypes were used to examine the effects of foliar applied glycine betaine (GB, 100 mM) on concentration of various osmolytes (such as proline, choline, GB and sucrose) under drought stress conditions. Drought stress caused a significant increase in proline content and GB content of wheat genotypes, both at maximum tillering and anthesis stages. Choline and sucrose were accumulated significantly at higher levels under stress conditions at both the stages. GB application increased the proline content and endogenous levels of GB in comparison to their stressed counterparts both at maximum tillering and anthesis stages but this increase was observed to be genotype specific. Furthermore, significant decrease in choline levels and sucrose contents of GB treated plants at anthesis stage and enhanced levels of proline questioned about involvement of GB in production of other osmolytes as well as stage specific response of wheat genotypes to GB spray. But these changes in osmolyte accumulation (OA) were not correlated with relative water content and stress tolerance index observed, under both GB sprayed and non-sprayed drought stressed conditions. So OA could not be considered as a selection criteria for drought tolerance in wheat.

Growth, phenological and yield responses of a bambara groundnut (Vigna subterranea (L.) Verdc.) landrace to imposed water stress under field conditions

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an underutilised species with potential to contribute nutritional and food security in marginal areas. Growth, phenology and yield of a local bambara groundnut landrace from Jozini, KwaZulu-Natal, characterised into three selections according to seed coat colour, namely Brown, Red and Light Brown, were evaluated under irrigated and rain-fed field conditions at Roodeplaat, Pretoria, over two seasons (2010/11 and 2011/12). Trials with three replicates were planted under rain-fed and irrigated conditions with seed colour as a subfactor. Emergence (up to 35 d after planting), plant height, leaf number, leaf area index, chlorophyll content index and stomatal conductance were measured in situ. Yield and components of yield were determined at harvest. The Red, Brown and Light Brown landrace selections emerged well (84%, 81% and 51%, respectively). Plant physiological and growth parameters of stomatal conductance, chlorophyll content index, plant height, leaf number, leaf area index and biomass accumulation were lower under rain-fed relative to irrigated conditions. Adaptations were landrace selection-specific, with the Brown and Red landrace selections showing better adaptation to rain-fed conditions. Under rain-fed conditions, bambara groundnut landrace selections flowered, senesced and matured earlier relative to irrigated conditions. Consequently, there were lower yields under rain-fed compared with irrigated conditions. The Red and Brown landrace selections may have drought-avoidance mechanisms. Seed colour may be used as a selection criterion for drought tolerance in bambara groundnut landraces.

Antioxidant Defence System in Chickpea (Cicer arietinum L.): Influence by Drought Stress Implemented at Pre- and Post-anthesis Stage

Significant differences in the antioxidant system of the leaves of four chickpea (Cicer arietinum L.) genotypes differing in tolerance to drought were observed in a pot experiment. Drought stress was imposed at pre- and post- anthesis stage (50 and 65 days after sowing). We studied the effect of drought stress on hydrogen peroxide (H2O2) content, lipid peroxidation and antioxidant enzyme activities in four chickpea genotypes viz., Tyson, ICC 4958, JG 315 and DCP 92-3. Drought treatment significantly increased hydrogen peroxide accumulation and lipid peroxidation, which indicated the extent of oxidative injury posed by stress conditions. Enzyme activities of Superoxide Dismutase (SOD), Peroxidase (POX), Catalase (CAT) and Ascorbate Peroxidase (APX) increased in chickpea leaves as a consequence of drought conditions and all the enzyme activities were significantly higher in drought stressed genotypes i.e., Tyson and ICC 4958 than in JG 315 and DCP 92-3. Relationship between Lipid Peroxidation (LPO), Hydrogen peroxide (H2O2), Superoxide Dismutase (SOD), Catalase (CAT), Peroxidase (POX) and Ascorbate Peroxidase (APX) was determined in order to find out whether these parameters can be used as selection criteria for drought tolerance in this crop. Early drought stress (pre-anthesis drought) was found to be more damaging than the late drought stress (post-anthesis drought).

Leaf dehydroascorbate reductase and catalase activity is associated with soil drought tolerance in bread wheat

A number of morphological, physiological and phenological traits have been suggested as significant markers of adaptation to drought in bread wheat (Triticum aestivum L.). This study was aimed at the identification of a relationship between dehydroascorbate reductase (DHAR, EC 1.8.5.1) and catalase (CAT, EC 1.11.1.6) activities in leaves of wheat plants and stability of yield components under water deficit. The single chromosome substitution lines of cv. Chinese Spring carrying separate chromosomes from the donor Synthetic 6x, an artificial hexaploid combining the genomes of the two wild species, Triticum dicoccoides (AABB) and Aegilops tauschii (DD), were the objects of the investigations. The activities of the DHAR and CAT were correlated with flag leaf relative water content and two indexes of stability of grain yield components under drought across the set substitution lines. The lines carrying a synthetic hexaploid homologous pair of chromosomes 1B, 1D, 2D, 3D or 4D all expressed a low constitutive level of DHAR and the lines carrying chromosomes 3B, 1D, 2D and 3D a low constitutive level of CAT. All were able to increase this level (by fourfold for DHAR and by 1.5-fold for CAT) in response to stress caused by water deficit. When challenged by drought stress, these lines tended to be the most effective in retaining the water status of the leaves and preventing the grain yield components from being compromised. The discovered genetic variability for enzymes activity in leaves of wheat might be a useful selection criterion for drought tolerance.

Physio-genetic behavior of maize seedlings at water deficit conditions

Drought stress is limiting global crop production more seriously than ever because of rapid change in global climate. Present investigations were made with a view to understand the traits which can be used as selection criteria for drought tolerance in maize at seedling stage. For this purpose twenty-five maize inbred lines were evaluated under water deficit conditions for traits like fresh shoot weight, fresh shoot length, fresh root length, fresh root weight, leaf venation, stomatal frequency and epidermal cell size. Significant differences were found among the genotypes for various physio-genetic traits. The genotypes 20P2-1, L5-1, 150P2-1, 70NO2-2, 150P1 and L7-2 were found good performer and may be exploited for developing drought tolerant synthetics and hybrids. Fresh shoot length and fresh root weight found overall direct and indirect contributor in fresh shoot weight and they were positive and significantly correlated with fresh shoot weight. Stomatal frequency and epidermal cell size had significantly decreasing direct and indirect effects on fresh shoot weight and significant genetic correlation with it. These results suggested that fresh shoot length and fresh root weight (Increased) stomatal frequency and epidermal cell size (decreased) might be used as selection criterion while selection for high fresh shoot yield under drought conditions.

Responses of Released Cultivars of Peanut to Terminal Drought for Traits Related to Drought Tolerance

The use of the surrogate traits with simple inheritance as selection criteria for drought tolerance should speed up the selection programs. The objectives of this study were to investigate the responses of released cultivars of peanut to end of season drought for traits related to drought tolerance and agronomics traits and to identify the released cultivars with tolerance to end of season drought. Ten peanut genotypes and two water regimes (field capacity; FC and 1/3 available water; 1/3 AW) were laid out in a split plot design with four replications for two years. The data were recorded for SPAD chlorophyll meter reading (SCMR), Specific leaf weight (SLW), biomass, pod yield, harvest index (HI), number of mature pods, 100-seed weight and number of seeds per pod. Drought increased SCMR and SLW and reduced biomass production, pod yield and seed size, whereas harvest index and number of pods per plants were not significantly affected. Maintaining high pod yield and number of pods per plant depended solely on high potential under well-watered conditions, whereas maintaining high biomass production and seed size and harvest index was dependent on both high potential and low reduction. SCMR and SLW were well associated and they had high correlations with biomass and pod yield. SCMR seemed to be more stable than SLW and it is recommended to be used as a surrogate trait for drought tolerance in peanut. The released cultivar KKU 60 was identified as drought tolerant by SCMR and SLW and by pod yield

In vitro and in vivo screening for drought tolerance in winter × spring wheat doubled haploids derived through chromosome elimination

The relative efficiency of in vitro and in vivo screening techniques for drought tolerance, comprising various parameters, namely germination (%), shoot length, root length, coleoptile length, root number, root/shoot ratio and seedling vigour index (SVI) under in vitro conditions and morpho-physiological and yield-contributing traits under in vivo conditions, was studied using 78 winter × spring wheat-derived doubled haploid lines of bread wheat along with 13 parental genotypes and two check varieties, HPW 155 and PBW 343. Analysis of variance for different in vitro parameters in control (0 MPa) and stress (−0.7 MPa) environments and various in vivo parameters under irrigated and rainfed environments indicated sufficient genetic variability and the differential response of the genotypes to the different stress levels for all the in vitro and in vivo parameters. Correlation studies revealed the significance of percentage germination, root number, coleoptile length and seedling vigour index under in vitro conditions and relative water content and excised leaf water loss under in vivo conditions as important selection criteria for drought tolerance, as these parameters were related with each other as well as with the drought susceptibility index (S). The significant positive rank correlation between the in vitro (−0.7 MPa) and in vivo (rainfed) stress conditions indicated that the performance of a genotype under field conditions is very similar to its performance under laboratory conditions. Hence, the selection precision for a crucial and complex trait like drought tolerance in wheat can be enhanced by exercising in vitro selection coupled with evaluation in the field. The drought susceptibility index ‘S’ should not be taken as the sole criterion to categorize genotypes as drought-tolerant or susceptible ones.