Drought Susceptible Research Articles

Evaluation of groundnut genotypes for late season drought tolerance

Fifty genotypes of groundnut including released varieties and advanced breeding lines were used to assess th drought tolerance. These genotypes were evaluated both in managed drought stress (DS) and non stress (NS) situations during post rainy season (Jan- April), 2011 at Oilseeds Farm, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The drought stress was imposed by withholding irrigation after 60 days after sowing for t drought stress trial. Observations were recorded for pod yield per plant and kernel yield per plant on random chosen five plants per entry per replication. The data were subjected to ANOVA and drought tolerance parameter <italic>viz.</italic>, drought susceptibility index (DSI) for pod yield per plant and kernel yield per plant. The results indicated that genotypes differed significantly for pod and kernel yield per plant. Among the genotypes, 7 and 6 genotypes were observed as highly drought tolerant based on pod and kernel yield per plant respectively. A total of 6 and 9 genotypes recorded as highly susceptible to drought for pod and kernel yield per plant respectively. Among these genotypes, each three drought tolerant (ICGV 91114, K1375 and ICGV 02125) and drought susceptible (ICGV 01279, ICGV 98170 and ICGV 98175) genotypes were selected for hybridization programme to develop mapping populations.

Comparative analysis of the drought-responsive transcriptome in soybean lines contrasting for canopy wilting

Drought stress causes significant yield losses in major oil seed crops, such as soybean [Glycine max (L.) Merr]. Few soybean lines have been identified as canopy-wilting tolerant; however, the molecular mechanism conferring tolerance is not fully understood. To understand the biological process, a whole genome transcriptome analysis was performed for leaf tissues of two contrasting soybean lines: drought-susceptible (DS) Pana and drought-tolerant (DT) PI 567690. A pairwise comparison of the DS and DT lines under drought and control conditions detected 1914 and 670 genes with a greater than two-fold change in expression under drought conditions. Pairwise treatment comparison and gene enrichment analysis on the DT line showed the down-regulation of genes associated with protein binding, hydrolase activity, carbohydrate/lipid metabolism, xyloglucan endo-transglycosylases associated with cell-wall, apoplast, and chlorophyll a/b binding proteins. On the other hand, genes that were associated with the biotic stress response, ion binding and transport, the oxido-reductive process and electron carrier activity were up-regulated. Gene enrichment analysis detected UDP glucuronosyl transferase activity-encoding genes to be differentially expressed in PI 567690 under drought stress conditions. We found valuable SNPs variation in aquaporin genes of the DT line that are conserved in known slower canopy-wilting lines, this should facilitate marker-assisted selection in soybeans with improved drought tolerance.

Differential responses in photosynthesis, growth and biomass yields in two mulberry genotypes grown under elevated CO2 atmosphere

This study was aimed to examine the responses of two mulberry genotypes (Morus alba L.), which include a drought tolerant (DT) Selection-13 (S13) and a drought susceptible (DS) Kanva-2 (K2) grown under elevated atmospheric CO2 concentration ([CO2]) of 550μmolmol−1. Although both genotypes exhibited positive responses to elevated CO2, S13 showed higher light saturated photosynthetic rates (A′) and apparent quantum efficiency (AQE), suggesting better Rubisco carboxylation. Increased water use efficiency (WUEi) in elevated CO2 grown S13 (ES13) was due to reduced stomatal conductance (gs) and transpiration (E). Elevated CO2 significantly increased chlorophyll a fluorescence characteristics including maximum quantum yield of primary photochemistry (FV/FM) and performance index (PIABS) suggesting an improved photosystem-II efficiency in both genotypes compared to their respective controls. Even though ES13 showed superior photosynthetic performance, accumulation of soluble and insoluble sugars (starch) were significantly low compared to elevated CO2 grown K2 (EK2), demonstrating higher sink capacity in ES13, which in turn resulted in better biomass yields. We conclude that S13 could be a potential genotype for mulberry-based short rotation forestry (SRF) to mitigate increasing atmospheric [CO2] as well as for the production of carbon neutral renewable bio-energy.

Genomic regions associated with grain yield under drought stress in wheat (Triticum aestivum L.)

Water deficit stress (WDS) is a serious constraint to wheat productivity in rain-fed and limited irrigation environments. Identifying genomic regions responsible for grain yield (GY) under WDS will aid in understanding the genetics of drought tolerance (DT) and development of DT cultivars. A population of 206 recombinant inbred lines derived from WL711/C306 was phenotyped for GY and related traits under water deficit and irrigated conditions in seven different environments to identify genomic regions associated with eleven yield related traits. Both the parents contributed positive alleles for the traits studied. A novel genomic region for GY under WDS, qGYWD.3B.1 was detected on chromosome 3BS of wheat. The yield enhancing allele under drought stress at this locus was contributed by DT parent C306. This genomic region explained 18.7 % of phenotypic variation for GY under WDS and co-located with genomic regions for GY components. Another novel, consistent genomic region for GY under WDS, qGYWD.3B.2 explained 19.6 % of phenotypic variation with positive allele coming from drought susceptible parent WL711. A novel genomic region for drought susceptibility index for GY, qDSIGY.4A.1 was consistently detected in six of seven environments explaining 15.6 % of phenotypic variation. Other important genomic regions for GY and biomass under WDS were mapped on chromosomes 7BL and 6AS, respectively. Fine mapping of the major QTLs on chromosome 3BS will enable identification of robust markers and candidate genes for marker-assisted breeding for DT in wheat.

Leaf greenness as a drought tolerance related trait in potato (Solanum tuberosum L.)

Maintenance of leaf greenness under drought stress is generally considered a positive trait as it indicates reduced chlorophyll degradation. This is particularly relevant at the end of the growth cycle, when delayed senescence a.k.a. stay-green may reflect maintenance of photosynthetic activity during the re-mobilization of carbon products to the harvested plant organs. In the present study, we analyzed the temporal trends of chlorophyll concentration or greenness measured using a SPAD meter (ChlSPAD), maximum net photosynthesis (Amax), stomatal conductance (gs), intrinsic water-use efficiency (Amax/E), nitrogen content per area (Narea), leaf length, plant cover and tuber and aboveground dry biomass in three potato varieties (Désirée, Unica and Sarnav). We compared plants grown at field capacity and under water restriction of 50% of field capacity. Watering treatments were imposed at tuber initiation onset. One week after water restriction initiation, a temporary rise of ChlSPAD was observed in the three genotypes. This increased leaf greenness under water restriction coincided with a decrease in leaf growth. Sarnav, which had the lowest drought susceptibility index, showed the lowest increase of ChlSPAD after water restriction as well as the higher average gs biomass accumulation, and lower Amax/E from tuber initiation onset through the initiation of senescence. We suggest that the highest greenness increase following water restriction in the most drought susceptible varieties is an expression of more conservative strategies under drought, which under moderate water stress (the most common water stresses in agriculture), are not useful from a productive point of view. Under this moderate stress, long growing cycle genotypes showed higher tuber yield driven by the longer period of biomass accumulation. Thus, lower chlorophyll loss rate and later onset of senescence was related to higher yield under water restriction. This study provides more insights on the mechanisms linking ChlSPAD temporal responses to moderate drought tolerance in potato.

Sequence of physiological responses in groundnut (Arachis hypogaea L.) subjected to soil moisture deficit

Responses of drought-tolerant (DT) and drought-susceptible (DS) pot-grown groundnut (Arachis hypogaea L.) varieties to changes in leaf relative water content (RWC) were studied. Water stress (WS) was imposed on 30-day-old plants for 2 weeks. Leaf RWC decreased significantly under WS conditions with simultaneous decrease in net photosynthetic rate (P N) and stomatal conductance (g s). Even though no significant difference was observed between DT and DS varieties with regard to RWC, DT varieties were able to maintain significantly higher P N than DS varieties. Higher values of water use efficiency (WUE) were also observed in DT varieties during WS conditions. The decline in P N due to WS could be attributed to both reduction in g s (i.e. stomatal limitation) and to reduction in chlorophyll content (Chl). No significant difference in leaf area index (LAI) was found between DT and DS types and LAI was not reduced by WS. Significant differences were found among the studied groundnut varieties, but not between DT and DS types, in terms of root, aboveground, and total dry mass. These growth parameters significantly decreased under WS conditions. Based on the results, a sequence of physiological responses in groundnut crop subjected to WS was postulated.

Epigenetic responses to drought stress in rice (Oryza sativa L.)

Cytosine methylation polymorphism plays a key role in gene regulation, mainly in expression of genes in crop plants. The differential expression of cytosine methylation over drought stress response was analyzed in rice using drought susceptible but agronomically superior lines IR 20 and CO 43, and drought tolerant genotypes PL and PMK 3 and their F1 hybrids. The parents and hybrids were subjected to two moisture regimes viz., one under drought condition and another under control condition. The cytosine methylation polymorphism in genomic DNA was quantified under both the conditions at the reproductive stage of the plant using the Methylation Sensitive Amplified Polymorphism (MSAP) technique devised by Xiong et al. (261:439-446, 1999). The results depicted that under drought condition, hyper-methylation was predominant in the drought susceptible genotypes while drought tolerant genotypes presented hypo-methylation behavior. While imposing drought, spikelet sterility per cent was positively correlated to percentage of methylation whereas, panicle length, number of seed per panicle, panicle weight, 100 seed weight, and yield/plant were negatively correlated indicating the role of epigenetic regulation in yield attributing traits in response to drought. Thus, methylation can be considered as an important epigenetic regulatory mechanism in rice plants to adapt drought situation. From this study, we speculate that the hyper- methylation may be an indicator of drought susceptibility and the hypo-methylation for drought tolerance and this methylation polymorphism can be effectively used in drought screening program.

Identification of Drought Tolerant Genotypes in Backcross Inbred Lines of Rice using Drought Indices

The experimental material for the present investigation consisted of 101 Backcross Inbred Lines (BILs) developed by two parents viz., Norungan (drought resistant, recurrent) and TKM 9 (drought susceptible, donor). The present investigation was envisaged to identify the drought tolerant BILs through drought indices like Drought Susceptibility Index (S) proposed by Fischer and Maurer (1978) based on the relationship of the change in relative yield (yield in drought / yield in absence of drought) of an individual cultivar to change in relative yield across a range of stress intensities on comparison and Drought Response Index (DRI) using linear regression on yield potential and days to 50% flowering given by Bidinger et al. (1987). Descriptive statistics revealed that the range of DSI and DRI values varied from -11.07 to 3.78 and -1.84 to 2.48 respectively. In general, the result of the investigation exhibits that, the cultures CB-07-701-283, CB-07-701-98, CB-07-701-280, CB- 07-701-174 and CB-07-701-156 recorded the lowest values of DSI and the cultures CB-07-701-161, CB-07-701-174, CB-07-701-268, CB-07-701-147 and CB-07-701-255 recorded the highest DRI values which ultimately indicates that these genotypes were highly tolerant to drought stress situa- tions and produced the highest grain yield. On comparing the DSI and DRI values, the culture CB- 07-701-174 (DSI: -7.69 and DRI: 2.33) was present in both the indices which strongly reveals that this genotype was highly resistant in nature and had significant higher grain yield under stress when compared to irrigated condition. It was suggested that, these genotypes are suitable for drought stress conditions and are appropriate for hybridization with the aim of increasing drought tolerance in further breeding programs.

Comparison of Tolerant Ability of Mature Field Grown Tea (<i>Camellia sinensis</i> L.) Cultivars Exposed to a Drought Stress in Passara Area

The response of some selected physiological and biochemical parameters of tea ( Camellia sinensis L.) plants to moisture stress was evaluated using field grown, mature plants, in Field Gene Bank at Passara, Sri Lanka, to identify traits that are associated with drought tolerance which could be used for cultivar screening programs. This study was carried out from July - October 2008. Known contrasting cultivars in terms of drought tolerance were selected from the existing gene bank for the measurements. Physiological and biochemical parameters were measured to study the response of tea plants to drought stress. Identification of traits was done by using cluster analysis, cultivar × environment interaction and drought susceptibility index. Reduction of leaf water potential up to -0.75 to -1.5 MPa at the end of the dry period indicated that the plants were exposed to a sufficient level of moisture stress. The drought tolerant cultivars maintained a high water status with substantial rate of photosynthesis as a result of osmotic adjustments, elevated total soluble sugars and also according to previous research, due to deep rooting. Drought susceptible cultivars maintained a lower water status with lower osmotic adjustment. With cluster analysis using rates of photosynthesis and transpiration, relative water content, stomatal conductance and leaf total soluble sugar content, the cultivars could be clearly grouped as tolerant and susceptible cultivars, which agreed with their tolerance level. The parameters which could be successfully incorporated into a drought screening procedure were rate of photosynthesis, stomatal conductance, transpiration rate, relative water content and total soluble sugar content. Key words: Cultivar differences; Drought; Physiological and biochemical responses; Tea ( Camellia sinensis L.). DOI: 10.4038/tar.v22i1.2671 Tropical Agricultural Research Vol. 22 (1): 66-75 (2010)

Heat and drought resistances criteria in spring bread wheat: Drought resistance parameters

Some spring bread wheat genotypes were evaluated for drought resistance using drought tolerance efficiency (DTE) and drought susceptibility index (DSI) under rainfed conditions in this study. Field trials were conducted in the Research Area of Field Crops Department, Agricultural Faculty, Cukurova University during 2002 - 2003 with high rainfall and 2003 - 2004 with low rainfall growth seasons. High variations were observed for drought resistance parameters both DTE and DSI in this study. While DTE values ranged from 65 - 98%, DSI values changed 0.077 - 1.761. The genotypes with high DTE and low DSI were evaluated as drought resistant; meanwhile, genotypes with low DTE and high DSI were considered as drought susceptible. Thus, genotypes Croc 1/Aegilops squarrosa, Genc 99, Weawer/WL 3926, Oasis/Kauz//*4 Bcn, and Punjab 96 with the lowest DSI and the highest DTE values were accepted drought resistant genotypes which may be used as the genetic sources for drought resistance. Key words: Drought tolerance efficiency, drought susceptibility index.

Photoassimilatory and Photorespiratory Behaviour of Certain Drought Tolerant and Susceptible Tea Clones

Net photosynthetic rate (PN) in the mother leaves was higher in the drought tolerant (DT) clones of tea (Camellia sinensis) while liberation of the fixed 14C in light from the mother leaves was higher in the drought susceptible (DS) clones. The DT clones translocated more photosynthates to the crop shoots (three leaves and a bud) from the mother leaf than the DS clones. Concentrations of RuBP carboxylase (RuBPC) or oxygenase (RuBPO) had no relationship with the drought tolerant nature of tea clones but their ratio correlated with the same. DT tea clones had higher catalase activity that could scavenge the hydrogen peroxide formed in the photorespiratory pathway and thereby reduced photorespiration rate (PR). The ratio of RuBPC/RuBPO had a positive correlation with PN and catalase activity. Negative correlation between RuBPC/RuBPO and PR and between catalase activity and RuBPO activity was established.

Effect of Water Stress on Expression of a 20 kD Cyclophilin-like Protein in Drought Susceptible and Tolerant Cultivars of Sorghum

Immunodetection studies revealed the presence of a 20 kD cyclophilin-like protein (designated as SorgCyp20) in leaves and seeds of sorghum (Sorghum bicolor L Moench). The expression of SorgCyp20 was temporally regulated in the leaves and after attaining maximum levels at either 60 or 70 days after sowing it declined after flowering. The effect of drought stress on SorgCyp20 levels in the leaves and seeds of sorghum was stage and cultivar dependent. The drought stress-induced enhancement in SorgCyp20 levels was many times higher in the leaves (3-fold increase at 30 days after sowing) and seeds (2.5-fold increase at 9 days post anthesis) of drought tolerant cv ICSV-272 than in the drought susceptible cv SPRU-94008B. The intercultivar differences in drought stress-induced changes in SorgCyp20 expression were not related to the difference in water potential thus suggesting differential regulation of SorgCyp20 in response to stress in the two sorghum cultivars.

Dynamics of Seed Protein Biosynthesis in Two Soybean Genotypes Differing in Drought Susceptibility

The dynamics of seed storage protein biosynthesis was studied under field conditions during two vegetative seasons. Two soybean (Glycine max L. Merr.) genotypes were examined: BOSA (drought tolerant) and L 121 (drought susceptible). Seed samples were taken from plants at three stages of seed maturation (50 and 70 d after flowering, and at full maturity). The earlier synthesis of the β-subunit of the 7S protein occurred in the drought susceptible cultivar. We have not found such differences in the synthesis of the α- and α′-subunits of the 7S protein. Our results did not confirm significant genotypic differences in protein composition of the mature seeds between the cultivars studied, but have pointed out to the differences in the dynamics of protein biosynthesis during seed maturation and desiccation.

Screening for Drought Resistance: Evaluation of Drought Susceptibility Index of Legume Plants under Natural Growth Conditions

Eighteen cultivars of legume species (field bean, soybean, field pea, lupine) were screened for drought tolerance in 3 year-long field experiments. The aim of the investigations was to evaluate the generic variation of drought susceptibility of the tested varieties. The experimental plots were equipped with an installation which enabled the limitation of the water content in soil and soil irrigation. The applied drought susceptibility index (DSI) considered the relations between seed yield of plants under drought conditions (YD) and that under conditions of good soil watering (YIR) as well as their dependence on the drought severity index (DS). The use of the index divided the cultivars into two groups of different drought tolerances. The group of drought resistant cultivars characterized by mean values of the DSI index 0.44 belonged Victor and Bronto of field bean species, Bareness and Mige of field pea species and Emir of lupine species. In general, the resistant cultivars when compared with the susceptible ones were characterized by lesser yield of seeds, which, however, was more stable both under conditions of drought and moistured plots. Any dependence of the degree of drought tolerance on the duration of the particular periods of plant growth was not observed in the experiments, however, both in’ drought susceptible and drought resistant cultivars there appeared the tendency to shorten the development phases under drought and to prolong them under artificial irrigation. In general, based on the results obtained, it can be concluded that legume plants belong to the species sensitive to water supply. The observed decrease of plant seed yield under moderate natural soil dryness in the year 1993 differed only a little from that found in experiments in the years 1994 and 1995, when soil dryness was much more severe.

Variation in the Antioxidant Metabolism of Drought Tolerantand Drought Susceptible Varieties of Sorghum Bicolor (L.) Moench. Exposed to High Light, Low Water and High Temperature Stress

Summary Seedlings of four varieties of Sorghum bicolor differing in drought tolerance under field conditions wereexposed to three components of drought stress in the laboratory. They were exposed to high light (10,000 lux), high temperature (36 ± 2 °C, and low water stress (−0.5 MPa) in different experiments. After 72 hours of exposure to each of these stresses, changes in lipid peroxidation, and the activities of catalase, superoxide dismutase and guaicol dependent peroxidase were assayed. Out of the four varieties, CSV-5, which is a drought susceptible variety, showed maximum increases in the level of malondialdehyde, which is a product of lipid peroxidation, under all three stress conditions. IS-22380, PA-59 and E-36 showed lesser lipid peroxidation. Superoxide dis mutase and catalase activities increased in the drought tolerant varieties. While IS-22380 seemed to adapt to stress conditions by manipulating the catalase levels, E-36 showed higher adaptability by manipulating the superoxide dismutase levels under water and temperature stress. Adaptation to light stress was manifested by increases in the levels of superoxide dismutase in the drought tolerant varieties. Thus, a drought tolerant variety can adapt to drought stress by diverse manipulations in the antioxidant system.

Wheat Breeding in a Water‐stressed Environment. I. Delineation of Drought Tolerance and Susceptibility

AbstractTo elucidate genotypic differences expressed through the grain yield of drought‐stressed wheat, 21 commercial varieties and advanced lines were evaluated in the field under a range of soil water levels to induce varying degrees of drought stress. This paper presents data on grain yield and yield‐based indices to indicate drought tolerance and drought susceptibility. AZS‐4 was identified as drought tolerant and AZS‐17 and ‘Pavon’ as drought susceptible. High gram yield under stress can be explained in terms of high yield potential, thus grain yield proved to be the best indicator of drought tolerance.

Synthesis of Osmotically Active Substances in Winter Wheat Leaves as Related to Drought Resistance of Different Genotypes1)

AbstractWater stress increased mono‐saccharides and decreased di‐saccharides concentration in four field grown genotypes, regardless of their different drought susceptibility. Sandy, a USA genotype known for giving satisfying yields in droughty environments, outstood the other cultivars in terms of betaine and proline concentration in leaf tissues; these aminoacids are therefore considered responsible for the most negative Ψs perceived in this cultivar.PV‐curve technique revealed for Tullio, the drought susceptible Italian genotype, an osmotic adjustment of –0.63 MPa, four times greater than in Pandas, though this drought resistant cultivar showed a similar content in osmotically active substances; the authors therefore hypothesize an alternative mechanism in the response to water shortage in Tullio.

Proline Accumulation during Drought Rhizogenesis in Brassica napus var. oleifera

Free proline accumulation, in response to gradual drought stress in Brassica napus var. oleifera (cv. Darmor), is detectable from a threshold shoot water potential (Υ) of −0.6 MPa. The earliest response occurs in the shoot apex just before the onset of the adaptive drought-induced rhizogenesis. Short tuberized roots (STRs), induced through water shortage, were found to contain a very high amount of free proline, reaching up to 4.6 % of total dry matter. The tap root bearing the STRs also exhibited a very high free proline level, quite in contrast to normal lateral roots where the values did not exceed 2.5 % of total dry matter. Proline accumulation during drought rhizogenesis was also high in other shoot parts, but especially in the apex where proline accounted for 8 % of the total dry matter. The highest proline levels were thus located in «survival organs» of rapeseed (shoot apex, hardened leaves, STRs and tap root). Furthermore, particularly noticeable was the lack of proline increase in the drought susceptible cotyledons. When stress conditions were relieved, after completion of drought rhizogenesis, proline was rapidly utilized and its rate of mobilization, directly related to the growth recovery of the different tissues, was especially high in the growth resuming drought-induced roots. Accordingly, proline can be considered as a storage compound supplying reductants, reduced N and carbon skeletons for post-stress growth recovery. Thus, B. napus' drought adaptive behaviour enabled the detection of a differential proline response within the plant, according to the level of drought tolerance or drought susceptibility of the different tissues. In addition, comparative experiments were performed in order to investigate the temporal relationship between drought rhizogenesis of rapeseed and proline accumulation under various water stress regimes. It is shown that rapid changes in Υ shoot of gell-watered plants subjected to water stress were associated with high net rates of proline accumulation, but induced only limited STRs production. In contrast, slower changes in Υ shoot caused less proline accumulation but higher rhizogenetic activity.

Performance of wheat and triticale cultivars in a variable soil—water environment I. Grain yield stability

Seventeen cultivars of Triticum aestivum, T. durum and triticale were grown for 5 years in irrigated and unirrigated conditions to investigate yield stability and its association with various morpho-physiological characters. Differences in rainfall and irrigation provided environments with variable water availability. Grain yield of all cultivars was reduced by drought stress and cultivars differed in their yield stability. The drought susceptibility index (S) was positively related to the regression slope of mean grain yield (Y) on the environmental index (X). On an average, T. aestivum cultivars were more drought resistant than triticales. Cultivars of T. durum were most drought susceptible. The drought resistance was not always associated with plant height. Cultivars were classified into four groups based on their yield potential and drought resistance.

Growth Analysis of Spring Wheat Cultivars of Varying Drought Resistance1

Field studies were undertaken to relate dry matter accumulation and loss patterns to drought resistance and yield performance of wheat. A total of 23 hexaploid (Triticum aestivum L.) and tetraploid (T. turgidura var. durum L.) wheat genotypes were grown under rainfed field conditions at Swift Current, Saskatchewan from 1975to 1978, and under both rainfed and irrigated conditions in 1979 and 1980. Weekly dry matter samples were taken in the 1975 to 1979 trials, starting before anthesis and continuing to maturity. Growth parameters were then related to apparent drought resistance, which was characterized by comparing rainfed and irrigated yields. The genotypes were divided into drought susceptible and drought resistant groups on the basis of a drought susceptibility index. In contrast to results in some other studies, Pitic 62 appeared to be somewhat drought susceptible, perhaps because of late flowering. Mean head yield:biological yield ratios (approximation of harvest index) ranged from 0.52 to 0.60 over the 5 years, and tended to be higher under moist or irrigated conditions than under dry conditions. Significant differences in preanthesis growth rates occurred in only I of the 5 years, and did not appear to be related to drought resistance or yield. There were consistent cultivar differences in stem dry weight reduction prior to maturity, but there was no obvious relationship between this trait and drought resistance. Leaf duration after anthesis was not correlated with yield or drought susceptibility index. Growth analysis is a labor intensive procedure that is unlikely to identify traits which are strongly related to drought resistance.