Drought Resistant Genotypes Research Articles

Variation in Polyamine Content among 12 Pollinated Wheat Genotypes under Drought Stress Condition

The present work aims to study the drought stress effects on polyamine content and its relationship with growth and development in seeds, during cell division (from the beginning and until 17 days after pollination) and grain filling (until reaching the physiological maturity) stages. Factorial experiment based on Randomized Complete Block (RCB) design was carried out with three replications. Two factors of the experiment were considered: the level of irrigation (irrigation without and with drought stress during cell division stage and with drought stress during grain filling stage) and the level of wheat genotype (drought-resistant, semi-resistant and sensitive genotypes). As control treatment, soil moisture content of the field was considered. For drought-stress treatment, the 50% of the soil moisture content in control treatment was established. According to the experimental results, Putrescine content value is higher in control treatment which develops seeds of drought-resistant genotypes than that are registered for semi-resistant and sensitive genotypes. Both drought stress treatments induced significant rises in putrescine amount in the different genotypes of the study. The rises of putrescine content in sensitive and semi-resistant genotypes, however, were higher than in resistant ones, and the highest rise in putrescine content appeared in manning semi-resistant genotype during the stage of grain filling (27 days after pollination). Exerting drought stress in both stages of cell division and grain filling led to significant increase in spermine and spermidine contents of developing seeds of entire genotypes of the study. The highest spermidine content during grain filling stage occurred in sensitive genotypes of Shark and Tevee’s, and the lowest occurred in semi-resistant genotype of Sabalan. The highest spermine content during cell division stage, though, happened in semi-resistant genotype of manning. In fact, spermine and spermidine act as analogous to plant hormones such as Auxin and Cytokine, or they cooperate with these hormones in order to take a role in cell division regulation of developing wheat seeds and development of sink strength. They, additionally, stabilize the cell division process of developing seeds under drought condition. According to the findings of the study, manning semi-resistant genotype is capable of having a high grain yield under drought condition by reason of reserving high amounts of polyamines.

Assessment of allelic diversity among drought-resistant cotton genotypes using microsatellite markers.

Drought, in conjunction with high temperature, is an important environmental constraint to cotton production. Development of cotton varieties with increased tolerance against adverse environmental conditions has been proposed as effective strategy for ensuring reliable yields. In the present study, 30 simple sequence repeat (SSR) primers were used to estimate genetic divergence among 22 cotton genotypes for drought stress tolerance. Genetic diversity is a prerequisite for developing drought resistant cotton genotypes. Eleven SSR primers out of 30 were able to discriminate among the cotton genotypes, implying that 37% of the primers were informative. In total, 41 alleles were detected, with an average of 3.72 alleles per primer. The number of alleles per locus ranged from one (JESPR-284) to six (JESSPR-302), and the allelic diversity in the experimental material was 0.40. Genetic similarity coefficients ranged from 0.87-1.00. The result of principal component analysis confirmed the clustering of 21 cotton genotypes in two groups leaving one genotype (CIM-109) ungrouped. Overall, genetic diversity among the 22 cotton genotypes was low. More polymorphic SSR markers are needed to explore the workable genetic variation among the screened cotton genotypes in future studies.

Physiological characterization of Turkish bread wheat genotypes for resistance to late drought stress

A number of physiological traits have been proposed as selection criteria for late drought resistance and grain yield improvement in wheat. To characterize them in terms of late drought resistance, 64 bread wheat genotypes were evaluated for canopy temperature difference (CTD), leaf senescence rate (LSR), SPAD chlorophyll value, initial fluorescence (Fo), maximum fluorescence (Fm), variable fluorescence (Fv), maximum quantum efficiency of PSII (Fv/Fm), leaf ash content, and grain ash content in two field experiments conducted in irrigated and late drought conditions during the 2011-12 and 2012-13 seasons in Erzurum, Turkey. The experiments were conducted in an 8 x 8 lattice design with two replicates. Significant variation was observed among the genotypes for all the traits. Late drought decreased the grain yield, CTD, SPAD, Fm, Fv, Fv/Fm, and leaf ash content but increased LSR and grain ash content. The drought sensitivity of the genotypes was determined by a ranking method based on 25 traits measured in the late drought conditions. According to the rank-sum (RS) values of the genotypes, four genotypes were defined as resistant, 15 genotypes as medium resistant, 34 genotypes as medium sensitive, and 11 genotypes as sensitive. Resistant genotypes M?fitbey and Dağdaş 94 produced the highest grain yields in late drought conditions and appeared to be promising parents for the breeding of resistant cultivars. RS was negatively correlated with CTD, SPAD, Fm, Fv, and Fv/Fm, while it was positively correlated with LSR. For screening late drought-resistant genotypes, 15 days post anthesis (15DPA) is the optimum time for Fv, CTD, and SPAD measurements. The stepwise multiple linear regression analysis indicated that the Fv15DPA, Fv25DPA, CTD15DPA, and SPAD15DPA could explain 75.2% of the total variation in RS. Therefore, the Fv15DPA, Fv25DPA, CTD15DPA, and SPAD15DPA traits can be used as selection criteria as a combination for the classifying of wheat genotypes in terms of late drought resistance.

Evidence for genotypic differences among elite lines of common bean in the ability to remobilize photosynthate to increase yield under drought

SUMMARYCommon bean (Phaseolus vulgaris L.) is the most important food legume for human consumption. Drought stress is the major abiotic stress limitation of bean yields in smallholder farming systems worldwide. The current work aimed to determine the role of enhanced photosynthate mobilization to improve adaptation to intermittent and terminal drought stress and to identify a few key adaptive traits that can be used for developing drought-resistant genotypes. Field studies were conducted over three seasons at Centro Internacional de Agricultura Tropical, Palmira, Colombia to determine genotypic differences in adaptation to intermittent (two seasons) and terminal (one season) drought stress compared with irrigated conditions. A set of 36 genotypes, including 33 common bean, two wild bean and one cowpea were evaluated using a 6 × 6 lattice design under irrigated and rainfed field conditions. Three common bean elite lines (NCB 226, SEN 56, SER 125) were identified with superior levels of adaptation to both intermittent and terminal drought stress conditions. The greater performance of these lines under drought stress was associated with their ability to remobilize photosynthate to increase grain yield based on higher values of harvest index, pod harvest index, leaf area index and canopy biomass. Two wild bean germplasm accessions (G 19902, G 24390) showed very poor adaptation to both types of drought stress. One small-seeded black line (NCB 226) was superior in combining greater values of canopy biomass with greater ability to mobilize photosynthates to grain under both types of drought stress. Two small-seeded red lines (SER 78, SER 125) seem to combine the desirable traits of enhanced mobilization of photosynthates to seed with effective use of water through canopy cooling under terminal drought stress. Pod harvest index showed significant positive association with grain yield under both types of drought stress and this trait can be used by breeders as an additional selection method to grain yield in evaluation of breeding populations for both types of drought stress.

Water deficit effects on grapevine woody tissue pigmentations

Water availability is an important environmental factor in viticulture. In a climate change context, vineyard management should be adapted to the new conditions. Drought-resistant rootstocks need to be selected. In this paper, reflectance spectroscopy is proposed as a new method to characterize the water stress effects on woody section pigmentations. Cabernet Sauvignon grafted on 4 different rootstocks (140Ru, 420A, M2 and M3) represented the plant material. Greenhouse controlled conditions allowed the comparison of well-watered (WW) and water-stressed (WS) plants. The physiological responses were characterized concerning daily water consumption, stem water potential, gas exchange, and plant growth. The water use efficiency was calculated and discussed as well. Spectroscopy analyses of woody sections indicated a major absorption band probably related to phenolic derivatives. Water stress produced characteristic spectrum modifications both in the Cabernet Sauvignon stem and in the rootstock xylem. These preliminary results encourage further studies addressed at the evaluation of drought-resistant genotypes, to distinguish their stress responses and to characterize the compositional aspects linked to drought tolerance.

Optimizing micropropagation of drought resistant Pyrus boissieriana Buhse.

The present study concentrated on introducing a micropropagation protocol for a drought resistant genotype from Pyrus boissieriana, which is the second most naturally widespread pear species in Iran with proper physiological and medicinal properties. Proliferating microshoot cultures were obtained by placing nodal segments on MS medium supplemented with BAP and IBA or NAA. The highest number of shoots (27 shoots per explant) were obtained with 1.5mgl-1 BAP and 0.05mgl-1 IBA, but this combination did not produce shoots of desirable length (>1.7cm). Combination of 1.75mgl-1 BAP and 0.07mgl-1 IBA was the best for the shoot multiplication in P. boissieriana with a sufficient number of shoot production (22.33 shoots per explant) and relatively more appropriate shoot length. The larger and greenish leaves were obtained when PG was added to the best multiplication treatment. Microshoot elongation was carried out in 1/2 and 1/4 MS medium containing 50-100mgl-1 PG with different concentrations of IBA or NAA at intervals of 30-60days. Significant increase in shoot length was detected after 45-60days of culture in the presence of PG. The highest shoot length (8cm) was recorded on 1/2 MS medium supplemented with 0.5mgl-1 IBA and 100mgl-1 PG. GA3 negatively affected number and length of shoots and generally caused generation of red leaves. The highest percentage of root induction (100%) and root length (9cm) were obtained on 1/6 strength MS medium supplemented with 0.005mgl-1 IBA. All plantlets were hardened when transferred to ex vitro conditions through a period of 25-30days. The results suggest axillary shoot proliferation of P. boissieriana could successfully be employed for propagation of candidate drought resistant seedling.

Role of geographical provenance in the response of silver fir seedlings to experimental warming and drought.

Changes in climate can alter the distribution and population dynamics of tree species by altering their recruitment patterns, especially at range edges. However, geographical patterns of genetic diversity could buffer the negative consequences of changing climate at rear range edges where populations might also harbour individuals with drought-adapted genotypes. Silver fir (Abies alba Mill.) reaches its south-western distribution limit in the Spanish Pyrenees, where recent climatic dieback events have disproportionately affected westernmost populations. We hypothesized that silver fir populations from the eastern Pyrenees are less vulnerable to the expected changing climate due to the inclusion of drought-resistant genotypes. We performed an experiment under strictly controlled conditions simulating projected warming and drought compared with current conditions and analysed physiology, growth and survival of silver fir seedlings collected from eastern and western Pyrenean populations. Genetic analyses separated eastern and western provenances in two different lineages. Climate treatments affected seedling morphology and survival of both lineages in an overall similar way: elevated drought diminished survival and induced a higher biomass allocation to roots. Increased temperature and drought provoked more negative stem water potentials and increased δ13C ratios in leaves. Warming reduced nitrogen concentration and increased soluble sugar content in leaves, whereas drought increased nitrogen concentration. Lineage affected these physiological parameters, with western seedlings being more sensitive to warming and drought increase in terms of δ13C, nitrogen and content of soluble sugars. Our results demonstrate that, in A. alba, differences in the physiological response of this species to drought are also associated with differences in biogeographical history.

English

Drought is one of the most important stress factors which adversely affect plants’ growth and productivity. Global climate change may make this situation more serious in the years ahead. Considering the long time span required for the generation of drought resistant genotypes in Rubber (Hevea brasiliensis) through conventional breeding, molecular interventions to engineer plants to have either drought responsive genes or genes expected to alter osmotic regulation would be very attractive. The glyoxalase pathway involving glyoxalase I and glyoxalase II enzymes is required for glutathione-based detoxification of methylglyoxal. In this study the effects of various abiotic stresses on the up-regulation of methylglyoxal levels and glyoxalase I activities in Hevea brasiliensis seedlings were investigated. Most of the stresses caused significant increase in methylglyoxal level and glyoxalase I activity, among which drought caused the highest induction of glx I followed by salinity, 2, 4-D, ABA, methylglyoxal, white light and CdCl2. The stress-induced increases in methylglyoxal and glyoxalase I activity found in the present study suggest an important role of glyoxalase I in conferring drought tolerance. The up-regulation of glyoxalase I under drought stress indicates its future utility in developing tolerance to drought stress in Hevea brasiliensis. In the present study, a partial cDNA sequence coding for glyoxalase I was amplified by PCR using specific primers. The 440 bp cDNA amplicon obtained was sequenced and subjected to online BLAST analysis. The sequence of Hevea brasiliensis glyoxalase I (GenBank Acc. No: GU598520) had six open reading frames. The ORF finder revealed the longest ORF of 336 bp. Glyoxalase I from Ricinus communis had the highest nucleotide sequence homology (90%) compared to the amplified gene. BLASTP analysis also showed high homology between the deduced protein sequence of the amplified gene and glyoxalases from other species. Our results suggest that the multi-stress inducibility of glyoxalase I in the present study may be due to the fact that it might protect the plants against MG that is formed under various stresses including drought and confers tolerance by increasing the GSH-based detoxification system and decreasing lipid peroxidation Key words: Glyoxalase I, Hevea brasiliensis, Methylglyoxal, drought tolerance, abiotic stress.

Assessment of genetic diversity for drought tolerance and determination of the best resistance indices for some common wheat (Triticum aestivumL.) genotypes

In order to evaluate genetic diversity of common wheat (Triticum aestivum L.) to identify the most drought resistant genotypes and also finding the best drought tolerance indices, an experiment was carried out in research center of Kabotarbad, Isfahan, Iran, using randomized complete block design in three replications. Twenty wheat genotypes were selected for this study. The experiment was done under normal (Yp) and water stress (Ys) conditions. The stress was applied after heading stage. The results showed that stress tolerance index (STI), geometric mean productivity (GMP) and mean productivity (MP) indices had the most correlation with the yield, therefore, they were used for screening drought tolerant varieties. Biplot analysis also showed that genotypes 10, 18, 19 and 20 had the highest grain yield under both the conditions. Genotypes 3, 6, 14 and 15 were also suitable for the stress condition. The principal component analysis (PCA) showed that two first components accounted for 99.945% of the variance for the observed genotypes. The first component had the most positive coefficients in both irrigated and stress conditions and also the highest GMP and STI values, therefore, it can be named as the yield potential component under drought condition and also the tolerance index. The second one had the most positive and highest correlation with tolerance index (TOL) and SSI and it can be referred as the drought susceptibility component.

Evaluation of bread wheat genotypes for early drought resistance via germinationunder osmotic stress, cell membrane damage, and paraquat tolerance

In order to develop genotypes with stable, higher yields in dry farming conditions, it is necessary to characterize genetic resources based on drought adaptation, determine suitable genotypes, and then use them in breeding programs. This study was carried out at the laboratories of the Field Crops Department of Ataturk University Agricultural Faculty. A total of 64 certified and local bread wheat genotypes were used to test germination characters under osmotic stress, cell membrane damage, and paraquat tolerance. There were significant differences among genotypes with respect to the selection parameters in this study. Average germination percentages in osmotic environment treatments ranged from 63.3% to 94.7%, total root lengths were 10.54-23.12 cm, and shoot lengths were 4.73-10.56 cm. Seed vigor indexes ranged from 1392.4 to 3048.6, cell membrane damage ranged from 0.16% to 47.26%, and chlorophyll content varied between 0.005 and 0.101 mg mL-1 g FW-1. Kirmizi Yerli, Conkesme, and Turkmen were considered drought-resistant based on two out of the three parameters tested. In addition, Yakar 99, Pehlivan, Izgi 2001, Ikizce 96, Mizrak, and Gerek 79 were considered drought-susceptible based on two out of the three parameters tested. Kirmizi Yerli, Conkesme, and Turkmen, which were notable in terms of both parameters, could be used as parents in breeding programs related to drought resistance.

Characterizing root response phenotypes by neural network analysis.

Roots play an immediate role as the interface for water acquisition. To improve sustainability in low-water environments, breeders of major crops must therefore pay closer attention to advantageous root phenotypes; however, the complexity of root architecture in response to stress can be difficult to quantify. Here, the Sholl method, an established technique from neurobiology used for the characterization of neural network anatomy, was adapted to more adequately describe root responses to osmotic stress. This method was used to investigate the influence of in vitro osmotic stress on early root architecture and distribution in drought-resistant and -susceptible genotypes of winter oilseed rape. Interactive changes in root architecture can be easily captured by individual intersection profiles generated by Sholl analysis. Validation using manual measurements confirmed that the number of lateral roots decreased, while mean lateral root length was enhanced, under osmotic stress conditions. Both genotypes reacted to osmotic stress with a shift in their intersection patterns measured with Sholl analysis. Changes in interactive root architecture and distribution under stress were more pronounced in the drought-resistant genotype, indicating that these changes may contribute to drought resistance under mild osmotic stress conditions. The Sholl methodology is presented as a promising tool for selection of cultivars with advantageous root phenotypes under osmotic stress conditions.

A Molecular Approach for Identification of Drought Resistant Rapeseed Genotypes Based on Gene Expression

Areas affected by drought have lately extended all over the world. Rapeseed ( Brassica napus L. ), one of the most important species for oil production, is sensitive to drought stress mainly during the early vegetative growth stage. The comparative proteome analysis pointed out that heat shock proteins 90 (HSP 90), 70 (HSP 70) and beta-2 tubulin have a role in the drought tolerance of rapeseed. The aim of this work was to develop a molecular approach suitable for the identification of the drought resistant rapeseeds genotypes and, at the same time, to study the tolerance mechanism related to specific genes expressions. The primers for the mentioned genes were designed according to data from NCBI Data Base and the genes expression was evaluated by RT- PCR technique. The total RNA was extracted, the cDNA was synthesized and the specific genes were amplified, the process being followed up in the presence of SYBR Green dye. The genes expression was investigated for two variants - control plants and drought stressed plants. It was found that all of the studied genes were up-regulated in known as tolerant genotype and therefore they were over-expressed in drought conditions. The most obvious differences were pointed out for HSP 70 gene. Â

Genotypic variation in grain yield and flowering pattern in terminal and intermittent drought screening methods in rainfed lowland rice

Rainfed lowland rice in the Mekong region is mostly grown in drought-prone areas, and drought resistant varieties could be selected using either terminal drought (severe water stress after flowering) or intermittent drought (frequent mild stress) screening. Delay in flowering is considered as a putative trait for selection of drought resistant genotypes, and its effectiveness as an indirect selection trait and its association with genotype's flowering duration, i.e. the time taken from the first to last flower in a plot, was evaluated under the two drought screening methods. These screening methods together with flood control were used at two locations, Chum Phae and Ubon in north-east Thailand using a total of 70 genotypes with different growing duration. Delay in flowering was estimated for the two drought screening methods and flowering of individual panicles within a plot was recorded to determine flowering duration of each genotype in the flood and terminal drought conditions.Mean reduction in grain yield was 52–55% under the terminal drought screening while it was 10–19% for the whole population and 23–33% for early flowering genotypes in the intermittent drought. Delay in flowering under intermittent drought condition at both locations was associated with yield reduction; genotypes that exhibited shorter delay in flowering had smaller yield reduction percentage and larger number of panicles. At Chum Phae, where grain yield reduction was associated with flowering time, genotypes with longer flowering duration under terminal drought had smaller yield reduction, and this was found even among genotypes that flowered about the same time under flood condition. However, there was no association between delay in flowering and flowering duration. It is concluded that delay in flowering appears promising as a selection criterion under intermittent drought conditions, provided a higher yield reduction can be achieved for example by using an increased irrigation interval.

Identification of two functional markers associated with drought resistance in maize

Drought is recognized as the major abiotic constraint to global food production. Molecular markers have become an important genetic tool for understanding genome dynamics and facilitating molecular breeding of drought resistance. Here, cleaved amplified polymorphic sequence (CAPS) markers dhnC397 and rspC1090 were identified based on the SNP A/G polymorphisms in the drought-resistance genes dhn1 and rsp41. The two alleles of both genes were easily and rapidly discriminated by polyacrylamide gel electrophoresis to reveal single nucleotide polymorphisms (SNPs) as functional markers. By validation of an integrated selection criterion for drought resistance, the average SI (selection index for drought resistance) of lines with superior drought-resistance genotypes was higher than those with opposite, less drought-resistant genotypes, and the SI of heterotic group B was higher than that of heterotic group A for both genes. Integrating the results of CAPS analysis and evaluation of drought resistance indicated that the SNPs in these two genes partly participate in conferring drought resistance in these maize lines of interest. Breeders can thus use the CAPS markers identified here as functional markers for the improvement of drought resistance in these maize lines and possibly others.

DROUGHT TOLERANCE OF LOCAL ROTE AND CHECK VARIETIES OF GROUNDNUT (Arachis hypogaea L.) UNDER DRY SEASON IN TWO LOCATIONS IN EAST NUSA TENGGARA

Groundnut is the most important pulse crop in East Nusa Tenggara (ENT); however, the crop yield in ENT is low due to erratic climatic condition, drought stress, and low yielding ability of most cultivated genotypes. Local Rote is a well-known local groundnut variety in ENT, which is a potential superior variety and parental source due its large seed size and high yielding ability. Information on its resistance to abiotic and biotic stresses is important for its future development. Five groundnut genotypes, Local Rote and check varieties were elucidated to identify drought resistant genotypes. The study was carried out in a split-plot design with three replicates in two locations during dry season 2013. Two irrigation regimes (optimum and stress conditions) were assigned as main plot and 5 groundnut geno-types as sub-plot. Research results revealed significant effect of irrigation by genotype interaction on observed yield and yield compo-nent characters in both locations. Seed yields of most tested genotypes were below their yield potential. Local Rote yielded best over two locations (1.26 t.ha -1 seed yield). Yields of check varieties were below 1.0 t.ha -1 . Local Rote was considered tolerant to drought based on STI, GMP, SSI and YL selection indices. Keywords: groundnut, local, variety, drought, tolerance

Early Osmotic Adjustment Responses in Drought‐Resistant and Drought‐Sensitive Oilseed Rape

The impact of osmotic stress on growth, physiology, and metabolism of winter oilseed rape (Brassica napus L.) was investigated by detailed analysis of biomass traits, hormone metabolites and osmolytes in two genetically unrelated drought-tolerant genotypes and two unrelated drought-sensitive genotypes. Seedlings were grown in vitro under controlled conditions and osmotic stress was simulated by applying a gradual treatment with polyethylene glycol (PEG 6000), followed by hypo-osmotic treatment of variants used for metabolite determination. The results provide a basis for the identification of reliable selection criteria for drought resistance in oilseed rape. The in vitro cultivation system established during this study enabled effective discrimination of early osmotic stress responses between drought-resistant and -susceptible oilseed rape genotypes that also show large differences in relative seed yield under drought conditions in the field. Clear physiological and metabolic differences were observed between the drought-resistant and drought-sensitive genotypes, suggesting that osmotic adjustment is a key component of drought response in oilseed rape. Unexpectedly, however, the drought-resistant genotypes did not show typical hormonal adjustment and osmolyte accumulation, suggesting that they possess alternative physiological mechanisms enabling avoidance of stress symptoms.

Some Physiological Parameters as Screening Tools for Drought Tolerance in Bread Wheat Lines (Triticum aestivam L.)

Two greenhouse experiments were carried out at the Institute of Biological Production Systems, Leibniz Universität Hannover, Germany during 2008/2009 and 2009/2010 growing seasons to study the influence of the osmotic adjustment (OA) capacity, relative water content (RWC) and specific leaf area (SLA) on tolerance to drought in 22 breeding lines, two parents and tolerant cultivar (Sahel 1) of bread wheat (Triticum aestivam L.) under drought conditions. Differences were seen in of the OA, RWC and of the different genotypes. Mean over all of OA, RWC and for breeding lines were -0.51 Mpa, 83.28% and 116.56 cm²g-1, respectively. Four of the breeding lines showed the greatest osmotic adjustment capacities, high RWC and good values under drought stress conditions better than the tolerant cultivar. The heritability of OA, RWC and was 0.56, 0.49 and 0.88, respectively. The results indicated that osmotic adjustment, as well as RWC and could be used as screening tools for drought resistant bread wheat genotypes in the greenhouse. This study also demonstrated the appropriate greenhouse screening methodology in this regard.

Drought resistance and soil water extraction of a perennial C4 grass: contributions of root and rhizome traits.

Previously, we showed that genotypic differences in soil water extraction were associated with drought response, but we did not study underground root and rhizome characteristics. In this study, we demonstrate a similar relationship between drought resistance and soil water extraction but investigate the role of underground organs. Eighteen bermudagrass genotypes (Cynodon spp.) from four climatic zones were assessed under continuous drought at two locations with contrasting soils and climates. The criterion for drought resistance was the duration required to reach 50% green cover (GC50) after water was withheld. GC50, physiological traits, rhizome dry matter (RhDM), root length density (RLD) and average root diameter (ARD) were determined in both locations; water extraction was measured in one location. Large genotypic variation for drought resistance was observed in both locations, with GC50 being 187-277 days in a clay soil and 15-27 days in a sandy soil. Drought-resistant genotypes had greater soil water extraction and a higher water uptake rate. GC50 was correlated with relative water content (r=0.76), canopy temperature differential (r=-0.94) and photosynthetic rate (r=0.87) measured during drought; RhDM (r=0.78 to ~0.93) before and after drought; and ARD after drought (r=0.82 to ~0.94); GC50 was not correlated with RLD. Ecotypes collected from the Australian Mediterranean zone had superior drought resistance and were characterised by a large rhizome network. This is the first comprehensive study with perennial C4 grasses describing the association between water extraction, root distribution, rhizomes and drought resistance.

Biochemical changes in two Vigna spp. during drought and subsequent recovery

Drought is one of the major environmental factors restricting crop production world over. The present experiment was conducted to evaluate the changes in important biochemical traits and yield of pulses under drought stress imposed during reproductive stage. Black gram (Vigna mungo L.) genotypes: T-9, PU-19 and green gram (Vigna radiata L.) genotypes: Pratap, TMB-37 were taken as test material in a randomized block design with three replications. Leaf chlorophyll content, nitrate reductase activity and total flavonoid were found to be positively correlated with soil moisture content, while negative correlations were obtained with proline and anthocyanin content. Significant differences among genotypes, treatments and interaction between the genotypes and treatment were observed for yield and other biochemical parameters, which demonstrated the existence of differences among the genotypes studied for drought tolerance. Genotypes T-9 of black gram and Pratap of green gram were found to be more tolerant to drought stress. Among the crops, black gram showed better drought tolerance than green gram. Biochemical parameters chlorophyll content, leaf proline content, nitrate reductase activity and anthocyanin content were identified as marker traits for selecting drought resistant pulse genotypes.

Superoxide dismutase and ascorbate peroxidase improve the recovery of photosynthesis in sugarcane plants subjected to water deficit and low substrate temperature

The physiological responses of C4 species to simultaneous water deficit and low substrate temperature are poorly understood, as well as the recovery capacity. This study investigated whether the effect of these abiotic stressors is cultivar-dependent. The differential responses of drought-resistant (IACSP94-2094) and drought-sensitive (IACSP97-7065) sugarcane cultivars were characterized to assess the relationship between photosynthesis and antioxidant protection by APX and SOD isoforms under stress conditions. Our results show that drought alone or combined with low root temperature led to excessive energetic pressure at the PSII level. Heat dissipation was increased in both genotypes, but the high antioxidant capacity due to higher SOD and APX activities was genotype-dependent and it operated better in the drought-resistant genotype. High SOD and APX activities were associated with a rapid recovery of photosynthesis in IACSP94-2094 plants after drought and low substrate temperature alone or simultaneously.