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1.
The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought. This study aimed at assessing root distributions, variations in root length density (RLD) and percentage of root distribution, and the relevance of root traits for yield of drought‐resistant peanut genotypes under different available soil water levels. The experiment was conducted in the dry season during the years 2003/04 and 2004/05. Eleven peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60‐3 and Tifton‐8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a split‐plot design with four replications. Roots were sampled by a core sampler at 37, 67 and 97 days after sowing (DAS). Root length was determined by a scanner and the WINRHIZO Pro 2004a software. RLD was calculated as the ratio of root length (cm) and soil volume (cm3). Graphical illustration of root distribution was constructed by merging RLD in the first and second soil layers (0–40 cm) as upper roots and pooling RLD at the third, fourth and fifth layers (40–100 cm) as lower roots. Pod yield, biomass and harvest index (HI) were recorded at harvest. A drought tolerance index (DTI) was calculated for each parameter as the ratio of the parameter under stress treatment to that under well‐watered conditions. Variations in RLD in 40 to 100 cm layer (RLD40 to 100 cm) were found under well‐watered conditions, and the peanut genotypes could be readily identified as high, intermediate and low for this trait. Changes in RLD in the 40 to 100 cm soil layer were found at 2/3 AW and were more evident at 1/3 AW. ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308 and KK 60‐3 were classified as drought responsive as they increased RLD in the deeper subsoil level in response to drought. In general, RLD under drought conditions was not related to biomass production. The ability to maintain the percentage of RLD (DTI for %RLD) was related to pod yield, DTI for pod yield and DTI for HI. ICGV 98300, ICGV 98303, ICGV 98305 exhibited high DTI (RLD40 to 100 cm) which may explain their high pod yield, DTI (PY) and DTI (HI). Based on these observations we classified them as drought‐avoiding genotypes.  相似文献   

2.
Cotton breeders in the United States strive to develop region‐specific genotypes adapted to low temperatures and variable soil moistures during early‐season planting. Nine elite upland cotton germplasm (Gossypium hirsutum L.) lines, representing public breeding programmes from nine states across the cotton belt, were evaluated for cold and drought stresses during seed germination and seedling growth stages. Lines were subjected to three treatments, such as low temperature well‐watered (22/14°C, WW), optimal temperature drought stress (30/22°C, DS) and optimal temperature well‐watered (30/22°C, WW; control), to examine genotypic variability for cold and drought tolerance. The treatment including drought stress was irrigated at 50% of the control. Shoot and root traits measured at 25 days after planting were significantly affected by drought and low temperature, where significant genetic variability among lines was observed for both shoot and root parameters. Response indices were developed to quantify variation in the degree of tolerance among the lines to low temperature and drought. Accordingly, OA‐33 was identified as the most low‐temperature‐tolerant line and Acala 1517‐99 as the most drought‐tolerant line. Identification of both cold‐ and drought‐tolerant genotypes suggests existing genotypic variability could provide breeders the opportunity to improve cultivar response to early‐season drought or cold conditions.  相似文献   

3.
Plant genotypes with higher drought tolerance through improved root characteristics are poorly studied in orchardgrass. In the current research, 30 orchardgrass genotypes were polycrossed and the resulting half‐sib families evaluated under both normal and water stress environments. Under water stress conditions, values for most root traits decreased at 0–30 cm soil depth, while at 30–60 cm depths, the root length (RL), root area (RA), root volume, percentage of root dry weight (RDW) and the ratio of root to shoot were increased. We identified drought‐tolerant genotypes with a high combining ability for root characteristics and a high yield potential. High estimates of heritability as well as genetic variation for root traits indicated that phenotypic selection would be successful in order to achieve genetic progress. Indirect selection to improve dry matter yield was most efficient when selecting for RL and RDW under water stress conditions. Significant associations between a drought tolerance index and RL, RA and root volume confirmed the importance of these traits in conferring drought tolerance of orchardgrass.  相似文献   

4.
Drought during the pre‐flowering stage can increase yield of peanut. There is limited information on genotypic variation for tolerance to and recovery from pre‐flowering drought (PFD) and more importantly the physiological traits underlying genotypic variation. The objectives of this study were to determine the effects of moisture stress during the pre‐flowering phase on pod yield and to understand some of the physiological responses underlying genotypic variation in response to and recovery from PFD. A glasshouse and field experiments were conducted at Khon Kaen University, Thailand. The glasshouse experiment was a randomized complete block design consisting of two watering regimes, i.e. fully‐irrigated control and 1/3 available soil water from emergence to 40 days after emergence followed by adequate water supply, and 12 peanut genotypes. The field experiment was a split‐plot design with two watering regimes as main‐plots, and 12 peanut genotypes as sub‐plots. Measurements of N2 fixation, leaf area (LA) were made in both experiments. In addition, root growth was measured in the glasshouse experiment. Imposition of PFD followed by recovery resulted in an average increase in yield of 24 % (range from 10 % to 57 %) and 12 % (range from 2 % to 51 %) in the field and glasshouse experiments, respectively. Significant genotypic variation for N2 fixation, LA and root growth was also observed after recovery. The study revealed that recovery growth following release of PFD had a stronger influence on final yield than tolerance to water deficits during the PFD. A combination of N2 fixation, LA and root growth accounted for a major portion of the genotypic variation in yield (r = 0.68–0.93) suggesting that these traits could be used as selection criteria for identifying genotypes with rapid recovery from PFD. A combined analysis of glasshouse and field experiments showed that LA and N2 fixation during the recovery had low genotype × environment interaction indicating potential for using these traits for selecting genotypes in peanut improvement programs.  相似文献   

5.
The relationship between biomass production and N2 fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N2 fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N2 fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N2 fixation were found at all water regimes. Biomass production and N2 fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N2 fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N2 fixation under drought stress also was due largely to high N2 fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N2 fixation at FC was not correlated with the reduction in N2 fixation at 2/3 AW and 1/3 AW. Positive relationships between N2 fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N2 fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.  相似文献   

6.
Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment was conducted in large soil tanks subjected to drought treatment of eighty barley genotypes at three‐leaf stage and gradually brought to severe drought by withholding irrigation for 30 days under glasshouse conditions. Also, root length of the same genotypes was measured from stress‐affected plants growing hydroponically. Drought tolerance was scored 30 days after the drought stress commenced based on the degree of the leaf wilting, fresh and dry biomass and relative water content. These characteristics were related to stomatal conductance, stomatal density, residual transpiration and leaf sap Na, K, Cl contents measured in control (irrigated) plants. Responses to drought stress differed significantly among the genotypes. The overall drought tolerance was significantly correlated with relative water content, stomatal conductance and leaf Na+ and K+ contents. No significant correlations between drought tolerance and root length of 6‐day‐old seedling, stomatal density, residual transpiration and leaf sap Cl? content were found. Taking together, these results suggest that drought‐tolerant genotypes have lower stomatal conductance, and lower water content, Na+, K+ and Cl? contents in their tissue under control conditions than the drought‐sensitive ones. These traits make them more resilient to the forthcoming drought stress.  相似文献   

7.
Increasing CO2 concentration ([CO2]) is thought to induce climate change and thereby increase air temperatures and the risk of drought stress, the latter impairing crop growth. The objective of this study was to investigate the effects of elevated [CO2] and drought stress on root growth of one maize genotype (Zea mays cv. Simao) and two sorghum genotypes (Sorghum bicolor cv. Bulldozer and Sorghum bicolor × Sorghum sudanense cv. Inka) under the cool moderate climate of Central Europe. It was hypothesized that root growth stimulation due to elevated [CO2] compensates for a reduced root growth under drought stress. Therefore, we established an experiment within a f ree‐a ir c arbon dioxide e nrichment system (FACE) in 2010 and 2011. Sorghum and maize genotypes were grown under ambient [CO2] (385 ppm CO2) and elevated [CO2] (600 ppm CO2) and in combination with restricted and sufficient water supply. Elevated [CO2] decreased root length density (RLD) in the upper soil layers for all genotypes, but increased it in deeper layers. Higher [CO2] enhanced specific root length (SRL) of “Simao” and “Bulldozer,” however, did not affect that of “Inka.” “Simao” achieved a higher SRL than the sorghum genotypes, indicating an efficient investment in root dry matter. Although elevated [CO2] affected the root growth, no interaction with the water treatment and, consequently, no compensatory effect of elevated [CO2] could be identified.  相似文献   

8.
Improving wheat production in drought‐prone areas is the key to meet the increasing global demand. The importance of root traits, especially, the structural traits such as root volume and rooting depth, has been well recognized to confer drought tolerance in wheat. However, generation of knowledge on root water uptake efficiency and its application in drought adaptation breeding had lagged behind. The main objective of this study was to evaluate the relevance of the root water uptake efficiency to biomass production under acute soil water deficit in six wheat genotypes. Pot experiments were conducted under polythene rainout shelters at Hokkaido University, Sapporo, Japan, in 2010 and 2011. Under drought that was measured as smaller critical fraction of transpirable soil water (FTSW), the root systems with less reduction water uptake efficiency were found to postpone the relative transpiration decline. This study also showed the existence of substantial genotypic variation on the root water uptake efficiency among the wheat genotypes. The expression of hydrophobic root morphology under drought environments, however, did not explain the results obtained on the relative root water uptake efficiency, indicating other regulative mechanisms in operation for the regulation of transverse water flow in the roots. These findings provide new understanding of drought adaptation in wheat through variations in the root water uptake efficiency.  相似文献   

9.
The study investigates the differential accumulation of osmolytes and their contribution to osmotic adjustment in leaf tissue of peanut under drought stress. Plants of four peanut cultivars, obtained from ICRISAT, with varying degrees of drought tolerance were subjected to 10, 15, and 20 days of drought stress by withholding irrigation to 20-day-old seedlings. Leaf samples were collected on 31st, 36th, and 41st days from these stressed plants along with their respective controls. The results indicated that ICGV 91114 was the most drought-tolerant variety followed by ICGS 76 and J 11, while JL 24 was the most drought susceptible. The leaves of ICGV 91114 maintained higher RWC and chlorophyll pigments under water stress compared to JL 24. The contents of all the biochemicals were found to be the maximum in ICGV 91114 and least in JL 24 during stress periods. Drought induced increase in the contents of TSS and TRS were significantly higher in ICGV 91114 under 15 days of water stress compared to the other three varieties and stress periods, while TLP, total free amino acids and total proline were higher in 20-day-old stressed plants of ICGV 91114 and the lowest in 10-day-old stressed plants of JL 24. In the control plants of all four varieties, there was a steady increase in the contents of all these biochemicals with an increase in the age of the plants. The results suggest that osmolytes act as important compatible solutes to maintain osmotic balance, to protect cellular macromolecules, and scavenge free radicals under water stress conditions.  相似文献   

10.
The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought‐stressed and non‐stressed conditions. The experiments were set‐up using a 10 × 10 alpha lattice design with two replications under water stress and non‐stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m2 was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m2. Shoot biomass ranged from 830 g/m2 (genotype Arenza) to 437 g/m2 (LM57), whilst root biomass ranged between 603 g/m2 for Triticale and 140 g/m2 for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress.  相似文献   

11.
Chlorophyll stability during drought might be a promising criterion for selection for drought resistance in peanut. The study describes two field trials conducted at Khon Kaen University, Thailand which investigate genotype × drought interactions in a wide range of peanut germplasm in general and assess the relationship between chlorophyll stability and genotypic performance in particular, under drought. Two field experiments (during 2003/2004 and 2004/2005 dry seasons) were conducted in a split plot design with three water regimes [field capacity, 2/3 available water (AW) and 1/3 AW] as main, and 12 peanut genotypes as subtreatments, replicated four times. Observations on total dry matter (TDM), chlorophyll density (ChlD) (chlorophyll content per unit leaf area), chlorophyll content (chlorophyll content per plant) and SPAD chlorophyll meter readings (SCMR) were recorded at 30, 60 and 90 days after emergence. Transpiration (T) and transpiration efficiency (TE) were computed using the data on amount of water input and TDM. Drought stress significantly reduced TDM, T and chlorophyll content across genotypes but significantly increased TE and ChlD in peanut. However, there were significant differences among genotypes for TE and chlorophyll parameters. The genotype × drought interaction effects for chlorophyll characters (content and density) were not significant suggesting a strong genetic effect. The correlation coefficients between TDM and chlorophyll content (r = 0.51, P = 0.01 to r = 0.91, P = 0.01) and between TE and ChlD (r = 0.46, P = 0.05 to r = 0.77, P = 0.01) were positive and significant. These findings suggest that chlorophyll parameters are strongly linked with drought tolerance in peanut. There were highly significant and positive relationships between ChlD and SCMR (r = 0.67, P = 0.01 to r = 0.93, P = 0.01), between SCMR and TE (r = 0.41, P = 0.05 to r = 0.80, P = 0.01) suggesting that SCMR could be used as a tool for rapid assessment of relative chlorophyll status in peanut genotypes as well as for the indirect selection of drought tolerance in peanut.  相似文献   

12.
In drought‐prone environments, sweet sorghum and sorghum‐sudangrass hybrids are considered worthy alternatives to maize for biogas production. The biomass productivity of the three crops was compared by growing them side‐by‐side in a rain‐out shelter under different levels of plant available soil water (PASW) during the growing periods of 2008 to 2010 at Braunschweig, Germany. All crops were established under high levels of soil water. Thereafter, the crops either remained at the wet level (60–80 % PASW) or were subjected to moderate (40–50 % PASW) and severe drought stress (15–25 % PASW). While the above‐ground dry weight (ADW) of sweet sorghum and maize was insignificantly different under well‐watered conditions, sweet sorghum under severe drought stress produced 27 % more ADW than maize. The ADW of sorghum‐sudangrass hybrids significantly lagged behind sweet sorghum at all levels of water supply. The three crops differed markedly in their susceptibility to water shortage. Severe drought stress reduced the ADW of maize by 51 %, but only by 37 % for sweet sorghum and 35 % for sorghum‐sudangrass hybrids. The post‐harvest root dry weight (RDW) in the 0–100 cm soil layer for maize, sweet sorghum and sorghum‐sudangrass hybrids averaged 4.4, 6.1 and 2.9 t ha?1 under wet and 1.9, 5.7 and 2.4 t ha?1 under severe drought stress. Under these most dry conditions, the sorghum crops had relatively higher RDW and root length density (RLD) in the deeper soil layers than maize. The subsoil RDW proportion (20–100 vs. 0–20 cm) for maize, sweet sorghum and sorghum‐sudangrass hybrids amounted to 6 %, 10 % and 20 %. The higher ADM of sweet sorghum compared with maize under dry conditions is most likely attributable to the deep root penetration and high proportion of roots in the subsoil, which confers the sorghum crop a high water uptake capacity.  相似文献   

13.
This study was conducted to evaluate the influence of seed priming on drought tolerance of pigmented and non‐pigmented rice. Seeds of pigmented (cv. Heug Jinju Byeo) and non‐pigmented (cv. Anjoong) rice were soaked in water (hydropriming) or solution of CaCl2 (osmopriming). Seeds were sown in soil‐filled pots retained at 70 (well‐watered) and 35% (drought) water‐holding capacity. Drought stress caused erratic and poor stand establishment and decreased the growth of both rice types. More decrease in plant height and leaf area under drought stress was noted in pigmented rice, whereas decrease in root length and seedling dry weight, under drought, was more obvious in non‐pigmented rice. Pigmented rice maintained more tissue water and photosynthesis and had more polyphenols, flavonoids and antioxidant activity than non‐pigmented rice. Seed priming was effective in improving stand establishment, growth, polyphenols, flavonoids and antioxidant activity; however, extent of improvement was more in pigmented rice under drought. In conclusion, drought caused erratic germination and suppressed plant growth in both rice types. However, pigmented rice had better drought tolerance owing to uniform emergence, and better physiological and morphological plasticity. Seed priming was quite helpful in improving the performance of both rice types under drought and well‐watered conditions.  相似文献   

14.
Chickpea (Cicer arietinum L.) is a dry season food legume largely grown on residual soil moisture after the rainy season. The crop often experiences moisture stress towards end of the crop season (terminal drought). The crop may also face heat stress at the reproductive stage if sowing is delayed. The breeding approaches for improving adaptation to these stresses include the development of varieties with early maturity and enhanced abiotic stress tolerance. Several varieties with improved drought tolerance have been developed by selecting for grain yield under moisture stress conditions. Similarly, selection for pod set in the crop subjected to heat stress during reproductive stage has helped in the development of heat‐tolerant varieties. A genomic region, called QTL‐hotspot, controlling several drought tolerance‐related traits has been introgressed into several popular cultivars using marker‐assisted backcrossing (MABC), and introgression lines giving significantly higher yield than the popular cultivars have been identified. Multiparent advanced generation intercross (MAGIC) approach has been found promising in enhancing genetic recombination and developing lines with enhanced tolerance to terminal drought and heat stresses.  相似文献   

15.
This study was conducted to evaluate drought tolerance and persistence in a germplasm of smooth bromegrass and association of forage productivity with different traits. Thirty‐six genotypes of smooth bromegrass were clonally propagated and evaluated under two soil moisture environments for three years (2013–2015). High genotypic variation was observed among genotypes for all the measured traits. Drought stress decreased mean values for traits related to productivity. Also, the long‐term stress for three years reduced the persistence of plants. Results indicated that indirect selection based on components of forage yield, which had high heritability and high correlation with yield, would be more effective to improve drought tolerance in this germplasm. The results of principal component analysis showed that there was a negative relationship between phenological traits with the persistence‐related traits and yield production. This suggests that selection for earliness may indirectly promote persistent genotypes. The results showed that some Hungarian genotypes are valuable gene sources for persistence. The most persistent genotypes from both groups (Iranian and foreign) were identified using the biplot method. These genotypes may be useful for the development of populations for future studies.  相似文献   

16.
Drought‐induced damages in crop plants are ranked at top amid all losses instigated by diverse abiotic stresses. Terminal drought (drought at reproductive phase) has emerged as a severe threat to the productivity of wheat crop. Different seed enhancement techniques, genotypes and distribution of crop plants in different spacings have been explored individually to mitigate these losses; however, their interaction has rarely been tested in improving drought resistance in wheat. This study was conducted to evaluate the potential role of different seed enhancement techniques and row spacings in mitigating the adversities of terminal drought in two wheat cultivars during two consecutive growing seasons of 2010–2011 and 2011–2012. Seeds of wheat cultivars Lasani‐2008 (medium statured) and Triple Dwarf‐1 (dwarf height) soaked in water (hydropriming) or CaCl2 (osmopriming) were sown in 20‐, 25‐ and 30‐cm spaced rows; just before heading, the soil moisture was maintained at 100 % field capacity (well watered) or 50 % field capacity (terminal drought) till maturity. Terminal drought significantly reduced the yield and related traits compared with well‐watered crop; however, osmopriming improved the crop performance under terminal drought. Among different row spacings, wheat sown in 20‐cm spaced rows performed better during both years of study. Wheat cultivar Lasani‐2008 performed better than cultivar Triple Dwarf‐1 under both well‐watered and stress conditions. Maximum net returns and benefit–cost ratio were recorded from osmoprimed seeds of cultivar Lasani‐2008 sown in 20‐cm spaced rows under well‐watered condition. Nonetheless, osmoprimed seeds of cultivar Lasani‐2008 sown in 20‐cm spaced rows were better able to produce good yield under terminal drought.  相似文献   

17.
Perennial grasslands provide numerous environmental benefits but their response to severe drought and therefore their sustainability in arid and Mediterranean areas have been little studied. Due to climate change, models of pasture production should be able to predict sward evolutions under increasing aridity. Our general goal was to identify plant traits and functional types that could be included in models aiming to analyse the dynamics of contrasting types of herbaceous plants grown in mixtures under drought. The two steps were: (1) to investigate the morpho-physiological traits associated with drought survival within a mixture of perennial herbaceous populations and to test whether the physiological traits measured under optimum conditions of growth in Spring may predict plant responses under subsequent summer drought and (2) to identify functional groups of populations exhibiting similar responses to the disturbance regime caused by severe drought. Seven different populations from five species were grown in monocultures (pots, long columns) and mixtures (containers, field). Standard leaf functional traits, aerial and root biomass were assessed under non-limiting water supply in Spring. In Summer, under continuous severe drought, leaf water status and plant survival were measured.Senescence of aerial tissues at the end of Spring, associated with endogenous summer dormancy, water status maintenance in basal tissues during the intense drought, and root biomass in the field were the variables best correlated with drought survival. The standard leaf functional traits specific leaf area (SLA) and leaf dry matter content (LDMC) measured in Spring under full irrigation, were uncorrelated with drought survival. These results suggested no general trade-off between growth potential and drought survival. Under conditions of optimal production in Spring, correlations were established between functional traits and variables associated with aerial biomass productivity which discriminated the group of forage cultivars from the other genotypes. Under summer drought, four main functional types of genotypes were defined according to their strategy of water use and therefore contrasting survival and persistence. This typology will be used to base further modelling study aiming to assess the effects of increasing aridity on the stability and productivity of herbaceous swards on the long term.  相似文献   

18.
Drought and high temperature are major environmental stress factors threatening wheat production during grain filling stage resulting in substantial yield losses. Four wheat genotypes (Suntop, IAW2013, Scout and 249) were planted under two temperature levels (25 and 30°C) and two water levels (15% and 25% soil moisture content). Wheat yield, leaf δ13C, plant rhizodeposition, shoot biomass and root traits were examined. Low moisture (drought stress) and high temperature (heat stress) decreased the grain yield of all wheat genotypes, in particular 249, while combined drought and temperature stresses had the most pronounced negative effect on plant biomass and grain yield. Decreasing soil water availability decreased the allocation of plant‐derived C to soil organic carbon (SOC) and to microbial biomass through rhizodeposition. Leaf δ13C decreased with increased yield, suggesting that higher yielding genotypes were less water stressed and allocated less C to SOC and microbial biomass through rhizodeposition. Wheat genotypes with lower root/shoot ratios and thinner roots were more efficient at assimilating C to the grain, while genotypes with higher root/shoot ratios and thicker roots allocated more C belowground through rhizodeposition at the expense of producing higher yield. Therefore, improving these traits for enhanced C allocation to wheat grain under variable environmental conditions needs to be considered.  相似文献   

19.
Developing tolerant genotypes is crucial for stabilizing maize productivity under drought stress conditions as it is one of the most important abiotic stresses affecting crop yields. Twenty seven genotypes of maize (Zea mays L.) were evaluated for drought tolerance for three seasons under well watered and water stressed conditions to identify interactions amongst various tolerance traits and grain yield as well as their association with SSR markers. The study revealed considerable genetic diversity and significant variations for genotypes, environment and genotype × environment interactions for all the traits. The ranking of genotypes based on drought susceptibility index for morpho-physiological traits was similar to that based on grain yield and principal component analysis. Analysis of trait – trait and trait – yield associations indicated significant positive correlations amongst the water relations traits of relative water content (RWC), leaf water potential and osmotic potential as well as of RWC with grain yield under water stressed condition. Molecular analysis using 40 SSRs revealed 32 as polymorphic and 62 unique alleles were detected across 27 genotypes. Cluster analysis resulted in categorization of the genotypes into five distinct groups which was similar to that using principal component analysis. Based on overall performance across seasons tolerant and susceptible genotypes were identified for eventual utilization in breeding programs as well as for QTL identification. The marker-trait association analysis revealed significant associations between few SSR markers with water relations as well as yield contributing traits under water stressed conditions. These associations highlight the importance of functional mechanisms of intrinsic tolerance and cumulative traits for drought tolerance in maize.  相似文献   

20.
Drought can be a critical limitation on peanut yield. A physiological trait that may help to ameliorate drought is limited transpiration (TRlim), defined as a limitation on further increases in transpiration rate (TR) under high vapour pressure deficit (VPD) conditions. The advantage of the TRlim trait is that it allows plant water conservation to increase soil water availability for use during late‐season drought. While this trait has been identified in peanut, there is no information of how readily the trait may be transfer to progeny lines. The objective of this study was to obtain preliminary information on the expression of the TRlim trait in two peanut progeny populations. One population was runner type of 88 RILs derived from the mating of Tifrunner × NC 3033. The second set was selected for the virginia‐type phenotype of large pods obtained from mating of PI 585005 (ICGV 86015) and N0808olJCT, both of which expressed the TRlim trait. A two‐tier screen was applied to both populations. The initial screen was based on exposure of de‐rooted shoots to silver ions. Fifteen runner type and 12 virginia type were selected for direct measures of transpiration response to varying VPD. The results from each of the two populations showed that an effective expression of the TRlim trait occurred in about 30% of the progeny in each population. While these results do not offer a definitive index of inheritance, they do indicate that there appears to be a strong possibility of transferring the TRlim trait to progeny genotypes.  相似文献   

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