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1.
Drought resistance is becoming an indispensable character for rice improvement due to the dwindling global water resources. Genetic improvement for drought resistance is achieved through physiological dissection and genetic analysis of independent component traits associated with crop productivity under stress. A subset mapping population of 93 near flowering recombinant inbred lines with uniform phenology was constituted for genetic analysis of reproductive stage drought resistance. The population was phenotyped for 22 physio-morphological traits under two contrasting water regimes imposed at reproductive stage. Broad sense heritabilities of morphological traits were lower under stress than irrigated. Predominant association of plant height, panicle exsertion and harvest index with grain yield were observed under stress. The sustenance of panicle exsertion through maintaining growth during moisture stress was found as a significant trait associated with the grain yield through minimizing spikelet sterility. Selective genotyping was carried out with 23 polymorphic microsatellite markers of the established target genomic regions for drought resistance. The study validated the association of a QTL region on the long arm of chromosome 1 with plant height, panicle length, panicle exsertion, biological yield and stomatal conductance under stress. This region, flanked by markers RM246 and RM315, was known to possess the semi-dwarf gene, sd-1. Role of another major interval lying between RM256 and RM149 on chromosome 8 in defining the drought resistance could be established through identification of QTLs associated with leaf rolling, panicle exsertion, plant height, panicle length, senescence and biological yield under moisture stress condition. Few other QTLs were also identified.  相似文献   

2.
The relationship between grain yield and carbon isotope discrimination (Δ) was analysed in wheat grown under different water regimes in the Ningxia Province (north‐west of China). When the association was significant, the relationships between grain yield, Δ and other drought tolerance related traits, such as leaf ash content (ma), chlorophyll concentration (Chl), relative water content (RWC), stomatal conductance (gS) and the ratio of internal CO2 leaf concentration to ambient CO2 concentration (Ci/Ca), were also examined. Using correlation analysis, the relationships were determined during two consecutive years in a set of 20 spring wheat cultivars (landraces, improved varieties and advanced lines) under rainfed and irrigated conditions, including saline conditions. The relationship between Δ and yield within environments highly depended on the quantity of water stored in the soil at sowing, the quantity and distribution of rainfall during the growth cycle, and the irrigation before anthesis. Δ predicted grain yield under limited irrigation (post‐anthesis water stress) but not under pre‐anthesis water stress (rainfed conditions), fully irrigated and saline conditions. Under limited irrigation, grain Δ correlated significantly to grain yield leaf ma at heading and maturity. It also significantly positively correlated to Chl, RWC, gS and Ci/Ca assessed at anthesis. A precise characterization of the timing and intensity of the abiotic constraints experienced by the crop is consequently needed before implementing the use of Δ in wheat breeding programmes.  相似文献   

3.
A large-effect QTL for grain yield under drought conditions (qtl12.1) was reported in a rice mapping population derived from Vandana and Way Rarem. Here, we measured the effect of qtl12.1 on grain yield and associated traits in 21 field trials: ten at IRRI in the Philippines and 11 in the target environment of eastern India. The relative effect of the QTL on grain yield increased with increasing intensity of drought stress, from having no effect under well-watered conditions to having an additive effect of more than 40% of the trial mean in the most severe stress treatments. The QTL improved grain yield in nine out of ten direct-seeded upland trials where drought stress was severe or moderate, but no effect was measured under well-watered aerobic conditions or under transplanted lowland conditions. These trials confirm that qtl12.1 has a large and consistent effect on grain yield under upland drought stress conditions, in a wide range of environments.  相似文献   

4.
Integrative physiological criteria, such as carbon isotope discrimination (Δ) and (mineral) ash content (ma) have been found to be very useful, under drought conditions, to elucidate the association between yield gains and variation of photosynthesis‐related traits and orientate future breeding efforts. Information on this association is scarce under irrigated conditions. The relationships between Δ, ma and yield were studied in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum) under optimal (drip) irrigation in the arid conditions of north‐west Mexico. Carbon isotope discrimination was analysed on leaves at booting stage and anthesis and on grain at maturity, whereas ash content was measured on the flag leaf at anthesis and maturity. At anthesis, there were differences between bread and durum wheat during grain filling for Δ, but not for ma. No relationship was found between grain yield and Δ. Leaf ash content at anthesis and maturity showed a broad variability within each species and were associated with grain yield. These results suggest that ash content in leaves could be also used as predictive criteria for yield not only under drought, but also under irrigated conditions, particularly when evaporative demand is high.  相似文献   

5.
Drought stress and zinc (Zn) deficiency are serious abiotic stress factors limiting crop production in Turkey, especially in Central Anatolia. In this study, the effects of Zn deficiency and drought stress on grain yield of 20 wheat cultivars (16 bread wheat, Triticum aestivum; four durum wheat, Triticum durum cultivars) were investigated over 2 years under rainfed and irrigated conditions in Central Anatolia where drought and Zn deficiency cause substantial yield reductions. Plants were treated with (+Zn: 23 kg Zn ha−1, as ZnSO4·7H2O) and without (−Zn) Zn under rainfed and irrigated conditions. Both Zn deficiency and rainfed treatments resulted in substantial decreases in grain yield. Significant differences were determined between both bread wheat and durum wheat cultivars in terms of drought stress tolerance. Considering drought sensitivity indices over 2 years, the bread wheat cultivars Yayla‐305, Gerek‐79, Dagdas‐94 and Bolal‐2973 were found to be more drought‐tolerant than the other cultivars under both −Zn and +Zn treatments. Especially the durum wheat cultivars Cakmak 79 and Selcuklu 97 showed much greater drought susceptibility under Zn deficiency, and irrigation alone was not sufficient to obtain satisfying grain yield without Zn application. The results indicate that sensitivity to Zn deficiency stress became more pronounced when plants were drought‐stressed. The effect of irrigation on grain yield was maximized when Zn was adequately supplied, leading to the suggestion that efficient water use in Central Anatolia seems to be highly dependent on the Zn nutritional status of plants.  相似文献   

6.
Wheat‐Dasypyrum villosum translocations T6V#2S·6AL and T6V#4S·6DL, carriers of Pm21 and PmV, respectively, confer high resistance to wheat powdery mildew. For better understanding of the difference in genetic effect between them, a RIL population was constructed based on the cross between “Yangmai 18” carrying T6V#2S·6AL and “Yangmai 22” carrying T6V#4S·6DL. Analysis of distribution of the translocations showed that T6V#2S·6AL is much more transmittable than T6V#4S·6DL. By comparing their effects on main agronomic traits, we firstly found that T6V#2S·6AL contributes greatly to top spikelet fecundity, but causes a decrease of 6.7%–10.5% of spike number. No stable effects of T6V#4S·6DL on agronomic traits were found, except for positive effect on plant height. Excitingly, a new recombinant, T6V#4S‐6V#2S·6AL carrying PmV, was screened and proved to have a higher transmission rate than the original translocation T6V#4S·6DL, which will greatly promote the utilization of PmV. The above conclusions of this research will provide important guidance for utilization of Pm21 and PmV more effectively, in wheat powdery mildew resistance breeding.  相似文献   

7.
Little is known of the relationship between hybrids and parental material with respect to water use and drought resistance. Responses of sorghum (Sorghum bicolor [L.] Moench) F1 hybrids to moisture deficits are partially determined by parental material. The yield and water use of six sorghum hybrids and their respective male and female parents were evaluated under stressed and well irrigated conditions during 1980 and 1981 at Tucson, Arizona. The soil was Comoro loamy sand (coarse-loamy, mixed, calcareous, thermic typic Torrifluvent) with an average available soil moisture of 16 % at field capacity. Changes in soil moisture were monitored semi-weekly by neutron modulation. Meteorological data were collected daily. The 1980 season had higher maximum temperatures and pan evaporation than the 1981 season. Differences in cumulative water use among entries were apparent within the same water treatments during 1981. Mean cumulative evapotranspiration (ET) for the stressed treatment was 248 and 281 mm for 1980 and 1981, respectively, and ET under well irrigated conditions was 419 and 528 mm for 1980 and 1981, respectively. Hybrids produced greater grain yield than their parents under both water treatments. This was due to greater seed number for hybrids. Seed numbers were more stable for hybrids over both treatments than for parents. Hybrids four and seven had the greatest grain yield in 1980 and 1981, respectively, under stressed conditions. Water use efficiency (WUE) was significantly different within water treatments but was not so between the irrigated and stressed treatments. Hybrids WUE was generally greater than that of parents except for hybrid five under irrigated conditions in 1981. Hybrids with WUE and stable yields were not necessarily reflective of parental material under stressed and non-stressed environments.  相似文献   

8.
Summary Wheat (Triticum aestivum L.) cultivars grown in the southern Great Plains of the U.S.A. are exposed to a wide range of moisture conditions due to large fluctuations in the amount and frequency of rainfall. Yield stability under those conditions is therefore a desirable trait for wheat breeders. Our primary objective was to quantify various genetic parameters for grain production in drought-stressed and irrigated environments. We also attempted to predict and measure yield responses when selection is practiced in either drought-stressed or irrigated environments, or both. Seventy F2-derived lines from the cross, TAM W-101/Sturdy, were evaluated at Goodwell, OK, under irrigated and naturally drought-stressed conditions in 1987 and 1988. Genetic variance and heritability estimates were higher in the irrigated environment than in the drought-stressed environment. The genetic correlation coefficient for yields in the two environments was 0.20±0.16, indicating that selection of widely adapted genotypes requires testing in both environments. Based on the genetic variance/covariance structure of this particular population, the linear index which maximized the combined expected gain in both environments was 0.66Y1 + 0.34Y2, in which Y1 and Y2 are yields in the irrigated and drought-stressed environments. This index is not expected to apply across all populations; rather, it further supports the hypothesis that testing in either environment alone (drought stressed or irrigated) may not be most effective for increasing either mean productivity or yield under drought stress.  相似文献   

9.
Thermometry and thermography are alternative methods used for measuring stomatal conductivity via transpirative cooling. However, the influence of mixed soil–plant information contained in thermal images compared to thermometric spot measurements on the measurement quality and relationships to agronomic traits remains unclear. To evaluate their respective influence, canopy temperature was measured simultaneously by two infrared thermometers (thermometry), which were oriented oblique to the plant canopy and mounted on a tractor, and a hand‐held, nadir oriented thermal camera (thermography) in irrigated and drought‐stressed spring barley cultivar trials in 2011. Canopy temperatures were separated from soil temperatures and extracted from the thermal images by matching thermal and RGB images. Thermometric measurements conducted at the beginning of shooting during a stable period of high radiation were more closely related to total plant biomass and straw yield at harvest than thermography under both irrigated and drought‐stressed conditions. Taking into account the results of this evaluation, thermometry was used for assessing the agronomic importance of stomatal sensitivity, the earliness of stomatal closure, of spring barley cultivars subjected to different water supply in 2013. In this year, 16 spring barley cultivars were grown under mild drought stress and rainfed conditions. A stomatal sensitivity index was derived relating canopy temperatures of the cultivars grown under rainfed and drought‐stressed conditions to each other. Under rainfed conditions, stomatal sensitivity was negatively related to grain protein yield with a coefficient of determination of R2 = .43. Under increasing terminal drought stress, positive regression slopes of stomatal sensitivity to grain yield, biomass yield and culms/m2 were observed with coefficients of determination amounting to R2 = .22, .31 and .36, respectively. Stomatal sensitivity negatively impacts agricultural production under well‐watered conditions, but maintains productivity under conditions of terminal drought.  相似文献   

10.
Wild species of the genus Oryza are a good source of beneficial alleles for enhancing rice yield under normal and adverse conditions. BC2F3 population was derived from a cross between Oryza sativa IR58025B and Oryza meridionalis Ng. (2n = 24, AA) a heat tolerant wild species to evaluate 12 yield traits under irrigated and aerobic conditions. Analysis of variance and genetic estimates indicated there is substantial genetic variation among progenies under both conditions. Grain yield had high heritability (61.9%) and genetic advance (36.4%) under irrigated conditions but moderate heritability (49.6%) and genetic advance (13.3%) under aerobic conditions indicating that selection for yield will be effective under both conditions. Panicle number, grain number, spikelet fertility, and test weight showed significant positive correlation with grain yield under both conditions. Families out-performing IR58025B for yield under both conditions were obtained providing evidence that phenotypically inferior O. meridionalis contributed to yield increase. This species can be a novel source of natural genetic variation for the improvement of rice under irrigated as well as under aerobic condition.  相似文献   

11.
Identification of hybrids for commercialization is crucial for sustainable maize production in sub-Saharan Africa (SSA). One hundred and ninety test crosses, 10 tester × tester crosses + 10 hybrid checks were evaluated across 11 environments, 2017 to 2019. Inheritance of grain yield under Striga infestation, optimal and across environments was influenced by additive genetic action, but there was greater influence of nonadditive gene action under drought stress conditions. Nine, seven and two inbreds had significant and positive general combining ability (GCA) effects for grain yield under Striga-infested, optimal and drought stress environments, respectively, and would contribute high grain yield to their progenies. Heterotic grouping methods based on specific and GCA, GCA effects of multiple traits and DArTseq markers classified the inbreds into five, three and two heterotic groups, respectively, across research conditions. The DArTseq markers method that classified the inbred lines into two major heterotic groups and was one of the most efficient methods should be adopted for practical purposes in maize breeding programmes in SSA. Hybrids TZEI 7 × TZdEI 352, TZEI 1238 × TZEI 7 and TZEI 1252 × TZEI 7 had outstanding grain yield under contrasting environments and should be tested on-farm for commercialization in SSA.  相似文献   

12.
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   

13.
Maize (Zea mays L.) is an important staple food crop in West and Central Africa (WCA). However, its production is constrained by drought. Knowledge and understanding of the genetics of hybrid performance under drought is invaluable in designing breeding strategies for improving maize yield. One hundred and fifty hybrids obtained by crossing 30 inbreds in sets using the North Carolina Design II plus six checks were evaluated under drought and well‐watered conditions for 2 years at three locations in Nigeria. The objectives of the studies were to (i) determine the mode of gene action controlling grain yield and other important agronomic traits of selected early inbred lines, (ii) examine the relationship between per se performance of inbreds and their hybrids and (iii) identify appropriate testers for maize breeding programmes in WCA. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P < 0.01) for grain yield and other traits under the research environments. The GCA accounted for 64.5 % and 62.3 % of the total variation for grain yield under drought and well‐watered conditions, indicating that additive gene action largely controlled the inheritance of grain yield of the hybrids. Narrow‐sense heritability was 67 % for grain yield under drought and 49 % under well‐watered conditions. The correlations between traits of early‐maturing parental lines and their hybrids were significant (P < 0.01) under drought, well‐watered and across environments. Mid‐parent and better‐parent heterosis for grain yield were 45.3 % and 18.4 % under drought stress and 111.9 % and 102.6 % under well‐watered conditions. Inbreds TZEI 31, TZEI 17, TZEI 129 and TZEI 157 were identified as the best testers. Drought‐tolerant hybrids with superior performance under stress and non‐stress conditions could be obtained through the accumulation of favourable alleles for drought tolerance in both parental lines.  相似文献   

14.
This study aimed to reduce the gap of knowledge on white lupin drought tolerance variation, by assessing the grain yield of 21 landraces from major historical cropping regions, one variety and two breeding lines in a large phenotyping platform that imposed controlled severely stressed or moisture‐favourable conditions after an initial stage of favourable growth. Drought stress reduced grain yield by 79%. Genetic correlation coefficients indicated moderate consistency of genotype responses across conditions for grain yield (rg = 0.76), fairly high consistency for straw yield (rg = 0.85) and harvest index (rg = 0.91), and high consistency for flowering time (rg = 0.99). However, low genetic correlation for yield (rg = 0.31) occurred among a subset of genotypes with early phenology. Specific adaptation to either condition implied significant (p = 0.05) genotype × condition interaction of crossover type between well‐performing genotypes. Early flowering was an important stress escape mechanism, but intrinsic drought tolerance could be inferred from responses of a few genotypes. Various landraces out‐yielded the improved germplasm under stressed or favourable conditions.  相似文献   

15.
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   

16.
Barley (Hordeum vulgare L.) is an important winter cereal crop grown in the semiarid Mediterranean, where late‐terminal drought stress during grain filling has recently become more common. The objectives of this study were to investigate the growth performance and grain yield of four barley cultivars under late‐terminal drought stress under both glasshouse and field conditions. At grain filling, four barley cultivars (Rum, ACSAD176, Athroh and Yarmouk) were exposed to three watering treatments: (1) well‐watered [soil maintained at 75 % field capacity (FC)], (2) mild drought stress at 50 % FC, (3) severe drought stress at 25 % FC in the glasshouse experiment and (1) well‐watered (irrigated once a week), (2) mild drought (irrigated once every 2 weeks), (3) severe drought (non‐irrigated; rainfed) in the field. As drought stress severity increased, gross photosynthetic rate, water potential, plant height, grain filling duration, spike number per plant, grain number per spike, 1000‐grain weight, straw yield, grain yield and harvest index decreased. In the glasshouse experiment, the six‐row barley cultivars (Rum, ACSAD176, and Athroh) had higher grain yield than the two‐row barley cultivar (Yarmouk), but the difference was not significant among the six‐row cultivars under all treatments. In the field experiment, Rum had the highest grain yield among all cultivars under the mild drought stress treatment. The two‐row cultivar (Yarmouk) had the lowest grain yield. In general, the traditional cultivar Rum had either similar or higher grain yield than the other three cultivars under all treatments. However, the yield response to drought differed between the cultivars. Those, Rum and ACSAD176, that were capable of maintaining a higher proportion of their spikes and grains per spike during drought also maintained a higher proportion of their yield compared with those in well‐watered treatment. In conclusion, cultivar differences in grain yield were related to spike number per plant and grain number per spike, but not days to heading or grain filling duration.  相似文献   

17.
Wheat cellular thermotolerance is related to yield under heat stress   总被引：3，自引：0，他引：3  
Cellular thermotolerance in terms of cellular membrane thermostability is often implied as an indication of crop heat tolerance and it is therefore considered as a possible selection criterion for heat tolerance. While there is ample genetic variability for cellular thermotolerance in wheat and other crop plants its relations to yield under heat stress is not sufficiently established. This study was performed to assess the genetic relations in wheat between cellular thermotolerance and yield under heat stress. In one study the co-segregation among cellular membrane thermostability (CMS), yield under chronic heat stress and yield under non-stress conditions was evaluated in a random inbred line (RIL) population of a cross between heat resistant (Danbata) and heat susceptible (Nacozari) cultivars. In a second study the same association was evaluated for yield under heat stress in 49 F7 breeding lines randomly selected from a breeding program. CMS was assayed in growth chamber grown and heat-hardened seedlings. Yield was evaluated under Mediterranean summer irrigated conditions where chronic heat stress caused a reduction in mean yield of the RIL population by 47% as compared with the normal winter growing conditions (non-stress). The RILs varied significantly (p<0.05) for CMS, biomass and yield under stress and non-stress conditions. The two parent cultivars did not differ in biomass or yield under non-stress (winter) conditions but they widely differed for both traits under heat stress. Yield of RILs under heat stress was well distributed between the extreme values of the parent cultivars. There was a significant RIL by season interaction for biomass (F = 9.74; p<0.0001) and yield (F = 10.08; p<0.0001), indicating specific adaptation to heat stress of certain lines in terms of their productivity. Broad-sense heritability for yield was high and nearly the same in the winter (h 2=0.71)and the summer (h 2=0.67). Broad-sense heritability for CMS was high (h 2=0.74). CMS was positively and significantly (p<0.01) correlated across 98 RILs with biomass (r = 0.60* *) and yield (r = 0.53**) under stress but rot with biomass or yield under non-stress conditions. The 49 breeding lines varied significantly (p<0.01) for CMS and yield under chronic heat stress in the summer season. CMS and yield were significantly correlated (r = 0.56**) across lines. Overall the associations between CMS and yield under heat stress were reasonably strong and significant but not perfect. Other factors besides cellular thermostability may support yield under heat stress. CMS alone cannot be used as the exclusive selection criterion for heat tolerance in wheat breeding. lt may be valuable as a supplemental criterion in the final breeding stages or as a rough selection tool to reduce a large population into the most likely heat tolerant core at the early stages of the breeding program.  相似文献   

18.
Rice production is severely constrained by the moisture stress. The present study was undertaken to transfer two important QTLs viz., (qDTY2.2 and qDTY4.1), which controls yield under moisture stress (DTY) into two elite varieties, that is, MTU1010 and NLR34449 through marker-assisted breeding. Foreground and background selections of backcross generations, that is, BC1F1, BC2F1 and BC2F2 identified several promising introgression lines (ILs) with two QTLs and single QTLs with an appreciable level of recovery of recipient parent genome. In ILs, the recovery of MTU1010 genome content was estimated to be 83%–93% while the recovery of NLR34449 was 84%–92%. The two-QTL ILs of MTU1010 and NLR34449 backgrounds (qDTY2.2 and qDTY4.1) have shown substantial yield advantage (32 to 84%) over the single-QTL ILs (either qDTY2.2 or qDTY4.1) under moisture stress conditions. Among all, two ILs, MBC-124 and NBC-127 are the best high yielding lines under moisture stress conditions. These outyielded ILs have the potential to be released as varieties in rainfed ecosystem and also can be used as donors in the existing breeding programme in rice.  相似文献   

19.
The differential response to field salinity of the parents of the ITMI wheat mapping population (cv. Opata 85 and the synthetic hexaploid W7984) was exploited to perform a QTL analysis of the response to salinity stress of a set of agronomic traits over two seasons. The material was irrigated either with potable water (EC of 1.0 dS m−1) or with diluted seawater (12.0 dS m−1). Grain yield was positively correlated with tiller number, plant height, percentage survival, ear weight, ear length, grain number per ear, grain weight and thousand grain weight, and negatively with time to booting, anthesis and physiological maturity, under both the control and salinity stress treatments. In all, 22 QTL were detected under control conditions, and 36 under salinity stress. Of the latter, 13 were major loci (LOD > 3.0) and eight were reproducible across both seasons. Chromosome 2D harboured 15 salinity stress associated QTL and chromosome 4A six such QTL. The remaining loci were located on chromosomes 2A, 5A, 6A, 7A, 1B, 4B, 3B, 6B, 7B and 6D.  相似文献   

20.
There is a lack of studies that have investigated grain yield, its components and photosynthesis in late stages of wheat growth, giving us insufficient understanding of how these factors interact to contribute to yield during this period. As a result, three field experiments were carried out examining 20 winter wheat genotypes of diverse origins under irrigated, terminal drought and dryland conditions in the southern Idaho. Our objective was to evaluate the interaction between post‐anthesis physiological traits, especially leaf‐level photosynthetic capacity, senescence and yield components on grain yield in different moisture regimes. Genotype differences were found in leaf‐level photosynthesis and senescence, canopy temperature depression, grain yield and yield components in each water regime. Grain yield was closely associated with traits related to grain numbers. In all three moisture regimes, positive correlations were observed between grain yield and photosynthesis that were dependent on the timing or physiological growth stage of the photosynthetic measurement: highly significant correlations were found in the mid‐ and late grain filling stages, but no correlations at anthesis. Consistent with these findings, flag leaf senescence at the late grain filling stage was negatively correlated with grain yield and photosynthetic rate (under terminal drought and dryland conditions). These findings provided evidence that grain yield was sink‐limited until the final stages of growth, at which time sustained photosynthesis and delayed senescence were critical in filling grain. Because the trends were consistent in moisture sufficient and deficient conditions, the results suggest that late‐season photosynthesis and delayed leaf senescence are driven by the size of the reproductive carbon sink, which was largely governed by factors affecting grain numbers.  相似文献   

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