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1.
More rapid progress in breeding peanut for reduced aflatoxin contamination should be achievable with a better understanding of the inheritance of, aflatoxin trait and physiological traits that are associated with reduced contamination. The objectives of this study were to estimate the heritability of aflatoxin traits and genotypic (rG) and phenotypic (rP) correlations between drought resistance traits and aflatoxin traits in peanut. One hundred-forty peanut lines in the F4:6 and F4:7 generations were generated from four crosses, and tested under well-watered and terminal drought conditions. Field experiments were conducted under the dry seasons 2006/2007 and 2007/2008. Data were recorded for biomass (BIO), pod yield (PY), drought tolerance traits [harvest index (HI), drought tolerance index (DTI) of BIO and PY, specific leaf area (SLA), and SPAD chlorophyll meter reading (SCMR)], and aflatoxin traits [seed infection and aflatoxin contamination]. Heritabilities of A. flavus infection and aflatoxin contamination in this study were low to moderate. The heritabilities for seed infection and aflatoxin contamination ranged from 0.48 to 0.58 and 0.24 to 0.68, respectively. Significant correlations between aflatoxin traits and DTI (PY), DTI (BIO), HI, biomass and pod yield under terminal drought conditions were found (rP = −0.25** to 0.32**, rG = −0.57** to 0.53**). Strong correlations between SLA and SCMR with A. flavus infection and aflatoxin contamination were also found. Positive correlations between SLA at 80, 90, and 100 DAP and aflatoxin traits were significant (rP = 0.13** to 0.46**, rG = 0.26** to 0.81**). SCMR was negatively correlated with aflatoxin traits (rP = −0.10** to −0.40**, rG = −0.11** to −0.66**). These results indicated that physiological-based selection approaches using SLA and SCMR might be effective for improving aflatoxin resistance in peanut.  相似文献   

2.
Variability of light interception and its derivatives are poorly understood at the field-scale in maize (Zea mays L.) and soybean [Glyine max (L.) Merr.]. Quantifying variability can provide reliable estimates of field-scale processes and reliable methodology. A field study was conducted during the 2005 growing season in a 31 ha maize and 23 ha soybean field rotated annually near Ames, IA to measure variability of cumulatively intercepted photosynthetically active radiation (CI-PAR) and radiation use efficiency (RUE) by deploying eight line quantum sensors in each field. Cumulative mean PAR interception for soybean was 575 MJ m−2 ending on day of the year (DOY) 249 compared with 687 MJ m−2 in maize ending on DOY 244. Soybean standard error (sX) for a single sensor was 4.48% and with six sensors was 1.83% of the final CI-PAR. Maize sX for a single sensor was 5.29% and with eight sensors was 1.87% of the final CI-PAR. Crop biomass was quantified weekly by collecting four 1 m2 samples. Soybean RUE using all sensors was 1.44 ± 0.06 g MJ PAR−1. The highest CI-PAR from a single sensor had RUE of 1.32 and the lowest was 1.55 g MJ PAR−1. Maize RUE using all sensors was 3.35 ± 0.09. The highest CI-PAR from a single sensor had RUE of 2.87 and the lowest was 3.70 g MJ PAR−1. Reliable transmitted PAR and RUE estimates are obtainable at the field-scale in maize and soybean with four and three sensors, respectively, assuming that crop biomass is accurately measured.  相似文献   

3.
The partitioning behavior of the glutenin proteins was evaluated in aqueous two-phase systems (ATPSs) formed by sulfate salts (lithium or sodium) and poly(ethylene glycol) (PEG) with average molar mass of 1500 g mol−1 or 4000 g mol−1. The partition coefficients for the glutenin proteins in each ATPS were investigated as a function of the temperature (278.2 K–318.2 K), tie line length (TLL) and electrolyte nature. In all ATPS, the majority of glutenin proteins spontaneously concentrate in the polymer-rich phase (Kp > 1). The partition coefficient is very dependent on the salt nature and the ATPS formed by PEG + lithium sulfate presents higher Kp values as compared with the ATPS formed PEG + sodium sulfate. An increase of molar mass of polymer promotes a decrease of Kp. Thermodynamic parameters of transfer (ΔtrG, ΔtrH and ΔtrS) were obtained by the application of the Van’t Hoff equation (VHE). The values obtained by VHE indicate that the transfer of glutenin proteins to the polymer-rich phase has an enthalpic origin.  相似文献   

4.
The nitrogen-driven trade-off between nitrogen utilisation efficiency (yield per unit nitrogen uptake) and water use efficiency (yield per unit evapotranspiration) is widespread and results from well established, multiple effects of nitrogen availability on the water, carbon and nitrogen economy of crops. Here we used a crop model (APSIM) to simulate the yield, evapotranspiration, soil evaporation and nitrogen uptake of wheat, and analysed yield responses to water, nitrogen and climate using a framework analogous to the rate-duration model of determinate growth. The relationship between modelled grain yield (Y) and evapotranspiration (ET) was fitted to a linear-plateau function to derive three parameters: maximum yield (Ymax), the ET break-point when yield reaches its maximum (ET#), and the rate of yield response in the linear phase (ΔY/ΔET). Against this framework, we tested the hypothesis that nitrogen deficit reduces maximum yield by reducing both the rate (ΔY/ΔET) and the range of yield response to evapotranspiration, i.e. ET# − Es, where Es is modelled median soil evaporation.  相似文献   

5.
Plant responses to water deficit need to be monitored for producing a profitable crop as water deficit is a major constraint on crop yield. The objective of this study was to evaluate physiological responses of cotton (Gossypium hirsutum) to various environmental conditions under limited water availability using commercially available varieties grown in South Texas. Soil moisture and variables of leaf gas exchange were measured to monitor water deficit for various varieties under different irrigation treatments. Lint yield and growth variables were also measured and correlations among growth parameters of interest were investigated. Significant differences were found in soil moisture, leaf net assimilation (An), stomatal conductance (g), transpiration rate (Tr), and instantaneous water use efficiency (WUEi) among irrigation treatments in 2006 while no significant differences were found in these parameters in 2007. Some leaf gas exchange parameters, e.g., Tr, and leaf temperature (TL) have strong correlations with An and g. An and WUE were increased by 30–35% and 30–40%, respectively, at 600 μmol (CO2) m−2 s−1 in comparison with 400 μmol (CO2) m−2 s−1. Lint yield was strongly correlated with g, Tr, WUE, and soil moisture at 60 cm depth. Relative An, Tr, and TL started to decrease from FTSW 0.3 at 60 cm and FTSW 0.2 at 40 cm. The results demonstrate that plant water status under limited irrigation management can be qualitatively monitored using the measures of soil moisture as well as leaf gas exchange, which in turn can be useful for describing yield reduction due to water deficit. We found that using normalized An, Tr, and TL is feasible to quantify plant water deficit.  相似文献   

6.
Effect of N supply on stalk quality in maize hybrids   总被引：1，自引：0，他引：1  
The identification of maize nitrogen (N) response for stalk quality is valuable in stalk breeding improvement, stalk lodging resistance and for use in bioenergy. This study analyzed the effect of two N levels and estimated quantitative genetic parameters for stalk quality in summer maize in the north China plain (NCP). Thirty hybrids were sampled and tested from three to four geographic locations under high nitrogen (HN) (225 kg N ha−1) and low nitrogen (LN) (0 kg N ha−1) during 2006–2008. Compared to HN level, stalk crude protein (CP) was significantly reduced (22.06%) under LN level. Ether extract (EE), ash content (AC), in vitro dry matter digestion (IVDMD) and lignin content (LC) were lower under LN level. Cellulose content (CC), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were increased with a reduction in N, however N did not significantly affect EE, ADF and LC. An increase in NDF and ADF content under low vs. high N level was mainly attributed to a reduction in CC. ADF and NDF exhibited positive correlation and both showed a positive correlation with CC but a negative correlation with LC, IVDMD and CP. Negative correlations between IVDMD and CC, IVDMD and LC, and CP and CC were also detected. The interaction variance of genotype × year × location (σ2GYL) for each N level, with the exception of σ2GYL for CC under HN, was significant and most stalk quality traits were evaluated in different locations and years. The estimates of genetic variance (σ2G) and heritability (h2) were greater under HN, with the exception of LC and EE. The interaction of genotype × nitrogen (σ2GN) for CP was more important than σ2G. The genotypic correlation coefficients (rG) for performance in different stalk quality traits between HN and LN were significant. However, it was necessary to evaluate both HN and LN for IVDMD. For other stalk quality traits, breeding maize under HN levels may serve to develop hybrids well adapted to high and/or low N level. The response to N trend was similar between high oil and normal maize hybrids.  相似文献   

7.
In Argentina, delayed sowing causes a decrease in seed yield and in radiation use efficiency (RUE) of peanut crops (Arachis hypogaea L.), but it is not known if RUE reduction is mainly due to reduced temperature during late reproductive stages or to a sink limitation promoted by decreased seed number in these conditions. We analyzed seed yield determination and RUE dynamics of two cultivars (Florman and ASEM) in four irrigated field experiments (Expn) grown at three sites and five contrasting sowing dates (between 17 October and 21 December) in three growing seasons. An additional field experiment was performed with widely spaced plants (i.e. with no interference among them) to evaluate the effect of peg removal on RUE and leaf carbon exchange rate (CER). Seasonal dynamics of mean air temperature and irradiance, biomass production (total and pods), and intercepted photosynthetically active radiation (IPAR) were followed. Seed yield and seed yield components (pod number, seeds per pod, seed number and seed weight) were determined at final harvest. Crop growth rate (CGR) and pod growth rate (PGR) were computed for growth phases of interest. RUE values for crops sown until 14 November were 1.89–1.98 g MJ−1 IPAR, within the usual range. RUE decreased significantly for cv. Florman in the late sowing of Exp1 (29 November) and for both cultivars in Exp3 (21 December sowing). Across experiments, seed yield (4.5-fold variation relative to minimum) was strongly associated (r2 = 0.87, P < 0.0001) with variations in seed number (3.5-fold variation relative to minimum), and to a lesser extent (r2 ≤ 0.54, P ≤ 0.001) to variations in seed weight (1.9-fold variation relative to minimum). Seed number was positively related (P < 0.01) to CGR (r2 = 0.66) and to PGR (r2 = 0.72) during the R3–R6.5 phase (seed number determination window), while crop growth during the grain-filling phase (i.e. between R6.5 and final harvest) was positively associated with grain number (r2 = 0.80, P < 0.001). No association was found between RUE and mean air temperature, neither for the whole cycle nor for the phase between R6.5 and final harvest, which showed the largest temperature variation (16.4–22.4 °C) across experiments. Use of mean minimum temperature records (range between 13.8 and 18.5 °C) did no improve the relationship. However, grain-filling phase RUE showed a positive (r2 = 0.69, P = 0.003) linear response to seed number across experiments. This apparent sink limitation of source activity was consistent with the reduced RUE (from 2.73 to 1.42 g MJ−1 IPAR) and reduced leaf CER at high irradiance (from ca. 30 to 15 μmol m−2 s−1) for plants subjected to 75% peg removal.  相似文献   

8.
Litchi downy blight caused by Peronophythora litchii is a devastating disease of litchi plants in China. Control of litchi downy blight requires numerous fungicide applications. A new carboxylic acid amide (CAA) fungicide, mandipropamid, was examined for its in vitro effects on multiple asexual stages of four single-sporangium P. litchii isolates and protective activity against downy blight in detached fruit assays. Though mandipropamid did not affect discharge of zoospores from sporangia, it strongly inhibited mycelial growth (mean EC50 = 0.0048 μg ml−1), sporangia production (mean EC50 = 0.0032 μg ml−1), germination of encysted zoospores (mean EC50 = 0.0023 μg ml−1), and germination of sporangia (mean EC50 = 0.0061 μg ml−1). On detached fruit, 0.39, 1.56 and 6.25 μg ml−1 of mandipropamid were superior in reducing downy blight compared to metalaxyl and flumorph, however, the 25 μg ml−1 application rate was necessary for all three CAA fungicides to completely inhibit the disease. In 2007, 100 isolates from Fujian, Guangdong, and Guangxi Provinces of China were characterized for the baseline sensitivity to mandipropamid. The isolates obtained from different provinces showed similar baseline sensitivities to mandipropamid. Baseline sensitivities formed a unimodal curve with mean EC50 values of 0.0055 ± 0.0012 μg ml−1 for inhibition of mycelial growth. The described baseline sensitivities of P. litchii populations will be useful for monitoring possible shifts in sensitivity to mandipropamid.  相似文献   

9.
In the framework of the E.U. project Fair CT 96-1913 “Environmental studies on sweet and fibre sorghum, sustainable crops for biomass and energy”, a research has been carried out with the aim to study the water and nitrogen balance and determine the critical N dilution curve of sweet sorghum cv. Keller. A field experiment was performed, where three irrigation treatments (I0 = dry control, I50 = 50% ETm restoration, I100 = 100% ETm restoration) and four nitrogen fertilization levels (N0 = no nitrogen control, N60 = 60 kg ha−1, N120 = 120 kg ha−1; N180 = 180 kg ha−1) were studied. The final yield was significantly affected by the amount of water distributed but not by the nitrogen level. The treatments watered up to crop establishment (I0) produced, in the average, 7.5 t ha−1 of dry matter, against 21.1 and 27.1 t ha−1 of I50 and I100, respectively. The crop determined a great reduction in nitrate concentration of soil water, irrespective of nitrogen supplied. The variation between N output and input (Δ) was negative in N0, N60 and N120 and positive in N180. The critical value of nitrogen uptake change in relation to the water availability. The amount of nitrogen supplied did not determine significant differences upon WUE. The crop seems to have a great potentiality in Mediterranean environment in terms of yield production.  相似文献   

10.
In the absence of serious post-anthesis stress, the potential supply of assimilates for grain filling in barley appears to exceed the storage (sink) capacity of the grains. The sink capacity is a function of the number of grains per unit land area and their potential size. In order to investigate the contribution of pre and early post-anthesis factors in the control of potential grain weight, regression analysis has been used to analyse data from field experiments conducted on winter barley crops cv. Pearl grown at six sites across the UK between 2002 and 2004. Crops were grown under a comparable husbandry regime with a full crop protection, growth regulator and fertilizer programme. The mean grain weight (MGW) varied from 35 to 46 mg at 100% dry matter over 17 site/year combinations. The variation in MGW between site/years was associated with differences in the rate rather than the duration of grain filling. MGW did not relate well to any measure of above ground growth or crop structure at ear emergence (Zadoks GS59). There was a significant positive linear relationship between MGW and the amount of radiation (PAR) intercepted per unit grain number between ear emergence and the start of rapid grain filling (r2 = 0.32, P = 0.023), but not over the whole grain filling period. This is consistent with the view that MGW is determined by potential grain size. A multiple regression model comprising five explanatory variables accounted for a much larger proportion of the total variation in MGW (r2 = 0.72, P = 0.013) than PAR interception on its own. There were significant positive associations of MGW with post-anthesis radiation use efficiency and PAR intercepted from GS59 to the start of rapid grain growth (RGG), and significant negative associations with the shoot number per plant, mean air temperature from GS39–59 and mean daily rainfall from GS59-RGG. The results suggest that both pre and post-anthesis conditions operate in concert to determine the potential grain weight of barley in temperate climates. The dry weight and water content of grains and ears followed a common pattern during grain growth for all site/years when the percentage moisture content was used as an index to normalise different rates of development. Use of the above data for predicting potential grain weight of barley prior to harvest is discussed.  相似文献   

11.
Wastage of agricultural chemicals and ensuing environmental pollution is an issue, where ineffective spray deposition is a major concern with conventional pesticide application methods. Electrostatic spraying is known to be one of the most effective methods to improve leaf abaxial (underside) surface deposition, overall deposition, and distribution on the plant targets. Deposition of charged sprays on leaf abaxial and adaxial (upper) surfaces as influenced by the spray charging voltage (system), application speed (operational), target height and orientation (target) parameters was studied in the laboratory. An air-assisted electrostatic induction spray charging system attached to a moving carriage was used to apply charged spray at uniform application (ground) speeds. Spray deposition (101–71 μm NMD), determined using a fluorescent tracer technique increased with charging (0–5.5 mC kg−1) on leaf abaxial and decreased with charging on adaxial surface. The deposition was higher on abaxial (0.66–1.33 μg cm−2) at 30° below (horizontal plane) and on adaxial (0.78–1.79 μg cm−2) at 0° (horizontal) target orientation for lower (0.278 m s−1) application speed. At all target heights, abaxial deposition increased with charging voltage (0–4.0 kV) for medium application speed (0.417 m s−1) and adaxial deposition decreased with charging voltage for lower application speed (0.278 m s−1). The medium application speed with higher charging voltage was optimum for abaxial and adaxial deposition. The droplet velocity and charging voltage were the key factors for obtaining desired spray deposition on targets. All the selected factors including target orientation (O), application speed (S), target surface (L), and charging voltage (V), and their interactions except between O and S were significant at lower (0.35 m) and medium (0.65 m) target heights. All the factors and their interactions except between O and V were significant at higher (0.95 m) height. Electrostatically charged spray improved the underside (abaxial) and overall deposition. The deposition was substantially influenced by factors such as charging voltage, application speed, plant target height, and target orientation.  相似文献   

12.
The efficacy of Hanseniaspora uvarum against gray mold by adding ammonium molybdate (NH4–Mo) and the mode of actions were evaluated. The results showed that H. uvarum at 1 × 106 CFU ml−1 plus 1 mmol l−1 NH4–Mo greatly reduced gray mold in grape fruits. NH4–Mo at concentrations of 1, 5, 10 and 15 mmol l−1 significantly inhibited spore germination and mycelium growth of Botrytis cinerea. Population growth of H. uvarum was markedly inhibited by NH4–Mo at 5 mmol l−1in vitro and not affected by addition of NH4–Mo at 1 and 5 mmol l−1 in wounds combination of NH4–Mo and H. uvarum induced higher activities of peroxidase (POD), polyphenoloxidase (PPO), phenylalanine ammonialyase (PAL), superoxide dismutase (SOD), catalase (CAT) and β-1,3-Glucanase than individual application of H. uvarum or NH4–Mo. The enhancement of disease control may be directly because of the inhibitory effects of NH4–Mo on spore germination and mycelial growth of B. cinerea in vitro, and indirectly because of the induced defense reactions by NH4–Mo in grape berries.  相似文献   

13.
Modeling plant carbon flow and grain starch accumulation in wheat   总被引：1，自引：0，他引：1  
The process of starch accumulation in grain directly influences the yield and quality formation in wheat. Since few studies have been aimed at modeling the grain starch accumulation, this study was undertaken to develop a simplified process model for predicting the rate of starch accumulation in wheat grain by focusing on the variation of plant carbon dynamics post-anthesis. Five different experiments involving genotypes, nitrogen rates and water regimes were conducted to support model development and model evaluation. The model proposed that the starch accumulation rate (STR) in individual grain was determined by the availability of carbon source in plant (GCAi) and the ability of starch synthesis in grain (f(Ai)), as influenced by the factors of temperature, water and nitrogen conditions within plants. The f(Ai) could be described in a two-section curve with post-anthesis growing degree days (GDD), first exponential increase and then linear decrease. The GCAi was determined by post-anthesis carbon assimilation and carbon remobilization from vegetative organs to grains. A genotypic parameter was incorporated into the model algorithm, i.e. the maximum rate of individual grain starch accumulation, to differentiate the ability of starch accumulation among cultivars. The overall performance of the model was validated with different data sets from three field experiments spanning 3 years and comprising various genotypes, nitrogen and water levels. The RMSE values for all treatments were averaged as 12.51%, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for grain starch accumulation of different wheat cultivars under various growing conditions.  相似文献   

14.
A highly efficient regeneration protocol for oilseed crop Crambe abyssinica has been developed using hypocotyls as explants in this study. Crambe is a potential engineering oilseed crop for industrial purposes as it contains 55-60% erucic acid in its oil and, more importantly, it does not outcross with any food oil seed crops. However, the low regeneration frequency with the currently available protocols is still a limiting factor for genetic modification of Crambe. In this study, we investigated the effects of N-source, C-source, AgNO3, cultural conditions as well as the concentration and combination of plant growth regulators (PGR) on the regeneration frequency of C. abyssinica. The results showed that all these factors, especially the N-source and PGR concentrations and combinations, played an important role in shoot regeneration. Among all the factors tested, the combination of using hypocotyls from C. abyssinica cv. galactica, the Lepiovre basal medium supplemented with 16 g l−1 glucose, 0.5 g l−1 AgNO3, 2.2 mg l−1 thidiazuron (TDZ), 0.5 mg l−1 α-naphthaleneacetic acid (NAA), 2.5 g l−1 Gelrite, seeds germinated in dark for 3 days and explants cultured in light, gave the best regeneration frequency (over 95%). The results also suggest that reducing the content of NH4+ or keeping a suitable NO3−/NH4+ ratio in the regeneration medium would be crucial to Crambe shoot regeneration.  相似文献   

15.
Milled rice from 11 varieties, with amylose levels from 1.2 to 35.6% dry base, were collected to study the impacts of amylose content on starch retrogradation and textural properties of cooked rice during storage. The relationship between amylose content and different properties was determined using Pearson correlation. Starch retrogradation enthalpy (ΔHr) of cooked rice was determined by differential scanning calorimetry. ΔHr values were found to be positively correlated with amylose content (0.603 ≤ r ≤ 0.822, P < 0.01) during storage. Textural properties were determined by a Texture Analyser. The hardness of cooked rice showed a positive correlation with amylose content (0.706 ≤ r ≤ 0.866, P < 0.01) and a positive correlation with ΔHr of cooked rice (r = 0.650, P < 0.01) during storage. The adhesiveness showed a negative correlation with amylose content (−0.929 ≤ r ≤ −0.678, P < 0.01) and a negative correlation with ΔHr of cooked rice (r = −0.833, P < 0.01) during storage. Hardness showed a negative correlation with adhesiveness (r = −0.820, P < 0.01). These results indicated that amylose content has significant effects on starch retrogradation and textural properties of cooked rice. The cooked rice with high amylose content is easy to retrograde, the cooked rice with low amylose content retrograded slowly. Sarch retrogradation contributes to the changes of textural properties of cooked rice during storage.  相似文献   

16.
Nitrogen (N) fertilizer represents a significant cost for the grower and may also have environmental impacts through nitrate leaching and N2O (a greenhouse gas) emissions associated with denitrification. The objectives of this study were to analyze the genetic variability in N-use efficiency (grain dry matter (DM) yield per unit N available from soil and fertilizer; NUE) in winter wheat and identify traits for improved NUE for application in breeding. Fourteen UK and French cultivars and two French advanced breeding lines were tested in a 2 year/four site network comprising different locations in France and in the UK. Detailed growth analysis was conducted at anthesis and harvest in experiments including DM and N partitioning. Senescence of either the flag leaf or the whole leaf canopy was assessed from a visual score every 3-4 days from anthesis to complete canopy senescence. The senescence score was fitted against thermal time using a five parameters monomolecular-logistic equation allowing the estimation of the timing of the onset and the rate of post-anthesis senescence. In each experiment, grain yield was reduced under low N (LN), with an average reduction of 2.2 t ha−1 (29%). Significant N × genotype level interaction was observed for NUE. Crop N uptake at harvest on average was reduced from 227 kg N ha−1 under high N (HN) to 109 kg N ha−1 under LN conditions while N-utilization efficiency (grain DM yield per unit crop N uptake at harvest; NUtE) increased from 34.0 to 52.1 kg DM kg−1 N. Overall genetic variability in NUE under LN related mainly to differences in NUtE rather than N-uptake efficiency (crop N uptake at harvest per unit N available from soil and fertilizer; NUpE). However, at one site there was also a positive correlation between NUpE and NUE at LN in both years. Moreover, across the 2 year/four site network, the N × genotype effect for NUpE partly explained the N × genotype effect for grain yield and NUE. Averaging across the 16 genotypes, the timing of onset of senescence explained 86% of the variation in NUtE amongst site-season-N treatment combinations. The linear regression of onset of senescence on NutE amongst genoytpes was not significant under HN, but at three of the four sites was significant under LN explaining 32-70% of the phenotypic variation amongst genotypes in NutE. Onset of senescence amongst genotypes was negatively correlated with the efficiency with which above-ground N at anthesis was remobilized to the grain under LN. It is concluded that delaying the onset of post-anthesis senescence may be an important trait for increasing grain yield of wheat grown under low N supply.  相似文献   

17.
We present a simple generic framework to quantify source–sink relationships during grain filling, by using a determinate growth function which has a unique property, namely being able of explicitly describing the time for the end of a growth process. This model framework was applied to analyze these relationships in plants of six wheat (Triticum aestivum L.) genotypes grown in pots in climate-controlled greenhouses under two temperature regimes (day/night: 20/15 and 25/20 °C). The function accurately described the sigmoid pattern of grain growth (sink activity), as its modified form did for the reversed sigmoid shape of flag-leaf area (source capacity), during grain filling. The six genotypes differed significantly in grain number as well as in grain yield, ranging from 54 to 81 grains and from 2.67 to 4.52 g DM per culm, respectively, when grown at 20/15 °C. Biomass and grain yield were significantly reduced by a rise of 5 °C. Grain nitrogen contents raised from 2.1 to 2.6% as a consequence of less carbon accumulation resulting in lower grain weights at the high temperature. On average, a rise of 5 °C in temperature reduced the duration of grain growth by 12 days (>30%), and increased the growth rate from 1.32 to 1.67 mg grain−1 d−1 (20%). Genotypic differences in grain-filling duration were also larger than in rate of grain growth. The genetic variation in the flag-leaf area duration (a proxy for the capacity for intercepting radiation and photosynthesis) was positively associated with sink size. Model analysis showed that whether or not the timing for the cessation of grain filling and for the end of post-anthesis source activity was synchronized depended on temperature. The quantitative approach yielded parameters that characterize genotypic differences of post-anthesis source and sink capacity in responding to environmental variables.  相似文献   

18.
Widening the range of organic nutrient resources, especially N sources, is a major challenge for improving crop productivity of smallholder farms in southern Africa. A study was conducted over three seasons to evaluate different species of indigenous legumes for their biomass productivity, N2-fixation and residual effects on subsequent maize crops on nutrient-depleted fields belonging to smallholder farmers under contrasting rainfall zones in Zimbabwe. Under high rainfall (>800 mm yr−1), 1-year indigenous legume fallows (indifallows), comprising mostly species of the genera Crotalaria, Indigofera and Tephrosia, yielded 8.6 t ha−1 of biomass within 6 months, out-performing sunnhemp (Crotalaria juncea L.) green manure and grass (natural) fallows by 41% and 74%, respectively. A similar trend was observed under medium (650–750 mm yr−1) rainfall in Chinyika, where the indifallow attained a biomass yield of 6.6 t ha−1 compared with 2.2 t ha−1 for natural fallows. Cumulatively, over two growing seasons, the indifallow treatment under high rainfall at Domboshawa produced biomass as high as 28 t ha−1 compared with ∼7 t ha−1 under natural fallow. The mean total N2 fixed under indifallows ranged from 125 kg ha−1 under soils exhibiting severe nutrient depletion in Chikwaka, to 205 kg ha−1 at Domboshawa. Indifallow biomass accumulated up to 210 kg N ha−1, eleven-fold higher than the N contained in corresponding natural fallow biomass at time of incorporation. Application of P to indifallows significantly increased both biomass productivity and N2-fixation, translating into positive yield responses by subsequent maize. Differences in maize biomass productivity between indifallow and natural fallow treatments were already apparent at 2 weeks after maize emergence, with the former yielding significantly (P < 0.05) more maize biomass than the latter. The first maize crop following termination of 1-year indifallows yielded grain averaging 2.3 t ha−1, significantly out-yielding 1-year natural fallows by >1 t ha−1. In the second season, maize yields were consistently better under indifallows compared with natural fallows in terms of both grain and total biomass. The first maize crop following 2-year indifallows yielded ∼3 t ha−1 of grain, significantly higher than the second maize crop after 1-year indifallows and natural fallows. The study demonstrated that indigenous legumes can generate N-rich biomass in sufficient quantities to make a significant influence on maize productivity for more than a single season. Maize yield gains under indifallow systems on low fertility sandy soils exceeded the yields attained with either mineral fertilizer alone or traditional green manure crop of sunnhemp.  相似文献   

19.
Among the yield components, grain weight is considered a conservative trait whose determination is still beyond our complete understanding. Crop physiology uses a whole approach to study this complex trait, which can provide helpful information to plant breeders and molecular biologists. This study emphasizes the understanding of pre- and post-anthesis determinants of final grain weight. A field experiment was carried out in two growing seasons evaluating two wheat cultivars contrasting in grain weight potential. Carpel weight at pollination, grain dimensions, grain water, dry matter and volume dynamics were assessed. Among grain dimensions, grain length was the trait, which explained final grain weight (r2 = 0.78; P < 0.01 and r2 = 0.94; P < 0.001 for the 1st and 2nd season, respectively) and it was the first trait to stabilize after anthesis. Water content of grains stabilized little later and also showed a strong association with final grain weight (r2 = 0.93; P < 0.01 and r2 = 0.98; P < 0.01 for the 1st and 2nd season respectively). Most importantly, carpel weight at pollination showed a positive and linear association with final grain weight (r2 = 0.79, P < 0.01 and r2 = 0.86 P < 0.01 for the 1st and 2nd season, respectively) irrespective of the cultivar and grain position. In addition, positive associations were also found between grain volume, water content, grain length, and carpel weight at pollination. Therefore, the associations between pre- and post-anthesis traits found in this study support the hypothesis that grain weight is determined before anthesis and fruit tissues (i.e., pericarp in cereals and sunflower) set an upper limit to grain weight.  相似文献   

20.
Gymnema sylvestre is an important medicinal plant which bears bioactive compound namely gymnemic acids. The present work deals with optimization of cell suspension culture system of G. sylvestre for the production of biomass and gymnemic acid and we investigated effects of macro elements (NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4 - 0.0, 0.5, 1.0, 1.5 and 2.0× strength) and nitrogen source [NH4+/NO3− ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20 and 14.38/37.60 (mM)] of Murashige and Skoog medium on accumulation of biomass and gymnemic acid content. The highest accumulation of biomass (165.00 g l−1 FW and 15.42 g l−1 DW) was recorded in the medium with 0.5× concentration of NH4NO3 and the highest production of gymnemic acid content was recorded in the medium with 2.0× KH2PO4 (11.32 mg g−1 DW). The NH4+/NO3− ratio also influenced cell growth and gymnemic acid production; both parameters were greater when the NO3− concentration was higher than that of NH4+. Maximum biomass growth (159.72 g l−1 of FW and 14.95 g l−1 of DW) was achieved at an NH4+/NO3− ratio of 7.19/18.80, and gymnemic acid production was also greatest at the same concentration of NH4+/NO3− ratio (11.35 mg g−1 DW).  相似文献   

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