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1.
Aspergillus section Flavi is able to produce aflatoxins (AFs) in vitro down to 0.85 aw with a potential maximum occurring between 0.95 and 0.99 aw, while in the field AFs increased significantly with kernel humidity below 0.95 aw. In order to clarify this apparent discrepancy, a 3-year field trial with artificial inoculation of maize ears with Aspergillus flavus strains was organised. The co-occurrence of Aspergillus section Flavi and Gibberella fujikuroi species complex (Gfsc) was observed. The incidence of A. flavus was significantly influenced by the year and negatively related to Gfsc incidence. In 2012, when the highest temperature and the lowest rain were registered, aflatoxin B1 (AFB1) content was the highest and aw < 0.95 in kernels was measured early throughout the growing season. In 2013 and 2014, the temperature was lower and rain more abundant, and aw decreased below 0.95 only close to harvest and AFB1 contamination was limited. The possibility of describing/predicting reasonably well aw dynamic based on temperature, (degree day) was confirmed. With aw > 0.95, a positive correlation between AFB1 production rate and aw was found, but a negative correlation resulted with aw < 0.95. Other factors than aw play a role, but aw = 0.95 should be considered as an indicator of suitable conditions for rapid aflatoxin accumulation.  相似文献   

2.
The efficacy of agrochemical treatments, based on three different fungicides combined with an insecticide, was tested in southern Italy for two years on three maize hybrids to control Fusarium ear rot of maize and the accumulation in the maize kernels of the carcinogenic mycotoxins fumonisins. Insect damage incidence and severity, disease incidence and severity, identification of Fusarium species and levels of fumonisin contamination in kernels were determined. Field trials showed in both years that natural colonization of maize kernels by the fumonisin producing species Fusarium proliferatum and F. verticillioides (up to 81.5 and 26.5%, respectively) and total fumonisin contamination (up to 68.2 μg g−1) were highly severe. For all hybrids and in both years, the treatment with the insecticide applied alone reduced the insect damage severity consistently and the content of fumonisins in the kernel only in half of the cases, whereas fungicide treatments applied in combination with the insecticide showed a further significant reduction of fumonisin contamination in the three hybrids and in both years.  相似文献   

3.
Field experiments were set up from 2001 to 2004 in North West Italy to determine the effects of plant density on the susceptibility of medium and medium-late maturity maize hybrids to ear rot and to mycotoxin contamination in natural infection conditions. The ears were rated for the incidence and severity of disease symptoms at harvest and the harvested kernels were analysed for mycotoxin fumonisin B1, zearalenone, deoxynivalenol, aflatoxin B1 and ochratoxin A.  相似文献   

4.
This study evaluated improved maize hybrids (Zea mays L.) with varying level of resistance to the maize weevil, Sitophilus zeamais Motschulsky, for yield and agronomic traits for two seasons. A total of 22 improved maize hybrids and three commercial standards were tested. Out of the 22 tested, two hybrids CKPH08035 (7.4–9.9 t ha−1) and CKPH08039 (7.3–9.8 t ha−1) significantly out yielded the commercial standards WH505 (8.8 t ha−1) and BH140 (5.5 t ha−1). In addition to yield, the improved hybrids also possess desirable traits including good plant height, good plant and ear aspects and good husk cover. The hybrid CKPH08004 had the lowest Dobie index of susceptibility and was regarded as resistant to S. zeamais. Weevils fed with the resistant hybrids produced low numbers of F1 generation weevils, had a high median developmental time and a low percentage of grain damage and grain weight loss. An increasing number of F1 generation resulted in an increasing grain damage and grain weight loss. We found an inverse relationship between the susceptibility index and percent mortality. However, the numbers of F1 generation, percent grain damage and grain weight loss were positively correlated with the susceptibility index. The use of resistant maize hybrids should be promoted in managing S. zeamais in stored maize under subsistence farming conditions in Africa.  相似文献   

5.
Water sorption of gluten and wheat starch films as a function of water activity was studied using gravimetric step-change sorption experiments. Films of different thicknesses were used with the aim to vary the characteristic diffusion time and to get insights in the contribution of the polymer-chain rearrangement in the sorption behaviour. It is shown that both starch and gluten are in the glassy state for a water activity aw below 0.9. From comparison of the dynamical sorption curves with a Fickian diffusion model, it is shown that water diffusion in gluten films seems Fickian for aw < 0.7, and non-Fickian for aw > 0.7, while for starch films, non-Fickian sorption behaviour is observed for aw > 0.1. The results show that polymer-chain rearrangement and the stress built up in the matrix play an important role in the sorption dynamics of these films. Even when the material is in the glassy state matrix relaxation phenomena play a role in the sorption behaviour of starch and gluten.  相似文献   

6.
Fumonisin contamination of maize grain starts in the field. Forecasting Fusarium infection and fumonisin synthesis could allow operators in the field to control contamination during the growing season and to make the best agronomic decisions for high quality yields while respecting the limits imposed by the European Union.A research project to develop a decision support system for the control of field-phase fumonisin contamination began in Italy in 2003. This paper presents a preliminary version of the engine of the decision support tool: FUMAgrain, a dynamic risk assessment model developed with data from the north of Italy. The structure of FUMAgrain is based on the pathosystem formed by maize, F. verticillioides and Ostrinia nubilalis (European Corn Borer). The elements of the pathosystem are simulated by three sub-models: (i) maize development, (ii) F. verticillioides infection and fumonisin synthesis, (iii) European Corn Borer wounding activity on maize grain. Inputs to the model are (i) planting date, (ii) hourly meteorological data including temperature, relative humidity, wind speed and rain intensity, (iii) information on the phenological development of the hybrid planted (flowering and dry-down), and (iv) information about the chemical treatment against European Corn Borer. FUMAgrain gives an initial risk alert at the end of flowering based on the meteorological conditions during this phase. A second alert follows maturation when an assessment is made from (i) maize grain moisture, (ii) European Corn Borer damage to the ear, and (iii) fumonisin synthesis risk. Following calibration and validation with data FUMAgrain demonstrated its good capability to simulate fumonisin synthesis in maize grain in Italy (calibration: R2 = 0.70; validation: R2 = 0.71) and its usefulness for determining the optimal harvest date while respecting grain safety levels required by the international market and limiting moisture content, hence drying costs.  相似文献   

7.
The grain yield of normal oil maize (Zea mays L.) might increase when pollinated by high oil maize (HOM) hybrids because of heterosis. To testify that the grain yield increase might be a result of improved photosynthetic rate and related traits, the normal oil maize (NOM) hybrid, Nongda108, was cross-pollinated by three HOM hybrids, HOM202, HOM115 and HOM4515 (for short as ND108pHOM202, ND108pHOM115 and ND108pHOM4515). We found that the ND108pHOM202 and ND108pHOM115 exhibited higher net photosynthetic rate (Pn), accompanied by larger stomatal conductance (gs) and transpiration rate (E). Moreover, delayed leaf senescence was observed in their leaves, including larger leaf area index (LAI) and higher Chl content and Chl a/b ratio. Apart from higher phosphoenolpyruvate carboxylase (PEPCase) activity, the soluble proteins were also higher in the two cross-pollinations. The higher leaf photosynthesis could explain the grain increase in ND108pHOM202 and ND108pHOM115. However, ND108pHOM4515 exhibited a decreased photosynthetic characteristic and yield performance. Significantly positive relation between grain yield and biomass (r2 = 0.96, P < 0.05), Pn and biomass (r2 = 0.74, P < 0.05) also suggested that the yield increase in the two cross-pollination treatments was generally owing to the higher photosynthetic rate and related photosynthetic traits.  相似文献   

8.
The rheological and functional properties of starch are influenced by the size and molar mass distribution of the polymer, the ratio of amylose (AMY) to amylopectin (AMP), and branching characteristics. Asymmetric Flow Field-Flow Fractionation (AF4) was applied to fractionate five different maize hybrids of varying AMY:AMP ratio. When coupled to detection by multi-angle light scattering and refractive index (MALS–RI), it was possible to determine mass percentage and the average weight-average molar mass (Mw) without the need for calibration standards. Sufficient resolution of amylose and amylopectin was achieved by applying a gradient cross-flow on a 17 cm trapezoidal channel with a 350 μm spacer. The observed Mw ranged from about 2 × 105 to 4 × 105 for amylose and from 1 × 108 to 4 × 108 for amylopectin. The corresponding z-average root-mean-square radii (Rz) for AMP ranged from 145 to over 300 nm. Low recoveries from the AF4 channel were found to be due primarily to the focusing step. The calculated mass percent of AMY and AMP from integrated RI peak areas agreed well with nominal values for the individual starch hybrids. Both qualitative and quantitative data were reproducible. The results show the AF4–MALS–RI method to be well suited for routine molecular characterization of starch.  相似文献   

9.
The effect of water activity (aw, 0·85–0·95), temperature (15–30 °C) and incubation period (2–4 weeks) on growth and calorific losses in relation to colonisation by three mycotoxigenic isolates ofAspergillus ochraceuswas studied on maize-based substrates. The calorific losses (kJ) of maize flour due to fungal growth in relation to temperature andawwere quantified and found to be maximal at 20–30 °C (10·52–16·18%, after 4 weeks at 0·95aw), with only slight losses at 0·85aw(0–7·14%), at both 15 and 20 °C. This suggests that growth of mycotoxigenicAspergillusspp. can significantly contribute to nutritional losses of this staple agricultural food. Calorific values correlated inversely with fungal biomass, with the latter being greatest at 0·95awafter both two and four weeks, and maximal at 30 °C. Most of the single, two-, three- and four-way interactions ofaw, temperature, time and isolate had a statistically significant (p<0·01) influence on calorific losses and fungal biomass.  相似文献   

10.
《Field Crops Research》2001,71(3):183-193
Light attenuation within a row crop such as maize is influenced by canopy architecture, which has to be defined in terms of the size, shape and orientation of shoot components. Cultural practices that improve the efficiency of light interception affect canopy architecture by modifying such components. Our objectives were to: (i) determine the nature and timing of leaf growth responses to plant population and row spacing; (ii) analyze light attenuation within fully developed maize canopies. Field experiments were conducted at Pergamino (33°56′S, 60°34′W) and Salto (34°33′S, 60°33′W), Argentina, during 1996/1997 and 1997/1998 on silty clay loam soils (Typic Argiudoll) that were well watered and fertilized. Four maize hybrids of contrasting plant type were grown at three plant populations (3, 9 and 12 plants m−2) and two row spacings (0.35 and 0.70 m). Plant population promoted larger changes in shoot organs than did row spacing. As from early stages of crop growth, leaf growth (V6–V8) and azimuthal orientation (V10–V11) were markedly affected by treatments. Modifications in shoot size and leaf orientation suggest shade avoidance reactions, probably triggered by a reduction in the red:far-red ratio of light within the canopy. An interaction between hybrid and plant rectangularity on leaf azimuthal distribution was determined, with one hybrid displaying a random azimuthal leaf distribution under most conditions. This type of hybrid was defined as rigid. The other hybrids showed modified azimuthal distribution of leaves in response to plant rectangularity, even at very low plant populations. These hybrids were defined as plastic. Once maximum leaf area index (LAI) was attained light attenuation did not vary among hybrids and row spacing for plant populations ≥9 plants m−2 (k coefficient: 0.55 and 0.65 for 9 and 12 plants m−2, respectively). A more uniform plant distribution increased light attenuation (k coefficient: 0.37–0.49) only when crop canopies did not reach the critical LAI.  相似文献   

11.
以转花青素合成转录因子Bi和Cl基因玉米的稳定表达株系与自交系B73-329(CK)进行杂交,研究花青素基因在玉米杂种F_1植株组织、器官中表达情况。结果表明,用转基因株系作为母本的杂交种F_1植株部分存在表型分离,用自交系B73-329作为母本的杂交种F_1植株不存在表型分离。转基因杂交种F_1植株,颖紫色,苞叶、茎鞘紫色,气生根紫色,与CK差异显著;转基因杂交种F_1植株叶片为绿色,转基因株系自交分离群体株系的叶片为紫色;转基因杂交种F_1植株绝大部分花丝为黄色,个别花丝红色,子粒绝大部分为黄色。抽丝、散粉期,转基因杂交种株高、穗位高等农艺性状与对照差异不显著,但是大部分产量显著低于对照,推测其主要原因在于花青素合成途径的引入导致植株能量代谢损耗所致。研究表明,转基因玉米杂交制种应用应以转基因株系作为父本。  相似文献   

12.
Fusarium verticillioides is a common maize pathogen which causes diseases on ears and synthesis of the mycotoxins, fumonisins, in kernels. Fumonisin production is influenced by both environmental conditions and agricultural inputs during growth and maturation of the maize plant. The aim of this research was to evaluate the effect of crop management techniques on fumonisin contamination in maize kernels. Experiments were conducted in Northern Italy during 2006 and 2007 using two maize hybrids with different precocity. Factors evaluated were seed planting time (March versus May), plant density (65,000 plants versus 80,000 plants per ha), N fertilization (200 kg N versus 400 kg N per ha), and chemical treatment to control European maize borer (ECB) (yes versus no). These factors were analyzed were as follows: (T1) May sowing, high plant density and N fertilization, (T2) March sowing time, high plant density and N fertilization, (T3) March sowing time, low plant density and balanced N fertilization, (T4) the same agronomic techniques as T3 plus a chemical treatment to control European maize borer. Ears were analyzed morphologically for ECB incidence and severity. Subsequently, kernels were analyzed chemically for fumonisins. Fumonisin contamination was reduced by 57%, 69% and 86% for T2, T3 and T4, respectively, compared to T1. This study clearly underlines that the application of good agricultural practices (GAP) in crop management strategies can effectively control fumonisin contamination of maize kernels.  相似文献   

13.
Near infrared (NIR) hyperspectral imaging and hyperspectral image analysis were evaluated for their potential to track changes in fungal contamination on and fungal activity immediately under the surface of whole maize kernels (Zea mays L.) infected with Fusarium verticillioides. Hyperspectral images of clean and infected kernels were acquired using a SisuChema hyperspectral pushbroom imaging system with a spectral range of 1000–2498 nm at predetermined time intervals after infection. Background, bad pixels and shading of acquired absorbance images were removed using exploratory principal component analysis (PCA). When plotting PC4 against PC5, with percentage sum of squares (%SS) 0.49% and 0.34%, three distinct clusters were apparent in the score plot and this was associated with degree of infection. Loading line plots, with prominent peaks at 1900 nm and 2136 nm, confirmed that the source of variation was due to changes in starch and protein. Partial least squares (PLS) regression models, with time as the Y variable, were calculated and also indicated that changes over time were apparent. Variable importance plots (VIP) confirmed the peaks observed in the PCA loading line plots. More systematic future experiments are needed to confirm this, but it can already be concluded that early detection of fungal contamination and activity is possible.  相似文献   

14.
Fumonisins are mycotoxins produced primarily by Fusarium verticillioides and Fusarium proliferatum on maize. These are secondary, carcinogenic metabolites and have been reported on maize worldwide. Field trials were conducted during 2010/2011 and 2011/2012 in six diverse maize production areas of South Africa to study the efficacy of an existing prophylactic fungicide regime for the control of foliar diseases, on the infection of grains of seven cultivars by fumonisin producing Fusarium spp. and fumonisin synthesis. Seven cultivars were selected to include both yellow and white, Bt and non-Bt and regionally adapted varieties. Azoxystrobin + difenoconazole (strobilurin, 200 g/L + triazole, 125 g/L) was applied 40–45 days after planting followed by flusilazole + carbendazim (silicone triazole, 125 g/L + benzimidazole, 250 g/L) with petroleum as adjuvant, 28–30 days later. Fumonisins in harvested kernels were analysed using High Performance Liquid Chromatography (HPLC) and fumonisin producing Fusarium spp. were quantified by means of quantitative Real Time PCR (qPCR). Mean natural colonisation of maize kernels by fumonisin producing Fusarium spp. was highest at Makhathini (33,696 pg/0.5 g of milled maize kernels) and the lowest at Potchefstroom (179 pg/0.5 g of milled maize kernels). Cultivars differed in susceptibility to fungal colonisation and fumonisin synthesis with PAN6P-110, DKC80-10 and CRN3505 proving most susceptible and LS8521B and DKC78-15B most resistant. Mean fumonisin contamination was highest at Makhathini (23.62 ppm) and lowest at Buffelsvlei (1.50 ppm). Analysis of variance showed no significant differences in colonisation of grain by fumonisin producing Fusarium spp. between sprayed and control treatments. Sprayed treatments had significantly higher fumonisin levels compared with unsprayed treatments. A highly significant cultivar × environment interaction was recorded for fungal colonisation. Highly significant environment × fungicide-treatment × cultivar interactions were recorded for fumonisin production. The strong interaction between cultivar and environment may be due to cultivar adaptation/behaviour under different environmental conditions. The use of a prophylactic fungicide spray regime for control of leaf diseases in maize did not reduce Fusarium ear rot in maize, however, significantly elevated fumonisin levels were recorded.  相似文献   

15.
《Field Crops Research》1999,61(3):201-210
The main objective of the present work was to determine if chlorophyll fluorescence techniques could be used under field conditions to detect differences in leaf photosynthetic rates among commercial maize hybrids known to differ in agronomic performance. Chlorophyll fluorometry was used to estimate thylakoid electron transport rates (Je) in leaves of three commercial maize hybrids on 13 days between 48 days after sowing and first frost. The maximum quantum efficiency of thylakoid electron transport at low PPFD (φ), and the thylakoid electron transport rate when PPFD absorbed by leaves was equal to 1200 μmol m−2 s−1 (Je1200) were estimated using a curve-fitting approach. Canopy absorptance of incident PPFD (αc) and leaf absorptance of incident PPFD (αl) were measured at regular intervals. Significant fluctuations in both φ and Je1200 were observed over the season, and these appeared to be associated with different leaf temperatures on different measuring days. Measured values of Je1200 declined in a linear fashion over the season, but the decline was more rapid in an older hybrid than in two more modern hybrids. All three hybrids could be differentiated from one another on the basis of Je1200 measurements in the last part of the growing season. The two newer hybrids did not differ in their mean crop growth rates during this part of the season, however, despite the observed difference in Je1200. Regression analyses revealed a strong relationship between mean crop growth rates and αcJe1200, supporting the idea that chlorophyll fluorescence can be used to assess photosynthetic performance of maize under field conditions.  相似文献   

16.
Fusarium verticilloides synthesizes fumonisins (FBs) in the field and during faulty storage of maize. FBs are worrisome because of their toxicological effects. Nine maize genotypes differing in physical grain properties, phytochemical profiles, and chemical compositions were evaluated. Kernels were tempered to 18% moisture and purposely contaminated with F. verticilloides to assess differences in mold growth and FBs. The genotype significantly influenced counts with mean values ranging from 12.9 CFU/mLx104 for the highly susceptible Blue Don Goyo to only 1.0 CFU/mLx104 for the Pob84C3 genotype. The concentrations of FBs in these two genotypes were 6.85 and 0.3 ppm, respectively. Popcorn kernels showed a relatively high level of Fusarium counts (7.0 CFU/mLx104) but low concentrations of FBs (1.4 ppm). The large-sized Cacahuacintle and Don Goyo kernels, which had the lowest test weights and highest 1000 kernel weight (TKW) showed the highest occurrence of CFU likely due to their low proportion of pericarp, bound phenolics (coumaric), diferulic acids and bound antioxidants. Correlations indicated that mold counts did not correlate (r2 = 0.6, P = 0.08) with FBs. However, grain thickness, hardness, TKW and bound phenolics were related to Fusarium counts. This research demonstrated that contrasting maize genotypes showed different susceptibilities to Fusarium growth and FBs contamination.  相似文献   

17.
Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization.To investigate the genome affinity reflected in chromosome pairing and segregation,we studied chromosome behaviors during meiosis in two interspecific F1 hybrids[O.minuta×O.australiensis(Om×Oa,BCE genome)and Oa×O.ridleyi(Or,EHJ genome)]by using both traditional staining methods and genomic in situ hybridization(GISH).GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes,but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported.In the hybrids,highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome.At diakinesis of these two hybrids,most chromosomes present as univalent,with low frequency as bivalents and occasionally as trivalents.In a pollen mother cell,2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa×Or,and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om×Oa.GISH results indicated that 51.52%bivalents in Oa×Or and 79.65%bivalents in Om×Oa involved allosyndetic association,which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids.In this study,we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids.The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs.A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization,and efficient and routine GISH analysis is helpful to monitor alien introgression in the process.  相似文献   

18.
Aflatoxin contamination of peanuts is one of the most concerns in peanut production in China. Applying non-aflatoxigenic Aspergillus flavus strains, based on competitive exclusion, has been proved to be a promising strategy to reduce aflatoxin contamination in pre-harvest peanuts. Two non-aflatoxigenic A. flavus strains collected in China, which have been proved effectively reducing aflatoxin in the laboratory, were mixed with high aflatoxin producer to the soil in peanut growing season. The two non-aflatoxigenic strains significantly (P ​< ​0.05) reduced aflatoxin contamination in peanut kernels under both normal and drought stresses in two fields. Compared to control, the total aflatoxin (sum of aflatoxin B1 and B2) was reduced 26.7–99.12% in field 1, and 84.96–99.33% in field 2. The aflatoxin was reduced 84.96–99.33% under drought stress in two fields. The present study indicated the non-aflatoxigenic A. flavus strains could be potential biocontrol agents for reducing aflatoxin contamination under field condition.  相似文献   

19.
Dry-milling performance of maize (Zea mays, L.) kernels primarily depends on their hardness. The flint type is harder than the dent and semi-dent maize, yielding a higher proportion of big endosperm pieces in the mill. Nevertheless, crop growing conditions could modify milling properties. The objective of this work was to analyze the effect of different crop environments and management practices on dry-milling quality of flint maize kernels. Two orange-flint hybrids from different eras of breeding differing in flint type expression and grain yield potential were evaluated. They were grown at three different locations of the Argentina's main maize-production area under different sowing dates, plant densities, and fertilization rates during two growing seasons. Crop post-silking growth, grain yield and its components (kernel number and weight), kernel size and hardness-associated properties (test weight, percent floaters and milling ratio), and flaking-grit yield were analyzed. Most of observed differences in physical properties of kernels, particularly for the high-yielding new hybrid with unstable flint expression, were associated with the source-sink ratio established during the post-silking period (explored range from 154 to 617 mg kernel−1). This variable mainly results from changes in crop growth during that period. Increases in weight per kernel improved hardness-associated properties. High crop grain yields together with top dry-milling quality were achieved when the new high-yielding hybrid was cropped with an appropriated crop management.  相似文献   

20.
The applicability of Raman spectroscopy combined with chemometrics using different preprocessed spectra data was examined to develop fast, low-cost, and non-destructive spectroscopic methods for classification and quantification of aflatoxin-contaminated maize samples within the aflatoxin concentration range of 0–1206 μg/kg. This technique will find useful application in evaluating large numbers (e.g. >2000) of samples from maize hybrid performance trials and breeding programs. The best discriminant models were obtained from the linear discriminant analysis (LDA). The LDA models on validation samples showed correct classification rates in the range of 94–100% and did not misclassify any aflatoxin contaminated samples as aflatoxin negative. Of the models for predicting aflatoxin concentration, the partial least squares regression (PLSR) models showed the best quality of regression (slopes of 0.939–0.990) and highest coefficient of determination (r2 = 0.941–0.957). The models provide limited applicability to quantify aflatoxin concentration below 20 μg/kg. No significant difference was observed between predicted values using Raman spectroscopy and reference values using high-performance liquid chromatography (HPLC) (p > 0.05), indicating the suitability of Raman spectroscopy to rapidly screen large numbers of maize samples for aflatoxin contamination.  相似文献   

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