Infected Kernels Research Articles

Prevalence of Fusarium species causing head blight of spring wheat, barley and oat in Ontario during 2001–2017

Fusarium spp. associated with fusarium head blight (FHB) on cereals in Ontario was monitored in this study. Nine species were recovered from 24 300 putatively infected kernels collected from 486 affected spring wheat fields from 2001 to 2017, 11 species from 13 250 kernels from 265 barley fields from 2005 to 2017, and nine species from 8800 kernels from 176 oat fields from 2008 to 2017. Fusarium avenaceum, F. equiseti, F. graminearum, F. poae and F. sporotrichioides were the most commonly isolated species, occurring in 23–66% of the infected fields and 1.3–27.0% of the infected kernels. In spring wheat, F. graminearum was predominant, occurring in 88% of fields and in 60.4% of kernels, and represented 90% of the pathogen population. In barley, F. poae and F. graminearum were equally dominant, occurring in 77% and 64% of fields, 17.6% and 17.0% of kernels, and represented 42% and 40% of the pathogen population, respectively. In oat, F. poae was predominant, occurring in 93% of fields and 23.5% of kernels, and represented 68% of the pathogen population. Growth seasons characterized as an FHB epidemic occurred in 11 of 17 years surveyed in spring wheat, 3 of 13 years surveyed in barley, and no epidemic years were observed over the 10-year period in oat. There were no significant differences in frequency of isolation of the Fusarium species, except for F. graminearum which increased by 60% in wheat and by 210% in barley in the FHB epidemic years compared with the non-epidemic years, suggesting that F. graminearum was responsible for the FHB epidemics in Ontario.

Correlations between the textural features of wheat kernels and the quantity of DNA of Fusarium fungi

The aim of this study was to determine the relationship between the surface textural features of wheat kernels and the quantity of DNA of fungi of the genus Fusarium. The images of kernels of four wheat cultivars were acquired on the ventral side and dorsal side with a flatbed scanner. Fungal DNA was quantified with specific TaqMan probes for F. culmorum and F. graminearum sensu stricto. In images acquired on the ventral side, the quantity of fungal DNA was most highly correlated with texture aHVariance from channel a in cultivar 1 (0.86), with one texture from channel R in cultivar 2 (0.80), with one texture from channel L (0.69) and one texture from channel X (− 0.69) in cultivar 3, and with one texture from channel b in cultivar 4 (0.70). In the images acquired on the dorsal side, the quantity of fungal DNA was most highly correlated with one texture from channel V in cultivar 3 (0.89), two textures from channel B in cultivar 1 (− 0.74), one texture from channel R (− 0.77), and two textures from channel Z (0.77) in cultivar 2, and one texture from channel a and textures from channel S (0.74) in cultivar 4. The results of this study indicate the usefulness of image analysis for detecting fungal infections in grain. The findings make a valuable contribution to the development of rapid, inexpensive, non-invasive, and effective methods for preliminary screening of infected and healthy kernels and for evaluating the severity of fungal infections in kernels.

Infection incidence, kernel colonisation, and mycotoxin accumulation in durum wheat inoculated with Fusarium sporotrichioides, F. langsethiae or F. poae at different growth stages

A 2-year field experiment was conducted to determine the effects of Fusarium sporotrichioides, F. langsethiae, or F. poae on durum wheat plants artificially inoculated at different growth stages. The percentage of symptomatic kernels was similar among the three species, but incidence of infected kernels was lower for F. langsethiae. Kernel colonization was higher when plants were inoculated before and during anthesis for F. sporotrichioides and F. poae, but unaffected by timing of inoculation for F. langsethiae. Production of T-2/HT-2 toxins was higher for F. sporotrichioides than for F. langsethiae. Significant accumulations of nivalenol were detected for F. poae. Across all three species, there was a weak correlation (r = 0.16; P = 0.031) between the incidences of symptomatic and infected kernels, but a stronger correlation (r = 0.53; P 0.58; P < 0.007) with infection incidence or fungal DNA in kernels, but only for F. sporotrichioides and F. poae.

Evaluation of wheat kernels infected by fungi of the genus Fusarium based on morphological features

AbstractThe aim of this study was to propose a nondestructive method for evaluating wheat kernels infected by fungi of the genus Fusarium based on the morphological features of kernels and for distinguishing infected kernels from healthy kernels. Images were acquired with a flatbed scanner to determine 59 geometric parameters (linear dimensions and shape factors). Wheat kernels were classified as infected or healthy with the use of Decision trees, Rules, Bayes, Lazy, Meta, and Functions classifiers in WEKA 3.9 software. The classification accuracy of the model based on 59 attributes ranged from 58.12% to 73.37%. The selection of the best attributes shortened the time of the analysis and improved classification results. Linear Forward Selection and MLP classifiers were characterized by the highest classification accuracy.Practical applicationsThe infection of cereal grains by fungi of the genus Fusarium is a food security challenge that can compromise the quantity and quality of yields in many agricultural regions. Selected fungi produce mycotoxins with carcinogenic, mutagenic, teratogenic, and immunotoxic effects for humans and animals. In this study, a nondestructive method was applied to evaluate wheat kernels infected by fungi of the genus Fusarium based on the morphological features of kernels and to distinguish infected kernels from healthy kernels. The proposed method can be used for rapid, inexpensive, and effective detection of fungal infections in cereal grain.

The Application of Computer Image Analysis Based on Textural Features for the Identification of Barley Kernels Infected with Fungi of the Genus Fusarium

Abstract The aim of this study was to develop discrimination models based on textural features for the identification of barley kernels infected with fungi of the genus Fusarium and healthy kernels. Infected barley kernels with altered shape and discoloration and healthy barley kernels were scanned. Textures were computed using MaZda software. The kernels were classified as infected and healthy with the use of the WEKA application. In the case of RGB, Lab and XYZ color models, the classification accuracies based on 10 selected textures with the highest discriminative power ranged from 95 to 100%. The lowest result (95%) was noted in XYZ color model and Multi Class Classifier for the textures selected using the Ranker method and the OneR attribute evaluator. Selected classifiers were characterized by 100% accuracy in the case of all color models and selection methods. The highest number of 100% results was obtained for the Lab color model with Naive Bayes, LDA, IBk, Multi Class Classifier and J48 classifiers in the Best First selection method with the CFS subset evaluator.

Evaluating a generic drought index as a predictive tool for aflatoxin contamination of corn: From plot to regional level

Corn (Zea mays L.) kernel infection by Aspergillus flavus and subsequent aflatoxin accumulation in grain can have a deleterious effect on both humans and animals that consume contaminated grain. Predicting the aflatoxin risk is challenging due to complex interactions of biotic and abiotic stress factors that govern and exacerbate the phenomenon. The goal of this study was to determine whether a drought index could be used to predict the risk for pre-harvest aflatoxin contamination in corn. Risk assessment was approached at: 1) field (plot) level with data obtained from an in-field controlled experiment (Mississippi study), and 2) state level, where corn fields were sampled at a county level (Georgia study). The data used for this study consisted of historical records on aflatoxin contamination collected over thirteen growing seasons from 2000 to 2011, 2013, and 2014 at Mississippi State, Mississippi (1), and from random corn fields in 53 counties across Georgia between 1977 and 2004 (2). A controlled experiment was conducted at Mississippi with two soil types (a Leeper silty clay loam and a Myatt loam), and three commercial hybrids characterized by different susceptibility levels to aflatoxin contamination. The Agricultural Reference Index for Drought (ARID), a generic drought index for calculating drought on daily basis was evaluated as an aflatoxin risk prediction tool. Mid-silk day was selected to split each growing season into two time periods, which were further divided into positive and negative weeks representing weeks after and before mid-silk, respectively. Weekly ARID factors were calculated for all periods to evaluate the in-season alterations in aflatoxin risk. In both studies, multiple logistic regression models were used to predict aflatoxin risk as a function of the weekly ARID values. In Mississippi, risk level changes were additionally tested according to soil type and corn hybrid aflatoxin susceptibility. The United States Food and Drug Administration restricts corn grain consumption by humans and young animals if the contamination level is above 20 μg/kg; thus, this threshold (20 μg/kg) was selected to develop a binary dependent variable for the logistic model from the raw aflatoxin data. The results revealed that ARID might be used as a predictive tool to assess aflatoxin risk, soil type and hybrid susceptibility to aflatoxin contamination were statistically significant independent factors, and there are critical week windows during the growing season when changes in drought conditions affect the likelihood for aflatoxin contamination. These findings can be used to minimize risk by adapting site-specific management strategies such as triggering irrigation during critical risk weeks, selecting the most appropriate hybrid for a given site/location based on soil type, and determining optimum harvest date.

Infection cycle of maize stalk rot and ear rot caused by Fusarium verticillioides.

Fusarium verticillioides, an important maize pathogen produces fumonisins and causes stalk and ear rot; thus, we are aimed to clarify its infection cycle by assessing enhanced green fluorescent protein (EGFP) expression in stalk and ear rot strains. Maize seeds were inoculated with stable and strongly pathogenic transformants. To investigate the degree of infection, inoculated plants were observed under a stereo fluorescence microscope, and affected tissue strains were detected using PCR. We found that both transformants infected maize. Hyphae infected the plants from radical to the stem and extended to the ear and infected ear kernels caused a second infection. This process formed the infection cycle.

Oxylipins from both pathogen and host antagonize jasmonic acid‐mediated defence via the 9‐lipoxygenase pathway in Fusarium verticillioides infection of maize

Oxylipins are a newly emerging group of signals that serve defence roles or promote virulence. To identify specific host and fungal genes and oxylipins governing the interactions between maize and Fusarium verticillioides, maize wild-type and lipoxygenase3 (lox3) mutant were inoculated with either F.verticillioides wild-type or linoleate-diol-synthase 1-deleted mutant (ΔFvlds1D). The results showed that lox3 mutants were more resistant to F.verticillioides. The reduced colonization on lox3 was associated with reduced fumonisin production and with a stronger and earlier induction of ZmLOX4, ZmLOX5 and ZmLOX12. In addition to the reported defence function of ZmLOX12, we showed that lox4 and lox5 mutants were more susceptible to F.verticillioides and possessed decreased jasmonate levels during infection, suggesting that these genes are essential for jasmonic acid (JA)-mediated defence. Oxylipin profiling revealed a dramatic reduction in fungal linoleate diol synthase 1 (LDS1)-derived oxylipins, especially 8-HpODE (8-hydroperoxyoctadecenoic acid), in infected lox3 kernels, indicating the importance of this molecule in virulence. Collectively, we make the following conclusions: (1) LOX3 is a major susceptibility factor induced by fungal LDS1-derived oxylipins to suppress JA-stimulating 9-LOXs; (2) LOX3-mediated signalling promotes the biosynthesis of virulence-promoting oxylipins in the fungus; and (3) both fungal LDS1- and host LOX3-produced oxylipins are essential for the normal infection and colonization processes of maize seed by F.verticillioides.

Resistance against Fusarium graminearum and the relationship to \u03b2-glucan content in barley grains

Fusarium head blight (FHB) caused by Fusarium graminearum (FG) is a destructive disease impacting barley worldwide. The disease reduces the grain yield and contaminates grains with mycotoxins, such as the trichothecene deoxynivalenol (DON). Although the infection mainly affects the grain yield, little is known about its impact on grain structural and biochemical properties. Yet, such information is instrumental to characterize the facets of resistance in the grains. After artificial inoculation of six barley cultivars with FG in a 2 years field test, different levels of symptoms on spikes, of colonisation of grains and of DON content were observed. The infections caused a reduction in grain weight and an average decrease of 10% of the β-glucan content in grains, indicating alterations of grain filling, composition and structure. According to our results, we postulate the presence of two distinct resistance mechanisms in the grain, tolerance to grain filling despite infection as well as the inhibition of mycotoxin accumulation. Differently to wheat, in barley, type IV resistance (tolerance of the grain to infection) is directly linked with type III resistance (resistance against kernel infection). The resistance against toxin accumulation (named type V resistance in wheat) appeared to be independent to all other resistance types. Generally, the resistance was significantly influenced by the environment and by genotype x environment interactions explaining the generally weak stability of resistance in barley. Interestingly, a significant and inverse relationship between DON contamination and β-glucan content in grains suggests that high β-glucan content in grains contributes to type V resistance.

Application of Image Texture Analysis for Evaluation of X-Ray Images of Fungal-Infected Maize Kernels

The feasibility of image texture analysis to evaluate X-ray images of fungal-infected maize kernels was investigated. X-ray images of maize kernels infected with Fusarium verticillioides and control kernels were acquired using high-resolution X-ray micro-computed tomography. After image acquisition and pre-processing, several algorithms were developed to extract image textural features from selected two-dimensional (2D) images of the kernels. Four first-order statistics (mean, standard deviation, kurtosis and skewness) and four grey level co-occurrence matrix (GLCM) features (correlation, energy, homogeneity and contrast) were extracted from the side, front and top views of each kernel and used as inputs for principal component analysis (PCA). The first-order statistical image features gave a better separation of the control from infected kernels on day 8 post-inoculation. Classification models were developed using partial least squares discriminant analysis (PLS-DA), and accuracies of 67 and 73% were achieved using first-order statistical features and GLCM extracted features, respectively. This work provides information on the possible application of image texture as method for analysing X-ray images.

Identification and functional analysis of the aspergillic acid gene cluster in Aspergillus flavus

Aspergillus flavus can colonize important food staples and produce aflatoxins, a group of toxic and carcinogenic secondary metabolites. Previous in silico analysis of the A. flavus genome revealed 56 gene clusters predicted to be involved in the biosynthesis of secondary metabolites. A. flavus secondary metabolites produced during infection of maize seed are of particular interest, especially with respect to their roles in the biology of the fungus. A predicted nonribosomal peptide synthetase-like (NRPS-like) gene, designated asaC (AFLA_023020), present in the uncharacterized A. flavus secondary metabolite gene cluster 11 was previously shown to be expressed during the earliest stages of maize kernel infection. Cluster 11 is composed of six additional genes encoding a number of putative decorating enzymes as well as a transporter and transcription factor. We generated knock-out mutants of the seven predicted cluster 11 genes. LC-MS analysis of extracts from knockout mutants of these genes showed that they were responsible for the synthesis of the previously characterized antimicrobial mycotoxin aspergillic acid. Extracts of the asaC mutant showed no production of aspergillic acid or its precursors. Knockout of the cluster 11 P450 oxidoreductase afforded a pyrazinone metabolite, the aspergillic acid precursor deoxyaspergillic acid. The formation of hydroxyaspergillic acid was abolished in a desaturase/hydroxylase mutant. The hydroxamic acid functional group in aspergillic acid allows the molecule to bind to iron resulting in the production of a red pigment in A. flavus identified previously as ferriaspergillin. A reduction of aflatoxin B1 and cyclopiazonic acid that correlated with reduced fungal growth was observed in maize kernel infection assays when aspergillic acid biosynthesis in A. flavus is halted.

The Aspergillus flavus Spermidine Synthase (spds) Gene, Is Required for Normal Development, Aflatoxin Production, and Pathogenesis During Infection of Maize Kernels.

Aspergillus flavus is a soil-borne saprophyte and an opportunistic pathogen of both humans and plants. This fungus not only causes disease in important food and feed crops such as maize, peanut, cottonseed, and tree nuts but also produces the toxic and carcinogenic secondary metabolites (SMs) known as aflatoxins. Polyamines (PAs) are ubiquitous polycations that influence normal growth, development, and stress responses in living organisms and have been shown to play a significant role in fungal pathogenesis. Biosynthesis of spermidine (Spd) is critical for cell growth as it is required for hypusination-mediated activation of eukaryotic translation initiation factor 5A (eIF5A), and other biochemical functions. The tri-amine Spd is synthesized from the diamine putrescine (Put) by the enzyme spermidine synthase (Spds). Inactivation of spds resulted in a total loss of growth and sporulation in vitro which could be partially restored by addition of exogenous Spd. Complementation of the Δspds mutant with a wild type (WT) A. flavus spds gene restored the WT phenotype. In WT A. flavus, exogenous supply of Spd (in vitro) significantly increased the production of sclerotia and SMs. Infection of maize kernels with the Δspds mutant resulted in a significant reduction in fungal growth, sporulation, and aflatoxin production compared to controls. Quantitative PCR of Δspds mutant infected seeds showed down-regulation of aflatoxin biosynthetic genes in the mutant compared to WT A. flavus infected seeds. Expression analyses of PA metabolism/transport genes during A. flavus-maize interaction showed significant increase in the expression of arginine decarboxylase (Adc) and S-adenosylmethionine decarboxylase (Samdc) genes in the maize host and PA uptake transporters in the fungus. The results presented here demonstrate that Spd biosynthesis is critical for normal development and pathogenesis of A. flavus and pre-treatment of a Δspds mutant with Spd or Spd uptake from the host plant, are insufficient to restore WT levels of pathogenesis and aflatoxin production during seed infection. The data presented here suggest that future studies targeting spermidine biosynthesis in A. flavus, using RNA interference-based host-induced gene silencing approaches, may be an effective strategy to reduce aflatoxin contamination in maize and possibly in other susceptible crops.

Classification of Fusarium-infected and healthy wheat kernels based on features from hyperspectral images and flatbed scanner images: a comparative analysis

Wheat infections caused by fungi of the genus Fusarium decrease yields and have serious economic consequences. The produced mycotoxins have harmful effects on human and animal health. The aim of this study was to develop classification models based on selected textural parameters to distinguish between infected and healthy wheat kernels. The classification accuracy of kernels positioned on the ventral side was determined at 78–100% in the model based on textural parameters from hyperspectral images, and at 95–100% based on images generated by a flatbed scanner. Kernels positioned on the dorsal side were correctly classified in 78–98% based on hyperspectral images, and in 92–100% based on colour images. In the models combining textural parameters from the ventral and dorsal sides of wheat kernels, classification accuracy reached 76–98% in hyperspectral images, and 94–100% in images generated by a flatbed scanner. The imaging technique—flatbed scanner and the ventral side of the kernels provided higher classification accuracy results. The results will contribute to further research aiming to develop models for the determination of fungal chemotypes and/or fungal species based on selected textural features of wheat kernels.

Fusarium graminearum Mycotoxins in Maize Associated With Striacosta albicosta (Lepidoptera: Noctuidae) Injury

Western bean cutworm, Striacosta albicosta (Smith; Lepidoptera: Noctuidae) has become a key pest of maize, Zea mays (L.), in Ontario, Canada which is challenging to control due to its lack of susceptibility to most Bt-maize events. Injury by S. albicosta may exacerbate Fusarium graminearum (Schwabe; Hypocreales: Nectriaceae) infection through provision of entry points on the ear. The objectives of this study were to: investigate the relationship between injury by S. albicosta and deoxynivalenol (DON) accumulation; evaluate non-Bt and Bt-maize hybrids, with and without insecticide and fungicide application; and determine optimal insecticide-fungicide application timing for reducing S. albicosta injury and DON accumulation. The incidence of injury by S. albicosta and ear rot severity were found to increase DON concentrations under favorable environmental conditions for F. graminearum infection. Incidence of S. albicosta injury was more important than severity of injury for DON accumulation which may be due to larval consumption of infected kernels. The Vip3A × Cry1Ab event provided superior protection from the incidence and severity of S. albicosta injury compared to non-Bt or Cry1F hybrids. Insecticide application to a Vip3A × Cry1Ab hybrid did not reduce injury further; however, lower severity of injury was observed for non-Bt and Cry1F hybrids when pyrethroids or diamides were applied at early VT or R1 stages. DON concentrations were reduced with application of prothioconazole fungicide tank-mixed with insecticide at late VT (before silk browning) or when insecticide was applied at early VT followed by prothioconazole at R1. The application of an insecticide/fungicide tank-mix is the most efficient approach for maize hybrids lacking high-dose insecticidal proteins against S. albicosta and F. graminearum tolerance. Results demonstrate that reducing the risk of DON accumulation requires a strategic approach to manage complex associations among S. albicosta, F. graminearum and the environment.

Genetic Control and Heritability of Fusarium Head Blight (FHB) Resistance in Spring Bread Wheat

Fusarium head blight (FHB) caused by Fusarium graminerum is one of the most important wheat diseases in Iran and worldwide. In this research, we assessed genetic control and the disease resistance heritability using generation mean and generation variance analyses. Five generations of F 1 , F 2 , F 3 , BC 1.1 and BC 1.2 developed from crossing an inbred line (resistant parent) and Falat (susceptible parent) along with two parents were infected by the fungus spores at spike emergence stage at field condition and after adequate incidence of disease, FHB resistance-related traits including percentage of infected florets, percentage of infected kernels (FDK) and disease incidence (DIC) were evaluated. Generation variance analysis showed that narrow-sense heritability of FDK was high (~64%), while that of DIC was very low, indicating the discrete genetic factors of these indices. Mean comparison indicated that means of F 1 , F 2 , BC 1.1 , BC 1.2 and F 3 located between that of two parents and were closer to resistant parent. Joint-scaling test suggested that FHB resistance wasn`t fitted to additive-dominance model. But in contrast, six-parameter model (mean [m], additive [a], dominance [d], additive × additive [aa], additive × dominance [ad], dominance × dominance [dd]) for all FHB resistance indices was best fitted. Therefore, it could be concluded that in the examined cross in addition to additive and dominance effects, epistatic effects also were involved in controlling wheat FHB resistance.

On-Farm Demonstrations with a Set of Good Agricultural Practices (GAPs) Proved Cost-Effective in Reducing Pre-Harvest Aflatoxin Contamination in Groundnut

Aflatoxin contamination in groundnut is an important qualitative issue posing a threat to food safety. In our present study, we have demonstrated the efficacy of certain good agricultural practices (GAPs) in groundnut, such as farmyard manure (5 t/ha), gypsum (500 kg/ha), a protective irrigation at 90 days after sowing (DAS), drying of pods on tarpaulins after harvest in farmers’ fields. During 2013–2015, 89 on-farm demonstrations were conducted advocating GAPs, and compared with farmers’ practices (FP) plots. Farmers’ awareness of GAPs, and knowledge on important aspects of groundnut cultivation, were also assessed during our experimentation in the selected villages under study. Pre-harvest kernel infection by Aspergillus flavus, aflatoxin contamination, and pod yields were compared in GAPs plots, vis-à-vis FP plots. The cost of cultivation in both the plots was calculated and compared, based on farmer’s opinion surveys. Results indicate kernel infections and aflatoxins were significantly lower, with 13–58% and 62–94% reduction, respectively, in GAPs plots over FP. Further, a net gain of around $23 per acre was realized through adoption of GAPs by farmers besides quality improvement of groundnuts. Based on our results, it can be concluded that on-farm demonstrations were the best educative tool to convince the farmers about the cost-effectiveness, and adoptability of aflatoxin management technologies.

Differentiation between Aspergillus flavus and Aspergillus parasiticus isolates originated from wheat

The species of the genus Aspergillus, A. flavus and A. parasiticus, are the most aflatoxin-producing fungi. All previous studies carried out under the production conditions of Serbia showed no presence of A. parasiticus on wheat kernel. On the basis of changes in climatic factors, such as occurrence of high temperatures and prolonged droughts, which favour increased frequency of Aspergillus spp., we assumed that this pathogen can also be present in Serbia. The significance of direct losses as a consequence of wheat kernel infection, as well as potential contamination with aflatoxins, have pointed out to the need to determine the presence of toxigenic potential of A. flavus and A. parasiticus isolates originating from Serbia. For that purpose, wheat kernel samples were collected in nine locations. According to morphological, toxicological and molecular traits of isolated fungi, the presence of A. flavus and A. parasiticus was confirmed. This is the first time that A. parasiticus was identified on wheat under climatic conditions in Serbia. This study indicates that these pathogens may be a potential danger in wheat production in the region of Serbia. This danger will be much more certain if global climatic changes continue as they will provide more intensive development of these pathogens.

Carbon Dioxide Mediates the Response to Temperature and Water Activity Levels in Aspergillus flavus during Infection of Maize Kernels.

Aspergillus flavus is a saprophytic fungus that may colonize several important crops, including cotton, maize, peanuts and tree nuts. Concomitant with A. flavus colonization is its potential to secrete mycotoxins, of which the most prominent is aflatoxin. Temperature, water activity (aw) and carbon dioxide (CO2) are three environmental factors shown to influence the fungus-plant interaction, which are predicted to undergo significant changes in the next century. In this study, we used RNA sequencing to better understand the transcriptomic response of the fungus to aw, temperature, and elevated CO2 levels. We demonstrate that aflatoxin (AFB1) production on maize grain was altered by water availability, temperature and CO2. RNA-Sequencing data indicated that several genes, and in particular those involved in the biosynthesis of secondary metabolites, exhibit different responses to water availability or temperature stress depending on the atmospheric CO2 content. Other gene categories affected by CO2 levels alone (350 ppm vs. 1000 ppm at 30 °C/0.99 aw), included amino acid metabolism and folate biosynthesis. Finally, we identified two gene networks significantly influenced by changes in CO2 levels that contain several genes related to cellular replication and transcription. These results demonstrate that changes in atmospheric CO2 under climate change scenarios greatly influences the response of A. flavus to water and temperature when colonizing maize grain.

Comparative Histological and Transcriptional Analysis of Maize Kernels Infected with Aspergillus flavus and Fusarium verticillioides.

Aspergillus flavus and Fusarium verticillioides infect maize kernels and contaminate them with the mycotoxins aflatoxin, and fumonisin, respectively. Genetic resistance in maize to these fungi and to mycotoxin contamination has been difficult to achieve due to lack of identified resistance genes. The objective of this study was to identify new candidate resistance genes by characterizing their temporal expression in response to infection and comparing expression of these genes with genes known to be associated with plant defense. Fungal colonization and transcriptional changes in kernels inoculated with each fungus were monitored at 4, 12, 24, 48, and 72 h post inoculation (hpi). Maize kernels responded by differential gene expression to each fungus within 4 hpi, before the fungi could be observed visually, but more genes were differentially expressed between 48 and 72 hpi, when fungal colonization was more extensive. Two-way hierarchal clustering analysis grouped the temporal expression profiles of the 5,863 differentially expressed maize genes over all time points into 12 clusters. Many clusters were enriched for genes previously associated with defense responses to either A. flavus or F. verticillioides. Also within these expression clusters were genes that lacked either annotation or assignment to functional categories. This study provided a comprehensive analysis of gene expression of each A. flavus and F. verticillioides during infection of maize kernels, it identified genes expressed early and late in the infection process, and it provided a grouping of genes of unknown function with similarly expressed defense related genes that could inform selection of new genes as targets in breeding strategies.

English

Aflatoxin contamination is a qualitative problem in groundnut (Arachis hypogaea L.) occurring at both pre-and post-harvest stages. These aflatoxins are secondary metabolites produced by Aspergillus flavus and A. parasiticus and have carcinogenic, hepatotoxic, teratogenic and immuno-suppressive effects. To evaluate the prevalence of A. flavus infection and aflatoxin contamination in groundnut oil mills/traders’ of Telangana and Andhra Pradesh (AP) pod samples were collected from eight selected oil mills/traders’ in Mahaboobnagar, Rangareddy, Nizamabad, Karimnagar (Telangana); and Anantapur (AP) districts. A total of 24 pod samples were collected (Three samples from the each selected oil mill). Aflatoxin contamination in kernels was estimated by indirect competitive ELISA. In Telangana, kernel infection ranged from 42 (Mahaboobnagar) to 90.7% (Nizamabad). In AP, Tadimarri mandal recorded kernel infection up to 29.3% whereas Tadipatri recorded up to 59.3%. Aflatoxins in kernels from these mills in Telangana were highest in Rangareddy (1205.2 µg kg-1 ) followed by Karimnagar (365.5 µg kg-1 ). Oil mills of Nizamabad and Mahaboobnagar have recorded aflatoxins to a tune of 4.9 and 11.5 µg kg-1 in Telangana. In AP, aflatoxins in pod samples were 2.8 µg kg-1 (Tadipatri) and 6148.4 µg kg-1 (Tadimarri).