Aflatoxin accumulation and kernel infection of maize hybrids inoculated with Aspergillus flavus and Aspergillus parasiticus

2010 ◽  
Vol 3 (1) ◽  
pp. 89-93 ◽  
Author(s):  
G. Windham ◽  
L. Hawkins ◽  
W. Williams
Keyword(s):  
Aspergillus Flavus ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Contamination ◽  
Maize Hybrids ◽  
Maize Germplasm ◽  
Kernel Infection ◽  
Needle Technique ◽  
Eastern Usa ◽  
Aflatoxin Accumulation ◽  
Maize Grain

Over a three year period, we compared aflatoxin accumulation and kernel infection in maize hybrids inoculated with Aspergillus flavus isolate NRRL 3357, A. flavus isolate NRRL 19772, Aspergillus parasiticus isolate NRRL 6111, and all combinations of these isolates. Maize hybrids were inoculated with the Aspergillus strains using the side-needle technique at 7 days after midsilk (50% of the plants had silks emerged). Aspergillus kernel infection and aflatoxin contamination were determined at ca. 63 days after midsilk. A. flavus isolate 3357 induced high levels of aflatoxin contamination in the maize grain which was similar to levels found when this isolate was combined with the other two Aspergillus isolates. Kernel infection levels were higher in one hybrid when a combination of isolates including isolate 3357 was used. A. flavus isolate 3357 has been used to evaluate maize germplasm for aflatoxin resistance in the south-eastern USA for over 30 years. Our studies determined that inoculating plants with A. flavus isolate 3357 alone was sufficient for inducing aflatoxin contamination in grain at our location. A combination of A. flavus isolates which include isolate 3357 might be more effective in increasing levels of kernel infection and could also induce higher levels of aflatoxin at locations that do not favour disease development.

scholarly journals Aspergillus flavus Infection and Aflatoxin Accumulation in Resistant and Susceptible Maize Hybrids

Plant Disease ◽  
1998 ◽  
Vol 82 (3) ◽  
pp. 281-284 ◽  
Author(s):  
G. L. Windham ◽  
W. P. Williams
Keyword(s):  
Aspergillus Flavus ◽  
Growing Season ◽  
Field Studies ◽  
Aflatoxin Contamination ◽  
Maize Kernel ◽  
Maize Hybrids ◽  
Kernel Infection ◽  
Harvest Dates ◽  
Needle Technique ◽  
Aflatoxin Accumulation

Field studies were conducted for 2 years in Mississippi to monitor maize kernel infection and aflatoxin accumulation caused by Aspergillus flavus at various times during the growing season. Hybrids resistant and susceptible to A. flavus were compared to determine temporal differences in infection and aflatoxin levels. The resistant hybrids tested were Mo18W × Mp313E, Mp420 × Tx601, and SC54 × SC76; and the susceptible hybrids tested were GA209 × Mp339, Mp307 × Mp428, and Mp68:616 × SC212M. The top ear of each plant was inoculated with a suspension containing A. flavus conidia at 7 days after midsilk (50% of the plants in a plot had silks emerged) using the side needle technique. Inoculated ears were harvested 35, 42, 49, 56, and 63 days after midsilk to determine kernel infection by A. flavus and aflatoxin contamination. Differences in aflatoxin levels between resistant and susceptible hybrids occurred in all harvest dates. However, significant differences between resistant and susceptible hybrids for kernel infection were not observed until 42 days after midsilk. Differences between resistant and susceptible hybrids occurred for kernel infection and aflatoxin concentrations 49, 56, and 63 days after midsilk. Incidence of kernel infection (8.1% for GA209 × Mp339) was the highest 49 days after midsilk, and aflatoxin concentrations (510 ng/g for Mp307 × Mp428) were the highest 63 days after midsilk. Maximum differences between resistant and susceptible hybrids for aflatoxin levels were observed 63 days after midsilk. Two of the resistant hybrids, Mo18W × Mp313E and Mp420 × Tx601, had significantly less aflatoxin than the three susceptible hybrids 63 days after midsilk.

scholarly journals Effects of the Southwestern Corn Borer on Aspergillus flavus Kernel Infection and Aflatoxin Accumulation in Maize Hybrids

Plant Disease ◽  
1999 ◽  
Vol 83 (6) ◽  
pp. 535-540 ◽  
Author(s):  
G. L. Windham ◽  
W. P. Williams ◽  
F. M. Davis
Keyword(s):  
Aspergillus Flavus ◽  
Field Studies ◽  
Aflatoxin Contamination ◽  
Leaf Axil ◽  
Corn Borer ◽  
Maize Hybrids ◽  
Kernel Infection ◽  
Aflatoxin Accumulation ◽  
Maize Cob ◽  
Southwestern Corn Borer

Field studies were conducted in 1995 to 1997 to determine the effect of the southwestern corn borer (SWCB) on Aspergillus flavus kernel infection and aflatoxin accumulation in maize hybrids. In 1995, when A. flavus conidia were applied to silks in a spray and SWCB neonate larvae in maize cob grits were placed in the leaf axil at the top ear of commercial hybrids, aflatoxin contamination and A. flavus kernel infection were highest in plants treated with both the fungus and the insect. In 1996, using the same inoculation and infestation techniques, aflatoxin levels and kernel infection were much lower than in 1995 and SWCB had no effect on aflatoxin contamination or kernel infection. In another study in 1996, the effect of SWCB on aflatoxin contamination and A. flavus kernel infection in hybrids resistant and susceptible to A. flavus was determined. The inoculation-infestation technique involved applying maize cob grits containing A. flavus conidia and SWCB larvae to silks. When SWCB was combined with A. flavus, aflatoxin levels and kernel infection were dramatically higher than in hybrids inoculated with A. flavus alone, regardless of whether the hybrids were resistant or susceptible to A. flavus. In 1997, the interaction of A. flavus and SWCB was determined on hybrids resistant and susceptible to A. flavus and on a commercial hybrid with and without the Bacillus thuringiensis (Bt) toxin. Maize cob grits were used to inoculate A. flavus and infest SWCB on the silks 7 or 21 days after midsilk (50% of the plants in a row had silks emerged). All four hybrids had the highest levels of Aspergillus spp. kernel infection and aflatoxin contamination when A. flavus and SWCB were applied at 21 days after midsilk. These studies indicate that SWCB can substantially increase aflatoxin levels when combined with A. flavus. However, inoculation and infestation techniques, placement of the fungus and the insect, and timing of inoculation and infestation are all critical in demonstrating a synergistic relationship between A. flavus and SWCB on aflatoxin contamination of maize.

scholarly journals Comparison of Two Inoculation Methods for Evaluating Maize for Resistance toAspergillus flavusInfection and Aflatoxin Accumulation

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
W. Paul Williams ◽  
Michael N. Alpe ◽  
Gary L. Windham ◽  
Seval Ozkan ◽  
J. Erik Mylroie
Keyword(s):  
Genetic Resistance ◽  
Aflatoxin Contamination ◽  
Conidial Suspension ◽  
Inoculation Methods ◽  
Maize Germplasm ◽  
Inoculation Techniques ◽  
Needle Technique ◽  
Aflatoxin Accumulation ◽  
Pericarp Thickness ◽  
Wheat Kernels

Aflatoxin, the most potent carcinogen found in nature, is produced by the fungusAspergillus flavusand occurs naturally in maize,Zea maysL. Growing maize hybrids with genetic resistance to aflatoxin contamination are generally considered a highly desirable way to reduce losses to aflatoxin. Developing resistant hybrids requires reliable inoculation methods for screening maize germplasm for resistance toA. flavusinfection and aflatoxin accumulation. The side-needle technique is a widely used inoculation technique: anA. flavusconidial suspension is injected underneath the husks into the side of the ear. This wounds the ear and limits expression of resistance associated with husk coverage, pericarp thickness, and seed coat integrity. In this investigation, the side-needle technique was compared with a second inoculation method that involved dispensing wheat kernels infected withA. flavusinto plant whorls at 35 and 49 days after planting. Results showed that although the side-needle technique produced higher levels of aflatoxin accumulation, differences inA. flavusbiomass produced by the two inoculation techniques were not significant. Both inoculation techniques were effective in differentiating resistant and susceptible single cross hybrids irrespective of the use ofA. flavusinfection or aflatoxin accumulation as a basis to define resistance.

scholarly journals Aspergillus flavus Infection and Aflatoxin Contamination of Preharvest Maize in Benin

Plant Disease ◽  
1997 ◽  
Vol 81 (11) ◽  
pp. 1323-1327 ◽  
Author(s):  
M. Sétamou ◽  
K. F. Cardwell ◽  
F. Schulthess ◽  
K. Hell
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin Contamination ◽  
Aspergillus Species ◽  
Geographic Pattern ◽  
Mussidia Nigrivenella ◽  
Aspergillus Infection ◽  
The North ◽  
Kernel Infection ◽  
Agroecological Zones ◽  
Aflatoxin Accumulation

Eighty and sixty maize fields were sampled in 1994 and 1995, respectively, to monitor Aspergillus infection and aflatoxin contamination of preharvest maize in Benin. Three Aspergillus species were isolated from different agroecological zones, with A. flavus being the most prevalent. The countrywide mean percentage of kernel infection was about 20% in both years. Aflatoxin was extracted from maize in at least 30% of the fields sampled. Toxin concentrations exhibited a distinct zonal variation, with relatively high levels in the Guinea Savanna. There was a trend toward higher rate of aflatoxin accumulation per percentage A. flavus infection from the south to the north. Damage by the ear borer, Mussidia nigrivenella, increased aflatoxin accumulation in maize. Hence, the geographic pattern observed in the occurrence of A. flavus and aflatoxin may be related to the incidence of M. nigrivenella.

Modelling the colonisation of maize by toxigenic and non-toxigenic Aspergillus flavus strains: implications for biological control

2008 ◽  
Vol 1 (3) ◽  
pp. 333-340 ◽  
Author(s):  
H. Abbas ◽  
R. Zablotowicz ◽  
H. Bruns
Keyword(s):  
Biological Control ◽  
Aspergillus Flavus ◽  
Growth Parameters ◽  
Biological Control Agent ◽  
Cyclopiazonic Acid ◽  
Aflatoxin Contamination ◽  
Tween 20 ◽  
Lag Phase ◽  
Gompertz Equation ◽  
Aflatoxin Accumulation

To successfully exploit biological control it is desirable to understand how the introduced agent colonises the host and interferes with establishment of the pest. This study assessed field colonisation of maize by Aspergillus flavus strains as biological control agents to reduce aflatoxin contamination. Maize (corn, Zea mays L.) ears were inoculated with A. flavus using a pin-bar technique in 2004 and 2005. Non-aflatoxigenic strains K49 (NRRL 30797) & CT3 (NRRL 30798) and toxigenic F3W4 (NRRL 30798) were compared against a carrier control (0.2% aqueous Tween 20). Ten ears were sampled over 12 to 20 days, visually assessed, and curves fit to a three compartment Gompertz equation or other best appropriate regressions. Aflatoxin was determined by HPLC and cyclopiazonic acid (CPA) by LC/MS. The Gompertz model describes growth parameters, e.g. growth constant, lag phase and maximum colonisation characterised patterns of maize colonisation for most inoculated treatments. Aflatoxin accumulation in maize inoculated with F3W4 was about 35,000 ng/g in 2004 and 2005, with kinetics of aflatoxin accumulation in 2005 well described by the Gompertz equation. Less than 200 ng/g was observed in maize inoculated with strains CT3 & K49 and accumulation was described by a linear or logistic model. Maize inoculated with strains CT3 and F3W4 accumulated a maximum of 220 and 169 µg/kg CPA, respectively, compared to 22 and 0.2 µg/kg in the control and K49 inoculated, respectively. This technique can be used to elucidate colonisation potential of non-toxigenic A. flavus in maize in relation to biological control of aflatoxin. The greatest reduction of aflatoxin and CPA in maize inoculated with strain K49 and Gompertz parameters on colonisation indicates its superiority to CT3 as a biological control agent. The dynamics of maize colonisation by A. flavus strains and subsequent mycotoxin accumulation generated by using the pin-bar technique has implications for characterising the competence of biocontrol strains for reducing aflatoxin contamination.

Evaluation of resistance to aflatoxin contamination in kernels of maize genotypes using a GFP-expressing Aspergillus flavus strain

2013 ◽  
Vol 6 (2) ◽  
pp. 151-158 ◽  
Author(s):  
K. Rajasekaran ◽  
C.M. Sickler ◽  
R.L. Brown ◽  
J.W. Cary ◽  
D. Bhatnagar
Keyword(s):  
Fungal Infection ◽  
Aspergillus Flavus ◽  
Fluorescent Protein ◽  
Aflatoxin Contamination ◽  
Clear Correlation ◽  
Aleurone Layer ◽  
Screening Assay ◽  
Maize Germplasm ◽  
Antifungal Proteins ◽  
Green Fluorescent

Resistance or susceptibility of maize inbreds to infection by Aspergillus flavus was evaluated by the kernel screening assay. A green fluorescent protein-expressing strain of A. flavus was used to measure fungal spread and aflatoxin levels in real-time following fungal infection of kernels. Among the four inbreds tested, MI82 showed the most resistance and Ga209 the least. TZAR101 was also resistant to fungal infection, whereas Va35 was susceptible to fungal infection. However, Va35 produced lower aflatoxin levels compared to the susceptible line Ga209. Fluorescence microscopy indicated that the site of entry of the fungus into the kernel was consistently through the pedicel. Entry through the pericarp was never observed in undamaged kernels. In view of these results, incorporation or overexpression of antifungal proteins should be targeted to the pedicel and basal endosperm region in developing kernels. Once the fungus has entered through the pedicel, it spreads quickly through the open spaces between the pericarp and the aleurone layer, ultimately colonising the endosperm and scutellum and, finally, the embryo. A clear correlation was established between fungal fluorescence and aflatoxin levels. This method provides a quick, reliable means of evaluating resistance to A. flavus in undamaged kernels and provides breeders with a rapid method to evaluate maize germplasm.

scholarly journals Interactions of Saprophytic Yeasts with anor Mutant of Aspergillus flavus

1999 ◽  
Vol 65 (6) ◽  
pp. 2738-2740 ◽  
Author(s):  
Sui-Sheng T. Hua ◽  
James L. Baker ◽  
Melanie Flores-Espiritu
Keyword(s):  
Aspergillus Flavus ◽  
Agar Plate ◽  
Aflatoxin Production ◽  
Aflatoxin Contamination ◽  
Orange Pigment ◽  
Yeast Strains ◽  
Norsolorinic Acid ◽  
Aflatoxin Accumulation ◽  
Food Commodities ◽  
Pigment Accumulation

ABSTRACT The nor mutant of Aspergillus flavus has a defective norsolorinic acid reductase, and thus the aflatoxin biosynthetic pathway is blocked, resulting in the accumulation of norsolorinic acid, a bright red-orange pigment. We developed a visual agar plate assay to monitor yeast strains for their ability to inhibit aflatoxin production by visually scoring the accumulation of this pigment of the nor mutant. We identified yeast strains that reduced the red-orange pigment accumulation in the normutant. These yeasts also reduced aflatoxin accumulation by a toxigenic strain of A. flavus. These yeasts may be useful for reducing aflatoxin contamination of food commodities.

scholarly journals Aspergillus Volatiles Regulate Aflatoxin Synthesis and Asexual Sporulation in Aspergillus parasiticus

2007 ◽  
Vol 73 (22) ◽  
pp. 7268-7276 ◽  
Author(s):  
Ludmila V. Roze ◽  
Randolph M. Beaudry ◽  
Anna E. Arthur ◽  
Ana M. Calvo ◽  
John E. Linz
Keyword(s):  
Aspergillus Parasiticus ◽  
Primary Source ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Transcript Accumulation ◽  
Potential Health ◽  
Asexual Sporulation ◽  
Norsolorinic Acid ◽  
Aflatoxin Accumulation ◽  
Regulatory Effects

ABSTRACT Aspergillus parasiticus is one primary source of aflatoxin contamination in economically important crops. To prevent the potential health and economic impacts of aflatoxin contamination, our goal is to develop practical strategies to reduce aflatoxin synthesis on susceptible crops. One focus is to identify biological and environmental factors that regulate aflatoxin synthesis and to manipulate these factors to control aflatoxin biosynthesis in the field or during crop storage. In the current study, we analyzed the effects of aspergillus volatiles on growth, development, aflatoxin biosynthesis, and promoter activity in the filamentous fungus A. parasiticus. When colonies of Aspergillus nidulans and A. parasiticus were incubated in the same growth chamber, we observed a significant reduction in aflatoxin synthesis and asexual sporulation by A. parasiticus. Analysis of the headspace gases demonstrated that A. nidulans produced much larger quantities of 2-buten-1-ol (CA) and 2-ethyl-1-hexanol (EH) than A. parasiticus. In its pure form, EH inhibited growth and increased aflatoxin accumulation in A. parasiticus at all doses tested; EH also stimulated aflatoxin transcript accumulation. In contrast, CA exerted dose-dependent up-regulatory or down-regulatory effects on aflatoxin accumulation, conidiation, and aflatoxin transcript accumulation. Experiments with reporter strains carrying nor-1 promoter deletions and mutations suggested that the differential effects of CA were mediated through separate regulatory regions in the nor-1 promoter. The potential efficacy of CA as a tool for analysis of transcriptional regulation of aflatoxin biosynthesis is discussed. We also identify a novel, rapid, and reliable method to assess norsolorinic acid accumulation in solid culture using a Chroma Meter CR-300 apparatus.

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