Wax and Cutin Layers in Maize Kernels Associated with Resistance to Aflatoxin Production by Aspergillus flavus

1995 ◽  
Vol 58 (3) ◽  
pp. 296-300 ◽  
Author(s):  
BAO Z. GUO ◽  
JOHN S. RUSSIN ◽  
THOMAS E. CLEVELAND ◽  
ROBERT L. BROWN ◽  
NEIL W. WIDSTROM
Keyword(s):  
Aspergillus Flavus ◽  
Potassium Hydroxide ◽  
Aflatoxin Production ◽  
Maize Kernel ◽  
Maize Hybrids ◽  
Maize Population ◽  
Maize Genotypes ◽  
Aflatoxin Accumulation ◽  
Maize Kernels ◽  
Susceptible Group

Thirteen maize hybrids and one maize population, MAS:gk, were screened for susceptibility to aflatoxin production by Aspergillus flavus. Marked differences in aflatoxin B1 production were detected among the maize genotypes tested. Most commercial hybrids consistently supported high levels of aflatoxin accumulation. Aflatoxin levels did not differ between intact and wounded kernels of these genotypes. However, different results were obtained from 4 of the 13 hybrids and the maize population MAS:gk. Levels of aflatoxin accumulation in intact kernels of these genotypes were lower than in the previous susceptible group of genotypes. In addition, aflatoxin levels were higher in wounded than in intact kernels. MAS:gk not only supported the lowest levels of aflatoxin production in intact kernels, but aflatoxin levels in endosperm-wounded kernels also were significantly lower in MAS:gk than in wounded kernels of all tested hybrids. Treatment with KOH to remove cutin from intact kernels prior to inoculation with A. flavus effected substantial increases in aflatoxin accumulation in MAS:gk, but only marginal increases in the susceptible hybrid Pioneer 3154. Removing wax from the surface of MAS:gk kernels greatly increased the susceptibility of this genotype to aflatoxin accumulation. When wax removal was combined with treatment with potassium hydroxide (KOH) or purified cutinase, aflatoxin levels in kernels were equal to those in wounded control kernels in both genotypes. These results indicated that wax and cutin layers of maize kernel pericarps may play a role in resistance to aflatoxin accumulation in MAS:gk and some other genotypes. However, results suggest further that resistance in MAS:gk also may be due to other preformed compounds as well.

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.

Growth of an Aspergillus flavus Transformant Expressing Escherichia coli β-Glucuronidase in Maize Kernels Resistant to Aflatoxin Production

1997 ◽  
Vol 60 (1) ◽  
pp. 84-87 ◽  
Author(s):  
ROBERT L. BROWN ◽  
THOMAS E. CLEVELAND ◽  
GARY A. PAYNE ◽  
CHARLES P. WOLOSHUK ◽  
DONALD G. WHITE
Keyword(s):  
Escherichia Coli ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Gene Promoter ◽  
Fungal Growth ◽  
Aflatoxin Production ◽  
Glucuronidase Activity ◽  
Glucuronidase Reporter ◽  
Aflatoxin Accumulation ◽  
Maize Kernels

Kernels of a maize inbred that demonstrated resistance to aflatoxin production in previous studies were inoculated with an Aspergillus flavus strain containing the Escherichia coli β-d-glucuronidase reporter gene linked to a β-tubulin gene promoter and assessed for both fungal growth and aflatoxin accumulation. Prior to inoculation, kernels were pin-wounded through the pericarp to the endosperm, pin-wounded in the embryo region, or left unwounded. After 7 days incubation with the fungus, β-glucuronidase activity (fungal growth) in the kernels was quantified using a fluorogenic assay and aflatoxin B1 content of the same kernels was analyzed. Kernels of a susceptible inbred, similarly treated, served as controls. Results indicate a positive relationship between aflatoxin levels and the amount of fungal growth. However, resistant kernels wounded through the pericarp to the endosperm before inoculation supported an increase in aflatoxin B1 over levels observed in nonwounded kernels, without an increase in fungal growth. Wounding kernels of the resistant inbred through the embryo resulted in both the greatest fungal growth and the highest levels of aflatoxin B1 for this genotype. Maintenance of resistance to aflatoxin B1 in endosperm-wounded kernels may be due to the action of a mechanism which limits fungal access to the kernel embryo.

scholarly journals Identification of a Maize Kernel Stress-Related Protein and Its Effect on Aflatoxin Accumulation

2004 ◽  
Vol 94 (9) ◽  
pp. 938-945 ◽  
Author(s):  
Z.-Y. Chen ◽  
R. L. Brown ◽  
K. E. Damann ◽  
T. E. Cleveland
Keyword(s):  
Regulatory Gene ◽  
Aflatoxin Production ◽  
Glyoxalase I ◽  
Constitutive Activity ◽  
Aflatoxin Biosynthesis ◽  
Maize Kernel ◽  
Kernel Infection ◽  
Maize Genotypes ◽  
Aflatoxin Accumulation ◽  
Resistant Genotypes

Aflatoxins are carcinogens produced mainly by Aspergillus flavus during infection of susceptible crops such as maize. Through proteomic comparisons of maize kernel embryo proteins of resistant and susceptible genotypes, several protein spots previously were found to be unique or upregulated in resistant embryos. In the present study, one of these protein spots was sequenced and identified as glyoxalase I (GLX-I; EC 4.4.1.5). The full-length cDNA of the glyoxalase I gene (glx-I) was cloned. GLX-I constitutive activity was found to be significantly higher in the resistant maize lines compared with susceptible ones. After kernel infection by A. flavus, GLX-I activity remained lower in susceptible genotypes than in resistant genotypes. However, fungal infection significantly increased methylglyoxal (MG) levels in two of three susceptible genotypes. Further, MG was found to induce aflatoxin production in A. flavus culture at a concentration as low as 5.0 μM. The mode of action of MG may be to stimulate the expression of aflR, an aflatoxin biosynthesis regulatory gene, which was found to be significantly upregulated in the presence of 5 to 20 μM MG. These data suggest that GLX-I may play an important role in controlling MG levels inside kernels, thereby contributing to the lower levels of aflatoxins found in resistant maize genotypes.

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.

Comparison of Constitutive and Inducible Maize Kernel Proteins of Genotypes Resistant or Susceptible to Aflatoxin Production

2001 ◽  
Vol 64 (11) ◽  
pp. 1785-1792 ◽  
Author(s):  
ZHI-YUAN CHEN ◽  
ROBERT L. BROWN ◽  
THOMAS E. CLEVELAND ◽  
KENNETH E. DAMANN ◽  
JOHN S. RUSSIN
Keyword(s):  
Aflatoxin Production ◽  
Maize Kernel ◽  
Antifungal Proteins ◽  
Maize Genotypes ◽  
Resistant Genotypes

Maize genotypes resistant or susceptible to aflatoxin production or contamination were compared for differences in both constitutive and inducible proteins. Five additional constitutive proteins were found to be associated with resistance in over 8 of the 10 genotypes examined. Among these, the 58- and 46-kDa proteins were identified as globulin-1 and globulin-2, respectively. Differences in the ability to induce specific antifungal proteins, such as the higher synthesis of the 22-kDa zeamatin in resistant genotypes, were also observed between resistant and susceptible kernels incubated under germinating conditions (31°C, 100% humidity). Both constitutive and inducible proteins appear to be necessary for kernel resistance. Embryo-killed kernels (unable to synthesize new proteins) supported the highest level of aflatoxins, whereas imbibed kernels (to hasten protein induction) supported the lowest among all treatments. This suggests that the synthesis of new proteins by the embryo plays an important role in conferring resistance. However, significantly lower levels of aflatoxin production in embryo-killed resistant kernels than in susceptible ones suggest that, in reality, high levels of constitutive antifungal proteins are indispensable to kernel resistance.

scholarly journals Evaluation of Arachis Species and Interspecific Tetraploid Lines for Resistance to Aflatoxin Production by Aspergillus flavus

2004 ◽  
Vol 31 (2) ◽  
pp. 134-141 ◽  
Author(s):  
H. Q. Xue ◽  
T. G. Isleib ◽  
H. T. Stalker ◽  
G. A. Payne ◽  
G. OBrian
Keyword(s):  
Aspergillus Flavus ◽  
Insect Pests ◽  
Low Cost ◽  
Aflatoxin Production ◽  
Management Program ◽  
Aflatoxin Contamination ◽  
Sources Of Resistance ◽  
Resistant Parent ◽  
Arachis Species ◽  
Aflatoxin Accumulation

Abstract Anatoxins are carcinogenic and extremely toxic secondary metabolites produced primarily by two fungi, Aspergillus flavus Link ex Fries and A. parasiticus Speare. Elimination of aflatoxin contamination in peanut (Arachis hypogaea L.) is a high priority of the peanut industry. Resistant cultivars should be an effective and low-cost part of an integrated aflatoxin management program. To date, no cultivated peanut has been reported with stable high levels of resistance to aflatoxin production. Arachis species and interspecific tetraploid lines have been evaluated for resistance to several peanut diseases and insect pests, and highly resistant accessions have been reported. Seven accessions of A. cardenasii Krapov. and W.C. Gregory, 29 of A. duranensis Krapov. and W.C. Gregory, and 17 interspecific tetraploid lines derived from A. hypogaea × A. cardenasii were inoculated with A. flavus strain NRRL 3357 and analyzed for aflatoxin content after incubation. On average, A. duranensis and A. cardenasii accumulated significantly less aflatoxin than A. hypogaea checks. The mean difference between the two wild species was not significant. Arachis duranensis accessions PI 468319 (GKBSPSc 30073), PI 468200 (GKBSPSc 30064), and PI 262133 (GKP 10038 sl.); and A. cardenasii accessions PI 262141 (GKP 10017) and PI 475997 (KSSc 36018) had reduced levels of aflatoxin accumulation and should be valuable sources of resistance to aflatoxin contamination. Of the interspecific tetraploid lines, only GP-NC WS 2 supported aflatoxin production not significantly different from resistant parent A. cardenasii GKP 10017, and it appears to be a line with reduced capacity for aflatoxin accumulation.

Production of the 14 kDa trypsin inhibitor protein is important for maize resistance against Aspergillus flavus infection/aflatoxin accumulation

2016 ◽  
Vol 9 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Z.-Y. Chen ◽  
M.L. Warburton ◽  
L. Hawkins ◽  
Q. Wei ◽  
Y. Raruang ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Trypsin Inhibitor ◽  
Aflatoxin Production ◽  
Field Resistance ◽  
Aflatoxin Contamination ◽  
Direct Role ◽  
Independent Events ◽  
Sequence Polymorphisms ◽  
Transgenic Lines ◽  
Aflatoxin Accumulation

Maize (Zea mays L.) is one of the major crops susceptible to Aspergillus flavus Link ex. Fries infection and subsequent aflatoxin contamination. Previous studies found the production of an antifungal 14 kDa trypsin inhibitor (TI) was associated with maize aflatoxin resistance. To further investigate whether the TI plays any direct role in resistance, a TI gene silencing vector was constructed and transformed into maize. Mature kernels were produced from 66 transgenic lines representing 18 independent events. A final total of twelve lines representing four independent events were confirmed positive for transformation, five of which showed significant reduction (63 to 88%) in TI transcript abundance in seedling leaf tissue and seven of which showed significant TI protein reduction (39-85%) in mature kernels. Six of the seven silenced transgenic lines supported higher levels of aflatoxin production compared to negative controls. To further confirm the role of TI in field resistance to aflatoxin accumulation, DNA sequence polymorphisms from within the gene or linked simple sequence repeats were tested in four quantitative trait loci (QTL) mapping populations for QTL effect, and three QTL with log of the odds scores of 11, 4.5, and 3.0 and possibly caused by the TI protein encoding gene were found. Sequence polymorphisms were also tested for association to aflatoxin levels in an association mapping panel, and three single nucleotide polymorphisms were found associated with aflatoxin accumulation (P<0.01). The data from both RNAi and genetic mapping studies demonstrated that production of the TI in maize is important for its resistance to A. flavus infection and/or aflatoxin production.

scholarly journals Amy1, the α-Amylase Gene of Aspergillus flavus: Involvement in Aflatoxin Biosynthesis in Maize Kernels

1999 ◽  
Vol 89 (10) ◽  
pp. 908-914 ◽  
Author(s):  
A. M. Fakhoury ◽  
C. P. Woloshuk
Keyword(s):  
Aspergillus Flavus ◽  
Type Strain ◽  
Wild Type Strain ◽  
Aflatoxin Production ◽  
Deficient Mutant ◽  
Wild Type ◽  
Amylase Gene ◽  
Endosperm Tissue ◽  
Bifunctional Inhibitor ◽  
Maize Kernels

Aspergillus flavus is the causal agent of an ear and kernel rot in maize. In this study, we characterized an α-amylase-deficient mutant and assessed its ability to infect and produce aflatoxin in wounded maize kernels. The α-amylase gene Amy1 was isolated from A. flavus, and its DNA sequence was determined to be nearly identical to Amy3 of A. oryzae. When Amy1 was disrupted in an aflatoxigenic strain of A. flavus, the mutant failed to produce extracellular α-amylase and grew 45% the rate of the wild-type strain on starch medium. The mutant produced aflatoxin in medium containing glucose but not in a medium containing starch. The α-amylase-deficient mutant produced aflatoxin in maize kernels with wounded embryos and occasionally produced aflatoxin only in embryos of kernels with wounded endosperm. The mutant strain failed to produce aflatoxin when inoculated onto degermed kernels. In contrast, the wild-type strain produced aflatoxin in both the endosperm and embryo. These results suggest that α-amylase facilitates aflatoxin production and growth of A. flavus from a wound in the endosperm to the embryo. A 14-kDa trypsin inhibitor associated with resistance to A. flavus and aflatoxin in maize also inhibited the α-amylase from A. flavus, indicating that it is a bifunctional inhibitor. The inhibitor may have a role in resistance, limiting the growth of the fungus in the endosperm tissue by inhibiting the degradation of starch.

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