Flavus Invasion Research Articles

In vitro Varietal Screening for Resistance to Aspergillus Flavus Invasion and Aflatoxin Production in Groundnut

In vitro Varietal Screening for Resistance to Aspergillus Flavus Invasion and Aflatoxin Production in Groundnut

Transcriptome and proteome analyses of resistant preharvest peanut seed coat in response to Aspergillus flavus infection

The infection of peanut (Arachis hypogaea L.) seed coat by the pathogenic fungus Aspergillus flavus has highly negative economic and health impacts. However, the molecular mechanism underlying such defense response remains poorly understood. This study aims to address this issue by profiling the transcriptomic and proteomic changes that occur during the infection of the resistant peanut cultivar J11 by A. flavus. Transcriptomic study led to the detection of 13,539 genes, among which 663 exhibited differential expression. Further functional analysis found the differentially expressed genes to encode a wide range of pathogenesis- and/or defense-related proteins such as transcription factors, pathogenesis-related proteins, and chitinases. Changes in the expression patterns of these genes might contribute to peanut resistance to A. flavus. On the other hand, the proteomic profiling showed that 314 of the 1382 detected protein candidates were aberrantly expressed as a result of A. flavus invasion. However, the correlation between the transcriptomic and proteomic data was poor. We further demonstrated by in vitro fungistasis tests that hevamine-A, which was enriched at both transcript and protein levels, could directly inhibit the growth of A. flavus. The results demonstrate the power of complementary transcriptomic and proteomic analyses in the study of pathogen defense and resistance in plants and the chitinase could play an important role in the defense response of peanut to A. flavus. The current study also constitutes the first step toward building an integrated omics data platform for the development of Aspergillus-resistant peanut cultivars. How to cite: Zhao X, Li C, Yan C, et al. Transcriptome and proteome analyses of resistant preharvest peanut seed-coat in response to Aspergillus flavus infection. Electron J Biotechnol 2019;39. https://doi.org/10.1016/j.ejbt.2019.03.003.

Biocontrol of toxigenic strain of Aspergillus flavus isolated from the root tubers of safed musli (Chlorophytum borivilianum Sant. F) using its rhizospheric mycoflora

Miraculous herb safed musli (Chlorophytum borivilianum Sant. F), family liliaceae, is well recognized for its immense potential as an aphrodisiac. The root tubers of this herbal drug were found to be invested with Aspergillus flavus during field and storage. Therefore, the present study was designed to explore the ability of 26 co-existing rhizospheric mycoflora to inhibit A. flavus invasion and subsequent aflatoxin contamination of safed musli. The interaction of these moulds with highly toxigenic strain (CB55) of A. flavus was evaluated by dual culture method and type of interaction was graded. Most likely antagonistic effects were shown by fifteen (15) moulds, out of which Type ‘C’ interaction was evidenced in the case of six moulds; A. clavatus, A. terreus, Botryotrichum piluliferum, Candida albicans, Cephalosporium acremonium, and Cunninghamella sp. Further, ‘D’ type interaction was displayed by seven moulds which include A. niger, Colletotrichum sp., Drechslera sp., Mucor haemalis, Mycelia sterilia, Rhizopus arrhizus and Stachybotrys atra and ‘E’ type interaction was noted in the case of Trichoderma viride and Trihcothecium roseum. Regarding human health it is critical to use an ecofriendly approach to control the invasion of toxigenic moulds with root tubers of safed musli.

Peanut Resistance Gene Expression in Response to Aspergillus flavus Infection During Seed Germination

AbstractAspergillus flavus produces potent mutagenic and carcinogenic polyketide‐derived secondary metabolites known as aflatoxins. Development of host plant resistance in peanut and other crops is the most environmentally friendly and cost‐effective method to eliminate the serious problem of aflatoxin contamination in grains. To confirm that putative peanut genes identified in a previous microarray study were involved in peanut resistance to A. flavus infection, 14 genes were selected for further investigation through real‐time PCR. The results revealed diverse patterns of gene expression during seed germination after A. flavus inoculation. Based on the expression levels and the relative‐expression patterns over a 7‐day period, the 14 host genes could be classified into six different groups belonging to three main biochemical and genetic defence processes of lipid metabolism, oxidative signalling and cell‐wall synthesis during counter‐attack. A network of gene expression patterns was activated in sequential order in response to A. flavus invasion in both resistant and susceptible peanut lines during seed germination. Understanding gene expression patterns in peanut will be useful to breeders and other scientists interested in incorporating genetic resources of resistance against A. flavus into peanut germplasm and/or commercial cultivars via conventional and/or molecular methods.

Breeding aflatoxin-resistant maize lines using recent advances in technologies – a review

Aflatoxin contamination caused by Aspergillus flavus infection of corn is a significant and chronic threat to corn being used as food or feed. Contamination of crops at levels of 20 ng g−1 or higher (as regulated by the USFDA) by this toxin and potent carcinogen makes the crop unsalable, resulting in a significant economic burden on the producer. This review focuses on elimination of this contamination in corn which is a major US crop and the basis of many products. Corn is also “nature's example” of a crop containing heritable resistance to aflatoxin contamination, thereby serving as a model for achieving resistance to aflatoxin contamination in other crops as well. This crop is the largest production grain crop worldwide, providing food for billions of people and livestock and critical feedstock for production of biofuels. In 2011, the economic value of the US corn crop was US$76 billion, with US growers producing an estimated 12 billion bushels, more than one-third of the world's supply. Thus, the economics and significance of corn as a food crop and the threat to food safety due to aflatoxin contamination of this major food crop have prompted the many research efforts in many parts of the world to identify resistance in corn to aflatoxin contamination. Plant breeding and varietal selection has been used as a tool to develop varieties resistance to disease. This methodology has been employed in defining a few corn lines that show resistance to A. flavus invasion; however, no commercial lines have been marketed. With the new tools of proteomics and genomics, identification of resistance mechanisms, and rapid resistance marker selection methodologies, there is an increasing possibility of finding significant resistance in corn, and in understanding the mechanism of this resistance.

Potential involvement of Aspergillus flavus laccases in peanut invasion at low water potential

Aspergillus flavus accumulates carcinogenic aflatoxins in peanuts, mainly in immature kernels during drought. Aspergillus flavus invasion induces accumulation of phytoalexins, mostly stilbenoids in peanut, as a plant defence mechanism. Because fungal laccases are often related to pathogenicity and can degrade stilbenoids, this study reports for the first time the expression of A. flavus laccases in the presence of kernels, hulls and low water potential in relation to the accumulation of phytoalexins in peanut kernels. Packed‐cell volume (PCV) of A. flavus biomass was significantly higher (P ≤ 0·01) in the presence of mature kernels, dead kernels, and mature and immature peanut hulls than the control. The presence of kernels and hulls lowered the level of expression of three A. flavus laccases by 4–6‐fold (P < 0·01), whereas 3% sucrose up‐regulated them by 35–304‐fold, and low water potential (−1·1 MPa) up‐regulated them by 85–248‐fold (P < 0·01). Phytoalexins that accumulated in peanut kernels in the presence of A. flavus and were quantified by HPLC‐DAD‐MS were primarily the stilbenoids: 3′‐isopentadienyl‐3,5,4′‐trihydroxystilbene (IPD), chiricanine‐A, arachidin‐2, arachidin‐3 and arahypin‐1. Apparent degradation of phytoalexins was observed when using a priori induction of phytoalexins in seeds in combination with a priori induction of laccases in A. flavus. The up‐regulation of laccase expression observed at −1·1 MPa and at high sucrose concentration could be contributing to peanut invasion in immature kernels under drought conditions.

Overexpression of ARAhPR10, a Member of the PR10 Family, Decreases Levels of <i>Aspergillus flavus</i> Infection in Peanut Seeds

Peanut (Arachis hypogaea L.) is one of the most susceptible host crops to Aspergillus flavus invasion and subsequent aflatoxin contamination. In this report, a new member of PR10 family putative resistant gene (designated as ARAhPR10, No. EU661964.1) encoding a PR10 protein was isolated and characterized. Analysis of qRT-PCR showed that the expression of ARAhPR10 was induced by pre-harvested A. flavus infection, but no significant difference was observed between resistant genotype “GT-C20” and susceptible genotype “Yueyou 7”. Seven transgenic peanut lines expressing the ARAhPR10 gene under the control of 35S promoter were obtained using the Agrobacterium tumefaciens-mediated method. Real time RT-PCR results showed that the expression level of the ARAhPR10 was significantly higher and the A. flavus infection and aflatoxin content were significantly lower in seeds of transgenic lines than that of the wild type. A significant negative correlation between ARAhPR10 expression at transcript level and seeds aflatoxin production was observed. Combining the previous results, it is suggested that ARAhPR10 expression play an important role in peanut host resistance to A. flavus infection and aflatoxin producing.

Pre-harvest aflatoxin contamination and soluble sugars of peanut

Peanut (Arachis hypogaea L.) is an important commercial crop throughout the world and is one of the most susceptible crops to Aspergillus flavus invasion (Guo et al., 2009)

Seed Coat Resistance of Groudnut to Aspergillus Flavus and Their Stability Performance in The Field

One of the weaknesses of the groundnut is the easiness to be infected by fungi, especially Aspergillus flavus that produces aflatoxin. Seed from the field experiments for all step of selection (F5 until to multilocation yield test) after processed then stored for 3 and 6 months, further tested their respons to A. flavus using a standard method. Examined for seed coat resistance to colonization of A. flavus were carried out in laboratory ILETRI (Indonesian of Legume and Tuber Crops Research Institute) since years of 2002 to 2006. Stability performance of resistance to A. flavus was analyzed with regression technique. Performance of resistance to A. flavus of selected lines tested were not consistant among 16 of testing envoronments. Among genotypes were also sigficantly different response to A. flavus invasion from location to location, indicated that those performance of some lines were not stable, except line of MHS/91278-99-C-180-5. The highest pod yield was occupied by line of J/91283-99-C-90-8 and stable, however it's resistance to A. flavus did not stable. The resistance of J/91283-99-C-90-8 to A. flavus antil to three months after after seed strored similar with variety of J-11. Keywords: groundnut, Aspergillus flavus , aflatoxin

Development and Evaluation of Peanut Germplasm with Resistance to <I>Aspergillus flavus</I> from Core Collection

Peanut (Arachis hypogaea L.), one of the main oil and cash crops in the world, is easily susceptible to Aspergillus flavus, resulting huge loss in its quality, so Aspergillus flavus infection greatly limits peanut production and industry in China. Therefore, it is imperative to develop new peanut germplasm with resistance to Aspergillus flavus in breeding program. The core collection is well accepted as a useful way to improve the efficiency of crop germplasm evaluation and utilization, which contains a subset of accessions from the entire collection that covers the most of available genetic information. In the present study, a total of 561 accessions of Chinese peanut core collection and 155 accessions of ICRISAT mini core collection were identified. Eight varieties with resistance to Aspergillus flavus invasion and aflatoxin production each were developed, including one (51002-6) with elite agronomic traits. The peanut germplasm with resistance to Aspergillus flavus invasion and aflatoxin production in ICRISAT mini core were more than those in Chinese peanut core collection. In addition, the percentages of accessions with resistance to Aspergillus flavus invasion in var. hypogaea, and accessions resistant to aflatoxin production in var. hirsuta were relatively high in comparison with others. Genetic diversity in the resistant peanut selections was evaluated based on morphological traits and SSR approach. ICG12625 with resistance to aflatoxin production and ICG4750 with resistance to aflatoxin invasion were evaluated by SSR, the genetic distance of them with high-yielding cultivars such as Zhonghua 5, Zhonghua 6 and Zhonghua 12 and Yuanza 9102 was larger. The primers were designed based on the conserved NBS-LRR domains of the disease resistance genes sequence, one RGA (Resistance gene analog) from genomic DNA of six different peanuts with resistance to Aspergillus flavus was obtained through PCR.

Overview of Research Progress on Peanut (Arachis hypogaea L.) Host Resistance to Aflatoxin Contamination and Genomics at the Guangdong Academy of Agricultural Sciences

Abstract Aflatoxin contamination in peanut is a serious and world-wide problem concerning food safety and human health. Plant-host resistance is a highly desirable tactic that can be used to manage this problem. This review summarizes research progress in peanut host resistance mechanisms to aflatoxin contamination at the Crops Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, China. Through systematic resistance evaluations, germplasm lines resistant to Aspergillus flavus invasion have been identified and two resistant cultivars were developed and released in South China. The resistance has been associated with testa wax and presence of cutin layer, active oxygen and membrane lipid peroxidation, phytoalexin accumulation, and antifungal proteins in the peanut kernels. Functional genomics will be a valuable tool to understand the comprehensive mechanisms governing the resistance pathways. In this paper we also summarized the advances made by our group in the area of genomic research, especially in mining EST-SSRs, development of a genetic linkage map and QTLs mapping in the cultivated peanut species.

Affinity Purification of Trypsin Inhibitor with Anti-Aspergillus Flavus Activity from Cultivated and Wild Soybean

Trypsin inhibitors (TI) from wild-type soybean (Glycine soya) (WBTI) and domesticated soybean (Glycine max) (SBTI) were purified using prepared chitosan resin-trypsin as filler on the affinity chromatography column. The SBTI/WBTI purification fold by affinity chromatography was 718- and 279-fold, with the activity recovery of 62% and 59%, respectively. It was found that SBTI and WBTI exerted a strong inhibition of Aspergillus. flavus growth, with IC(50) of 1.6 and 1.0 micromol/l. This growth inhibition was possibly the result of the inhibition on alpha-amylase activity of A. flavus by both the SBTI and WBTI. This was further supported by the fact that in the presence of SBTI and WBTI at 9.0 and 6.0 microg/g (peanut) on peanuts inhibited the germination and growth of A. flavus. Accordingly, characterization of the mode of action of SBTI and WBTI could constitute a first step leading to resistance to A. flavus invasion.

Evaluation of selected geocarposphere bacteria for biological control of Aspergillus flavus in peanut

Selected bacterial strains isolated from the region of peanut pod development (geocarposphere) and two additional bacterial strains were screened as potential biological control agents against Aspergillus flavus invasion and subsequent aflatoxin contamination of peanut in laboratory, greenhouse, and field trials. All 17 geocarposphere strains tested delayed invasion of young roots and reduced colonization by the fungus in a root-radicle assay used as a rapid laboratory prescreen. In a greenhouse study, seven bacterial strains significantly reduced pod colonization by A. flavus compared to the control. In a field trial, conducted similarly to the greenhouse assay, pods sampled at mid-peg from plants seed-treated with suspensions of either 91A-539 or 91A-550 were not colonized by A. flavus, and the incidence of pods invaded from plants treated with either 91A-539 or 91A-599 was consistently lower than nonbacterized plants at each of five sampling dates. At harvest, 8 geocarposphere bacterial strains significantly lowered the percentage of pods colonized (> 51%) compared to the control. Levels of seed colonization ranged from 1.3% to 45% and did not appear related to aflatoxin concentrations in the kernels.

A low-cost microcomputer system to monitor and control an environmental control plot facility

Since 1980, six 67.1-m 2 environmental control plots with apparatus for soil temperature manipulation and motorized shelters for rainfall exclusion have been used for the study of Aspergillus flavus invasion and aflatoxin contamination of peanuts during drought stress. Manual controls and the absence of an alarm system for the plots have mandated daily monitoring and adjustments of thermostats for soil temperature control and visual inspection for proper shelter operation, especially during severe thunderstorms. Prior to 1987 experiments, a microcomputer-based control system was assembled to control the operation of the facility and provide telephone alarms for soil temperature discrepancies, improper shelter operation, or electrical power interruptions. Commercially available components were used to construct the system which cost approximately US$2000. At the end of a 50-day evaluation period, the system had provided an average plot soil temperature of 27.4°C with a setting of 26.7°C. The 95% confidence interval for the treatment period average during the tests was between 25.9°C and 27.9°C. Alarm annunciation and telephone notification were also provided as expected in response to plot temperature extremes and a power outage.

Comparative Susceptibility of Four Experimental Peanut Lines and the Cultivar Florunner to Preharvest Aflatoxin Contamination

Abstract Four peanut genotypes, selected as resistant to invasion by Aspergillus flavus in laboratory screening with rehydrated, stored seed and Florunner cultivar were subjected to preharvest drought and temperature conditions conducive to A. flavus invasion and aflatoxin contamination. Preharvest aflatoxin contamination of peanuts has been previously correlated with geocarposphere temperature and moisture conditions during drought. All genotypes tested were highly contaminated with aflatoxin. This study indicates that a critical assessment should be made of the value of using the current laboratory method to select germplasm for resistance to A. flavus invasion and assuming resistance to aflatoxin contamination under field conditions.

Growing Season and Location Effects on Water Uptake and Drying Rates of Peanut Seeds from Genotypes Resistant and Susceptible to Invasion by Aspergillus flavus Lk. ex. Fr.1,2

AbstractAs a means to detect differences in testae properties between peanut (Arachis hypogaea L.) seeds from genotypes resistant to invasion by A. flavus Lk. ex Fr. and seeds from genotypes susceptible to the fungus, the water uptake and drying characteristics of the seeds were compared. Testae properties that could aid in control of A. flavus invasion of peanut seeds and the effect of growing conditions on these properties were sought.Seeds of both genotypes were grown in Puerto Rico in 1972 and Puerto Rico and Texas in 1973. Growing season and location significantly affected rate and total water uptake of cured seeds. With or without testae, the rate and total water uptake were greater for seeds grown in Puerto Rico than those grown in Texas. When growing conditions produced seeds with comparatively high water uptake capabilities (Puerto Rico), intact seeds of ‘Florunner’ and the genotypes resistant to invasion by A. flavus had slower water uptake rates than genotypes more susceptible to mold invasion. The data suggest that there are functional differences, indicative of structural differences, between testae of resistant and susceptible genotypes. When growing conditions produced seeds with comparatively low water uptake capabilities (Texas), there was less distinction between resistant and susceptible genotypes (based on water uptake patterns). However, one susceptible genotype retained a higher rate and total water uptake than all other genotypes. These data indicate that growing conditions affected testae structure that regulates the rate of water uptake by the seeds.Seed drying tests showed that Florunner and genotypes resistant to A. flavus invasion dried to moisture levels (10% or less) unfavorable for A. flavus growth at rates significantly faster than the susceptible genotypes. Drying patterns were unaffected by growing location.Lipid and protein contents of the seeds were not correlated with water uptake characteristics, although they varied with growing season and location.Slow rates of water uptake and the rapid drying rates of seeds of the resistant genotypes are attributes favorable to control of A. flavus invasion. If these attributes, along with resistance to A. flavus invasion, could be genetically transferred to other peanut genotypes, it is likely that contamination of peanuts by A. flavus could be reduced.

Susceptibility of Freshly Picked Ear Corn to Invasion by Fungi1

High-moisture ear corn held 9 days at 23 C remained free of visible mold or evidence of Aspergillus flavus invasion provided there was no mechanical damage of the kernels.