Screening Groundnuts for Resistance to Seed Invasion by Aspergillus flavus and to Aflatoxin Production

Research on responses of groundnuts to seed colonization and infection by Aspergillus flavus and/or aflatoxin production is reviewed, and progress made in this field at ICRISAT is summarized. Several laboratory and field screening procedures are developed to screen groundnuts for resistance to A. flavus infection and/or aflatoxin production. Research on the effects of environmental factors on pod and seed invasion by A. flavus has produced information useful in the development of field screening methods. Imposed drought stress is used to improve large-scale field screening of groundnut genotypes for resistance to preharvest infection of seeds by A. flavus. Several genotypes were found resistant to infection, and some of them were also resistant to in vitro seed colonization by A. flavus in laboratory inoculation tests. Two genotypes supported only very low levels of aflatoxin B1 production when seeds were colonized by an aflatoxin-producing strain of A. flavus

Analytical methods for detection and estimation of aflatoxins*

The aflatoxins are a group of highly toxic metabolites produced by the fungi Aspergillus flavus and Aspergillus parasitucus. Four of these metabolites designated aflatoxins B1, B2, G1, and occur commonly in commodities infected with these fungi. The distinguishing letters refer to the colour of the fluorescence exhibited by the compunds on this layer chromatograns (TLC) when viewed in ultra violet light (UV), and the suffixes refer to their respective positions on such chromatograms. The term aflatoxin is used to refer to any member of a group of these chemical compounds of related structure. Aflatoxins are extremely poisonous to farm and domestic animals and to human and are known to have strong cancer roducing properties, of these four naturally occuring aflatoxins,aflatoxin B1 is the most potent hepatocarcinoge

The aflatoxin contamination problem in groundnut-control with emphasis on host plant resistance

Invasion of groundnuts by the aflatoxin-producing fungi Aspergillus flavus and Aspergillus parasiticus, and subsequent production of aflatoxins, is a serious problem in most groundnut growing countries..

Research on the Aflatoxin Problem in Groundnut at ICRISAT

Aflatoxin contamination of groundnuts is a serious problem in most groundnut producing countries and as such is given high research priority at ICRISAT. Since 1979, we have concentrated on selecting cultivars resistant to seed invasion and colonization by toxigenic strains of Aspergillus flavus, and/or to aflatoxin production. Resistance to invasion and colonization by A. flavus of rehydrated, mature seed has been found, and confirmed, in some cultivars. Such resistance is of value in the event of the stored groundnuts absorbing sufficient moisture to permit fungal growth. We have also screened cultivars for field resistance to invasion of seeds by A. flavus, both under natural conditions and with inoculum of the fungus added to the soil in the pod zone. Some cultivars with resistance to seed colonization also showed resistance to field invasion by A. flavus. None of the cultivars tested has yet shown complete resistance to aflatoxin production, but significant differences occurred in amounts of aflatoxin produced in seeds inoculated with a toxigenic strain of A. flavus

Screening for Resistance to Aspergillus flavus Invasion and Aflatoxin Production in Groundnuts

Aflatoxlns are highly toxic and carcinogenic substances which are produced by certain strains of fungi of the Aspergillus flavus and Aspergillus parasiticus groups when growing under favourable conditions upon suitable substrates..

Mycotoxin-producing fungi in groundnuts. Potential for mycotoxin contamination.

Research on aflatoxin contamination of groundnuts following invasion by toxigenic strains of Aspergillus flavus has provided guidelines for elimination or reduction of the problem. Unfortunately, groundnut growers in the semi-arid tropics (SAT) have not adopted the recommended practices. The possible use of genetic resistance to seed invasion by A. flavus and to aflatoxin production is considered and some research data presented. Many species of fungi have been found associated with groundnut seeds and several are known to be capable of producing mycotoxins on suitable substrates. Reports of natural occurrence of mycotoxins in groundnuts are reviewed, and the natural occurrence of citrinin and zearalenone reported. Preliminary data on mycotoxin production by fungi isolated from groundnuts are presented

Research on the aflatoxin problem in groundnut at ICRISAT

Aflatoxin contamination of groundnut is a serious problem in most groundnut producing countries and as such is given high research priority by the Groundnut Improvement Program of ICRISAT. Since 1979 we have concentrated on selecting cultivars resistant to seed invasion and colonization by toxigenicAspergillus flavus, and/or to aflatoxin production following invasion by the fungus. Resistance to invasion and colonization byA. flavus of rehydrated, mature seed has been found, and confirmed, in some cultivars. We have also screened several groundnut cultivars for seed resistance in the field, both under natural conditions and with the inoculum of the fungus added to the soil in the pod zone. Some cultivars with resistance to seed colonization also showed resistance to seed invasion byA. flavus. None of the cultivars tested has shown complete resistance to aflatoxin production but significant cultivar differences occurred in the amounts of aflatoxin produced in seeds inoculated with a toxigenic strain ofA. flavu

Aflatoxin Production in Groundnut Cultivars Resistant and Susceptible to Seed Invasion by Aspergillus flavus

The use of groundnut cultivars resistant to seed invasion and colonization by Aspergillus flay us is a possible means nf preventing or reducing aflatoxin contamination. Such resistance wax identified in several cultivars, one of which was the released commercial Indian cultivar J11. No direct relationship wax found between resistance to seed colonizaion by A.flavus and the guar tity of a flatoxins produced h hen seeds were colonized by toxigenic strains of the fungus. So'r of the cultivars with seed resistance to A. flayits colonization have been found resistant to fungal pod rot

Techniques for diagnosis of Pseudomonas solanacearum and for resistance screening against groundnut bacterial wilt: Training Manual-1

Bacterial wilt, caused by Pseudomonas solanacearum, is a widespread and destructive disease of such economically important crops as banana, egg-plant, groundnut, pepper, potato, tobacco, and tomato, in the tropics, sub-tropics, and warm temperateregions. The pathogen has a wide host range and an exceptional ability to survive in th roots of nonhost plants and in the soil. This manual presents techniques for detection, isolation, and identification of all variants of the wilt pathogen. The use of enzyme-linked immunosorbent assay (ELISA) todetect the bacterium in plant tissues, seed, and soil is emphasized. DNA-based diagnostics for P. solanacearum are described, as are an infectivity titration technique to determine the virulence of the wilt pathogen, and several inoculation techniques used in evaluating host-plant resistance togroundnut bacterial wil