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Aflatoxin contamination in groundnut (Aspergillus flavus) Photo: arian.suresh from Chennai, India · CC BY 2.0 · source ↗

Aflatoxin contamination in groundnut (Aspergillus flavus)

Aflatoxins are a group of highly toxic and carcinogenic secondary metabolites produced by Aspergillus flavus and A. parasiticus growing on groundnut pods and kernels. Aflatoxin B1 is classified as a Group 1 human carcinogen by IARC. For Indian groundnut farmers, especially in Rayalaseema, aflatoxin is the single biggest food-safety and export-rejection risk: FSSAI permits a maximum of 15 ug/kg total aflatoxins in groundnut for human consumption, while EU and Japanese buyers enforce stricter limits (4-10 ug/kg).

Identification

Aflatoxin contamination is invisible to the eye in many cases. Heavy Aspergillus infection shows as olive-green to yellow-green powdery mould on kernels, especially under the seed coat or in damaged areas. Wrinkled, shrivelled, discoloured or rancid-smelling kernels are higher-risk and should be discarded. Quantitative detection requires lab tests (ELISA, HPLC, immunochromatographic strips); colour and smell alone are not reliable indicators.

Hosts and lifecycle

A. flavus is a saprophyte and opportunistic plant pathogen ubiquitous in tropical soils. It infects groundnut at three stages: (1) pre-harvest in the field, especially under end-of-season drought stress when pod surfaces crack; (2) at harvest if pods sit in the field through rain; (3) post-harvest during storage when seed moisture exceeds 8-9 percent. Optimum conditions are 28-32 deg C with high humidity and damaged or stressed pods. Once colonised, the fungus produces aflatoxins B1, B2, G1, G2 depending on the strain.

Damage and economic impact

Contaminated groundnut is rejected outright by export markets and oil processors. For the farmer, contamination shows up as lower-grade pricing at the mandi or rejection at FCI procurement. Health impact is severe: chronic exposure causes liver cancer, immune suppression and stunting in children. ICRISAT, ICAR-DGR and ANGRAU monitoring in Anantapur has found that 30-60 percent of farm-stored samples exceed FSSAI limits in drought years.

Management

  • Pre-harvest: avoid end-of-season drought stress; irrigate critical pegging-to-podding stage where possible; use resistant varieties (ICGV 91278, ICGV 91283, ICGV 88145, J 11 carry partial pre-harvest resistance per ICRISAT); manage termites and other pod-damaging pests to reduce entry wounds.
  • Harvest: harvest at physiological maturity (75-85 percent mature pods); do not let dug plants lie in heaps; never leave pods in the field through unseasonal rain.
  • Drying: dry pods to less than 9 percent moisture (kernels less than 7 percent) within 3-5 days of harvest. Use raised drying yards or tarpaulin; avoid direct ground contact.
  • Storage: store in clean, ventilated structures; use moisture-proof bags (PICS, Super Grain Bags) where available; keep storage moisture below 65 percent RH; protect from rats and insects.
  • Bio-control: ICRISAT-developed AflasafeIN02 (atoxigenic A. flavus strains) sprayed in the field 2-3 weeks before flowering reduces aflatoxin by 80-90 percent in groundnut and maize; commercial availability in India is limited.
  • Testing: aflatoxin strip tests at mandi level are increasingly available; farmers in export-linked value chains (Pondicherry, Andhra HPS) test routinely.

See also: Stem rot of groundnut, Root-knot nematode in groundnut, Groundnut crop, Kadiri 6 groundnut.

Sources

  1. Aflatoxin management in groundnut. ICAR-Directorate of Groundnut Research, Junagadh.
  2. Aspergillus flavus and aflatoxin in groundnut. ICRISAT, Patancheru.
  3. Aspergillus flavus factsheet. CABI Plantwise.