Peanuts that keep aflatoxin at bay: a threshold that matters

Authors: SHARMA, KIRAN - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India; POTHANA, ARUNIMA - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India; PRASAD, KALYANI - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India; SHAH, DILIP - Danforth Plant Science Center; KAUR, JAGDEEP - Danforth Plant Science Center; Bhatnagar, Deepak; CHEN, ZHI-YUAN - Louisana State University; RARUANG, YENJIT - Louisana State University; Cary, Jeffrey; Rajasekaran, Kanniah - Rajah; SUDINI, HARI KISHAN - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India; BHATNAGAR-MATHUR, POOJA - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2017
Publication Date: 5/15/2018
Citation: Sharma, K.K., Pothana, A., Prasad, K., Shah, D., Kaur, J., Bhatnagar, D., Chen, Z.-Y., Raruang, Y., Cary, J.W., Rajasekaran, K., Sudini, H.K., Bhatnagar-Mathur, P. 2018. Peanuts that keep aflatoxin at bay: a threshold that matters. Plant Biotechnology Journal. 16:1024-1033.

Interpretive Summary: Peanut is a protein-rich food available for a significant percent of the human population. Unfortunately this crop often gets contaminated with a fungal toxin called aflatoxin, which causes liver cancer. The most widely explored strategy for the control of aflatoxin contamination is the development of pre-harvest host plant resistance. This is because A. flavus infects and produces aflatoxins in susceptible peanut crop prior to harvest. In collaboration with scientists at the International Crop Research Institute for Semi-Arid Tropics in India and scientists in the USA, ARS scientists assisted in developing peanut lines resistant to the fungal (Aspergillus) growth and toxin production. Peanut lines were developed using resistant genes from wild alfalfa species (medick or burclover) and also by host plant-induced gene silencing of key fungal genes that govern toxin production. The resulting peanut plants demonstrated a high degree of resistance that yielded a near-immune trait to the fungus and toxin production. The availability of aflatoxin-free peanuts will be extremely important for people in sub-Saharan Africa and South Asia to improve food safety. This research is also useful to other biotechnologists to develop food and feed crops with resistance to Aspergillus and aflatoxin contamination.

Technical Abstract: High levels of aflatoxin in peanuts pose major health hazards for vulnerable populations of Sub-Saharan Africa (SSA) and South Asia. We used two independent approaches to generate peanuts that exhibit strong resistance to both A. flavus seed infection and aflatoxin production. A high level of genetic resistance was achieved in several peanut lines by expressing antifungal plant defensins MsDef1 and MtDef4.2, and through host-induced gene silencing (HIGS) of aflM and aflP aflatoxin biosynthetic pathway genes. These approaches provided a dual shield against three different A. flavus morphotypes and resulted in significant decreases in aflatoxin contamination. Transcriptomic signatures revealed key mechanisms of host-pathogen interactions in the resistant genotypes, and provided clues about regulation of aflatoxin synthesis, packaging, export control and the role of reactive oxygen species-scavenging enzymes that render better protection against infection by A. flavus and aflatoxin accumulation. We demonstrate that near-immune peanut lines with very low aflatoxin levels can be achieved, offering a panacea for serious health, food safety and trade issues in the semi-arid regions of SSA and South Asia.