Breeding Peanut for Resistance to Aflatoxin Contamination at ICRISAT

Abstract

Peanut plays an important role in the livelihoods of poor farmers and in the rural economy of many developing countries. Aflatoxin contamination in peanut seeds, caused by Aspergillus flavus, hampers international trade and adversely affects health of consumers of peanut and its products. It can occur in the field when the crop is growing, during harvesting and curing, and in storage and transportation. Aflatoxin research on peanut at ICRISAT focuses on identification and utilization of genetic resistance to preharvest seed infection and aflatoxin production by A. flavus and pre and post harvest management practices to minimize contamination. Breeding for aflatoxin resistance has been a contentious issue in peanut for nearly four decades since the first report of host resistance to aflatoxin production by A. flavus. Despite global efforts, progress in aflatoxin resistance breeding has been limited due to the low level of resistance to different components of resistance (preharvest seed infection and aflatoxin production, and in vitro seed colonization by A. flavus), their variable performance due to high G 3 E interaction, lack of reliable screening protocols, and limited understanding of genetics of resistance. Efforts to combine the three independently inherited components of resistance did not produce expected results towards improving the host plant resistance to aflatoxin contamination. Although breeding lines have shown better performance for resistance to aflatoxin contamination at ICRISAT, they need wider evaluation under diverse growing conditions. The search for better sources of resistance in the cultivated and wild Arachis germplasm continues, and recent developments in the area of transgenic research through modification of aflatoxin biosynthesis pathway or use of genes with antifungal and anti-aflatoxin properties appear encouraging. Meanwhile, the available improved breeding lines coupled with pre and post harvest aflatoxin management practices can help to significantly reduce aflatoxin contamination in farmers' fields. It is expected that transgenic resistance against fungal infection and aflatoxin production in combination with conventional breeding efforts may lead to the development of agronomically superior peanuts that are free of aflatoxin contamination.

International agricultural research to reduce food risks: case studies on aflatoxins

“…Sources of all the three types of resistance (preharvest seed infection, in vitro seed colonization, and aflatoxin production) have been reported (Nigam et al 2009;Waliyar et al 1994), and in spite of high genotype by environment interaction, a number of germplasms with high levels of resistance across environments have been identified (Nigam et al 2009). More importantly, some of the germplasm lines contained very low aflatoxin (0.4-1.0 ppb) in comparison to high levels (171-305 ppb) in susceptible controls.…”

Study of the genetic diversity of the aflatoxin biosynthesis cluster inAspergillussectionFlaviusing insertion/deletion markers in peanut seeds from Georgia, USA

“…In the United States alone, control of aflatoxins costs the peanut industry between 25 and 58 million dollars annually (Lamb and Sternitzke 2001;Leidner 2012). In addition, worldwide efforts have not yet produced aflatoxin-resistant breeding lines of peanut (Nigam et al 2009). …”

Resistance to pre-harvest aflatoxin contamination in ICRISAT’s groundnut mini core collection

“…Breeding the plant for resistance to seed infection and/or aflatoxin contamination is one of the economically feasible options in managing both pre-and post-harvest aflatoxin contamination in groundnut. Resistance breeding to groundnut aflatoxin contamination can be achieved by imparting resistance to pre-harvest seed infection, in vitro seed colonization (IVSC) by A. flavus and aflatoxin production (Nigam et al 2009). However, independently inherited nature of these three types of resistance coupled with high G x E interaction makes it difficult to improve the host plant resistance in groundnut (Utomo et al 1990;Upadhyaya et al 1997;Nigam et al 2009).…”

“…Resistance breeding to groundnut aflatoxin contamination can be achieved by imparting resistance to pre-harvest seed infection, in vitro seed colonization (IVSC) by A. flavus and aflatoxin production (Nigam et al 2009). However, independently inherited nature of these three types of resistance coupled with high G x E interaction makes it difficult to improve the host plant resistance in groundnut (Utomo et al 1990;Upadhyaya et al 1997;Nigam et al 2009). Despite the constraints, many researchers have focused on the identification of new sources of resistances for all these three types.…”

“…Over the years, around 3000 groundnut germplasm accessions including wild Arachis germplasm accessions were evaluated for resistance to aflatoxin contamination Nigam et al 2009;Holbrook et al 2009). However, considering the number of groundnut germplasm accessions available in gene banks (around 15, 000), many precious germplasm accessions might not get evaluated for this important trait.…”