Location: National Peanut Research Laboratory
2022 Annual Report
Objectives
Objective 1
Identify and integrate beneficial genes from disease-resistant peanut and wild peanut sources into genetically stable peanut germplasm.
Sub-objective 1A.
Screening for aflatoxin accumulation under laboratory conditions.
Sub-objective 1B.
Identification of disease resistance-associated genes and plant defense mechanisms.
Sub-objective 1C.
Integration of beneficial alleles from wild diploid Arachis species into genetically stable peanut germplasm.
Objective 2
Define specific defensive roles of peanut phytoalexins against Aspergillus spp. and other fungal pathogens and identify their genetic sources as potential resistance to fungal diseases and aflatoxin contamination.
Sub-objective 2A.
Determination of phytoalexin profiles in experimental and field seeds and search for new phytoalexins.
Sub-objective 2B.
Study of potential involvement of pegs in contamination of peanut seeds with aflatoxins.
Approach
Peanut (Arachis hypogaea) is one of the major food crops in the world. Most of the pathogens that attack peanuts are of fungal origin and are evident etiological factors of over 40 economically important peanut diseases. Aspergillus flavus and A. parasiticus are opportunistic fungal parasites that often invade peanut seeds and produce carcinogenic aflatoxins. Contamination of peanuts with aflatoxins is an important food safety issue and threatens the competitiveness of the United States agriculture in the world market. Aflatoxin monitoring and reprocessing of contaminated peanuts is a passive and costly practice to prevent aflatoxins from entering the food chain. Current peanut cultivars often demonstrate limited resistance to fungal pathogens. Therefore, wild peanut species have received substantial consideration as sources of disease resistance because the narrow genetic base of cultivated peanuts cannot provide the necessary levels of resistance to defend the peanut plant. A prospective approach to reduce disease pressure and aflatoxin contamination is to develop resistant peanut cultivars through introgression of beneficial genes and alleles from wild peanut species into elite cultivars. To achieve this goal, the first objective to identify and integrate beneficial genes from disease-resistant peanut and wild peanut sources into genetically stable peanut germplasm will use this approach. In conjunction with this objective, another promising strategy/second objective is to define specific defensive roles of peanut phytoalexins against Aspergillus spp. and other fungal pathogens and identify their genetic sources as potential resistance to fungal diseases and aflatoxin contamination. Both approaches will generate new knowledge on the mechanisms of peanut resistance to fungal invasion and a faster release of enhanced germplasm and cultivars. The ultimate goal of this project is to reduce peanut disease load and to develop improved germplasm. The beneficiaries of the successful accomplishment of the project goal are breeders and all segments of the peanut industry.
Progress Report
Significant progress has been made toward Objective 1. A total of 120 plants from 12 accession of six wild diploid Arachis species, and 200 individual plants from a segregating mapping population were planted in screenhouses at the ARS location in Dawson, Georgia, for seed increase. Seeds from the wild peanut species will be used for evaluation of resistance to aflatoxin accumulation, while seeds from the mapping population will used for generation advancement. Novel interspecific hybrids involving two A-genome and two non-A genome species have been initiated. The F1 hybrids generated from these crosses will be followed by whole genome duplication. The evaluation of wild species resistance to aflatoxin accumulation will be accompanied by the quantitative instrumental analyses of all known peanut phytoalexins. The experimental setup for the planned research is in active preparation.
In terms of practical application, substantial progress has been made toward Objective 2A. In the course of the present project, the research team obtained valuable data on the formation and accumulation of polyphenols in peanut seeds. These data led to the development of a new technology on the enhancement of peanut seed health benefits by boosting the polyphenol content. This technology is patentable since it is simple and inexpensive, and the final product can be considered a functional food that may have a positive effect on health beyond basic nutrition. The procedure involves treatment of whole commercial seeds with a food-grade chemical followed by roasting. This project is close to completion. The stakeholders are expected to adopt this novel approach.
Accomplishments
