Optimal Plot Size is Key to Reducing Variability Associated with Aflatoxin Contamination while Designing Field Screening Experiments

Aflatoxin contamination in peanuts can occur at pre-, post-harvest, and in storage. Breeding for aflatoxin resistance is a priority trait and an important component of integrated aflatoxin management. However, the progress is limited due to sampling and field screening protocols which often don’t produce reproducible results. To identify good resistance sources, a reliable screening protocol and a sampling strategy are critical. In this study, we attempted to determine an optimal plot size to reduce the field variability associated with measuring aflatoxin in peanuts sampled from small field plots. A total of 9 peanut genotypes, including six MAGIC population lines, one released variety, and two standard checks were sown in a field during post-rainy 2023-24. The standard checks consist of a known resistant variety (J11) and a known susceptible variety (JL 24). Each genotype was sown in a single row with a length of 70 m (with 0.5m spacing for every 6m) in a sick field at ICRISAT and each plot is divided into 40 subplots of 1.5 m length. The experiment followed a randomized complete block design (RCBD) with three replications. The plots were inoculated with toxigenic Aspergillus flavus strain three times during the crop growth period starting from 35 days after sowing with a 15-day interval. After harvest, pods from each of 40 subplots were collected separately for aflatoxin quantification through indirect competitive ELISA. Results indicate significant genotype differences (p=0.0001) but no significant difference (p=0.9029) among replications. The ideal plot size for minimizing standard error was 9m. Further experimentation and validation are required to see whether these results are reproducible.