Genetic and Seed Treatment Effects in Organic Peanut

Abstract

Stand establishment has been a challenge for organic peanut production in the Southeastern United States. Field experiments were conducted in 2007 and 2009 in research plots certified for organic production to evaluate the potential of genotype selection, shelling procedure, and seed treatment with Bacillus subtilis to improve stand establishment and seedling emergence rates, reduce incidence of Aspergillus crown rot, and increase seedling biomass. Seed of 15 peanut genotypes were mechanically shelled or hand-shelled, and treated with B. subtilis or untreated prior to planting in early June. Percent stand was estimated for each plot 17–21 days after planting (DAP), and percent seedlings affected by Aspergillus crown rot and plant biomass were estimated 21–24 DAP. Seed treatment significantly affected stand establishment for three genotypes each year, Georgia-01R both years, C-99R and Tifguard in 2007, and C34-24-69 and C724-19-25 in 2009. In all of these cases, the hand-shelled plots had significantly greater stands than the mechanically shelled plots for untreated and/or B. subtilis treated seed. B. subtilis treatment improved stands for two of the mechanically shelled treatments that significantly responded to hand shelling. Despite low incidence, there was a significant reduction of crown rot in the hand-shelled plots compared to the mechanically shelled plots across years and genotypes. The cultivar Georganic, which has been planted to organic peanut systems in Georgia in recent years, was among the genotypes with the lowest seedling establishment rates and biomass. Based on these results, it is recommended that sorting thresholds for damaged seed be higher for seed destined for organic production, and that breeding efforts that include assessments of factors involved in seedling establishment and growth be prioritized.

Efficacy of Peanut Seed Treatments for Organic Management in Georgia

“…4 and 5), although final totals of both stand counts and dead plants were equal to the untreated in all three field experiments (including the Blackshank location in 2010 -data not shown). Other studies have suggested that B. subtilis has the potential to aid in germination and emergence for improved stand establishment (Cantonwine et al, 2011;Ruark and Shew, 2010;Turner and Backman, 1991). The most favorable responses to B. subtilis have been under stressed conditions, such as seed that were mechanically shelled (Cantonwine et al, 2011), or unfavorable planting conditions from limited water, poor rotation, or cool soils (Turner and Backman, 1991).…”

“…Other studies have suggested that B. subtilis has the potential to aid in germination and emergence for improved stand establishment (Cantonwine et al, 2011;Ruark and Shew, 2010;Turner and Backman, 1991). The most favorable responses to B. subtilis have been under stressed conditions, such as seed that were mechanically shelled (Cantonwine et al, 2011), or unfavorable planting conditions from limited water, poor rotation, or cool soils (Turner and Backman, 1991). Yet, in the previous research from South Georgia, only one out of 15 genotypes in each year of the trial had a positive plant stand response that was solely related to B. subtilis seed treatment (Cantonwine et al, 2011).…”

“…The most favorable responses to B. subtilis have been under stressed conditions, such as seed that were mechanically shelled (Cantonwine et al, 2011), or unfavorable planting conditions from limited water, poor rotation, or cool soils (Turner and Backman, 1991). Yet, in the previous research from South Georgia, only one out of 15 genotypes in each year of the trial had a positive plant stand response that was solely related to B. subtilis seed treatment (Cantonwine et al, 2011). Warm soil temperatures at the 10 cm depth in the Lang-Rigdon-2010 experiment (25 C) and very hot and dry conditions at the Ponder-2011 experiment (36 C) may have caused greater pressure from A. niger to overburden the B. subtilis treatment, or poor establishment conditions for B. subtilis where it could not suppress the pathogen.…”

“…A study conducted in North Carolina evaluating the efficacy of peanut seed or soil treated with organically acceptable seedling disease treatments, such as biocontrol organisms, activated charcoal, copper hydroxide, or hot water showed that seed treated with the biocontrol agent Bacillus subtilis showed the most promise among the other treatments tested (Ruark and Shew, 2010). Cantonwine et al (2011) found that genotype and seed integrity were more important factors than B. subtilis seed treatment to improve plant stand and reduce Aspergillus crown rot, but the rate of the B. subltilis seed treatment used in the experiment was lower than that used by Ruark and Shew (2010).…”

Identifying interest, risks, and impressions of organic peanut production: A survey of conventional farmers in the Virginia–Carolina region

“…Currently, certified organic peanut production is limited to the southwestern region of the United States (Guerena & Adam, 2008); however, research continues to be conducted to facilitate the successful production of organic peanut in the southeastern region of the United States. Alternative products and methods for seed treatment and weed control have been the main focus of this effort (Cantonwine, Holbrook, Culbreath, Tubbs, & Boudreau, 2011; Johnson, 2019). Lack of postharvest infrastructure is also a challenge for farmers in the southeastern region of the United States.…”