Mycotoxin occurrence andAspergillus flavussoil propagules in a corn and cotton glyphosate-resistant cropping systems

Abstract

The effects of cotton-corn rotation and glyphosate use on levels of soil-borne Aspergillus flavus, aflatoxin and fumonisin contamination in corn and cotton seed were determined during [2002][2003][2004][2005] in Stoneville, Mississippi (USA). There were four rotation systems (continuous cotton, continuous corn, cotton-corn and corn-cotton) for both glyphosate-resistant (GR) and non-GR cultivars-herbicide system arranged in a randomized complete block design with four replications. Aspergillus flavus populations in surface (5-cm depth) soil, sampled before planting (March/April), mid-season (June) and after harvest (September), ranged from 1.47 to 2.99 log (10) cfu g À1 soil in the four rotation systems. Propagules of A. flavus were higher in the continuous corn system compared to the continuous cotton system on three sample dates, and cotton rotated with corn decreased A. flavus propagules in three of nine sample dates. Propagules of A. flavus were significantly greater in plots with GR cultivars compared to non-GR cultivars in three samples. In cotton seed, aflatoxin and fumonisin levels were similar ( 4 mg kg À1 and non-detectable, respectively) regardless of rotation and glyphosate. In corn grain, aflatoxin was above the regulatory level (!20 mg kg À1 ) only in GR cultivar in 2004 and 2005. Fumonisin was higher in non-GR cultivar (4 mg kg À1) regardless of rotation in 2004; however, in 2002, 2003 and 2005, aflatoxin and fumonisin levels were similar regardless of rotation and glyphosate. These results indicate the potential for increased aflatoxin and fumonisin levels (1 of 4 years) in corn; however, climatic conditions encountered during this study did not allow for mycotoxin production. In laboratory incubation studies, fairly high concentrations of glyphosate were required to inhibit A. flavus growth; however no short-term effect of soil treatment with glyphosate on A. flavus populations were observed. These data suggest that altered populations of A. flavus or higher aflatoxin concentrations in corn grain were due to indirect effects of the GR cropping system.

Survey of Aspergillus section Flavi presence in agricultural soils and effect of glyphosate on nontoxigenic A. flavus growth on soil-based medium

“…Other authors, Reddy et al . (), informed different results to those found in the present study when evaluated the glyphosate effect on A. flavus growth on in vitro conditions and showed at 10 mmol l −1 , a partial and temporal inhibition in growth on potato dextrose agar medium. Whereas on water agar medium, this parameter was reduced by 50 and 80% at lower glyphosate concentrations, 5 and 10 mmol l −1 , respectively.…”

“…These results are comparable to those found previously by Barberis et al (2013), who showed in toxigenic A. flavus strains, a significant increase in growth rate from 0Á5 mmol l À1 of glyphosate only at water activity conditions (a W ) of 0Á93 and 0Á95; while at 0Á98 a W , a significant increase in this parameter was also observed at 0Á5, 1Á0 and 1Á5 mmol l À1 depending on the strains evaluated. Other authors, Reddy et al (2007), informed different results to those found in the present study when evaluated the glyphosate effect on A. flavus growth on in vitro conditions and showed at 10 mmol l À1 , a partial and temporal inhibition in growth on potato dextrose agar medium. Whereas on water agar medium, this parameter was reduced by 50 and 80% at lower glyphosate concentrations, 5 and 10 mmol l À1 , respectively.…”

“…In field studies from the USA, A. flavus propagules were greater in continuous corn harvest soil compared with either cotton or wheat harvest (Abbas et al 2004;Reddy et al 2007). Likewise, Griffin et al (1981) observed greater A. flavus propagules associated with continuous corn or peanuts harvest soil.…”

Effect of in vitro glyphosate on Fusarium spp. growth and disease severity in maize

“…Xenobiotic compounds, such as pesticides, also have a considerable effect on fungal development. Previous studies have shown significant changes on both growth rate and mycotoxin production of Aspergillus species caused by GP …”

“…Previous studies have shown significant changes on both growth rate and mycotoxin production of Aspergillus species caused by GP. [10][11][12][13][14][15] Several maize (Zea mays L.) diseases can affect yield, nutritive value, and quality of the grains. Fusarium sp.…”