Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

Aspergillus flavus is the major producer of carcinogenic aflatoxins worldwide in crops. Populations of A. flavus are characterized by high genetic variation and the source of this variation is likely sexual reproduction. The fungus is heterothallic and laboratory crosses produce ascospore-bearing ascocarps embedded within sclerotia. However, the capacity for sexual reproduction in sclerotia naturally formed in crops has not been examined. Corn was grown for 3 years under different levels of drought stress at Shellman, GA, and sclerotia were recovered from 146 ears (0.6% of ears). Sclerotia of A. flavus L strain were dominant in 2010 and 2011 and sclerotia of A. flavus S strain were dominant in 2012. The incidence of S strain sclerotia in corn ears increased with decreasing water availability. Ascocarps were not detected in sclerotia at harvest but incubation of sclerotia on the surface of nonsterile soil in the laboratory resulted in the formation of viable ascospores in A. flavus L and S strains and in homothallic A. alliaceus. Ascospores were produced by section Flavi species in 6.1% of the 6,022 sclerotia (18 of 84 ears) in 2010, 0.1% of the 2,846 sclerotia (3 of 36 ears) in 2011, and 0.5% of the 3,106 sclerotia (5 of 26 ears) in 2012. For sexual reproduction to occur under field conditions, sclerotia may require an additional incubation period on soil following dispersal at crop harvest.

A biopesticide, afla-guard(®), has been developed for controlling aflatoxin contamination in peanuts. This product provides the means of introducing a competitive, non-aflatoxigenic strain ofAspergillus flavus into soils where peanuts are being grown. The introduced strain competitively excludes toxigenic strains naturally present from invading developing peanuts. The biocontrol technology was made commercially available in 2004 by Circle One Global, Inc., upon receiving U.S. Environmental Protection Agency section 3 registration of afla-guard(®) as a biopesticide. The product was applied to approximately 2000 ha of peanuts in Georgia and Alabama during the 2004 crop year. Application of afla-guard(®) changed the composition ofA. flavus soil populations from an average 71.1% toxigenic strains in untreated fields to only 4.0% in treated soils. Analyses of farmer's stock peanuts being delivered at seven different locations showed a consistent reduction in aflatoxin contamination in peanuts from fields treated with afla-guard(®). Over all locations, aflatoxin averaged 78.9 ng/g in untreated peanuts compared with 11.7 ng/g in treated peanuts, an 85.2% reduction. Peanuts from treated and untreated fields were stored together in separate warehouse bins at two different locations. Aflatoxin analyses at the Unadilla, GA location showed that 48.4% of shelled edible lots from untreated fields contained unacceptable levels of aflatoxin (>15 ng/g). At the Dawson, GA location, 15.8% of shelled lots from untreated fields contained >15 ng/g. At both locations, no shelled edible lots from treated fields contained >15 ng/g. Mean aflatoxin concentrations in edible peanuts from untreated and treated fields at Unadilla were 36.2 and 0.9 ng/g, respectively. At Dawson the respective means were 7.2 and 2.2 ng/g.

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Smut disease caused by the fungal pathogen Thecaphora frezii Carranza & Lindquist is threatening the peanut production in Argentina. Fungicides commonly used in the peanut crop have shown little or no effect controlling the disease, making it a priority to obtain peanut varieties resistant to smut. In this study, recombinant inbred lines (RILs) were developed from three crosses between three susceptible peanut elite cultivars (Arachis hypogaea L. subsp. hypogaea) and two resistant landraces (Arachis hypogaea L. subsp. fastigiata Waldron). Parents and RILs were evaluated under high inoculum pressure (12000 teliospores g-1 of soil) over three years. Disease resistance parameters showed a broad range of variation with incidence mean values ranging from 1.0 to 35.0% and disease severity index ranging from 0.01 to 0.30. Average heritability (h2) estimates of 0.61 to 0.73 indicated that resistance in the RILs was heritable, with several lines (4 to 7 from each cross) showing a high degree of resistance and stability over three years. Evidence of genetic transfer between genetically distinguishable germplasm (introgression in a broad sense) was further supported by simple-sequence repeats (SSRs) and Insertion/Deletion (InDel) marker genotyping. This is the first report of smut genetic resistance identified in peanut landraces and its introgression into elite peanut cultivars.