Search

Row crops normally grown in Southeast USA are cotton (Gossypium hirsutum L.), corn (Zea mays L.), and peanut (Arachis hypogea L.) with a focus on the higher economic value for peanut. Peanut is typ...

Wild diploid Arachis species are potential sources of resistance to early (ELS) and late (LLS) leaf spot diseases caused by Passalora arachidicola (syn. Cercospora arachidicola Hori), and Nothopassalora personata (syn. Cercosporidium personatum (Berk. & Curt.) Deighton), respectively. Within section Arachis, limited information is available on the extent of genetic variation for resistance to these fungal pathogens. A collection of 78 accessions representing 15 wild species of Arachis section Arachis from the U.S peanut germplasm collection was evaluated for resistance to leaf spots. Screening was conducted under field (natural inoculum) conditions in Dawson, Georgia, during 2017 and 2018. Accessions differed significantly (P < 0.01) for all three disease variables evaluated, which included final defoliation rating, ELS lesion counts, and LLS lesion counts. Relatively high levels of resistance were identified for both diseases, with LLS being the predominant pathogen during the two years of evaluation. This research documents new sources of resistance to leaf spot diseases selected from an environment with high inoculum pressure. The presence of ELS and LLS enabled the selection of resistant germplasm for further introgression and pre-breeding.

Currently, there are 13.9 million hectares of loblolly pine (Pinus taeda L.) in the Southern United States. Reforested hectares could be used for intercropping oilseed crops such as carinata (Brassica carinata) and white lupin (Lupinus albus L.). The oil obtained from these crops could be used for bio-jet fuel production to reduce the carbon footprint of the aviation sector. This study determines the profitability for three scenarios: loblolly pine with no intercropping (baseline), loblolly pine with carinata (once every three years), and loblolly pine with carinata and white lupin rotated annually. We ascertained the land expectation value (LEV) for three site indices of 15.3 m, 18.3 m, and 21.3 m. Carinata and white lupin were planted during the initial eight, seven, and six years for site indices 15.3 m, 18.3 m, and 21.3 m, respectively. Sensitivity and risk analyses were undertaken for determining the influence of input variables on LEVs and the probability of loss for intercropping production systems relative to a baseline production system, respectively. For site index 21.3 m, the LEV of loblolly pine with no intercropping was $2816/ha at a 21-years rotation period. Intercropping with carinata only and both carinata and white lupin yielded LEVs of $3346/ha and $3607/ha at a 21-years rotation period, respectively. The LEVs of production systems were sensitive to interest rate, price, and yield of carinata seeds. The intercropping approach had > 50% probability of being less profitable than loblolly pine alone in over half of the scenarios considered. Future research should focus on the impacts of intercropping on loblolly pine yield and adoption behavior of forest landowners.

Early leaf spot (ELS) and late leaf spot (LLS) are major fungal diseases of peanut that can severely reduce yield and quality. Development of acceptable genetic resistance has been difficult due to a strong environmental component and many major and minor QTLs. Resistance genes (R-genes) are an important component of plant immune system and have been identified in peanut. Association of specific R-genes to leaf spot resistance will provide molecular targets for marker-assisted breeding strategies. In this study, advanced breeding lines from different pedigrees were evaluated for leaf spot resistance and 76 candidate R-genes expression study was applied to susceptible and resistant lines. Thirty-six R-genes were differentially expressed and significantly correlated with resistant lines, of which a majority are receptor like kinases (RLKs) and receptor like proteins (RLPs) that sense the presence of pathogen at the cell surface and initiate protection response. The largest group was receptor-like cytoplasmic kinases (RLCKs) VII that are involved in pattern-triggered kinase signaling resulting in the production reactive oxygen species (ROS). Four R-genes were homologous to TMV resistant protein N which has shown to confer resistance against tobacco mosaic virus (TMV). When mapped to peanut genomes, 36 R-genes were represented in most chromosomes except for A09 and B09. Low levels of gene-expression in resistant lines suggest expression is tightly controlled to balance the cost of R-gene expression to plant productively. Identification and association of R-genes involved in leaf spot resistance will facilitate genetic selection of leaf spot resistant lines with good agronomic traits.

Napier grass (Pennisetum purpureum (L) Schum) is being developed as a bioenergy crop for production in the southeastern United States. Important criteria for selecting a feedstock are cost, consist...

Peanut smut caused by Thecaphora frezii is a severe fungal disease currently endemic to Argentina and Brazil. The identification of smut resistant germplasm is crucial in view of the potential risk of a global spread. In a recent study, we reported new sources of smut resistance and demonstrated its introgression into elite peanut cultivars. Here, we revisited one of these sources (line I0322) to verify its presence in the U.S. peanut germplasm collection and to identify single nucleotide polymorphisms (SNPs) potentially associated with resistance. Five accessions of Arachis hypogaea subsp. fastigiata from the U.S. peanut collection, along with the resistant source and derived inbred lines were genotyped with a 48K SNP peanut array. A recently developed SNP genotyping platform called RNase H2 enzyme-based amplification (rhAmp) was further applied to validate selected SNPs in a larger number of individuals per accession. More than 14,000 SNPs and nine rhAmp assays confirmed the presence of a germplasm in the U.S. peanut collection that is 98.6% identical (P < 0.01, bootstrap t-test) to the resistant line I0322. We report this germplasm with accompanying genetic information, genotyping data, and diagnostic SNP markers. Fil: Massa, Alicia N.. National Peanut Research Laboratory; Estados Unidos Fil: Bressano, Marina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentina Fil: Soave, Juan H.. Criadero El Carmen; Argentina Fil: Buteler, Mario I.. Criadero El Carmen; Argentina Fil: Seijo, José Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina Fil: Sobolev, Victor S.. National Peanut Research Laboratory; Estados Unidos Fil: Orner, Valerie A.. National Peanut Research Laboratory; Estados Unidos Fil: Oddino, Claudio Marcelo. Criadero El Carmen; Argentina Fil: Soave, Sara J.. Criadero El Carmen; Argentina Fil: Faustinelli, Paola Carmen. National Peanut Research Laboratory; Estados Unidos Fil: de Blas, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Lamb, Marshall C.. National Peanut Research Laboratory; Estados Unidos Fil: Arias, Renee S.. National Peanut Research Laboratory; Estados Unidos

Draft genomes of 16 isolates of Aspergillus flavus Link and Aspergillus parasiticus Speare, identified as the predominant genotypes colonizing peanuts in four farming regions in Ethiopia, are reported. These data will allow mining for sequences that could be targeted by RNA interference to prevent aflatoxin accumulation in peanut seeds.

Peanut (Arachis hypogaea L.) is an important food and oilseed crop worldwide. Yield and quality can be significantly reduced by foliar fungal diseases, such as early and late leaf spot diseases. Acceptable levels of leaf spot resistance in cultivated peanut have been elusive due to environmental interactions and the proper combination of QTLs in any particular peanut genotype. Resistance gene analogs, as potential resistance (R)-genes, have unique roles in the recognition and activation of disease resistance responses. Novel R-genes can be identified by searches for conserved domains such as nucleotide binding site, leucine rich repeat, receptor like kinase, and receptor like protein from expressed genes or through genomic sequences. Expressed R-genes represent necessary plant signals in a disease response. The goals of this research are to identify expressed R-genes from cultivated peanuts that are naturally infected by early and late spot pathogens, compare these to the closest diploid progenitors, and evaluate specific gene expression in cultivated peanuts. Putative peanut R-genes (381) were available from a public database (NCBI). Primers were designed and PCR products were sequenced. A total of 214 sequences were produced which matched to proteins with the corresponding R-gene motifs. These R-genes were mapped to the genome sequences of Arachis duranensis and Arachis ipaensis, which are the closest diploid progenitors for tetraploid cultivated peanut, A. hypogaea. Identification and association of specific gene-expression will elucidate potential disease resistance mechanism in peanut and may facilitate the selection of breeding lines with high levels of leaf spot resistance.

Interest and focus on development of renewable biofuels has been increasing over the past decade leading to the introduction of a wide cadre of renewable feedstocks. As a result, numerous perennial warm-season grasses have been introduced and management practices evaluated to determine their suitability as biofuel feedstocks. “Merkeron” napier grass (Pennisetum purpureum) plots were established in 2010 and harvested during crop years 2011 through 2015 adjacent to an on-going peanut (Arachis hypogaea L.), corn (Zea mays L.), and cotton (Gossypium hirsutum L.) cropping systems study conducted at the USDA/ARS Multi-crop Irrigation Research Farm in Shellman, GA (84 36 W, 30 44 N) on a Greenville fine sandy loam (fine, kaolinitic, thermic Rhodic Kandiudults). Napier grass was produced in both non-irrigated and two irrigated levels with different levels of nitrogen and potassium fertilizers. Peanut, corn, and cotton were produced in non-irrigated and full irrigation regimes. Breakeven prices for napier grass ranged from $65 to $84 Mg−1 at variable and total costs. The breakeven napier grass price was estimated such that the net returns were equal between napier grass and peanut, cotton, corn cropping systems. At variable production cost, comparative breakeven napier grass prices for non-irrigated, 50% irrigated, and full irrigated regimes were $77, $117, and $112 Mg−1, respectively. Napier grass did not compete economically against traditional irrigated cropping systems. Depending on traditional crop prices and bioenergy feed stock prices, napier grass could offer economic opportunities in non-irrigated production environments, riparian buffer zone edges, or non-cropped marginal production areas.

Aflatoxin contamination is a major constraint in food production worldwide. In peanut (Arachis hypogaea L.), these toxic and carcinogenic aflatoxins are mainly produced by Aspergillus flavus Link and A. parasiticus Speare. The use of RNA interference (RNAi) is a promising method to reduce or prevent the accumulation of aflatoxin in peanut seed. In this study, we performed high-throughput sequencing of small RNA populations in a control line and in two transformed peanut lines that expressed an inverted repeat targeting five genes involved in the aflatoxin-biosynthesis pathway and that showed up to 100% less aflatoxin B1 than the controls. The objective was to determine the putative involvement of the small RNA populations in aflatoxin reduction. In total, 41 known microRNA (miRNA) families and many novel miRNAs were identified. Among those, 89 known and 10 novel miRNAs were differentially expressed in the transformed lines. We furthermore found two small interfering RNAs derived from the inverted repeat, and 39 sRNAs that mapped without mismatches to the genome of A. flavus and were present only in the transformed lines. This information will increase our understanding of the effectiveness of RNAi and enable the possible improvement of the RNAi technology for the control of aflatoxins.

Common soil fungi, Aspergillus flavus and Aspergillus parasiticus, are opportunistic pathogens that invade preharvest peanut seeds. These fungi often produce carcinogenic aflatoxins that pose a threat to human and animal health through food chains and cause significant economic losses worldwide. Detection of aflatoxins and further processing of crops are mandated to ensure that contaminated agricultural products do not enter food channels. Under favorable conditions, the fungus-challenged peanut seeds produce phytoalexins, structurally related stilbenoids, capable of retarding fungal development. The purpose of the present study was to evaluate the potential influence of peanut phytoalexins on fungal development and aflatoxin formation in the course of peanut-fungus interaction. The present research revealed that during such interaction, aflatoxin formation was completely suppressed in A. flavus and A. parasiticus strains tested, when low concentrations of spores were introduced to wounded preincubated peanuts. In most of the experiments, when fungal spore concentrations were 2 orders of magnitude higher, the spores germinated and produced aflatoxins. Of all experimental seeds that showed fungal growth, 57.7% were aflatoxin-free after 72 h of incubation. The research provided new knowledge on the aflatoxin/phytoalexin formation in the course of peanut-fungus interaction.

With global increases in the production of cellulosic biomass for fuel, or “biofuel,” concerns over potential negative effects of using land for biofuel production have promoted attention to concepts of agricultural landscape design that sustainably balance tradeoffs between food, fuel, fiber, and conservation. The Energy Independence Security Act (EISA) of 2007 mandates an increase in advanced biofuels to 21 billion gallons in 2022. The southeastern region of the USA has been identified as a contributor to meeting half of this goal. We used a GIS-based approach to estimate the production and N-removal potential of three perennial biofeedstocks planted as conservation buffers (field borders associated with riparian buffers, and grassed waterways) on the Coastal Plain of Georgia, USA. Land cover, hydrology, elevation, and soils data were used to identify locations within agricultural landscapes that are most susceptible to runoff, erosion, and nutrient loss. We estimated potential annual biomass production from these areas to be: 2.5–3.5 Tg for giant miscanthus (Miscanthus × giganteus), 2–8.6 Tg for “Merkeron” napier grass (Pennisetum purpureum), and 1.9–7.5 Tg for “Alamo” switchgrass (Panicum virgatum). When production strategies were taken into consideration, we estimated total biomass yield of perennial grasses for the Georgia Coastal Plain at 2.2–9.4 Tg year−1. Using published rates of N removal and ethanol conversion, we calculated the amount of potential N removal by these systems as 8100–51,000 Mg year−1 and ethanol fuel production as 778–3296 Ml year−1 (206 to 871 million gal. US).

Aflatoxins are among the most powerful carcinogens in nature. The major aflatoxin-producing fungi are Aspergillus flavus and A. parasiticus. Numerous crops, including peanut, are susceptible to aflatoxin contamination by these fungi. There has been an increased use of RNA interference (RNAi) technology to control phytopathogenic fungi in recent years. In order to develop molecular tools targeting specific genes of these fungi for the control of aflatoxins, it is necessary to obtain their genome sequences. Although high-throughput sequencing is readily available, it is still impractical to sequence the genome of every isolate. Thus, in this work, the authors proposed a workflow that allowed prescreening of 238 Aspergillus section Flavi isolates from peanut seeds from Georgia, USA. The aflatoxin biosynthesis cluster (ABC) of the isolates was fingerprinted at 25 InDel (insertion/deletion) loci using capillary electrophoresis. All isolates were tested for aflatoxins using ultra-high-performance liquid chromatography. The neighbor-joining, three-dimension (3D) principal coordinate, and Structure analyses revealed that the Aspergillus isolates sampled consisted of three main groups determined by their capability to produce aflatoxins. Group I comprised 10 non-aflatoxigenic A. flavus; Group II included A. parasiticus; and Group III included mostly aflatoxigenic A. flavus and the three non-aflatoxigenic A. caelatus. Whole genomes of 10 representative isolates from different groups were sequenced. Although InDels in Aspergillus have been used by other research groups, this is the first time that the cluster analysis resulting from fingerprinting was followed by whole-genome sequencing of representative isolates. In our study, cluster analysis of ABC sequences validated the results obtained with fingerprinting. This shows that InDels used here can predict similarities at the genome level. Our results also revealed a relationship between groups and their capability to produce aflatoxins. The database generated of Aspergillus spp. can be used to select target genes and assess the effectiveness of RNAi technology to reduce aflatoxin contamination in peanut.

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 (h 2 ) 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. This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Fil: Bressano, Marina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentina. Universidad Nacional de Córdoba; Argentina Fil: Massarini, Alicia. Usda Ars National Peanut Research Laboratory; Estados Unidos. Universidad de Buenos Aires. Facultad de Ingeniería. Postgrado-Maestría en Política y Gestión de la Ciencia y Tecnología; Argentina Fil: Arias, Renee S.. Usda Ars National Peanut Research Laboratory; Estados Unidos Fil: de Blas, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Oddino, Claudio Marcelo. Criadero El Carmen; Argentina Fil: Faustinelli, Paola Carmen. Usda Ars National Peanut Research Laboratory; Estados Unidos Fil: Soave, Sara Josefina. Criadero El Carmen; Argentina Fil: Soave, Juan H.. Criadero El Carmen; Argentina Fil: Pérez, Maria A.. Universidad Católica de Córdoba. Facultad de Ciencias Agropecuarias; Argentina Fil: Sobolev, Victor S.. Usda Ars National Peanut Research Laboratory; Estados Unidos Fil: Lamb, Marshall C.. Usda Ars National Peanut Research Laboratory; Estados Unidos Fil: Balzarini, Monica Graciela. Universidad Nacional de Córdoba; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatologia y Modelizacion Agricola. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Unidad de Fitopatologia y Modelizacion Agricola.; Argentina Fil: Buteler, Mario I.. Criadero El Carmen; Argentina Fil: Seijo, José Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina

Aspergillus flavus accumulates carcinogenic aflatoxins in peanuts, mainly in immature kernels during drought. Aspergillus flavus invasion induces accumulation of phytoalexins, mostly stilbenoids in peanut, as a plant defence mechanism. Because fungal laccases are often related to pathogenicity and can degrade stilbenoids, this study reports for the first time the expression of A. flavus laccases in the presence of kernels, hulls and low water potential in relation to the accumulation of phytoalexins in peanut kernels. Packed-cell volume (PCV) of A. flavus biomass was significantly higher (P ≤ 0·01) in the presence of mature kernels, dead kernels, and mature and immature peanut hulls than the control. The presence of kernels and hulls lowered the level of expression of three A. flavus laccases by 4–6-fold (P < 0·01), whereas 3% sucrose up-regulated them by 35–304-fold, and low water potential (−1·1 MPa) up-regulated them by 85–248-fold (P < 0·01). Phytoalexins that accumulated in peanut kernels in the presence of A. flavus and were quantified by HPLC-DAD-MS were primarily the stilbenoids: 3′-isopentadienyl-3,5,4′-trihydroxystilbene (IPD), chiricanine-A, arachidin-2, arachidin-3 and arahypin-1. Apparent degradation of phytoalexins was observed when using a priori induction of phytoalexins in seeds in combination with a priori induction of laccases in A. flavus. The up-regulation of laccase expression observed at −1·1 MPa and at high sucrose concentration could be contributing to peanut invasion in immature kernels under drought conditions.

This research was conducted in experimental plots in Georgia from 2004 through 2006 and assessed the prospects for transitioning to a totally organic management system for cotton. The seasonal abundance of insect pests and their natural enemies over the 3-yr transitional period are reported herein. The heliothines, Heliothis virescens (F.) and Helicoverpa zea (Boddie), and stink bugs, mainly Nezara viridula (L.), Euschistus servus (Say), and Euschistus quadrator (Rolston), were the 2 groups of insect pests found on cotton. Heliothine larvae were observed each year of the study but, in general, infestations of heliothines were higher in 2004 than in the other 2 yrs. Stink bugs were observed in relatively high numbers, and the percent of cotton bolls damaged by these pests was high only during year 2 of the study. Over the 3-yr period, the red imported fire ant, Solenopsis invicta Buren, various spiders, including Oxyopes scalaris Hentz and Peucetia viridans (Hentz), the big-eyed bug, Geocoris punctipes (Say), and the pirate bug, Orius insidiosus (Say), were the most abundant predators of the heliothines and stink bugs. The endoparasitoid Toxoneuron nigriceps Viereck and an ascovirus also contributed to larval mortality of H. virescens. The endoparasitoid Trichopoda pennipes (F.) parasitized adults of N. viridula.

Peanut (Arachis hypogea L.) is typically sown in single or twin rows centered on 91-cm beds. A planter capable of sowing 8 peanut rows on a 182-cm bed was developed by USDA-ARS. This planting pattern optimizes plant spacing and may contribute to crop advantages. Management of soil borne diseases in peanut may be affected by planting patterns. Replicated field experiments were conducted in 2002, 2003, and 2004 at two locations each year near Dawson, Georgia to compare interactions of planting patterns and disease management programs. Three fungicide application regimes were factored over single row, twin row, and diamond planting patterns, for a total of 9 treatments. A block calendar schedule with 14-d intervals was compared with two weather advisory programs, including AU-Pnuts and an experimental version of AU-Pnuts using minimum daily soil temperature (MDST) as a guide for fungicide selection. The seeding rate of each planting pattern was 22 seed/m2. There were no planting pattern by fungicide program interactions. Twin row and diamond planting patterns were often superior in yield than single rows; however, diamond patterns did not yield better than twin rows. Incidence of peg, pod, and limb rot caused by Rhizoctonia solani and stem rot caused by Sclerotium rolfsii was not severe in any trial and was not affected by planting pattern. Despite low disease presence, the calendar program was consistently better for yield and overall disease control than the two advisory programs. Yield was similar for the three fungicide treatments in four of six experiments. Grade of twin row and diamond planted peanut was 0.7 points better than single row peanut over three years at one location. Net return based on crop value less fungicide program cost was more closely tied to yield than variable input costs for fungicide programs.

Proper crop rotation is essential to maintaining high peanut yield and quality. However, the economic considerations of sustainable cropping systems must incorporate commodity prices, production costs, and yield responses of the crops within the cropping system. Research was conducted at the USDA/ARS National Peanut Research Laboratory's Multi-crop Irrigation Research Farm in Shellman, Georgia to determine the average net returns of irrigated and non-irrigated cropping systems consisting of peanut (Arachis hypogea L.), cotton (Gossypium hirsutum L.), and corn (Zea mays L.). Five replicated cropping systems provided data on yield responses from irrigated and non-irrigated rotation sequences defined as: continuous peanuts (PPP), cotton/peanuts/cotton (CPC), corn/peanuts/corn (MPM), cotton/cotton/peanuts (CCP), and cotton/corn/peanuts (CMP). The peanut yield in the PPP rotation was 3300 kg/ha in the non-irrigated treatment. Non-irrigated yields in CPC and MPM rotation sequences were 3940 and 3890 kg/ha, respectively and yields in CCP and CMP rotation sequences were 4770 and 4710 kg/ha, respectively. The peanut yield in the PPP rotation was 4080 kg/ha in the irrigated treatment. Irrigated yields in CPC and MPM rotation sequences were 5280 and 5230 kg/ha, respectively and yields in CCP and CMP rotation sequences were 5940 and 6010 kg/ha, respectively. The economic returns of the cropping systems were analyzed for 3 different price level combinations. Production costs (variable and fixed) were obtained from partial budgets. Returns were defined as the 3 year average net returns of each cropping system and were calculated for each price level combination which resulted in 57 comparable average net returns for the irrigated and non-irrigated treatments. Net returns were influenced by rotation sequence, price, and irrigation.

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.

This is the first report of Pantoea ananatis on urediniospores of Puccinia arachidis. Presence of the bacterium is relevant for research and management of peanut rust. Accepted for publication 18 May 2013. Published 29 July 2013.