Evaluation of African-bred maize germplasm lines for resistance to aflatoxin accumulation

Aflatoxins, produced by the fungus Aspergillus flavus, contaminate maize grain and threaten human food and feed safety. Plant resistance is considered the best strategy for reducing aflatoxin accumulation. Six maize germplasm lines, TZAR101–TZAR106, were released by the International Institute of Tropical Agriculture-Southern Regional Research Center (IITA-SRRC) maize breeding collaboration for use in African National Programs and U.S. maize breeding programs. The present investigation was conducted to evaluate aflatoxin reduction by these lines in a U.S. environment. As germplasm lines, resistance was demonstrated by the lines tested in 2010 and 2014 trials. In 2010, TZAR106 was among the lines with the lowest toxin accumulation, and in 2014, along with TZAR102, supported low aflatoxin. When evaluated as single cross hybrids in 2012, 2013 and 2014, several crosses involving IITA-SRRC lines accumulated low toxin. In 2012, TZAR103 × HBA1 was one of 4 lines with the lowest concentration of aflatoxin. In 2014, five IITA-SRRC hybrids were among the lowest with TZAR102 × Va35 and TZAR102 × LH132 being the two lowest. Results demonstrate significant aflatoxin reduction by IITA-SRRC lines in a U.S. aflatoxin-conducive environment (at Mississippi State University). Further testing in different locations and environments is needed to further evaluate the potential usefulness of these germplasm lines

Gap-filling eddy covariance methane fluxes:Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands

Time series of wetland methane fluxes measured by eddy covariance require gap-filling to estimate daily, seasonal, and annual emissions. Gap-filling methane fluxes is challenging because of high variability and complex responses to multiple drivers. To date, there is no widely established gap-filling standard for wetland methane fluxes, with regards both to the best model algorithms and predictors. This study synthesizes results of different gap-filling methods systematically applied at 17 wetland sites spanning boreal to tropical regions and including all major wetland classes and two rice paddies. Procedures are proposed for: 1) creating realistic artificial gap scenarios, 2) training and evaluating gap-filling models without overstating performance, and 3) predicting half-hourly methane fluxes and annual emissions with realistic uncertainty estimates. Performance is compared between a conventional method (marginal distribution sampling) and four machine learning algorithms. The conventional method achieved similar median performance as the machine learning models but was worse than the best machine learning models and relatively insensitive to predictor choices. Of the machine learning models, decision tree algorithms performed the best in cross-validation experiments, even with a baseline predictor set, and artificial neural networks showed comparable performance when using all predictors. Soil temperature was frequently the most important predictor whilst water table depth was important at sites with substantial water table fluctuations, highlighting the value of data on wetland soil conditions. Raw gap-filling uncertainties from the machine learning models were underestimated and we propose a method to calibrate uncertainties to observations. The python code for model development, evaluation, and uncertainty estimation is publicly available. This study outlines a modular and robust machine learning workflow and makes recommendations for, and evaluates an improved baseline of, methane gap-filling models that can be implemented in multi-site syntheses or standardized products from regional and global flux networks (e.g., FLUXNET)

Identifying and developing maize germplasm with resistance to accumulation of aflatoxins

Special Issue: aflatoxins in and other cropsEfforts to identify maize germplasm with resistance to Aspergillus flavus infection and subsequent accumulation of aflatoxins were initiated by the US Department of Agriculture, Agricultural Research Service at several locations in the late 1970s and early 1980s. Research units at four locations in the south-eastern USA are currently engaged in identification and development of maize germplasm with resistance to A. flavus infection and accumulation of aflatoxins. The Corn Host Plant Resistance Research Unit, Mississippi State, MS, developed procedures for screening germplasm for resistance to A. flavus infection and accumulation of aflatoxins. Mp313E, released in 1990, was the first line released as a source of resistance to A. flavus infection. Subsequently, germplasm lines Mp420, Mp715, Mp717, Mp718, and Mp719 were released as additional sources of resistance. Quantitative trait loci associated with resistance have also been identified in four bi-parental populations. The Crop Protection and Management Research Unit and Crop Genetics and Breeding Research Unit, Tifton, GA, created a breeding population GT-MAS:gk. GT601, GT602, and GT603 were developed from GT-MAS:gk. The Food and Feed Safety Research Unit, New Orleans, LA, in collaboration with the International Institute for Tropical Agriculture used a kernel screening assay to screen germplasm and develop six germplasm lines with resistance to aflatoxins. The Plant Science Research Unit, Raleigh, NC, through the Germplasm Enhancement of Maize (GEM) Project provides to co-operators diverse germplasm that is a valuable source of resistance to A. flavus infection and accumulation of aflatoxins in maiz

The Presence of Mycotoxins and Fungi in Rice and Corn in the Southern United States

none[Synopsis] Fumonisins (≦4.3 ppm) were measured in rice (Oryze sativa L.) samples naturally infected with Fusarium sheath rot disease associated with F. proliferatum. F. proliferatum cultures isolated from these samples produced fumonisins (≦230μ g/g), moniliformin (≦6018 μ g/g), and beauvericin (≦1350 μ g/g). Deoxynivalenol (DON, vomitoxin), and zearalenone (ZEA, F-2) were detected in 94 and 77 respectively, of 100 Fusarium rice scab samples from Arkansas in 1996, at≦ 1.6 μ g/g and 2.2μ g/g. Aflatoxins and fumonisins were found in 10 and 5 of 100 Fusarium rice scab samples, at ≦ 28.6 ng/g and 500 ng/g, respectively. F. graminearum cultures were isolated and representative cultures (10) produced DON and its derivatives ≦ 430μg/g and zearalenone atc 9,883 μ g/g. False smut in rice caused by Ustilaginoidea virens produced a water-soluble compound that was found to be phytotoxic to duckweed (Lemna pausicostata L.), but not cytotoxic to mammalian cell lines at 200 μ g/g. In 1998, major aflatoxin contamination occurred in corn in the southern USA. Over 300 corn samples from 77 different hybrids were analyzed and at least 86％ of the samples had 20 ng/g aflatoxins or higher (4 to 2,506 ng/g). All the samples contained fumonisins (1.2 to 47 μ g/g). Deoxynivalenol was detected in some of these samples, but not zearalenone. In summary, we have observed DON, zearalenone, fumonisins and aflatoxins, and the fungi that produce them on rice and corn. The toxins are present at levels that are of concern for food safety

The Presence of Mycotoxins and Fungi in Rice and Corn in the Southern United States

[Synopsis] Fumonisins (≦4.3 ppm) were measured in rice (Oryze sativa L.) samples naturally infected with Fusarium sheath rot disease associated with F. proliferatum. F. proliferatum cultures isolated from these samples produced fumonisins (≦230μ g/g), moniliformin (≦6018 μ g/g), and beauvericin (≦1350 μ g/g). Deoxynivalenol (DON, vomitoxin), and zearalenone (ZEA, F-2) were detected in 94 and 77 respectively, of 100 Fusarium rice scab samples from Arkansas in 1996, at≦ 1.6 μ g/g and 2.2μ g/g. Aflatoxins and fumonisins were found in 10 and 5 of 100 Fusarium rice scab samples, at ≦ 28.6 ng/g and 500 ng/g, respectively. F. graminearum cultures were isolated and representative cultures (10) produced DON and its derivatives ≦ 430μg/g and zearalenone atc 9,883 μ g/g. False smut in rice caused by Ustilaginoidea virens produced a water-soluble compound that was found to be phytotoxic to duckweed (Lemna pausicostata L.), but not cytotoxic to mammalian cell lines at 200 μ g/g. In 1998, major aflatoxin contamination occurred in corn in the southern USA. Over 300 corn samples from 77 different hybrids were analyzed and at least 86％ of the samples had 20 ng/g aflatoxins or higher (4 to 2,506 ng/g). All the samples contained fumonisins (1.2 to 47 μ g/g). Deoxynivalenol was detected in some of these samples, but not zearalenone. In summary, we have observed DON, zearalenone, fumonisins and aflatoxins, and the fungi that produce them on rice and corn. The toxins are present at levels that are of concern for food safety