Application of reflectance spectroscopy to identify maize genotypes and aflatoxin levels in single kernels

Spectroscopy is a rapid, non-destructive, and low-cost analytical technique that has the potential to complement more resource-intensive analytical methods. We explored the use of spectral methods to differentiate maize genotypes and assess aflatoxin (AF) contamination in maize kernels. We compared the performance of two instruments: a research-grade ultraviolet-visible-near infrared (UV-Vis-NIR) spectrometer that measures reflectance from 304 -1,085 nm, and a miniaturised NIR spectrometer that measures reflectance from 740-1,070 nm. Both systems were used to predict AF levels in maize kernels from a single genotype and across 10 genotypes, and to predict genotype for the latter. A partial least square discriminant analysis model was trained on 70% of the kernels and tested on the remaining 30%. The classification accuracy for 10 maize genotypes was 71-72% using the UV-Vis-NIR instrument on 1,170 kernels, and 65-66% using the NIR device on 740 kernels. The classification accuracy for 247 AF-contaminated kernels of a single genotype using the UV-Vis-NIR instrument was 71, 82, and 92% for AF thresholds of 20, 100, and 1000 μg/kg, respectively. Using the same spectrometer on 872 kernels from 10 genotypes, AF classification accuracy was 67, 90, and 95% in validation sets for AF thresholds of 20, 100, and 1000 μg/kg, respectively. The UV-Vis-NIR instrument and the NIR device had similar classification accuracies for AF thresholds of 100 and 1000 μg/kg, whereas the NIR device had higher accuracy for the AF threshold of 20 μg/kg. Reflectance spectroscopy outperformed visual sorting and the bright greenish yellow fluorescence test in identifying AF levels. Applying spectral analysis to estimate mycotoxin levels and to identify maize genotypes could contribute to regional toxin surveillance and action efforts. Further, using AF-associated spectral features for grain sorting can reduce AF exposure.

Childhood Socioeconomic Position and Pubertal Onset: Implications for Breast Cancer

Higher socioeconomic position (SEP) has been associated with increased risk of breast cancer. Its relationship with the age of menarche, which is inversely associated with risk of breast cancer, and to the age of pubertal onset, is less clear. We studied the relationship of SEP to pubertal onset in a multiethnic cohort of girls aged 6–8 years at baseline and followed for 5–8 years in the Breast Cancer and the Environment Research Program in three study sites across the United States that included annual clinical examinations performed from 2004 to 2012. Analyses were conducted with accelerated failure time models using a Weibull distribution, with left, right and interval censoring. Among 1059 girls, an index of SEP comprised of household family income, mother's education and whether the home was owned or rented was assessed for associations with pubertal onset, measured by breast budding (Tanner Stage B2) and pubic hair development (Tanner Stage PH2). Girl's BMI% at entry to the study and black or Hispanic race/ethnicity were the strongest predictors of age at pubertal onset by both measurements, but the SEP index was an independent predictor in adjusted models. Girls from the lowest quintile of SEP entered puberty on average 6% earlier (6.0–7.5 months) than girls from the highest quintile (time ratio = 0.94, 95% confidence interval 0.91–0.97) adjusted for BMI%, race/ethnicity and their interaction. The meaning of SEP in this relationship bears further study, but our results suggest that early life social circumstances beyond race/ethnicity and body size may influence the timing of pubertal development.

Identifying and developing maize germplasm with resistance to accumulation of aflatoxins

Efforts 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 maize.

Aflatoxin accumulation and kernel infection of maize hybrids inoculated with Aspergillus flavus and Aspergillus parasiticus

Over a three year period, we compared aflatoxin accumulation and kernel infection in maize hybrids inoculated with Aspergillus flavus isolate NRRL 3357, A. flavus isolate NRRL 19772, Aspergillus parasiticus isolate NRRL 6111, and all combinations of these isolates. Maize hybrids were inoculated with the Aspergillus strains using the side-needle technique at 7 days after midsilk (50% of the plants had silks emerged). Aspergillus kernel infection and aflatoxin contamination were determined at ca. 63 days after midsilk. A. flavus isolate 3357 induced high levels of aflatoxin contamination in the maize grain which was similar to levels found when this isolate was combined with the other two Aspergillus isolates. Kernel infection levels were higher in one hybrid when a combination of isolates including isolate 3357 was used. A. flavus isolate 3357 has been used to evaluate maize germplasm for aflatoxin resistance in the south-eastern USA for over 30 years. Our studies determined that inoculating plants with A. flavus isolate 3357 alone was sufficient for inducing aflatoxin contamination in grain at our location. A combination of A. flavus isolates which include isolate 3357 might be more effective in increasing levels of kernel infection and could also induce higher levels of aflatoxin at locations that do not favour disease development.

Pregnancy outcomes, infant mortality, and arsenic in drinking water in West Bengal, India

Between 2001 and 2003, the authors studied pregnancy outcomes and infant mortality among 202 married women in West Bengal, India. Reproductive histories were ascertained using structured interviews. Arsenic exposure during each pregnancy, including all water sources used, was assessed; this involved measurements from 409 wells. Odds ratios for spontaneous abortion, stillbirth, neonatal mortality, and infant mortality were estimated with logistic regression based on the method of generalized estimating equations. Exposure to high concentrations of arsenic (> or =200 microg/liter) during pregnancy was associated with a sixfold increased risk of stillbirth after adjustment for potential confounders (odds ratio (OR) = 6.07, 95% confidence interval (CI): 1.54, 24.0; p = 0.01). Arsenic-related skin lesions were found in 12 women who had a substantially increased risk of stillbirth (OR = 13.1, 95% CI: 3.17, 54.0; p = 0.002). The odds ratio for neonatal death was 2.81 (95% CI: 0.73, 10.8). No association was found between arsenic exposure and spontaneous abortion (OR = 1.01, 95% CI: 0.38, 2.70) or overall infant mortality (OR = 1.33, 95% CI: 0.43, 4.04). This study adds to the limited evidence that exposure to high concentrations of arsenic during pregnancy increases the risk of stillbirth. However, there was no indication of the increased rates of spontaneous abortion and overall infant mortality that have been reported in some studies.

Comparison of Aflatoxigenic and Nonaflatoxigenic Isolates of Aspergillus flavus using DNA Amplification Fingerprinting Techniques

Aspergillus flavus is a filamentous fungus that produces mycotoxins in many food and feed crops, such as maize (Zea mays L.). Isolates were analyzed for toxin production by nucleic acid profiles in an attempt to differentiate aflatoxigenic from nonaflatoxigenic isolates. A total of 41 aflatoxigenic and 34 nonalfatoxigenic isolates were included in the study. The isolates were evaluated initially using DNA amplification fingerprinting (DAF) without clear resolution of the groups. A weak association of aflatoxigenic isolates was observed, as evidenced by their clustering in 18 of 81 trees recovered from maximum parsimony analysis of binary characters derived from arbitrary signatures from amplification profiles (ASAP) data; nonaflatoxigenic isolates exhibited a pattern of paraphyletic laddering. Up to five markers unambiguously supported the aflatoxigenic isolate grouping, but the presence of alternative conflicting topologies in equally parsimonious trees precluded the observation of meaningful statistical support. With additional markers for genome of A. flavus, this method could be used to resolve toxigenic from nontoxigenic strains. This additional work could resolve aflatoxigenic isolates of A. flavus present on maize plants using ASAP, which would reduce labor intense costs and potentially lead to faster determination of resistant cultivars in breeding efforts.

A prospective study of spontaneous abortion: relation to amount and source of drinking water consumed in early pregnancy

In 1992, we published four retrospective studies, conducted primarily within a single California county, which found higher spontaneous abortion rates among women who drank more tapwater than bottled water in early pregnancy. The current prospective study extends that investigation to other water systems. Pregnant women from three regions in California were interviewed during their first trimester. Multivariate analyses modeled the amount and type of water consumed at 8 weeks' gestation in each region in relation to spontaneous abortion rate. In Region I, which was within the previous study area, the adjusted odds ratio (OR) comparing high (> or = 6 glasses per day) consumption of cold tapwater with none was 2.17 [95% confidence interval (CI) = 1.22-3.87]. Furthermore, when women with high cold tapwater and no bottled water consumption were compared with those with high bottled water and no cold tapwater consumption, the adjusted odds ratio was 4.58 (95% CI = 1.97-10.64). Conversely, women with high bottled water consumption and no tapwater had a reduced rate of spontaneous abortion compared with those drinking tapwater and no bottled water (adjusted OR = 0.22; 95% CI = 0.09-0.51). Neither tap nor bottled water consumption altered the risk of spontaneous abortion in Regions II and III. Although controlling for age, prior spontaneous abortion, race, gestational age at interview, and weight somewhat strengthened the association in Region I, the distribution of these confounders did not vary appreciably across regions. This study confirms the association between cold tapwater and spontaneous abortion first seen in this county in 1980. If causal, the agent(s) is not ubiquitous but is likely to have been present in Region I for some time.

Genotoxicity of malathion in human lymphocytes assessed using the micronucleus assay in vitro and in vivo: a study of malathion-exposed workers

The aerial application of malathion, a widely used organophosphate insecticide, has raised public concerns about potential adverse health effects. We therefore studied micronucleus formation in human lymphocytes as a biomarker of genotoxicity both in vitro and in vivo. Lymphocytes were cultured either as whole blood or after Ficoll isolation and treated with malathion in doses from 5 to 100 micrograms/ml for 48 h. A significant increase in micronucleated cells (47.5/1000 versus 16.0/1000 in DMSO control, p < 0.001) was found in isolated lymphocytes at high dose levels (75-100 micrograms/ml), concurrent with cytotoxicity and a strong inhibition of proliferation (p < 0.001). Many of the treated cells also possessed multiple micronuclei. Antikinetochore-antibody staining revealed that the majority of malathion-induced micronuclei were kinetochore-negative. A significant dose-response was also observed in whole blood cultures, although the increase in micronucleated cells was lower than in isolated lymphocyte cultures (p = 0.03). When the same technique was applied to lymphocytes of 38 intermittently malathion-exposed workers involved in the Mediterranean Fruit Fly Eradication Program in California, no change in either proliferation or micronucleus level was observed compared with an unexposed control group. We conclude that malathion has a relatively low potential to cause chromosome damage in vitro, and corresponding doses are much higher than ones that even professional applicators are likely to be exposed to in vivo. The potential risk of chromosome damage for malathion exposure in vivo is therefore relatively low. More studies are needed to assess the possibility of interaction of malathion with other pesticides through combined exposure.