Insights into the maternal pathway for Cucumber green mottle mosaic virus infection of cucurbit seeds.

Cucumber green mottle mosaic virus (CGMMV), genus Tobamovirus, is a major pathogen of cucurbits that primarily affects cucumber, melon, and watermelon crops. The aim of this study was to reveal the contribution of CGMMV-infected female flowers to disease spread. Using a fluorescent in situ hybridization (FISH) technique, we show that ovaries and ovules of CGMMV-infected cucumber and melon plants showed a CGMMV-specific fluorescence signal prior to and following anthesis. The fluorescence signal was prominent but sporadic. Ripe fruits of infected melon plants showed strong signals in the funiculus, the seed stalk, which connects the developing seed to the interior ovary wall. Importantly, in seeds, a strong fluorescence signal was observed in the perisperm-endosperm (PE) envelope, which underlies the seed coat and surrounds the embryo. Interestingly, the fluorescence signal was not uniformly distributed in the PE envelope but was localized to a specific envelope layer. These results have important epidemiological implications for CGMMV management and commercial seed production, particularly regarding the improvement of seed disinfection methods that will contribute to limit the global distribution of the virus.

Impact of biosolids and wastewater effluent application to agricultural land on corticosterone content in lettuce plants.

We studied corticosterone occurrence in lettuce plants grown on three biosolids amended soils under irrigation with either tap water or secondary wastewater effluent. Corticosterone was examined as it has possible implications for human health. It is a major glucocorticoid, and as such has an effect on regulation of metabolism, immune functions and stress response. The plants were grown in 220-L lysimeters packed with 3 soils which represent a wide range of physicochemical properties. Lettuce was grown in cycles (two in summer and two in winter) during 3 years, and in every spring season the sludges were re-applied. Corticosterone was quantified using ELISA and LCMS, and was found in the biosolids, tap water, wastewater effluent and lettuce plants. The respective ranges of concentrations were: 11-92 ng g(-1), 0.5-1.6 ng L(-1), 4.2-4.7 ng L(-1); and 1-900 ng g(-1) dry weight. A positive relationship was found between corticosterone concentrations in winter-grown lettuces and the plants fresh weight. The corticosterone content of the plants did not correspond with either the type of irrigation water or the biosolids type and rate of application or the soil properties.

Impact of biosolids and wastewater effluent application to agricultural land on steroidal hormone content in lettuce plants.

One of the major concerns for human health in the past decade is the potential dangers posed by increased concentrations of steroidal hormones in soils and water. These hormones are considered to be endocrine disrupting compounds (EDCs), which may harm human health when exposed to high concentrations, or in the case of long term exposure to lower concentrations. In a 3 year study, two steroids, estrone and testosterone, were measured in lettuce plants irrigated with wastewater effluents and freshwater and treated with several types of biosolids. The relative contribution of the different factors, mainly irrigation water and biosolids, to the hormone levels in the lettuce plants was determined. It was found that irrigation water, which contained significant amounts of hormones, had the most substantial effect, whereas biosolids had only minor influence on hormone levels in the lettuce. The hormone levels in the plants were compared to the FDA recommendation for daily consumption in food, and were found to exceed the recommended level (when consumed by a typical individual), and therefore could have negative physiological impacts. Overall this study shows that biosolids have little effect on hormone uptake by lettuce, and it emphasizes the negative impact of irrigation water on these levels, which is of concern to public health.