Factors influencing reversion from virus infection in sweetpotato.

Viruses limit sweetpotato (Ipomoea batatas) production worldwide. Many sweetpotato landraces in East Africa are, however, largely virus-free. Moreover, some plants infected by the prevalent Sweet potato feathery mottle virus (SPFMV) may be able to revert to virus-free status. In this study, we analysed reversion from SPFMV, Sweet potato virus C, Sweet potato mild mottle virus, Sweet potato chlorotic stunt virus (SPCSV) and Sweet potato leaf curl Uganda virus using the indicator plant I. setosa and PCR/reverse-transcriptase PCR. We also investigated environmental factors (temperature and soil nutrients) that may influence reversion from virus infection. We tested reversion in the East African cultivars New Kawogo, NASPOT 1 and NASPOT 11, and the United States cultivars Resisto and Beauregard. Reverted plants were asymptomatic and virus was undetectable in assayed parts of the plant. After graft inoculation, only the East African cultivars mostly reverted at a high rate and from most viruses though cultivar Beauregard fully reverted following sap inoculation with Sweet potato virus C. None of the tested cultivars fully reverted from single or double infections involving SPCSV, and reversion was only observed in co-infections involving potyviruses. Root sprouts derived from SPFMV-reverted plants were also virus free. Reversion generally increased with increasing temperature and by improved soil nutrition. Overall, these results indicate variation in reversion by cultivar and that the natural ability of sweetpotato plants to revert from viruses is malleable, which has implications for both breeding and virus control.

Impact of drying and composting procedures on the concentrations of 4-nonylphenols, di-(2-ethylhexyl)phthalate and polychlorinated biphenyls in anaerobically digested sewage sludge.

Enhanced treatments of sewage sludge produce a more manageable product for agricultural use by stabilizing the material, removing water, and reducing the possibility of pathogen transfer. We investigated the impact of pilot-scale composting and drying of sludge on physicochemical characteristics and on the concentrations of some organic contaminants. During the 143 day composting procedure, organic matter fell 22% and moisture by half. Concentrations of 4-nonylphenols (4-NPs) fell by 88% and di-(2-ethylhexyl) phthalate (DEHP) by 60%; losses continued throughout the procedure. Losses of total polychlorinated biphenyls (PCBs) were 11%, mostly from the lower molecular weight congeners, suggesting volatilization as the most likely loss mechanism. The drying process was much shorter, 40 days, yet organic matter content decreased by 27% and moisture by 85%. Losses of 4-NPs (39%) and DEHP (22%) were less than in composting and stopped when moisture content became constant. There were no losses of PCBs. Both treatments are simple, practical procedures that reduce the volume of waste and are applicable in situ on farms. Composting would be the method of choice for reducing organic contaminants but requires much longer times than drying.

Control strategies for sweet potato virus disease in Africa.

Sweet potato virus disease (SPVD), caused by dual infection with the whitefly-borne Sweet potato chlorotic stunt virus (SPCSV) and the aphid-borne Sweet potato feathery mottle virus (SPFMV), is the most serious disease of sweet potato in Africa. SPVD has been known there since at least the 1940s, although it took several decades to elucidate its aetiology. It occurs throughout Africa and is particularly prevalent in the Great Lakes region. Production of sweet potato is largely by resource-poor farmers, growing mostly local landraces and for home consumption and so control strategies need to be appropriate to these circumstances. Most high yielding and/or early maturing landraces in Uganda are susceptible to SPVD and most resistant landraces are low-yielding, forcing farmers to compromise between the conflicting requirements of large and/or early yields, and food security. Accordingly, two strategies were tested to avoid the disadvantages associated with such compromises. These were deploying high-yielding SPVD-resistant cultivars and phytosanitation practices to enable susceptible landraces to be grown successfully. In on-farm trials in Masaka and Rakai Districts of Uganda, some SPVD-resistant cultivars bred at Namulonge Agricultural and Animal Research Station (NAARI), in Wakiso District, out-yielded local landraces. Other trials at NAARI and at nearby farms showed that roguing diseased cuttings within 1 month of planting and isolation from diseased crops, even by as little as 15m, can considerably decrease spread of SPVD to susceptible cultivars. This indicates that phytosanitation can protect desirable susceptible cultivars, even if adopted only locally. A dual approach of deploying both resistant varieties and phytosanitation provides farmers with a valuable increase in their choice of control strategies for SPVD.

Sediments are major sinks of steroidal estrogens in two United Kingdom rivers.

The occurrence of intersex fish in a number of European rivers has been attributed to exposure to estrogenic chemicals present in sewage treatment work (STW) effluents. To further understand the environmental fate of these contaminants, the estrogenic activity of effluents, water, and sediments were investigated both upstream and downstream of the major STW discharge in two United Kingdom rivers. Estrogenic activity, determined using the yeast estrogen-receptor transcription screen, of the major STW effluents on both rivers was similar, ranging from 1.4 to 2.9 ng 17beta-estradiol equivalents (EEQ)/L. Estrogenic activities of surface waters 1 km upstream and downstream of both STW inputs were less than the limits of detection (0.04 ng/L); however, levels of estrogenic activity in sediments were between 21.3 and 29.9 ng EEQ/kg and were similar at both upstream and downstream sites. Effluent and sediment extracts were fractionated by reverse phase-high-performance liquid chromatography, and estrogenic active fractions were further analyzed by gas chromatography-mass spectrometry. The major active chemicals in the two effluents and in the sediments were estrone with lesser amounts of 17beta-estradiol; however, at one site, a number of other unidentified estrogenic fractions were detected in the sediments. These results suggest that riverine sediments are a major sink and a potential source of persistent estrogenic contaminants.

The ability of cultivars of sweetpotato in East Africa to 'revert' from Sweet potato feathery mottle virus infection.

Asymptomatic field plants are the normal source of the vine cuttings used as sweetpotato planting material in Africa. Previous and new tests of such East African material, mostly using the very sensitive method of graft inoculation to the indicator plant Ipomoea setosa, showed that a majority tested virus-negative. This was despite their never having undergone any science-based therapy. To investigate how this occurs, in a replicated greenhouse experiment, plants of susceptible cultivars from the USA and Peru and three resistant Ugandan cultivars were graft-inoculated with Sweet potato feathery mottle virus (SPFMV), the commonest virus infecting sweetpotato. When the grafts were established, cuttings were taken, rooted and proved to be infected. The health status of each of these new plants was then followed over a 10-week period using a quantitative polymerase chain reaction assay. Most of the plants of the Ugandan cultivars eventually tested SPFMV-negative whereas those of the USA and Peru seldom did. Furthermore, in subsequent graft-inoculations of scions from the tip, top, middle and base of the vine of every plant to I. setosa plants, again, most of the scions of the Ugandan cultivars tested SPFMV-negative whereas those of the USA and Peru seldom did. These tests demonstrate the phenomenon of reversion in the Ugandan cultivars and can explain how most unprotected Ugandan sweetpotato field plants tested SPFMV-negative.

Polychlorinated biphenyls in bile of patients with biliary tract cancer.

BACKGROUND: Polychlorinated biphenyls (PCBs) are anthropogenic, organic compounds. Although banned in the 1970s, PCBs are poorly biodegradable and hence ubiquitous in the environment. They accumulate in adipose tissue and are implicated various malignancies, including breast and pancreatic cancer. The hepatobiliary system is the main excretory route for such xenobiotic toxins. Incidence rates of intrahepatic biliary tract cancer are increasing worldwide. Measurement and comparison of PCB levels in bile from human patients with benign and malignant bile duct disease has not previously been done. OBJECTIVES: To compare PCB concentrations in bile from patients with malignant (n=8) and non-malignant (n=7) biliary disease. METHODS AND RESULTS: Fifteen human bile samples, collected endoscopically, were analysed using gas chromatography mass spectrometry for seven target PCB congeners (28, 52, 101, 118, 153, 138, and 180), known to occur in the environment and food. Amongst males, total PCB concentrations in bile ranged from 6 ng mL(-1) (aged 73 years) to 49 ng mL(-1) (aged 90 years); and in females between 8 ng mL(-1) (aged 33 years) to 43 ng mL(-1) (aged 67 years) bile. Although there was no overall difference in mean PCB levels between non-cancer and cancer patients, levels of congener 28 were significantly higher in patients with biliary tract cancer (p<0.05). CONCLUSIONS: Despite the banning of PCBs over 30 years ago, these xenobiotics are present in the bile of patients with biliary disease. PCB levels tend to increase with age, suggesting chronic bioaccumulation. Further research is necessary to investigate the relevance of increased levels of congener 28 in bile in biliary tract cancer.