The role and mechanisms of microbes in dichlorodiphenyltrichloroethane (DDT) and its residues bioremediation.

Environmental contamination with dichlorodiphenyltrichloroethane (DDT) has sever effects on the ecosystem worldwide. DDT is a recalcitrant synthetic chemical with high toxicity and lipophilicity. It is also bioaccumulated in the food chain and causes genotoxic, estrogenic, carcinogenic, and mutagenic effects on aquatic organisms and humans. Microbial remediation mechanism and its enzymes are very important for removing DDT from environment. DDT and its main residues dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) can biodegrade slowly in soil and water. To enhance this process, a number of strategies are proposed, such as bio-attenuation, biostimulation, bioaugmentation and the manipulation of environmental conditions to enhance the activity of microbial enzymes. The addition of organic matter and flooding of the soil enhance DDT degradation. Microbial candidates for DDT remediation include micro-algae, fungi and bacteria. This review provide brief information and recommendation on microbial DDT remediation and its mechanisms.

Evaluation of Soybean Entries in the Pan-African Trials for Response to Coniothyrium glycines, the Cause of Red Leaf Blotch.

Red leaf blotch (RLB), caused by the fungus Coniothyrium glycines, is an important disease of soybean known to cause yield losses across soybean-growing regions in Africa. Fungicides are one option to manage this disease, but utilization of host resistance may be a better option suited for smallholder soybean farmers in Africa. Fifty-nine soybean entries were evaluated for RLB severity in nine field locations in Ethiopia, Kenya, Uganda, and Zambia. Disease incidence was 100% and disease severity differed (P < 0.01) among entries at eight of the nine locations. Mean severity ratings ranged from 1.4 to 3.2 based on a 0-to-5 scale, with higher disease severities recorded in Ethiopia followed by Zambia. Eight of the 59 entries were common to all nine locations and had severity ratings ranging from 1.6 to 2.9. The cultivar SC Signal had the lowest RLB severity ratings in the combined analysis over locations. Based on correlations of weather variables to RLB severity, mean rainfall from planting to 30 days before assessment date had a positive correlation (r = 0.70; P = 0.035), as did mean morning maximum wind speed (r = 0.88; P = 0.016). Other variables, such as temperature and relative humidity, did not correlate to RLB severity. This is the most comprehensive report to date on the occurrence of RLB in the region, which for the first time demonstrates an association between rainfall and wind speed with RLB severity. It also represents the first extensive report evaluating soybean genotypes for resistance against RLB in multiple environments.