Harnessing the Hydrocarbon-Degrading Potential of Contaminated Soils for the Bioremediation of Waste Engine Oil

Waste engine oil pollution is an endemic problem in African countries as waste oil is often discharged into the environment without adequate treatment because waste oil recycling facilities are not readily available. In this study, laboratory-based microcosms (natural attenuation, biostimulation, bioaugmentation and combined treatment of biostimulation?Cbioaugmentation) were set up with soils (from old hydrocarbon biopiles) spiked with waste engine oil and monitored for 3 months. Total petroleum hydrocarbon analysis showed that biostimulation and biostimulation?Cbioaugmentation accelerated hydrocarbon degradation with over 84% reduction (<10,000 mg?kg^?1) by week 8. It took another 2 weeks for other microcosms to get below this classification of low-level contaminated waste and landfill disposal level. The highest degradation rate of 92% was obtained in biostimulated?Cbioaugmented microcosms (week 10). However, by week 12, there were no significant differences in hydrocarbon levels in naturally attenuated and treated microcosms. 16S rRNA and ITS-based denaturing gradient gel electrophoresis profiling showed diverse bacterial and fungal communities with some dominant members belonging to hydrocarbon-degrading Proteobacteria, Ascomycetes and Basidiomycetes. This research has therefore shown that hydrocarbon-polluted soils possess substantial microbial hydrocarbon-degrading capacity which was successfully harnessed for degrading engine oil. In developing countries without recycling facilities but readily available hydrocarbon-contaminated soils, using such soils for ex situ monitored natural attenuation could be an effective, low-cost and environment-friendly option for treating waste engine oil.     

Genetic diversity of tropical maize inbred lines combining resistance to Striga hermonthica with drought tolerance using SNP markers

Striga hermonthica and drought are the major stresses limiting maize yields in sub‐Saharan Africa. The search for diverse maize lines’ tolerance to drought and resistance to S. hermonthica (DTSTHR) is very crucial for yield improvement in areas affected by the two stresses. Understanding the genetic diversity among the lines is important to develop cultivars resistant to S. hermonthica and tolerant to drought. The lines were developed from biparental crosses of drought‐tolerant and Striga‐resistant lines. A total of 128 DTSTHR maize lines were characterized using single‐nucleotide polymorphism (SNP) markers. Results of the cluster analysis based on 3297 SNP markers showed four distinct groups consistent with the pedigrees of the lines. Furthermore, model‐based analysis also formed the same groups of the DTSTHR lines. Integrating the pedigree information with combining ability and the SNP analyses may provide defined heterotic groups for maize improvement work in West and Central Africa. These results also help breeders to utilize DTSTHR lines present at IITA for developing biparental crosses without disrupting the heterotic groups they have established in their breeding programmes.