Attempt to silence genes of the RNAi pathways of the root-knot nematode, Meloidogyne incognita results in diverse responses including increase and no change in expression of some genes

Control of plant-parasitic nematodes (PPNs) via host-induced gene silencing (HIGS) involves rational selection of genes and detailed assessment of effects of a possible knockdown on the nematode. Some genes by nature may be very important for the survival of the nematode that knockdown may be resisted. Possible silencing and effects of 20 such genes involved in the RNA interference (RNAi) pathways of Meloidogyne incognita were investigated in this study using long double-stranded RNAs (dsRNAs) as triggers. Two of the genes, ego-1 and mes-2, could not be knocked down. Expression of six genes (xpo-1, pash-1, xpo-2, rha-1, ekl-4, and csr-1) were significantly upregulated after RNAi treatment whereas for 12 of the genes, significant knockdown was achieved and with the exception of mes-2 and mes-6, RNAi was accompanied by defective phenotypes in treated nematodes including various degrees of paralysis and abnormal behaviors and movement such as curling, extreme wavy movements, and twitching. These abnormalities resulted in up to 75% reduction in infectivity of a tomato host, the most affected being the J2s previously treated with dsRNA of the gfl-1 gene. For 10 of the genes, effects of silencing in the J2s persisted as the adult females isolated from galls were under-developed, elongated, and transparent compared to the normal saccate, white adult females. Following RNAi of ego-1, smg-2, smg-6, and eri-1, reduced expression and/or the immediate visible effects on the J2s were not permanent as the nematodes infected and developed normally in tomato hosts. Equally intriguing was the results of RNAi of the mes-2 gene where the insignificant change in gene expression and behavior of treated J2s did not mean the nematodes were not affected as they were less effective in infecting host plants. Attempt to silence drsh-1, mut-7, drh-3, rha-1, pash-1, and vig-1 through HIGS led to reduction in nematode infestation by up to 89%. Our results show that genes may respond to RNAi knockdown differently so an exhaustive assessment of target genes as targets for nematode control via RNAi is imperative

Determining Acid and Metalliferous Drainage Potential of Waste Rock on a Mine

Acid and Metalliferous Drainage (AMD) is recognised as serious environmental problem in the mining industry. This is because environmental issue of AMD poses serious threat to water quality, vegetation cover and social licence of the mining operations. AMD occurs when reactive sulphide bearing materials are exposed to oxidising conditions. It has now become imperative for some mining companies to test sulphide bearing minerals for their AMD potential before major mining excavations are done. This work determines the AMD potential of fifty (50) waste rock samples from a Mine using Acid Base Accounting (ABA) techniques. Mineralogical studies on the sample indicated that the major sulphide mineral assemblages present were pyrite, arsenopyrite and chalcopyrite. Paste pH showed that 20% of the samples had undergone weathering and as such AMD generation had already started. Approximately 22% of the sample had conductivity levels between 1000 to 10,000 µS/cm and this shows a typical AMD chemical characteristic of high salinity. Acid Base Accounting showed that 32% of the samples were acid generating. Exactly 16% were non-acid forming and 52% were uncertain. The analysis showed that the potential for AMD generation exists for the waste rock material and can affect the local environment, specifically water quality if preventive measures are not taken.   Keywords: Sulphide, Waste Rock, Acid Base Accounting, Paste pH, Conductivit

Assessing the influence of land-use change on the variability of soil chemical properties in semi-arid zone of Ghana

The study aimed at providing basis to consider spatial variability in soil fertility to inform effective decision making in mineral fertilizer recommendations. The study area was classified into six land-use categories using a rural rapid appraisal technique with the aid of the farmers in the community, and by remote sensing satellite imagery (Quick bird). Land-use categories varied significantly in their nutrient, organic carbon content, and stock with coefficient of determination ranging from 0.14 to 0.46. This is reflected in decline in soil nutrient, organic carbon content, and stock with increasing number of years the land was put under cultivation except for permanently cultivated fields. Permanantly cultivated fields were located in the homestead and benefited from nutrient imports from the bush fields. The two farm types also differed significantly with respect to soil nutrients, organic carbon and stock. Soil organic carbon content was 8.2 and 4.5 g kg-1 for the homestead and bushfields, respectively. Soil organic carbon stock estimated for the two farm types were 125 and 74 t ha-1 for the homestead and bush fields, respectively. The study shows a distinct zone of nutrient enhancement within the homestead and bushfields that should be sampled separately when sampling the zone for fertilizer recommendations

Leverage and firm investment: the role of information asymmetry and growth

Purpose This paper aims to demonstrate how financial leverage impacts firm investment and the extent to which this relationship is conditional on the level of information asymmetry as well as growth. Design/methodology/approach The paper relies on data from 2,403 Indian firms during the period 1995-2014, generating a total of 19,544 firm-year observations. Analysis is conducted by using various panel econometric techniques. Findings Drawing insights from agency theories, the paper uncovers that financial leverage is negatively and significantly related to firm investment. It is also observed that the impact of financial leverage on firm investment is significant for high information asymmetric firms. Finally, the paper shows that the relationship between leverage and firm investment is significant for low-growth firms. However, no significant relationship is found between leverage and investment for high-growth firms. Originality/value This paper provides fresh evidence on the leverage–investment nexus and, to the authors’ knowledge, it the first paper to examine the extent to which this leverage–investment relationship is driven by the level of information asymmetry

Modeling nutrient and water productivity of sorghum in smallholder farming systems in a semi-arid region of Ghana

The CERES-sorghum module of the Decision Support System for Agro-Technological Transfer (DSSAT) model was calibrated for sorghum (Sorghum bicolor (L.) Moench) using data from sorghum grown with adequate waterand nitrogen and evaluated with data from several N rates trials in Navrongo, Ghana with an overall modified internal efficiency of 0.63. The use of mineral N fertilizer was found to be profitable with economically optimal rates of 40 and 80 kg N ha−1 for more intensively managed homestead fields and less intensively managed bush fields respectively. Agronomic N use efficiency varied from 21 to 37 kg grain kg−1 N for the homestead fields and from 15 to 49 kg grain kg−1 N in the bush fields. Simulated grain yield for homestead fields at 40 kg N ha−1 application was equal to yield for bush fields at 80 kg N ha−1. Water use efficiency generally increased with increased mineral N rate and was greater for the homestead fields compared with the bush fields. Grain yield per unit of cumulative evapo-transpiration (simulated) was consistently higher compared with yield per unit of cumulative precipitation for the season, probably because of runoff and deep percolation. In the simulation experiment, grain yield variability was less with mineral N application and under higher soil fertility (organic matter) condition. Application of mineral N reduced variability in yield from a CV of 37 to 11% in the bush farm and from 17 to 7% in the homestead fields. The use of mineral fertilizer and encouraging practices that retain organic matter to the soil provide a more sustainable system for ensuring crop production and hence food securit

Institutions and Poverty: A Critical Comment Based on Evolving Currents and Debates

Tebaldi & Mohan (2010, JDS) have established an empirical nexus between institutions and monetary poverty. We first, reflect their findings in light of recent development models, debates and currents in post-2010 literature. We then re-examine their results with a non-monetary and multidimensional poverty indicator first published in 2010. Our findings confirm the negative relationship and the nexus disappears with control for average income. Hence, confirming the conclusions of the underlying study that institutions could have an indirect effect on multidimensional poverty. In other words, the poverty eradication effect of institutions is through income-average as opposed to income-inequality. We discuss the confirmed findings in light of implications to: (1) debates over preferences in economic rights; (2) China’s development/outlook; (3) the Chinese model versus sustainable development; (4) the Fosu conjectures; (5) Piketty’s & Kuznets’ celebrated literatures and (6) future research to ascertain the inequality mechanism