Azide-based mutagenesis suppresses Striga hermonthica seed germination and parasitism on maize varieties

Small-scale farmers currently produce more than 90% of the maize grown in Kenya. However, the parasitic weed, Striga hermonthica has become a menace because it is a widespread parasitic weed causing severe damages to major cereals like maize and sorghum. Mutant lines of maize were createdin the laboratory using sodium azide (NaN3) and their performance in respect to the degree of Striga resistance screened. The presence of active chemical stimulants in the root exudate was further investigated. This is the first report on mutagenic conversion of Striga-susceptible to Striga-resistant maize varieties (K9908, K9910 and K9911). Stable performances of the new  arieties have been demonstrated in Striga-infested fields in western Kenya by  agronomic researcher

Antimicrobial resistance and plasmid profiles of Aeromonas hydrophila isolated from River Njoro, Kenya

The purpose of this study was to investigate the presence of Aeromonas hydrophila at commonly used water collection points on the River Njoro and to determine the in-vitro antimicrobial susceptibility and plasmid profiles of isolates. In total, 126 samples were collected and 36.5% of them were positive for A. hydrophila. The A. hydrophila were recovered on membrane filters, cultured on Trypticase Soy agar, Bile aesculin agar and Aeromonas Medium agar. They were further characterized using cytochrome oxidase and API 20E tests. Detection of drug susceptibility was determined using modified disc diffusion method to ampicillin (25 ìg), cefaclor (30 ìg), ceftizoxime (30 ìg), cefixime (5 ìg), cefazidime (30 ìg), gentamicin (200 ìg), streptomycin (25 ìg), chloramphenicol (50 ìg), nalidixic acid (30 ìg) and ciprofloxacin (1 ìg). Most of the isolates showed multi-drug resistance to two or more antibiotics. Chloramphenicol, nalidixic acid, ciprofloxacin, cefazidime and cefixime were the most sensitive drugs with 100% efficacy whereas ampicillin, cefaclor and streptomycin were the most resistant drugs having 100, 67 and 50 resistance, respectively. There was low resistance against ceftizoxime (16.7%) and gentamicin (23.3%). These results indicates that all A. hydrophila isolated from River Njoro had complete resistance to ampicillin and showed variable resistance to cefaclor, streptomycin, gentamycin and ceftizoxime. R-plasmids were extracted from multi-drug resistance strains and separated by agarose gel (0.8%) electrophoresis for profiling. Plasmid profiling revealed that most of the multi-drug resistant isolates contained one plasmid of 21.0 kb. Although some strains exhibited different antimicrobial resistance patterns, all of their plasmids were of the same size (21.0 kb). However, there were no plasmids in the antimicrobial sensitive isolates. This study also indicates that plasmid 21.0 kb is common in A. hydrophila and is important for antimicrobial resistance and virulence. Further studies are required to ascertain the role of this plasmid as a virulence marker.Key words: Aeromonas hydrophila, antimicrobial resistance, plasmid profile

Inheritance of Striga hermonthica adaptive traits in an earlymaturing white maize inbred line containing resistance genes from Zea diploperennis

Striga hermonthica can cause as high as 100% yield loss in maize depending on soil fertility level, type of genotype, severity of infestation and climatic conditions. Understanding the mode of inheritance of Striga resistance in maize is crucial for introgression of resistance genes into tropical germplasm and deployment of resistant varieties. This study examined the mode of inheritance of resistance to Striga in early‐maturing inbred line, TZdEI 352 containing resistance genes from Zea diploperennis. Six generations, P1, P2, F1, F2, BC1P1 and BC1P2 derived from a cross between resistant line, TZdEI 352 and susceptible line, TZdEI 425 were screened under artificial Striga infestation at Mokwa and Abuja, Nigeria, 2015. Additive‐dominance model was adequate in describing observed variations in the number of emerged Striga plants among the population; hence, digenic epistatic model was adopted for Striga damage. Dominance effects were higher than the additive effects for the number of emerged Striga plants at both locations signifying that non‐additive gene action conditioned inheritance of Striga resistance. Inbred TZdEI 352 could serve as invaluable parent for hybrid development in Striga endemic agro‐ecologies of sub‐Saharan Africa

Antimicrobial resistance and plasmid profiles of Aeromonas hydrophila isolated from River Njoro, Kenya

The purpose of this study was to investigate the presence of Aeromonas hydrophila at commonly used water collection points on the River Njoro and to determine the in-vitro antimicrobial susceptibility and plasmid profiles of isolates. In total, 126 samples were collected and 36.5% of them were positive for A. hydrophila. The A. hydrophila were recovered on membrane filters, cultured on Trypticase Soy agar, Bile aesculin agar and Aeromonas Medium agar. They were further characterized using cytochrome oxidase and API 20E tests. Detection of drug susceptibility was determined using modified disc diffusion method to ampicillin (25 μg), cefaclor (30 μg), ceftizoxime (30 μg), cefixime (5 μg), cefazidime (30 μg), gentamicin (200 μg), streptomycin (25 μg), chloramphenicol (50 μg), nalidixic acid (30 μg) and ciprofloxacin (1 μg). Most of the isolates showed multi-drug resistance to two or more antibiotics. Chloramphenicol, nalidixic acid, ciprofloxacin, cefazidime and cefixime were the most sensitive drugs with 100% efficacy whereas ampicillin, cefaclor and streptomycin were the most resistant drugs having 100, 67 and 50 resistance, respectively. There was low resistance against ceftizoxime (16.7%) and gentamicin (23.3%). These results indicates that all A. hydrophila isolated from River Njoro had complete resistance to ampicillin and showed variable resistance to cefaclor, streptomycin, gentamycin and ceftizoxime. R-plasmids were extracted from multi-drug resistance strains and separated by agarose gel (0.8%) electrophoresis for profiling. Plasmid profiling revealed that most of the multi-drug resistant isolates contained one plasmid of 21.0 kb. Although some strains exhibited different antimicrobial resistance patterns, all of their plasmids were of the same size (21.0 kb). However, there were no plasmids in the antimicrobial sensitive isolates. This study also indicates that plasmid 21.0 kb is common in A. hydrophila and is important for antimicrobial resistance and virulence. Further studies are required to ascertain the role of this plasmid as a virulence marker

Phase Competition in Ln0.5a0.5mno3 Perovskites

Single crystals of the systems Pr0.5(Ca1-xSrx)0.5MnO3, (Pr1-yYy)0.5(Ca1-xSrx)0.5MnO3, and Sm0.5Sr0.5MnO3 were grown to provide a series of samples with fixed ratio Mn(III)/Mn(IV)=1 having geometric tolerance factors that span the transition from localized to itinerant electronic behavior of the MnO3 array. A unique ferromagnetic phase appears at the critical tolerance factor tc= 0.975 that separates charge ordering and localized-electron behavior for t<tc from itinerant or molecular-orbital behavior for t>tc. This ferromagnetic phase, which has to be distinguished from the ferromagnetic metallic phase stabilized at tolerance factors t>tc, separates two distinguishable Type-CE antiferromagnetic phases that are metamagnetic. Measurements of the transport properties under hydrostatic pressure were carried out on a compositions t a little below tc in order to compare the effects of chemical vs. hydrostatic pressure on the phases that compete with one another near t=tc.Comment: 10 pages. To be publised in Phys. Rev.

Prevalence of multidrug resistant enteropathogenic bacteria causing diarrhea in Kibera community in Nairobi, Kenya

Diarrhea cases are on the increase in Kibera slum resulting in use of enormous amounts of antimicrobial agents and as a result, some pathogens develop resistance. This study was conducted in order to characterize some of the Gram-negative bacteria incriminated in the cause of diarrhea and their antimicrobial sensitivity. A total of 150 stools from children and adults collected from Kibera Community Health Centre were cultured in selective media and biochemical tests were done on suspected colonies. Serotyping using specific antisera was used to confirm species identity. Direct antimicrobial sensitivity tests using the Kirby-Bauer method were performed on ampicillin, tetracycline, kanamycin, chloramphenicol, streptomycin, gentamicin, ciprofloxacin and norfloxacin. The enteropathogenic bacteria identified in Kibera were pathogenic Escherichia coli with prevalence rate of 14%, while Shigella had a rate of 12%, Salmonella 8%, Yersinia enterocolitica 4% and no Vibrio cholerae. Most of the isolates showed multidrug resistance to two or more antibiotics. Norfloxacin and ciprofloxacin were the most sensitive drugs with 100% efficacy whereas ampicillin and gentamicin were the most resistant drugs having 84.2%and 68.4% resistance respectively. These results shows that even the antibiotics considered to be potent in treating diarrhoea are gradually becoming ineffective and should be closely monitored. Keywords: multi-drug resistance, diarrhea and enterics Journal of Tropical Microbiology and Biotechnology Vol. 2(1) 2006: 24-3

Journal of Ecology and the Natural Environment Full Length Research Paper Molecular diversity of arbuscular mycorrhizal fungi (AMF) in Lake Victoria Basin of Kenya

Arbuscular mycorrhizal fungi (AMF) play a key role in land reclamation, sustaining soil fertility and cycling of nutrients, which in turn increases plant vigour and productivity. AMF differ in both structural characteristics and global distribution, which is strongly correlated with the respective functional role. This study investigated the molecular diversity of arbuscular mycorrhizal fungi (AMF) in selected representative farmlands across Lake Victoria Basin and wheat farms in Njoro District of Kenya. Native AMF genera were identified by morphological techniques and their molecular diversity assessed by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) techniques and genetic distance analysis. In all five field sites, three AMF genera were identified with varying relative abundances, namely, Glomus (50%), Scutellospora (30%) and Gigaspora (16%). Lambwe fields had the highest spore densities (13 spores per gram dry weight) and evenness (0.84) while Kibos and Njoro had least spore count (4- ditto) and evenness (0.32), respectively. The AMF population from Njoro wheat farms had highest heterozygosity (He = 0.257) and hence was the most genetically diverse compared to other populations. Key words: Glomus spp., Gigaspora spp., Scutellospora spp., molecular diversity