The Cell Membrane of a Novel Rhizobium phaseoli Strain Is the Crucial Target for Aluminium Toxicity and Tolerance

Soils with low pH and high aluminium (Al) contamination restrict common bean production, mainly due to adverse effects on rhizobia. We isolated a novel rhizobium strain, B3, from Kenyan soil which is more tolerant to Al stress than the widely used commercial strain CIAT899. B3 was resistant to 50 µM Al and recovered from 100 µM Al stress, while CIAT899 did not. Calcein labeling showed that less Al binds to the B3 membranes and less ATP and mScarlet-1 protein, a cytoplasmic marker, leaked out of B3 than CIAT899 cells in Al-containing media. Expression profiles showed that the primary targets of Al are genes involved in membrane biogenesis, metal ions binding and transport, carbohydrate, and amino acid metabolism and transport. The identified differentially expressed genes suggested that the intracellular γ-aminobutyric acid (GABA), glutathione (GSH), and amino acid levels, as well as the amount of the extracellular exopolysaccharide (EPS), might change during Al stress. Altered EPS levels could also influence biofilm formation. Therefore, these parameters were investigated in more detail. The GABA levels, extracellular EPS production, and biofilm formation increased, while GSH and amino acid level decreased. In conclusion, our comparative analysis identified genes that respond to Al stress in R. phaseoli . It appears that a large portion of the identified genes code for proteins stabilizing the plasma membrane. These genes might be helpful for future studies investigating the molecular basis of Al tolerance and the characterization of candidate rhizobial isolates that perform better in Al-contaminated soils than commercial strains

Effects of water hyacinth (Eichhornia crassipes [mart.] solms) compost on growth and yield of common beans (Phaseolus vulgaris) in Lake Victoria Basin

ABSTRACT Water hyacinth (Eichhornia crassipes) has become a problem in water bodie

Distribution and phenotypic characteristics of common bean (Phaseolus vulgaris L.) nodulating bacteria in diverse soils

Bacteria were isolated from the root nodules using common bean as a trap host. Growth and morphological characteristics of the bacterial isolates were described on yeast extract mannitol mineral salts agar and broth media. The results showed that over 67% of the isolates produced extracellular polysaccharide with an entire margin and convex elevation. The others differentiated into cream yellow, cream white and milky white colouration with colony area ranging from 0.8 to 26 mm2. The population levels of bacteria nodulating common bean varied in soils and were not affected by the cropping system. However, selected soil parameters greatly influenced the occurrence and distribution of these bacteria. The isolation of indigenous bacteria in all the soils with different cropping systems is an indication that the soils are favourable for nitrogen fixation. Based on the differences in cultural characteristics of the isolates, our data demonstrate the presence of high diversity of bacteria associated with bean nodules

Genetic Diversity of Cowpea (Vigna unguiculata (L.) Walp.) Accession in Kenya Gene Bank Based on Simple Sequence Repeat Markers

Increased agricultural production is an urgent issue. Projected global population is 9 million people by mid of this century. Estimation projects death of 1 million people for lack of food quality (micronutrient deficit) and quantity (protein deficit). Majority of these people will be living in developing countries. Other global challenges include shrinking cultivable lands, salinity, and flooding due to climate changes, new emerging pathogens, and pests. These affect crop production. Furthermore, they are major threats to crop genetic resources and food security. Genetic diversity in cultivated crops indicates gene pool richness. It is the greatest resource for plant breeders to select lines that enhance food security. This study was conducted by Masinde Muliro University to evaluate genetic diversity in 19 cowpea accessions from Kenya national gene bank. Accessions clustered into two major groups. High divergence was observed between accessions from Ethiopia and Australia and those from Western Kenya. Upper Volta accessions were closely related to those from Western Kenya. Low variation was observed between accessions from Eastern and Rift Valley than those from Western and Coastal regions of Kenya. Diversity obtained in this study can further be exploited for the improvement of cowpea in Kenya as a measure of food security

Genetic diversity of symbiotic bacteria nodulating common bean (Phaseolus vulgaris) in western Kenya.

Biological nitrogen fixation (BNF) in legumes plays a critical role in improving soil fertility. Despite this vital role, there is limited information on the genetic diversity and BNF of bacteria nodulating common bean (Phaseolus vulgaris L.). This study evaluated the genetic diversity and symbiotic nitrogen fixation of bacteria nodulating common bean in soils of Western Kenya. The genetic diversity was determined using 16S rRNA gene partial sequences while BNF was estimated in a greenhouse experiment. The sequences of the native isolates were closely affiliated with members from the genera Pantoea, Klebsiella, Rhizobium, Enterobacter and Bacillus. These results show that apart from rhizobia, there are non-rhizobial strains in the nodules of common bean. The symbiotic efficiency (SE) of native isolates varied and exhibited comparable or superior BNF compared to the local commercial inoculants (CIAT 899 and Strain 446). Isolates (MMUST 003 [KP027691], MMUST 004 [KP027687], MMUST 005 [KP027688], KSM 001 [KP027682], KSM 002 [KP027680], KSM 003 [KP027683] and KSM 005 [KP027685]) recorded equal or significantly higher SE (p < 0.05) compared to N supplemented treatments. The results demonstrate the presence of genetic diversity of native bacteria nodulating bean that are effective in N fixation. These elite bacterial strains should be exploited as candidates for the development of Phaseolus vulgaris inoculants

HIV-1 Drug-Resistant Mutations in Relation to Virological Failure among Adults in Busia County, Kenya

Introduction: Busia County of Kenya with a Human Immune-deficiency Virus prevalence rate of 7.7% is two-fold higher than the Kenyan national prevalence at 4.9%. Antiretroviral (ARV) therapy is standard care for all HIV infected patients to mitigate viral loads. The current ARV therapy coverage in the county is 95% among adults. Recently there has been an observation of virologic failure due to viral drug resistance. Limited information on HIV-1 drug-resistance exists with the ARV therapy scale-up in the county. Therefore, this study was designed to investigate the existing&nbsp; -1 drug-resistant mutations among adults in Busia County attributable to virological failure.Materials and Methodology: The samples were analyzed for viral load and HIV-1 drug-resistance targeting the pol gene. Viral load was detected and quantified by real time PCR. Alignment of sequences was done using Recall software and HIV-1 drug-resistance was determined by Stanford University HIV database.Results: Of 50 samples, 37(74.0%) had mutations and 34(68.0%) had viral loads of 1000cp/ml and above. Generally, a total of 142 (82 in males and 60 in females) mutations were detected. M184V, K65R, K70R, D67N and T215F were the predominant mutations encoding resistance to nucleoside reverse transcriptase inhibitors. K103N, Y181C, G190A and K101E were predominant to nonnucleotide reverse transcriptase inhibitor mutations. L231, V82A, 150L, E138G, G48V, I501T, I54V and M461were the protease inhibitor mutations identified. About 30(60%) samples had mutations encoding for NRTIs, 34(68%) for NNRTIs, and 6(12%) for PIs ARVs. We observed an association between samples with mutations and viral load of 1000 cp/ml and above (Fisher’s exact test of &lt;0.05) and virological failure especially in males (Fisher’s exact test of 0.013).Conclusion: There is need for the change in the recombination of treatment regimens especially the NNRTIs and NRTIs as first line therapy. There is also need for more investigations as to why males are resisting drugs than females, this will inform intervention. Routine HIV drug-resistance testing is needed before the initiation of any ARVs. This will minimize resistance. Keywords: ARVs, HIV-1, drug resistance, mutations, viral load, NNRTIs, NRTIs, PI

IMPACT OF LAND USE ON THE DISTRIBUTION AND DIVERSITY OF ENTOMOPATHOGENIC NEMATODES IN EMBU AND TAITA DISTRICTS, KENYA

Natural entomopathogenic nematodes (EPNs) are considered as potential biological control agents against soil-borne insect pests. This study was conducted to determine the impact of land use on the distribution, occurrence and diversity of entomopathogenic nematode community. Isolation of EPNs was done using the baiting technique and application of morphological identification methods revealed presence of the genus Steinernema. Land use intensification negatively affected the occurrence and recovery frequency in soils of Embu and Taita districts. The occurrence of EPNs was high in soils from coffee than maize and beans which had more nematodes than planted forest and napier grass followed by natural forest and tea respectively. PCR-RFLP of the internal transcribed spacer region on the ribosomal(r) DNA of the EPN isolates and digestion of the products by Alu I enzyme showed molecular variations among the isolates. The study has demonstrated that the frequency of occurrence and species variation of EPNs is different in various land uses