Remmy W. Kasili

Diversity of fungi in sediments and water sampled from the hot springs of Lake Magadi and Little Magadi in Kenya

Lake Magadi and Little Magadi are saline, alkaline lakes lying in the southern part of Kenyan Rift Valley. Their solutes are supplied by a series of alkaline hot springs with temperatures as high as 86°C. Previous culture-dependent and independent studies have revealed diverse prokaryotic groups adapted to these conditions. However, very few studies have examined the diversity of fungi in these soda lakes. In this study, amplicons of Internal Transcribed Spacer (ITS) region on Total Community DNA using Illumina sequencing were used to explore the fungal community composition within the hot springs. Operational taxonomic units (OTUs) were analyzed using QIIME 1.8.0, taxonomy assigned via BLASTn against SILVA 119 Database and hierarchical clustering was done using R programming software. A total of 334, 394 sequence reads were obtained from which, 151 OTUs were realized at 3% genetic distance. Taxonomic analysis revealed that 80.33% of the OTUs belonged to the Phylum Ascomycota, 11.48% Basidiomycota while the remaining consisted of Chytridiomycota, Glomeromycota and early diverging fungal lineages. The most abundant Ascomycota groups consisted of Aspergillus (18.75%), Stagonospora and Ramularia (6.25% each) in wet sediment at 83.6°C, while Penicillium and Trichocomaceae (14.29% each) were dominant in wet sediment at 45.1°C. The results revealed representatives of thermophilic and alkaliphilic fungi within the hot springs of Lake Magadi and Little Magadi. This suggests their ability to adapt to high alkalinity, temperature and salinity. Key words: Fungi, hot springs, temperature, DNA, diversity.

Development stage, storage temperature and storage duration influence phytonutrient content in cowpea (Vigna unguiculata L. Walp.)

Cowpea (Vigna unguiculata) plays an important role in sustainable food security and livelihood improvement in Sub-Saharan Africa (SSA). The crop is rich in phytonutrients and minerals, which are key in solving malnutrition and hunger crisis, a major challenge in SSA. However, physiological status, storage temperature and duration affect phytonutrient levels and postharvest life of the leafy vegetable. Despite the significant importance of cowpeas, the maturity and postharvest storage effects on quality of the leafy vegetable remains unrevealed. The aim of this study was to analyze the dynamics of phytonutrients in cowpea leaves during development under field conditions in Kenya and in storage. The total carbohydrates (glucose, fructose, sucrose and starch) were highest at 90 d after planting (105.9 ± 2.5 g kg-1) compared to 30, 60 and 120 d. The total Phenolics (Gallic acid equivalents) increased gradually with age up to 12.0 ± 0.2 g kg-1 by 120 d. Catechin equivalent flavonoids, trolox equivalent antioxidants (TEA) and chlorophyll were highest in concentrations at 60 d after planting with 8.0 ± 0.5 g kg-1, 26.19 ± 0.5 g kg-1 and 5.7 ± 0.4 g kg-1, respectively. Quercetin equivalent flavonoids and total carotenoids did not show significant changes with age, while mineral concentration dynamics were specific for each element. Storage of cowpea leaves at room temperature (50–55 % relative humidity) led to a stronger decline of phytonutrients after 4 d, but mostly they remained stable at cold storage (5 °C). Results of this study highlight the importance of developmental stage at harvest, storage conditions and duration for the optimal availability of phytonutrients in freshly consumed leaves and for postharvest management strategies.

Screening for potential Striga hermonthica fungal and bacterial biocontrol agents from suppressive soils in Western Kenya

Striga hermonthica is a hemiparasitic weed that causes huge grain yield losses to small-scale farmers in Africa. Effective biocontrol agents against S. hermonthica can sustainably mitigate these losses. This study characterized the biocontrol potential of culturable fungal and bacterial isolates from S. hermonthica suppressive soils of western Kenya. These isolates were screened for their ability to produce antibiotic compounds and extra cellular enzymes and also their ability to cause S. hermonthica seed decay. Genomic DNA of the selected bacterial and fungal isolates was extracted and partial characterization of 16S rRNA and 18S rRNA genes performed respectively. Analysis show that antibiosis and enzymatic properties of potential biocontrol isolates correlated positively. Isolate KY041696 recorded high antibiosis, enzymatic and seed decay values. This study also revealed that bioactive bacterial isolates belonged to Bacillus, Streptomyces and Rhizobium genera. In this study, no fungal isolate caused S. hermonthica seed decay. This study therefore provides baseline information on the potential biocontrol microbes against S. hermonthica in Western Kenya that could be exploited further in the management of the weed.

Diversity of threatened local mango landraces on smallholder farms in Eastern Kenya

Abstract Mango fruits are highly nutritious and economically important to Kenyan farmers, who cultivate three categories of cultivars/landraces; local small-fruited, local big-fruited and improved, introduced cultivars. The small-fruited landraces are said to be well adapted to the local environment but are being replaced by introduced cultivars before their diversity has been documented. This study aimed at assessing morphological and genetic diversity of 36 local mango landraces from 35 randomly selected farms in Eastern Kenya. Fruits were collected from three locations for morphological characterization using the ‘Descriptors for Mango’ of the International Plant Genetic Resources Institute. Leaves of the same accessions were sampled for genetic diversity assessment using microsatellites. Morphological characterization showed that mean fruit length was 5.6–12.5 cm, while mean fruit weight was 93–578 g. Fruit shape was mostly ‘roundish’, while fruit ground colour ‘green’. Hierarchical cluster analysis with seven discriminant morphological variables resulted in four clusters. Analysis of molecular variance (AMOVA) indicated that variation was high (97%) among, but low (3%) within groups. Phylogenetic analysis using Neighbor Joining method resulted in three clusters that lacked consistency with the morphological clusters. Findings from this study may assist to select superior local mango accessions for future breeding programmes and to develop ‘conservation through use’ strategies for Kenyan local mangoes to retain their valuable genetic resources.