Determination of ploidy among yam (Dioscorea spp.) landraces in Kenya by flow cytometry

Yam (Dioscorea spp.), a traditional crop in Kenya has not undergone improvement and little has been done to understand its genetic background. The taxonomy and phylogeny of the local landraces has not been fully studied. The main cultivated species is Dioscorea minutiflora Engl. Others found with low distribution are Dioscorea alata L., Dioscorea bulbifera L. and Dioscorea odoratissima Pax. Flow cytometry was used to estimate the ploidy level of 155 accessions of Kenyan yam including two checks, TDr.18544 a tetraploid and TDc.98136 an octoploid from International Institute of Tropical Agriculture (IITA), Nigeria. Also included in the study were Dioscorea dumetorum Pax, Dioscorea asteriscus Burkill and Dioscorea schimperiana Kunth which are yam wild relatives. Leaf samples were harvested from the field genebank and nuclei extracted using an extraction buffer (Partec GmbH, Munster Germany). Plant nuclei were isolated and stained with propidium iodide then analyzed in a flow cytometer. Seven ploidy levels of 3x (11.4%), 4x(37.5%), 5x(29.2%), 6x(14.6), 7x(3.1%); 8x(3.1%) and 10x(0.6%) were observed. Tetraploids (4x) formed the highest proportion followed by pentaploids (5x). The highest ploidy, decaploid, (10x), was found in D. odoratissima Pax, a conspecific form of Dioscorea preahensilis found under cultivation in two farms in Western Kenya. No diploids were observed in the study. Ploidy level was not associated with geographical habitat of the landraces while farmer-named varieties were not associated with ploidy levels. The findings generated new knowledge and form a basis for future yam research and improvement in the country. Further work is required to establish the phylogeny of Kenyan yam landrace

Effect of Legume Cover Crops on Soil Moisture and Orange Root Distribution

Inadequate rain is a major hindrance to soil moisture and crop root growth in arid and semi-arid areas of Kenya. A field study was conducted in Ganda, Vitengeni and Matuga locations within the coastal lowland region of Kenya from May, 2012 to April, 2015 to evaluate the effects of three leguminous cover crops on soil moisture retention and orange tree feeder root distribution. Treatments included mucuna (Mucuna pruriens), cowpea (Vigna unguiculata), dolichos (Lablab purpureus) cover crops and unplowed fallow of natural vegetation as a control. The experiment was laid out in randomized complete block design (RCBD) and each treatment was replicated four times. Data collected were: soil particle size distribution, soil moisture content and orange dry root density. The data collected was subjected to analysis of variance (ANOVA) using procedures of R statistical analysis version 3.3.2. Mean separation was done using the least significant difference (LSD) value at 5% level of significance. Results indicated that mucuna, dolichos and cowpea cover crops significantly (P=.05) increased soil moisture content. The mucuna treated plots recorded an increase in SMC by 39.0% and 33%, dolichos increased by 34.4% and 28.9% and cowpea by 33.6% and 27.3% at soil depth 0-20 and 20-40 cm, respectively, over their own controls. Mucuna and dolichos significantly (P=.05) increased orange feeder root distribution. Mucuna treated plots supported the highest increase in orange root distribution by 36.5% and 31.8%, dolichos increased by 30.2% and 34.1% while cowpea increased by 18.3% and 18.8% in soil depth 0-20 and 20-40 cm respectively compared to their own control. It can be concluded that the three legumes; mucuna, cowpea and dolichos cover crop improved soil moisture and root distribution in orange production. The overall ranking was as follows: mucuna > dolichos > cowpea. From the finding, the use of mucuna and dolichos cover cropping system is recommended as a soil management practice aimed at improving the orange productivity. Further evaluation on the long term (>3 years) effects of cover crops on soil moisture and orange root distribution under different agro ecological zones is suggested

Factors Influencing Adoption of Tissue Culture Banana in Western Kenya

The objective of the study was to assess the factors influencing the likelihood of adoption and intensity of adoption of Tissue culture banana in four counties of West Kenya. The study utilized cross-section data to analyze the effect of farmers’ demographic, socioeconomic and institutional setting, market access and physical attributes on the probability and intensity of TCB adoption. A double hurdle model was fitted on the data collected from randomly selected 330 farmers between July 2011 and November 2011. Secondary data were also used to complement the primary data. The study depicted relatively low adoption of TCB was 32% % of total sampled size. The results of the study provided empirical evidence of a significant influence on likelihood TCB adoption were availability of TCB planting material, proportion of banana income to the total farm income, per capita household expenditure and the location of the farmer in Kisii County, while those that significantly influenced the intensity of TCB adoption were. occupation of farmers, occupation of farmers, family size, labour source, farm acreage, farm fertility status, availability/access of TCB plantlets to farmers, distance to banana market, use of manure in planting bananas, agricultural extension services, average index technology attributes, bundumy was positive (sugarcane zone). Therefore, the results of the study suggest that the probability of adoption and intensity of use of TCB should be enhanced by taking cognizance of these variables in order to meet the priority needs of smallholder farmers who were target group and to alleviate the food shortage problem in the country in general and in the study area in particular. Opening up more TCB multiplication centres and widening the technology to other banana cultivars would enhance the impact of the technology

Assessment of the virulence spectrum and its association with genetic diversity in Magnaporthe oryzae populations from sub-Saharan Africa

A collection of 122 isolates of Magnaporthe oryzae, from nine sub-Saharan African countries, was assessed for virulence diversity and genetic relatedness. The virulence spectrum was assessed by pathotype analysis with a panel of 43 rice genotypes consisting of differential lines carrying 24 blast resistance genes (R-genes), contemporary African rice cultivars, and susceptible checks. The virulence spectrum among isolates ranged from 5 to 80%. Five isolates were avirulent to the entire rice panel, while two isolates were virulent to similar to 75% of the panel. Overall, cultivar 75-1-127, the Pi9 R-gene donor, was resistant to all isolates (100%), followed by four African rice cultivars (AR105, NERICA 15, 96%; NERICA 4, 91%; and F6-36, 90%). Genetic relatedness of isolates was assessed by single nucleotide polymorphisms derived from genotyping-by-sequencing and by vegetative compatibility tests. Phylogenetic analysis of SNPs of a subset of isolates (n = 78) revealed seven distinct clades that differed in virulence. Principal component analysis showed isolates from East Africa were genetically distinct from those from West Africa. Vegetative compatibility tests of a subset of isolates (n = 65) showed no common groups among countries. This study shows that blast disease could be controlled by pyramiding of Pi9 together with other promising R-genes into rice cultivars that are adapted to East and West African regions

Integrated strategies for durable rice blast resistance in sub-Saharan Africa

Rice is a key food security crop in Africa. The importance of rice has led to increasing country-specific, regional, and multinational efforts to develop germplasm and policy initiatives to boost production for a more food-secure continent. Currently, this critically important cereal crop is predominantly cultivated by small-scale farmers under suboptimal conditions in most parts of sub-Saharan Africa (SSA). Rice blast disease, caused by the fungus Magnaporthe oryzae, represents one of the major biotic constraints to rice production under small-scale farming systems of Africa, and developing durable disease resistance is therefore of critical importance. In this review, we provide an overview of the major advances by a multinational collaborative research effort to enhance sustainable rice production across SSA and how it is affected by advances in regional policy. As part of the multinational effort, we highlight the importance of joint international partnerships in tackling multiple crop production constraints through integrated research and outreach programs. More specifically, we highlight recent progress in establishing international networks for rice blast disease surveillance, farmer engagement, monitoring pathogen virulence spectra, and the establishment of regionally based blast resistance breeding programs. To develop blastresistant, high yielding rice varieties for Africa, we have established a breeding pipeline that utilizes real-Time data of pathogen diversity and virulence spectra, to identify major and minor blast resistance genes for introgression into locally adapted rice cultivars. In addition, the project has developed a package to support sustainable rice production through regular stakeholder engagement, training of agricultural extension officers, and establishment of plant clinics