Evaluation of resistance reaction of maize germplasm to common foliar diseases in Kenya

Use of resistance varieties is the most practical method of managing crop diseases. There is a great variation in terms of resistance reaction to diseases among the various maize germplasm and with the liberization of seed market, the sector has witnessed proliferation of massive introduction of new varieties whose reaction to diseases cannot be ascertained. This study was conducted to evaluate the reaction of maize varieties to northern leaf blight (NLB), common maize rust, gray leaf spot (GLS) and maize streak disease (MSD). The experiment was conducted at Kabete Field Station, University of Nairobi for two seasons namely short rains and long rains. The germplasm was bought from the commercial seed stockists and the landraces obtained from KARI Katumani and from farmers. The diseases were assessed by monitoring and scoring for disease incidence and severity. The appropriate scoring keys were used for determination of disease severity. All the varieties showed symptoms of the four diseases in both seasons but the intensity of the diseases differed significantly among the different varieties. Disease incidence was highest for common rust with a mean of 14.29% for the variety DH04, while disease incidence was highest (19.21%) for northern leaf blight in season two for Kinyanya which is a landrace. Gray leaf spot and the common smuts had the lowest mean incidence ranging from 0 to 0.25% for common smut and 0 to 2.6% for gray leaf spot. Season two had comparatively higher disease incidence means compared to season one. Meteorological data showed that season two had more rains and this explains the reasons behind this. Though all the varieties screened were found to be affected by the diseases to various levels, the varieties displayed significant differences in the disease incidence and severity. This shows that use of resistance varieties should be considered in the management of maize diseases. Focus should also be on pyramiding genes for resistance in the breeding programmes to develop varieties with multiple resistance to different diseases. Key words: Disease incidence and severity, disease score, symptoms, varietie

Challenges and Opportunities in Cassava Production among the Rural Households in Kilifi County in the Coastal Region of Kenya

In Kenya, food security and poverty alleviation are some of the most important factors that the country must address in order to achieve the vision 2030. Cassava has potential not only as food for humans, but also as feed for livestock and as a substrate for biofuel production.  Although various constraints have been reported to afflict farmers in cassava production, a base line survey in the study sites (Kilifi and Kaloleni) was necessary to identify specific constraints facing farmers in this region so as to identify areas of intervention in production and utilization. Lack of disease free planting materials was identified as one of the major constraints since cassava mosaic disease (CMD) and the cassava brown streak disease (CBSD) pose serious threats in yield losses. The two diseases are transmitted by vectors and by diseased planting materials and almost all the farmers obtain their planting materials from their neighbours thus aiding in disease dissemination and compounding the problem. There is need to enable the community produce quality cassava seed and operate sustained cassava business, integrate legumes into cassava cropping systems and create an innovative value addition chain for utilization of cassava. Eighty percent of Kenya is marginal area and cassava being drought tolerant can enable the potential of these areas to be tapped thus helping to deal with the persistent food insecurity which is a common feature in these areas. Key words: Cassava, cowpeas, cultivars, production constraints, utilizatio

Evaluation of growth characteristics of selected beauveria bassiana islolates under laboratory conditions in Kenya

Published online: July 2018An evaluation of the growth characteristics of nine B. bassiana isolates was conducted under laboratory conditions. Tests for spore concentration, viability, germination percentage, relative hyphal growth and speed of conidial germination were done. Isolate J59 showed the highest spore concentration of 120 and 114.2 spores per ml during the first and second assay respectively. Isolate J57 had the most viable number of spores in both assays. The highest germination percentage of over 80% was recorded for isolate J57. The relative hyphal growth was highest for the isolateRI under 6 days after inoculation followed closely by isolate J57 in both assays. In all the observed days, isolates BBC and BVT recorded the lowest relative hyphal growth but highest conidial germination at 2 to 10 hours after inoculation. Evaluation of growth is an important prerequisite for evaluation when considering the B. bassiana isolates for control of storage pests

Genetic diversity of local and introduced cassava germplasm in Burundi using DArTseq molecular analyses

Open Access Journal; Published online: 24 Jan 2022In Burundi most small-scale farmers still grow traditional cassava landraces that are adapted to local conditions and have been selected for consumer preferred attributes. They tend to be susceptible, in varying degrees, to devastating cassava viral diseases such as Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD) with annual production losses of US$1 billion. For long term resistance to the disease, several breeding strategies have been proposed. A sound basis for a breeding program is to understand the genetic diversity of both landraces and elite introduced breeding cultivars. This will also assist in efforts to conserve landraces ahead of the broad distribution of improved varieties which have the possibility of replacing landraces. Our study aimed at determining the genetic diversity and relationships within and between local landraces and introduced elite germplasm using morphological and single nucleotide polymorphism (SNP) markers. A total of 118 cultivars were characterized for morphological trait variation based on leaf, stem and root traits, and genetic variation using SNP markers. Results of morphological characterization based on Ward’s Method revealed three main clusters and five accessions sharing similar characteristics. Molecular characterization identified over 18,000 SNPs and six main clusters and three pairs of duplicates which should be pooled together as one cultivar to avoid redundancy. Results of population genetic analysis showed low genetic distance between populations and between local landraces and elite germplasm. Accessions that shared similar morphological traits were divergent at the molecular level indicating that clustering using morphological traits was inconsistent. Despite the variabilities found within the collection, it was observed that cassava germplasm in Burundi have a narrow genetic base

Optimisation of a somatic embryogenesis and transformation protocol for farmer-preferred cassava cultivars in Kenya

Cassava ( Manihot esculenta Crantz ) is a major food crop in developing countries, and holds potential for industrial use. It is, however, affected by various biotic and abiotic stresses that greatly affect its production. The existing regeneration and transformation protocols are not compatible with all cassava cultivars, thus efficient and robust transformation and regeneration protocols for farmer-preferred cultivars need to be optimised for ease of transfer of novel genes. The objective of this study was to develop an efficient transformation and regeneration protocol for a farmer-preferred Kenyan cassava cultivar. We cultured immature leaf lobe and stem explants on Murashige and Skoog (MS) medium, supplemented with varying concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), Picloram and \ue1-naphthalene acetic acid (NAA). Plants were recovered on media with 6-Benzylaminopurine (BAP) and GA3 under a 16 hour light/8 hour darkness photoperiod regime. Results showed high regeneration and transformation frequencies for both cultivars. High frequencies of callus induction (>98%) for both cultivars, were obtained when 2,4-D and Picloram were used. Similarly, both auxins initiated somatic embryogenesis, with Picloram producing the highest frequency of somatic embryos (>92%) in TMS 60444, using stem explants. Gus assays revealed high frequencies of transformation of >77% (TMS 60444) and 60% (Kibanda meno mkubwa). This protocol offers promising perspectives for rapid improvement of these cultivars and, therefore, provides a platform for cleaning planting materials, as well as cassava genetic improvement programmes such as control of viral diseases.Le manioc ( Manihot esculenta Crantz ) est une culture vivri\ue8re de grande importance pour les pays en d\ue9veloppement, avec un potentiel pour l\u2019usage industriel. N\ue9anmoins, le manioc est sujet \ue0 des stress d\u2019origines biotique et abiotique, affectant sa production. Les protocoles de r\ue9g\ue9n\ue9ration et de transformation existante ne sont pas compatibles avec toutes les accessions de manioc. Ainsi, il est n\ue9cessaire de d\ue9velopper des protocoles de r\ue9g\ue9n\ue9ration et de transformation efficaces pour les accessions adopt\ue9es par les paysans, afin de faciliter les transferts de g\ue8nes d\u2019int\ue9r\ueat. L\u2019objectif de cet etude \ue9tait de d\ue9velopper un protocole de r\ue9g\ue9n\ue9ration et de transformation adapte a la vari\ue9t\ue9 de manioc. Des feuilles et tiges immatures ont \ue9t\ue9 cultiv\ue9es sur des media Murashige et Skoog (MS), auxquels diff\ue9rentes concentrations de 2,4-dichlorophenoxyacetic acide (2,4-D), Picloram et \ue1-naphtal\ue8ne ac\ue9tique acide (NAA). Les plantes ont \ue9t\ue9 recouvertes de 6-Benzylaminopurine (BAP) et GA3 sous une photop\ue9riode de 16h jour/8h nuit. Les r\ue9sultats ont montr\ue9 des fr\ue9quences \ue9lev\ue9es de r\ue9g\ue9n\ue9ration et de transformation pour les deux cultivars Kibanda meno mkubwa et TMS 60444. Des fr\ue9quences \ue9lev\ue9es d\u2019induction de callosit\ue9s (>98%) ont \ue9t\ue9 obtenues pour les deux cultivars, lorsque 2,4-D et Picloram ont \ue9t\ue9 utilis\ue9s. De la m\ueame fa\ue7on, les deux embryogen\ue8ses somatiques initi\ue9es a l\u2019auxine, avec des explants de tiges et du Picloram ont exhibe la fr\ue9quence la plus \ue9lev\ue9e d\u2019embryon somatique (>92%) en TMS 60444. Des essais de Gus ont r\ue9v\ue9l\ue9s des fr\ue9quences \ue9lev\ue9es de transformation >77% (TMS 60444) et 60% (Kibanda meno mkubwa). Ce protocole offre des perspectives pour l\u2019am\ue9lioration rapide de ces cultivars, et par cons\ue9quent, fournit une plateforme pour la production de mat\ue9riels de culture propres, mais aussi servira d\u2019outil dans les programmes d\u2019am\ue9lioration g\ue9n\ue9tique visant la lutte contre les maladies virales

Constraints of rehabilitating degraded semi-arid lands of Kenya using indigenous perennial grasses

Land degradation which among others include loss of vegetation is rampant in Kenya, destroying both the fragile arid and semiarid lands and the non-arid areas. Efforts to rehabilitate semiarid areas by re-vegetation has often failed. This study was carried out to determine factors responsible for these failures. The study was conducted in the semi-arid district of Kibwezi. Three (3) grass species Cenchrus ciliaris, Enteropogon macrostachyus and Eragrostis superba were used for revegetating the land, while agro-pastoralists in the area were interviewed through questionnaires to get their perceptions on the failures of reseeding. Low rainfall, poor seed quality, lack of enough seed, flush floods, destruction by grazing animals were found to be factors limiting the success of reseeding