Abstract.A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.

Efficient isolation, purification and identification techniques of a new pathogenic fungus of cashew were developed.In the study, aspects related to identification, characterization of conidial morphology and infection of the Cryptosporiopsis spp fungus were investigated. Macroscopic observations of symptoms and signs of cashew blight disease as well as isolation, culturing and morphological characterization of its causative agent were carried out. Cryptosporiopsis spp fungus penetration and infection mechanisms on susceptible cashew leaves were studied. Cashew leaves were inoculated with fungal suspensions by pricking with pin, clipping with scissors and painting a fungal suspension onto the leaves with a paintbrush. Pathogenecity assays were performed on cashew leaves, nuts and apples. Irregular spot lesions, with a brown margin, formed on leaves especially on the young leaves. Direct conidial transfer was found to be the efficient method of isolation because it was less prone to contamination. Blight macroconidia are typical of Cryptosporiopsis having ellipsoidal, rounded at the apex, tapering into a scar at the base. Stomatal penetration of Cryptosporiopsis spp was visible through the simple staining technique using lactophenol solution. Penetration was by germinating conidia through a cuticle that caused an infection in leaves. Paint brush method of inoculation was found to be more effective as compared to other two methods based on the lesion size. Leaves inoculated with Cryptosporiopsis spp isolate began curling after 72 h thereafter developed dark, irregularly shaped spots with brown margins. An increased understanding of cashew blight is important for developing strategies for its management.

Rust (Uromyces appendiculatus) is a major foliar disease that reduces yield and pod quality in beans.The field trial of French beans was established at Jomo Kenyatta University of Agriculture and Technology (JKUAT). Single plant extracts and combinations of Boscia angustifolia, Zanthoxylum chalybeum and Melea volkensii were used to evaluate their effect on U. appendiculatus in the field. During the growing period, beans were infected with rust from natural inoculum at the field. Physiological responses such as carbon dioxide assimilation, transpiration (E), stomatal conductance (gs), and photosynthetic rate (Pn) of French beans treatments were examined after extracts of three antifungal plants were sprayed. B. angustifolia -Z. chalybeum combination and single plant treatment M. volkensii had positive effects on enhancing the rate of photosynthesis in bean plants. The high regressions between stomatal conductance and rate of transpiration in the treatments indicated that stomatal conductance and rate of transpiration were interdependent and it was interpreted to mean that stomatal conductance enhanced rate of transpiration at different times of the day. These plant extracts however caused an increase in the rate of transpiration of the bean plants, which resulted in loss of water. Results reveal bioactive potential of the flora from M. volkensii and a combination of B. angustifolia and Z. chalybeum to produce metabolites with potential applications as botanical pesticides.

Objective: To determine the most effective method of extracting metabolites from the two herbs Ziziphus abyssinica and Tamaridus. Indicus. Methodology and results: The methods used included cold and soxhlet extraction using methanol as the solvent and hot extraction using distilled water. To determine the efficiency in which compounds are extracted TLC was performed on silica gel aluminium plates using ethyl acetate: formic acid: glacial acetic acid: water (100:11:11:27). To determine the quantity of phenolic compounds in the extract, the Folin and Ciocalteau's method (1927) was used, using Gallic acid in various concentrations. For the total quantity of flavonoid compounds, the method of Miliauskas et al. (2004) was used. To determine the Proanthocyanidin content in the extract a method previously reported by Ayoola et al, 2006 was used. To measure the antioxidant capacity of the extracts the hydrogen donating or free radical scavenging activity, was measured using the stable radical DPPH. The compounds extracted by all the methods were about seven but the difference was noted when the individual compounds were analysed. The cold extraction on the herb extract of Z. abyssinica had significantly high amount of total phenols 1.99g/100g of sample than both soxhlet and water extraction with 1.51g and 0.61g/100g of sample respectively. The results of T. indicus indicate that the extracts from the soxhlet and cold extraction methods contained a significantly low amount of all the three compounds compared to the water extracts Conclusion and application of results: The method best suited for obtaining extracts from the two herbs T. indicus and Z. abyssinica is, cold method of extraction with methanol as the solvent for Z. abyssinica and hot extraction using distilled water for T. indicus. The results obtained give guidance to the fact that using both herbs would result in a better preservative than using one herb since the identified compounds would complement each other.

To evaluate their performance for seedling traits at seedling stage (under hydroponics), plant water relations under water stress and ultimately grain yield, and to estimate the genetic variability of the regenerates, the parent plants of local sorghum cultivars in Kenya using simple sequence repeats (SSR) markers were analyzed. The research involved Seredo, El Gardam and Mtama 1 sorghum cultivars. The TC (Tissue culture) regenerates were produced through somatic embryogenesis in Linsmaier and Skoog (LS) media augmented with an osmoticum, NaCl (100 mM) in attempt to improve the parent plant for water stress tolerance. The genetic variability was investigated using five SSR markers and seven morphological traits associated with water stress tolerance. The amplified DNA fragments were screened by gel electrophoresis using 2% agarose. Cluster and principal component analysis (PCA) were done using NTSYS-pc version 2.2. The SSR detected 11 alleles with an average of 2.2 alleles per locus. The number of alleles per locus ranged from two to three and the allelic polymorphism information content (PIC) value ranged from 0.344 for Xcup14 to 0.730 for Xgap72 with an average of 0.559. These results show that the cultivars differed for morphological and SSR markers. The average genetic similarity based on the morphological traits (0.922 with a range of 0.845 to 0.989) was higher than SSR markers (0.625 with a range of 0.306 to 0.944). The results also show that the classification of these sorghum cultivars may be useful to the breeders to plan crosses for preferred traits. The results also show that the sorghum microsatellites can be used to distinguish the cultivars and to estimate genetic diversity due to somaclonal variation. Overall, this study shows that tissue culture technique might not add value in producing somaclonal variation in sorghum.