Levels of control of Chilo partellus stem borer in segregating tropical Bt maize populations in Kenya

In Kenya, stem borers destroy an estimated 400,000 metric tons, or 13.5%, of farmers' annual maize harvest costing about US$80 millions. Bacillus thuringiensis (Bt) maize controls stem borers without harming humans, livestock and the environment and was sown to 140m ha-1 globally in 2009. Two public Bt maize lines of cry1Ab::ubi gene (Event 216 and Event 223) were crossed with two non-Bt maize inbred lines, CML144 and CML159. The efficacy in the control of Chilo partellus stem borers in the parents, F1 and F2:3 successive generations were studied in a biosafety level 2 greenhouse. The Btgene effectively reduced stem borer damage with lower values for number of exit holes, tunneling length, proportion of stalk tunneled, number of larvae and number of pupae than the non Bt-maize and the check cultivars. The F1 generations values for all damage parameters studied were comparable to those for the Bt-maize inbred lines as expected. The F2:3 generations showed a spread of damage parameters from resistant to susceptible. These results suggest that the Cry1A(b) genes in the study was inherited following the Mendelian segregation.Key words: Bt maize, Chilo partellus, Bt -endotoxins, biosafety, greenhouse

Analysis of Kenyan isolates of Fusarium solani f. sp. phaseoli from common bean using colony characteristics, pathogenicity and microsatellite DNA

Fusarium solani (Mart) f.sp. phaseoli (Burk) Synd. and Hans., is a plant pathogenic fungus that causes root rot in garden bean (Phaseolus vulgaris L.). To evaluate methods used in classifying strains of thispathogen, 52 Fusarium solani f.sp. phaseoli isolates from infected bean plants grown on different farms in Taita hills of Coast province, Kenya, were cultured and characterized using morphology, pathogenicity and microsatellite DNA. All the isolates showed high variability in aerial mycelial growth, mycelia texture, pigmentation (mycelia colour) when cultured on potato dextrose agar medium, and conidial measurements on Spezieller Nahrstoffarmer agar medium. Colonies were grouped intoluxuriant, moderately luxuriant and scanty on aerial mycelial growth; fluffy and fibrous based on mycelial texture; purple, pink and white based on mycelia colour; aid long, medium and short macroconidial length. All the isolates were pathogenic on GLP-2 (Rosecoco), a susceptible bean variety commonly grown in Kenya. DNA analysis showed that the isolates carried a high genetic diversity(gene diversity = 0.686; mean number of alleles = 9). Neighbour-Joining phylogenetic clusters reconstructed using microsatellite variation showed three major clusters. However, the microsatellitegroupings were independent of the altitude, colony characteristics and virulence of the isolates