Evaluation of rhizosphere, rhizoplane and phyllosphere bacteria and fungi isolated from rice in Kenya for plant growth promoters

Rice (Oryza sativa L.) is the most important staple food crop in many developing countries, and is ranked third in Kenya after maize and wheat. Continuous cropping without replenishing soil nutrients is a major problem in Kenya resulting to declining soil fertility. The use of chemical fertilizers to avert the problem of low soil fertility is currently limited due to rising costs and environmental concerns. Many soil micro-organisms are able to solubilize the unavailable phosphorus, increase uptake of nitrogen and also synthesize growth promoting hormones including auxin. The aim of this study was to isolate and characterize phyllosphere, rhizoplane and rhizosphere micro-organisms from Kenyan rice with growth promoting habits. In this study whole plant rice samples were collected from different rice growing regions of Kenya. 76.2%, over 80% and 38.5% of the bacterial isolates were positive for phosphate solubilization, nitrogenase activity and IAA production whereas 17.5% and 5% of the fungal isolates were positive for phosphate solubilization and IAA production respectively. Hence these micro-organisms have potential for utilization as bio-fertilizers in rice production

Evaluating the Potential of Juice from Some Sweet Sorghum Varieties Grown In Kenya to Crystallize

Sweet sorghum (Sorghum bicolor (L) Moench) is a crop analogous to sugarcane with similar accumulation of sugars in its juicy stems. An earlier research study on agronomic trials carried out by Jomo Kenyatta University of Agriculture and Technology established that some of the imported varieties of Sweet Sorghum had sufficiently high amounts of sugar content in their Juice. The present study was undertaken with the objective of determining the potential of some of these sweet sorghum varieties to produce crystal sugar. This was with the long term goal of trying to find alternative uses for sweet sorghum. The sweet sorghum varieties were planted at the University research farm, and stalks of sixteen varieties were crushed using electrical roller mill to produce SS juice which was then subjected to a number of analyses including, total and specific sugar determination and apparent purity. The total sugars in degree Brix varied from 15.050 to 21.500, sucrose concentration ranged from 6.05g/l to72.77g/l, glucose 2.65g/l to 16.41g/l and fructose 2.66g/l to 17.16g/l whereas apparent purity(AP) ranged from 33.89% to 83.91%.The variation could have been  brought about by varietal differences. The juice of variety RIO had the highest sucrose purity of 83.91% which was further clarified by liming and double carbonation method. The resulting juice was concentrated into syrup by evaporation. Supersaturation for crystallization was attained by cooling, followed by seeding. According to the present study, the following sweet sorghum cultivars; Rio, CMSXS636, IESV91018LT, IESV93042SH and SPV1411 could have potential in crystal raw sugar production because they have AP greater than 75% and a relatively higher sucrose concentration. The Rio sweet sorghum variety with the highest sucrose purity of 83.91% and sucrose concentration of 40.86g/l was selected and subjected to crystal sugar production processes. The Rio juice subjected to crystallization process failed to produce crystals probably due to the presence of dextran, aconitic acid and starch. Key words: Brix, Sucrose, apparent purity, Clarification, Crystal Sugar,

Morphological Characterization and Determination of Aflatoxin-Production Potentials of Aspergillus flavus Isolated from Maize and Soil in Kenya

This study aimed at morphologically identifying Aspergillus flavus in soil and maize and at determining their aflatoxin-producing potentials. Five hundred and fourteen isolates obtained from maize and soil in Kenya were cultivated on Czapeck Dox Agar, Malt Extract Agar, Sabouraud Dextrose Agar, Potato Dextrose Agar, and Rose-Bengal Chloramphenicol Agar. Isolates were identified using macro-morphological characteristics. Micromorphological characteristics were determined using slide cultures. Aflatoxin production was determined by direct visual determination of the UV fluorescence of colonies on Coconut Agar Medium, Yeast Extract Sucrose agar, and Yeast Extract Cyclodextrin Sodium Deoxycholate agar and by Thin Layer Chromatography. Forty-three presumptive A. flavus isolates were identified; aflatoxin was detected in 23% of the isolates by UV fluorescence screening and in 30% by Thin-Layer Chromatography (TLC). The aflatoxins produced were: aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), and aflatoxin G1 (AFG1); some isolates produced only AFB1, whereas others produced either AFB1 and AFB2 or AFB1 and AFG1. The highest incidence of A. flavus (63%) and aflatoxin production (28%) was recorded in samples from Makueni District. Isolates from Uasin Gishu (21%) and Nyeri (5%) were non-aflatoxigenic. Bungoma District recorded 11% positive isolates of which 2% were aflatoxin producers. The occurrence of aflatoxin-producing A. flavus emphasises the need for measures to eliminate their presence in food crops