PROF. SHIBAIRO SOLOMON I.

This study was designed to evaluate the influence of manure and mineral fertilization on yield, Kjeldahl nitrogen (as protein equivalents), Vitamin C and nitrate accumulation in Amaranthus hypochondriacus. The vegetables were produced in field trials, set up in the University of Nairobi, Kenya, during the long rains period between March and May in 2007 and 2008 using diammonium phosphate (DAP; 20, 40 and 60 kg N ha-1) and manure; 40 kg N kg ha-1,) and the yield, Kjeldahl nitrogen (K-N; a proxy for protein content), vitamin C and nitrate levels were measured. The manure treatment produced little increase in productivity though it increased K-N levels. The DAP treatments produced increases in yield, but these saturated at 40 kg N ha -1. The K-N content of the leaves was high, ranging from 2.5 % to just over 4 %, and, broadly, increased with fertiliser application though the variation between the treatments was lower than that for yields. Nitrate levels, however, also increased with DAP fertilisation, resulting in an increase in the nitrate:K-N at high DAP applications, especially in younger plants. There were no clear correlations between ascorbic acid content and K-N. Nonetheless, the plants grown under different fertilisation regimes can be placed into three broad groups; those characterised with low to moderate K-N contents and low to high ascorbic acid contents, moderate to high K-N and low to high ascorbic acid content, and lastly high K-N and low ascorbic contents. Therefore, the growth environment of amaranth, can have a major impact not only on the productivity of the crop but its nutritional value. In this respect the mineral nutrient supply to the crop is of particular importance.

This study was undertaken to characterize the alpha subgroup of the proteobacteria causing the huanglongbing (HLB) disease of citrus from three different ecological zones of Kenya namely the Lower highlands (LH2, LH3, 1800-1900 m above sea level); Upper midlands (UM3, UM4, 1390-1475m), Lower midlands (LM5, LM4, LM3 of 1290-1340-1390m), by isolation and sequencing DNA encoding the L10 and L12 ribosomal proteins and the intergenic region. A 7I6-basepair DNA fragment was amplified and sequenced and consisted of 536 basepairs of DNA encoding the L10 protein, 44 basepairs of DNA intergenic region and 136 basepairs of DNA that partially encodes the L12 protein. Sequences of rpL10/L12 protein genes from Kenyan strains were 98% and 81% similar to the South African ‘Candidatus Liberibacter africanus strain Nelspruit' and the Asian ‘Candidatus Liberibacter asiaticus' strains, respectively. The intergenic rDNA sequence of Kenyan strain from UM and LM showed 84% similarity with ‘Candidatus L. africanus strain Nelspruit' and 50% similarity with ‘Candidatus L. asiaticus' strain. However, the LH strain had an 11- basepairs deletion, while the LM4 had a 5- basepair deletion in the intergenic region compared to ‘Candidatus L. africanus strain Nelspruit'. The L10 amino acid sequence was 100% homologous among HLB bacteria obtained from the agro-ecological zones in Kenya and the L10 protein sequence was also homologus to ‘Candidatus L. africanus strain Nelspruit'. Nevertheless, the L10 amino acid sequence of ‘Candidatus L. asiaticus' and the ‘Candidatus L. africanus subsp. capensis' differed from the Kenyan strains by 18.36% and 11.82%, respectively. Phylogenetic analysis of both the L10/L12 rDNA sequences and the L10 amino acid sequences clustered the Kenyan strains of the ‘Candidatus Liberibacter' species with members of alpha subdivision of proteobacteria.

Potato is the second most important food crop after maize in Kenya. In the traditional areas of potato production with a bimodal rainfall pattern in the country, poor sprouting, due to seed tuber dormancy, is a major drawback. There is little time between growing seasons to permit adequate sprouting of the seed tubers. Therefore, effects of pit, dark and cold pre-storage treatments and their duration on dormancy breaking and sprouting of seed potato tubers of variety Asante were determined. Tubers were evaluated for sprouting, number of sprouts per tuber and sprout vigor for 12 weeks. Pit and dark pre-storage treatments resulted in significantly higher sprouting, number of sprouts per tuber and vigor scores than cold pre-storage treatment and the control (diffused light storage). 100% sprouting of seed potato tubers was attained under pit storage by the fourth week for all pre-storage treatment durations while dormancy ended after 6 weeks of storage in the control. Sprouting was suppressed during cold pre-storage treatment. In pit and dark pre-storage treatments, vigor scores increased with increasing duration of pre-storage treatment while in the cold, vigor scores were reduced with longer pre-storage treatment duration. Pit and dark pre-storage treatments for short durations of up to one week respectively followed by two weeks of diffused light storage are recommended to break dormancy and promote sprouting of good quality seed potato tubers of Asante variety.