School of Agriculture and Biotechnology
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Item Genetic mapping and identification of quantitative trait loci for yield and drought tolerance in tea(2015) Kamunya, S.M.; Kireger, E.K.; Wachira, F.N.; Sharma, R.S.; Korir, R.; Maritim, T; Kiplang’at, J.; Sharma, V.; Chalo, R.; Ahuja, P.S.Accelerated breeding and selection of improved tea (Camellia sinensis (L.) O. Kuntze) cultivars requires sound knowledge and understanding of genetics associated with desirable attributes.Quantitative trait loci (QTL) mapping for yield and drought tolerance in tea was performed using 42 F1 clonal progeny derived from a cross between tea cultivars TRFCA SFS150 and AHP S15/10 that had been established at two distinct tea growing regions in Kenya. The 100 informative markers identified in the cross that exhibited 1:1 segregation ratio were used to construct a linkage map of tea. The map consisted of 30 (19 maternal and 11 paternal) linkage groups that spanned 1411.5 cM with mean interval of 14.7 cM between loci. QTL analysis was carried out for yield and drought tolerance produced nine putative yieldQTLs and 13QTLs for drought tolerance. None of theQTLs was congruently detected in the two sites owing to G x E interactions. Markers OPT-18- 2500 and OPO-02-900 had pleiotropic effects in that they were significantly associated with yield at Timbilil (YLD-T; P = 0.007) and drought tolerance at Kangaita (DT-K; P = 0.003). The implications of the current study with respect to mapping population, G x E and marker-assisted selection are discussed.Item Antioxidant, antimicrobial and synergistic activities of tea polyphenols(2015) Koech, K.R.; Wachira, F.N.; Ngure, R.M.; Wanyoko, J.K.; Bii, C.C.; Karori, S.M.; Kerio, L.C.Microbial resistance to conventional antibiotics has become an increasing global problem and there is a need to find out novel, potent antimicrobial agents with alternative modes of action as accessories to antibiotic therapy. This study investigated the antioxidant, antimicrobial and synergistic properties of tea polyphenols. The tea germplasm from Kenya, China and Japan that are grown in Kenya were characterised for their biochemical profiles. The total phenolic content, theaflavins and thearubigins content of different tea products used in this study were determined spectrophotometrically according to Folin-Ciocalteus and flavognost methods respectively. The individual catechin contents were characterised by high performance liquid chromatography (HPLC) and identified according to their HPLC retention times, elution order and comparison with authentic standards. The antioxidant activity of tea polyphenols was determined using UV-Vis spectrophotometer on its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. The Agar Disc Diffusion method was used to screen for antimicrobial and synergistic activities of the tea liquors. Black, green, purple coloured leaf and white (silvery tips) tea products characterised for their biochemical profiles differed significantly in the levels of total polyphenols, total catechins, catechins fractions, theaflavins and thearubigins (P ≤ 0.05). Green, purple coloured leaf (aerated) and black tea from terminal buds and white tea products analysed in this study exhibited slightly higher antioxidant activity compared to black tea. The different types of tea products assayed in this study exhibited significant influence on the inhibition zone diameters against bacteria and fungi exposed to the tea extracts. Methicillin and penicillinase resistant S. aureus ATCC 25923, C. albicans ATCC 90028 and a clinical isolate of C. neoformans were more susceptible to all tea extracts than E. coli and S. typhi. There was synergism between most tea extracts and penicillin G against methicillin and penicillinase resistant S. aureus ATTC 25923.Item Transcriptome-based identification of drought responsive genes in the tea plant(2015) Maritim, T.K.; Wachira, F.N.; Kamunya, S.M.; Mireji, P; Mwendia, C.; Muoki, R.C.; Wamalwa, M.; Stomeo, F.; Martina, K.P.Tea (Camellia sinensis L. (O) Kuntze) is one of the most widely consumed beverages worldwide. Tea growing areas in Kenya often experience drought periods which cause accumulated soil water deficit. These adversely affect tea production and hence necessitate a need to develop drought-adapted tea cultivars that can withstand the stress challenge. Development of such cultivars can be facilitated by better understanding of genetic mechanisms underlying tolerance of the tea plant to water deficit. Tea plants respond to water deficit through poorly understood molecular processes. The present study was therefore, designed with the objective of identifying genes putatively conferring tolerance in the tea plant. Drought tolerant (TRFCA SFS150) and susceptible (AHP S15/10) tea cultivars, both 18-month old, were each separately exposed to water stress or control conditions of 18% and 34% soil moisture content, respectively, for three months in a randomized complete block (RCB) design with three replicates. Fresh shoots (n = 5) were randomly selected and separately harvested from each treatment and replicate. Total RNA of the shoots were extracted, their mRNA reverse transcribed and sequenced on Roche 454 high-throughput pyrosequencing platform. Overall, 232,853 reads were generated. The reads were quality-filtered, trimmed and assembled into 460 long transcripts (contigs). Contigs were annotated using BLAST searches against similar proteins in the Arabidopsis proteome and blast2go against non-redundant database to determine gene ontologies. Drought-related genes including heat shock proteins (HSP70), superoxide dismutase (SOD), catalase (cat), peroxidase (PoX), calmoduline-like protein (Cam7) and galactinol synthase (Gols4) were induced in plants exposed to drought. Additionally, the expressions of HSP70 and SOD were higher in the drought tolerant relative to the susceptible cultivar under drought conditions. Loci with known functional links to physiological and biochemical features of drought response appear to mediate tolerance to drought in C. sinensis. The loci present potential molecular markers for drought tolerance that can be explored through functional genomics to better understand molecular mechanisms underlying drought tolerance in C. sinensis.Item Assessing the effect of grading on the in vitro availability of Fe, Zn, Cu, Pb and Cd from CTC black tea(2015) Moseti, K.O.; Kinyanjui, T.; Wanyoko, J.K.; Wachira, F.N.In vitro analyses of trace element content in biological systems play an increasingly important role in assessing the environmental impact on health. A quantitative study of five trace elements namely Fe, Zn, Cu, Pb and Cd in cut, tear and curl (CTC) black Tea of different grades randomly sampled from four tea growing countries in East Africa, viz., Kenya, Uganda, Rwanda and Tanzania was carried out. The total element content as well as the water extractable content of the tea samples was done by Atomic Absorption Spectroscopy (AAS). Data obtained was analyzed using Graph-pad Prism statistical software for Windows, version 5.0 and P < 0.05 considered to be statistically significant. The significance of the difference between means for black tea and tea infusions was determined by one way ANOVA and the least significant difference test was used for mean separation where significant differences were recorded among group means. It was observed that tea contains the studied elements and only a very small portion of the total element content lixiviates into tea liquor during tea making process. The general extractability pattern of the elements studied was in the order Fe > Zn > Cu > Pb > Cd, indicating that tea is an important dietary source of Fe, Zn and Cu. Taking into account the high tea to water ratio used in preparing the analysed tea extracts, these data is best regarded as the extractability potential of the tea liquor and does not reflect the actual concentrations contained in the tea liquor that we actually consumed. However, the need to enact safety guidelines with regard to the liquor element composition is imperative.Item The anti-inflammatory properties of Kenyan tea(2015) Karori, S.M .; Ngure, R.M.; Wanyoko, J.K.; Wachira, F.N.An in vivo study was carried out to determine the effect of different types of Kenyan tea extracts on male Swiss albino mice infected with Trypanosoma brucei brucei isolate KETRI 2710. The isolate produced a similar clinical picture after a pre-patent period of five days post-infection (DPI). Parasitemia levels in the untreated mice and those given different tea developed exponentially at similar rates reaching the peak of parasitemia 8 DPI. Between 9 and 13 DPI parasitemia decreased more rapidly in tea treated compared to the untreated mice which indicated that tea lowered parasitemia. Anaemia indicated by a fall in erythrocyte packed cell volume (PCV) occurred within 4 DPI and remained below the normal levels until the terminal stages of the disease. A significant difference (P < 0.05) was observed 11 DPI between the tea treated and the untreated mice indicating that tea enhanced resistance to erythrocyte destruction. Mice treated with tea exhibited significantly (P < 0.01) reduced parasite induced hypoalbuminemia as compared to the untreated demonstrating that tea ameliorated inflammation induced by T. brucei brucei. Black tea, which is the principle tea product from Kenya, displayed remarkable properties some even comparable to those of green tea. Tea was more efficacious than dexamethasone, an established anti-inflammatory drug, demonstrating its therapeutic potential.