| dc.description.abstract | Global tomato production is characterized by inconsistent quality and yields partly
emanating from biotic constraints attributed to fungal foliar diseases. In Kirinyaga
County, where tomato production is a major source of livelihoods, there exists knowledge
gaps on prevalence fungal foliar diseases such as early blight, late blight and Septoria
spot, and the susceptibility of locally grown tomato varieties to the infection. The
objective of this study was to assess the prevalence of three fungal foliar diseases, isolate
and characterize the pathogens, assess varietal susceptibility of some locally grown
tomatoes to the pathogens under control conditions, and determine the biocontrol
potential of some rhizospheric Streptomyces sp. Incidence and severity was assessed
using a cross sectional survey design on established macro plots within tomato farms.
Pathogen characterization was carried out using morphological and molecular techniques.
Susceptibility of tomato varieties to the fungal pathogens was evaluated by artificial
inoculation in a greenhouse arranged in a completely randomised design (CRD).
Antifungal activity of Streptomyces was determined in-vitro in co-plate culture and in vivo under artificial inoculation using CRD in the greenhouse. Molecular characterization
for fungal pathogen and Streptomyces involved BLASTIN analysis of DNA amplicon
Sanger sequenced nucleotides and use of NCBI databases. Percentages data of disease
incidences and severity were subjected to analysis of variance (ANOVA) using Kruskal
Wallis H test at α = 0.05. Median comparison was performed using Steel Dwass
Critchlow Fligner (SDCF) with bonferroni adjustment in Statistical Analysis Software
(SAS) version 9.4. Conidia lengths (µm) was subjected to ANOVA and significant means
separated by Least significance difference (LSD) at α = 0.05. Susceptibility data (%) was
subjected to ANOVA and significance means separated using LSD at α = 0.05. Zones of
inhibitions for the antifungal activity of Streptomyces isolates in co-plate culture were
analysed using ANOVA and significance means separated using LSD at α = 0.05.
Disease reduction data on antifungal activity of Streptomyces were analysis by Kruskal
Wallis H test and medians of significant means compared by SDCF α = 0.05 in SAS.
Incidences and severity of early blight, late blight and Septoria leaf spot in tomato farms
differed significantly (p < 0.05) among the villages and agro-ecological zones. Incidence
of early blight ranged from 35.7% to 76.65% with severity ranging from17.15% to
50.87%. The incidence of Septoria leaf spot ranged from 23.56% to 93.42% with severity
ranging from 16.67% to 44.44%. The incidence of late blight ranged from 33.33% to
86.63% with severity ranging from 16.67% to 33.33%. The incidence of early blight was
significantly higher in AEZ UM3 (Median= 75%), the incidence of Septoria leaf spot was
significantly higher in AEZ LM4 (Median = 83.33%) while the incidence of late blight
was significantly higher in AEZ UM3 (Median= 50%). The severity of early blight was
significantly higher in AEZ UM3 (Median = 38.89%), Septoria leaf spot was
significantly severe in AEZ LM4 (Median = 40.28%) while late blight was significantly
higher in AEZ UM4 (Median = 32.72%). Morphologies of pathogens differed
significantly (p < 0.05) with conidia lengths from 52.8 and 204.20µm (Early blight
pathogen), 37.20 and 102.30 µm (Septoria leaf spot pathogen) and 26.4 µm to 49.3 µm
(Late blight pathogen). Molecular characterization of some selected culture implicated
Alternaria solani and A. alternate involvement in causing early blight. Tomato varieties
differed in their susceptibility to foliar fungal pathogens (p < 0.05). Kilele F1 was the
most susceptible variety (73.84%) while Terminator F1 was least susceptible (56.48%) to
late blight pathogens. Kilele F1 was the most susceptible variety (57.99%) while
Terminator F1 was least susceptible (37.73%) to Septoria leaf spot pathogens. Riotinto F1
was the most susceptible variety (72.11%) while Terminator F1 was least susceptible
(56.48%) to late blight pathogens. Streptomyces assessed differed in their antifunal
activity significantly (p < 0.05). Tomato inoculated with Streptomyces isolate Strep6 | en_US |
