Antagonistic Potential of Local Endophytic Fungi Against Root-Knot Nematodes (Meloidogyne Spp.) on Tree Tomato (Solanum Betaceum) In Nyandarua County, Kenya
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Date
2025-11
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Kenyatta University
Abstract
Tree tomato (Solanum betaceum Cav.) is a significant emerging horticultural
cash crop in Kenya with an estimated economic value of over KES 0.5 billion and has
many nutritional and health benefits. Root-knot nematode (RKNs) infestations which
results in significant yield losses, pose a threat to tree tomato growing in Kenya.
Chemical nematicides have been the main method of controlling RKNs. However,
chemical nematicides can be harmful to the environment and human health. Thus, safer
alternatives to current techniques of management are needed. The study's objectives
were: (i) to determine effects of the endophytic fungi associated with tree tomato roots
on second stage juveniles (J2s) of RKN in vitro; (ii) to characterize endophytic fungi
with potential against J2s of RKN; (iii) to ascertain whether Velum® Prime SC 500 (ai =
fluopyram 500g/L) is compatible with endophytic fungi in vitro and under greenhouse
conditions, and (iv) to assess the effectiveness of combining Velum® Prime, Lantana
camara L. leaf extract, and the most effective endophytic fungus (Colletotrichum
nigrum) against RKNs on tree tomatoes in both in vitro and in vivo settings. The
experiments were laid down in completely randomized and randomized complete block
designs in the greenhouse and in the field, respectively, with four replicates per
treatment and terminated 90 days after transplanting. Data on initial and final nematode
populations, total number of RKN J2s, the galling and egg mass indices, the nematode
reproduction factor, height of shoot, and weights of dry roots and shoots were all
recorded. The data were analysed using ANOVA with SAS software version 9.2, and
significant means were separated using Tukey's Honest Significant Difference test at a
5% level (P≤0.05). Regression and correlation analyses were performed to ascertain the
connections between RKN disease parameters. Forty four endophytic fungi isolated
from tree tomato roots belonged to nine genera (Fusarium sp., Colletotrichum sp.,
Aspergillus sp., Penicillium sp., Didymella sp., Periconia sp., Microsphaeropsis sp.,
Rhizoctonia sp. and Purpureocillium sp.). Fusarium sp. (37%) and Purpureocillium sp.
(34%) were most abundant in roots and eggs of RKNs respectively. Colletotrichum
nigrum caused the highest mortality of J2s of 87 % followed by Aspergillus ustus and
Fusarium solani with 63.5% each in-vitro. Velum® Prime did not inhibit colony growth
of C. nigrum on PDA media. Colletotrichum nigrum combined with Velum® Prime
significantly reduced J2s in soil and nematode reproduction factor in the greenhouse
and were therefore compatible. Undiluted Lantana leaf extract + 1 × 106 C. nigrum
caused mortality of J2s with 81% and 83 % in tests I and II, in-vitro. Colletotrichum
nigrum + Lantana leaf extract + Velum® Prime significantly reduced plant disease
parameters (J2s, gall and egg mass indices and nematode reproduction) and also
increased plant growth parameters (shoot height and dry weights) in the greenhouse and
in the field compared to control. New knowledge on integrated nematode management
using endophytic fungi and Lantana leaf extract against second stage juveniles of RKNs
will help farmers in adopting affordable and eco-friendly methods to improve tree
tomato production and increase yield. There is need to commercialize C. nigrum
product and promote use of safe strategies to manage RKNs.
Description
A Thesis Submitted In Fulfillment Of the Requirements for the Award of the Degree of Doctor of Philosophy in Plant Pathology in the School of Agriculture and
Environmental Sciences, Kenyatta University. November, 2025
Supervisors,
Waceke Wanjohi
Maina Mwangi