Authors:
Ngugi, CN
., Haukeland
, S., Wachira, PM
., Mbaka, JN
. and Okoth.S , Keniya |
Abstract:
Entomopathogenic nematodes (EPNs), Steinernema and Heterorhabditis are insect parasitic
nematodes used as biological agents for the management of economically important pests in
agriculture. New EPN isolates can be characterised by morphology, morphometric characteristics
and molecular analysis. The aim of this study was to describe an indigenous EPN isolate TK1
based on morphometric and morphological characteristics. The nematode was isolated from soils
in an avocado orchard in Kenya Agricultural and Livestock Research Organisation (KALRO),
Kandara. Insect baiting technique using last instar larvae of Galleria mellonella was used to
establish and multiply the nematode isolate. Twenty 3rd stage infective juveniles (IJs) and
1stgeneration males of TK1 were heat killed and fixed. The measurements were expressed in %
ratios and Means±SD ranges. The IJs were characterized by, body length of 834.54±87.36µm
(658.60-986.89µm), short hyaline of 20.47±3.33µm (13.45-24.95µm) and tail length of
53.22±8.35µm (40.30-71.51) µm. The heat killed1st generation males were J shaped but strongly
curved posteriorly almost spiral; excretory pore 106.37±13.77µm (84.51-140.13µm) and more
posterior to the head; pharynx was short 119.39± 13.57µm (93.10-150.77µm). The spicule was
82.05±13.94µm (57.86-128.30µm) and gubernaculum was 45.28±5.89µm (34.48-54.87µm)
about half the spicule length and a short tail (19.97±2.84µm (14.20-25.70) µm. Comparative
analysis revealed relatedness to African glaseri Steinernematids S. karii, S. pwaniensis, S.
ethiopense and
S. jeffreynse in IJs body length, c ratio; absence mucron and a value in males. From the results
the isolate was Steinernema species in the feltiae-glaseri group of EPNs. Molecular examinations
and further morphological investigations using scanning electron microscope are necessary to
establish the actual identity, correct placement and phylogenic relationship of isolate TK1 with
other Steinernematids. |
