Occurrence, Abundance and Distribution of Nematodes of Banana Linked to Altitude in Selected Banana Production Areas with Focus on Pathogenicity of Pratylenchus Goodeyi in Kenya
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Date
2022
Authors
Nyang'au, Nyagwonda Douglas
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Banana (Musa spp.) is a popular fruit crop in Kenya, where it is largely
cultivated by smallholder farmers. However, plant pathogens, such as plant parasitic
nematodes, have been blamed for the fall in output (PPN). A survey of bananabased
subsistence farming systems in Kenya's banana-growing counties was done
with the objective to a) assess farmers' awareness regarding PPN, b) explore the
variability regarding PPN species associated with banana genotypes in Kenya and if
the prevalence and abundance of these PPN species vary with altitude and c)
differential ability of Pratylenchus goodeyi populations to infect banana. One
hundred and eighty (180) farms from 12 major banana producing areas with varying
altitudes ranging from 1100-2000 m above sea level were surveyed. Farms were
selected following a purposive sampling method. A structured questionnaire was
administered to every farmer whose orchard was selected for sampling. From each
production area, 30 soil and 30 root samples were randomly collected from 15
banana farms. On each farm, one soil and one root sample were collected from both
dessert (Cavendish) and cooking (EAHB) banana cultivars. A total of 720 samples
were collected from the survey study. Nematode damage was scored on five
functional roots randomly selected and scored for the extent of necrosis in the root
cortex as a percentage. Nematodes were extracted from 5g of roots and 100 ml soil
using a modified Baermann technique and identified to the genus level. Besides,
two pot experiments were set up to assess the differential ability of Pratylenchus
goodeyi derived from diverse altitudinal gradients to infect banana. Mean values of
root necrotic indices (RNI %) from the survey and pot trials were arcsine (√x)
transformed. Nematode relative abundances and genera diversity were computed.
The nematode counts were subjected to log10(x+1). Data were subjected to a twoway
ANOVA using R- version 3.5.1 system statistical software and means
separated by the Tukey's test at P≤0.05. Results showed that only 2.3% of the
farmers were aware of nematode damage and symptoms, with none applying any
management measures. The highest abundance of PPN was recorded at an altitude
range of 1601-2000 masl with Pratylenchus, Meloidogyne and Helicotylenchus spp.
as the predominant genera. Across mid and high altitudes, EAHB showed higher
numbers of nematodes than Cavendish. Screening tests on P. goodeyi revealed that
populations from Embu had higher plant infectivity as they recorded the highest
reproduction rates. Ng‟ombe showed higher infectivity than Sukari Ndizi banana in
both trials. The results revealed that nematode damage is more common at higher
altitudes and on the EAHB genotype. The findings suggest that strengthening
farmers' awareness of pathogen dissemination mechanisms and increasing their
availability to disease-free planting supplies should be part of Kenya's banana
nematode management strategy. The findings from our study can be used to advise
farmers on nematode management techniques suitable for different altitudes.
Description
A Thesis Submitted in Partial Fulfillment of the Requirement for the Award of the Degree of Master of Science Crop Protection (Plant Pathology Option) in the School of Agriculture and Enterprise Development, Kenyatta University, June 2022
Keywords
Occurrence, Abundance, Distribution, Nematodes, Banana Linked, Altitude, Selected Banana Production Areas, Focus on Pathogenicity, Pratylenchus Goodeyi, Kenya