| dc.description.abstract | Passion fruit (Passiflora edulis Sims) is an important economic crop in the world as an income earner and for food and nutrition security. Among the biotic stresses constraining production, woodiness disease is important causing economic losses wherever passion fruit is grown worldwide. In Kenya, passion fruit is a source of income to many small scale farmers. Although viral diseases are reported to be present in Kenya, there is limited,information on the causal agents and the relationship with aphid species found in passion fruit agroecosystem.
This study was undertaken to identify the causal agents of woodiness disease, incidence and distribution; monitor and identify the potential aphid vectors, determine virus transmission ability of the aphid species present in the orchards and to evaluate the effect of aphid repellant sources such as plastic reflective mulch to manage aphid vectors. A survey was undertaken in major passion fruit growing areas in the Rift Valley,
Central and Eastern provinces of Kenya in 2008 and 2010. The area was stratified according to administrative districts and agroecozones from which 130 fields were selected along rural roads. Suspected passion fruit leaf samples collected were assayed using ELISA and RT-PCR techniques for detection and identification of the viruses. Sequence diversity for Cowpea aphid borne mosaic virus (CABMV) was determined. Experiments for monitoring aphid vectors and evaluating aphid repellant sources were laid out in randomized complete block design in two sites.
The presence and abundance of aphids were monitored using yellow water pan traps. The aphids captured were counted and identified under a stereomicroscope and using a dichotomous key. The viruses were distributed widely with moderate to high incidence in all the passion fruit growing surveyed areas. The incidence was significantly (p<0.05) higher in the upper midland zones (82%) compared to the lower highland zones (50%).
The most common virus had 45% incidence. Coat protein sequence analysis for the most common virus isolated from Kenya, was closely related to South African passiflora virus and CABMV. Based on sequence identity, the virus was identified as a strain of CABMV. There was a high homology of the amino acid sequences among the Kenyan isolates suggesting a low diversity with strain differences. Other viruses present were Cucumber mosaic virus (CMV) and an unidentified potyvirus. | en_US |
