Phenotypic characterization and molecular Studies of Kenyan passion fruit (passiflora edulis (Sims))genotypes based on SSR markers
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Date
2016-10
Authors
Matheri, Felix
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
Passion fruit (Passiflora edulis) was introduced to Kenya in the 1920s by
European farmers. The fruit is a significant income earner for the country from
both local and international markets. There are increased research activities on
variety improvement and development of new varieties with the hall marker of
this research being the KPFs 4, 11, 12 by KALRO. The KPFs are hybrids
developed through natural crosses of the coastal yellow varieties and purple
variety. Despite these gains in breeding, there is little information of both
phenotypic and molecular variability of these new cultivars as well as the
existing ones. The present study aimed at evaluating the molecular and
phenotypic variation in the hybrid and parent varieties. Phenotypic
characterization was done by targeting 7 morpho-agronomic descriptors with
three biological replicates. Analysis was done using MINITAB 16 software,
for description principle components and construction of a dendrogram using
the Eucledian distance tool. The first principal component alone accounted for
51.3% variance, while the first two components accounted for cumulative
variance of 74.3%. Molecular characterization was done using SSR markers.
Eleven (11) markers were polymorphic while one marker; PE 20 was
monomorphic. Calculation of genetic distance, PIC, allele number as well as
gene diversity was done using Powermarker® version 3.25 while phylogeny
reconstruction was done using DARWIN version 6. On the other hand,
AMOV A was calculated using GenAlex 6.502. The PIC ranged from 0.2929
(PE 04) to 0.6179 (PE 90) with a mean of 0.3909 indicating that marker PE 90
was highly informative and other markers were reasonably informative. The
mean PIC of 0.3909 indicated that generally, all the 11 polymorphic markers
were informative and as such can be utilized for further analysis of Passiflora
edulis genome. The dissimilarity matrix indicated that KRC-2 and KRP-2 had
the highest level of dissimilarity, confirming the known molecular variation
that exists between the yellow and purple varieties where the respective
genotypes belong to. Several genotypes had a dissimilarity of 0% and
indication that they shared closer ancestry compared to other genotypes. The
phylogenetic tree discriminated the samples into three main clusters with
several sub-clusters carrying different fruit populations, indicating genetic
relatedness among members of the same population. From the phylogenetic
tree, genetic variability was highest between genotype KRC-2 and KRP-4
which are coastal and purple varieties respectively. This corroborates the
findings of dissimilarity matrix where they had a dissimilarity of 76%. The
AMOVA indicated intra-population variation of 91% while inter-population
variation was 9%. From the results, Molecular and phenotypic characterization
proved to be useful tools for discrimination of various genotypes of Passiflora
edulis. The results from this study will enable better detection and
management of genetic variability that could hinder adoption of the KPF as an
alternative crop for the semi-arid agro-ecologies.
Description
A thesis submitted in partial fulfillment of the requirements for the award of the degree of master of science (biotechnology) in the school of pure and applied sciences-of Kenyatta University