Citation
Mohd Raffi, Mohd Akmal
(2018)
Systematics, DNA barcoding and conservation of Vanilla species from Peninsular Malaysia.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
Among the 25 000 orchid species in Orchidaceae family, Vanilla is the most appreciated
as it is the only genus with species of high commercial agriculture value for its vanillin
production. The species from Peninsular Malaysia which represents the secondary gene pool of
the cultivated Vanilla planifolia serves as valuable resources for genetic improvement in
Vanilla. However, the potential of each species still remain in secrecy as the
genus is not comprehensively studied yet. This study was conducted to assess the native
species through systematics and molecular investigations. The data obtained will be used in their
conservation management. Therefore, efforts in locating, collecting and documenting local
Vanilla were initiated. The field samplings were conducted from 2011 to 2017 in the
states of Kedah, Perak, Pahang, Kelantan, Terengganu, Selangor, Negeri Sembilan and Johor. In
general, wild Vanilla populations in Peninsular Malaysia were difficult to locate because they were
found in many habitats. The diversity in the genus was updated with the discovery of two new
species to science, Vanilla norashikiniana R. Go et A. Raffi and Vanilla sanguineovenosa R.
Go et A. Raffi which made up the total count from this region to be represented by seven confirmed
species. Vanilla spp. most likely could tolerate the cardinal temperature of 17 to 27 oC, relative
humidity of 72 to 92% and 64 mm to 733 mm of monthly precipitation. Five important
growth events and their interactions with different environmental cues were presented with the
emphasized on the flowering stages. The fluctuations of temperature and high light intensity
were seen as the natural flowering promoters. Anthesis in Vanilla spp. were ideal to
be categorized into five important phases: floral evocation, floral bud emergence, ovary
development, size increment in bud and ovary and anthesis. Ephemeral flowering sequences of both
newly described taxa were photographed where the anthesis and senescence processes were
completed within 24 hours. Investigations at the histological level on accessions from Perak
revealed the taxonomic value of the marginal outlines from leaf transverse sections. Somatic chromosome counts (2n) among selected
accessions including two new species were found to be different in their most frequent number but
shared a common denominator of 2n= 24. Species discrimination inferred by the phylogenetic
trees generated from nuclear ribosomal internal transcribed spacer (nrITS) region had classified
the accessions into their respective genotypes with two unidentified genotypes suggesting presence
of additional species in this region. Barcoding gap was also reported in genetic
distance analysis with the speciation threshold recommended to be at 1.5%
divergence. Finally, provisional conservation action plan was proposed based on the
identified threats of which natural disasters and over collection from the wild were
noted as the major threats. Five approaches were evaluated to be pragmatic and should be
incorporated in the genus conservation action plan which were species mapping based on the
documented localities, local community involvement of Orang Asli, propagation via stem cuttings
using BAP, DNA barcodes deposition in BOLD and GenBank and also public education via MyBIS. This
project as a whole has successfully documented important findings in the botany and natural history
of the genus Vanilla from Peninsular Malaysia and these data are beneficial to the species
strategic management planning.
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