MSc

Longan (Dimocarpus longan Lour.), is an important commercially cultivated fruit
tree, belonging to the family Sapindaceae. It is commonly known as dragon-eye. In
Kerala, it is known by the names chempoovam, mullai etc. It is widely cultivatedin
many Asian countries like China, Thailand, and Taiwan etc. Recently many other
countries including India, Sri Lanka etc. have started cultivating longan tree as a
commercial fruit tree. Longan is used as a traditional medicine in China due to its
high medicinal and nutraceutical value.
The global demand for longan fruit has hiked rapidly due to its sweet taste and
nutritional value. Fruit consist of a white edible juicy aril which is surrounded by a
leathery pericarp. The fruit is rich in various bioactive polyphenols, vitamin C,
volatile compounds, minerals, amino acids, proteins, fats, carbohydrates etc.
Longan leaf, fruit pericarp, seed and pulp were used for extracting various
polyphenols. Extracts from various parts of longan have shown pharmaceutical
properties like antioxidance, anti-tyrosinase, anti-cancerous, anti-glycated,
immunomodulatory activity, antihypertensive etc. Thus the importance of fruit can
also be emphasized due to its richness in nutritional value.
The longan tree is a subtropical fruit tree native to the southern regions of China and
Indo-Burma. D. longan is indigenous to India's Western Ghats, ranging from
Konkan to Tinnevelly. Other distributions in India include Eastern Bengal and
Western Peninsular regions. In the Western Ghats region of Kerala, longan is a
species widely distributed in evergreen forests. There is a small distribution in the
semi-evergreen forests of Kerala as well. The diversity of indigenous longan
populations in Western Ghats has never been studied before. In this study,
morphological and genetic diversity of longan populations from six different
locations in the Western Ghats regions of Kerala were selected. Among these six
locations, three were located in the north of Palghat gap and three were in the South
ii
of Palghat gap. Morphological parameters like crown shape, branching pattern, tree
height, tree girth, leaf length and leaf width was considered for studying the
morphological diversity. Results from morphological traits revealed that the
population from Meppadi region from north of Palghat gap stood different from
other longan populations. Cluster analysis conducted using UGPMA method based
on the morphological traits showed that population from Mankulam was closely
related to the Meppadi population. The populations from six locations were divided
into two major clusters. ISSR primers were used to investigate the genetic diversity
existing among the six populations. 15 ISSR primers screened from total of 19
primers were used to amplify the DNA sample from different longan populations.
Average polymorphism rate of 69.51% was observed. Matrix data was obtained and
hierarchical dendrogram was produced using UGPMA method in NTsys pc
2.02 and DARwin software which clusters the populations into two major groups.
Jaccard’s dissimilarity index was calculated using R software and the values ranged
from 0.00 to 0.51. Genetic relation existing between the natural populations of
longan in Kerala, cultivated longan cultivars and litchi were identified. Cluster
analysis using UGPMA method pooled different populations into four major
clusters and study proved that litchi is genetically more related to the cultivated
longan variety rather than the wild populations. This is the first report on the
molecular characterization of D. longan from Western Ghats regions in India. The
results from this research study can provide valuable information to distinguish,
classify and identify the origin of longan populations in India and can be applied for
future breeding programs.