Genetic And Morphological Diversity In Monodora Myristica
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Genetic And Morphological Diversity In Monodora Myristica
CHAPTER 1.
INTRODUCTION
1.1 Background Information
Monodora myristica (Gaertn.)Dunal, commonly known as African nutmeg or calabash nutmeg, is a tropical tree belonging to the Annonaceae family. Its seeds are widely used as a low-cost nutmeg alternative because to their comparable scent and flavour. Today, it is less widespread beyond its region of manufacture.Celtnet Recipes, 2011.
Monodora has 15 to 20 species, including Monodora borealis, Monodoraclaessensii, and Monodoragrandiflora.Monodoramyristica is distinguished by its very long and pendulous pedicels, undulate upper bract, and huge globose fruit with a black and smooth but coarsely ribbed surface (Burkill, 1985).
Calabash nutmeg trees are endemic to tropical West Africa, where they grow naturally in evergreen forests ranging from Liberia to Nigeria and Cameroon. It is also indigenous to Angola, Uganda, and West Kenya (Weiss, 2002).
The slave trade in the 18th century brought the tree to the Caribbean islands, where it thrived and became known as Jamaican nutmeg (Barwick 2004). It was brought to the Bogor Botanical Garden in Indonesia in 1897, when the trees flowered regularly but no fruit could be obtained (Weiss, 2002).
1.2 Genetic Diversity in Plants
Genetic diversity refers to any variation in the nucleotides, genes, chromosomes, or entire genomes of animals. At the most fundamental level, it is reflected by variations in the sequences of nucleotides (adenine, cytosine, guanine, and thymine) that make up the DNA within the organism’s cells. Nucleotide variation is evaluated for specific portions of the chromosome, known as genes.
Thus, each gene is a hereditary segment of DNA that occupies a certain location on the chromosome and governs a specific trait of an organism (Harrison et al, 2004).
Diversity increases the likelihood of populations adapting to changing surroundings. More variation increases the likelihood that certain people in a group will have variations of alleles that are appropriate for the environment.
Such individuals are more likely to live and generate offspring with that allele. Because of these people’ accomplishment, the population will be able to continue for future generations.
Most creatures are diploid, which means they have two sets of chromosomes and thus two copies of each gene (known as alleles). Some species, however, can be haploid, triploid, tetraploid, or more (meaning they have one, three, four, or more sets of chromosomes) (Harrison et al, 2004).
Within any given organism, there may be differences between the two (or more) alleles for each gene. This variation or polymorphism is introduced either by mutation of one of the alleles or as a result of reproduction processes, particularly when organisms migrate or hybridise, resulting in parents from distinct populations and gene pools. Harmless mutations and sexual recombination may allow the emergence of novel features, increasing variety (Andayani et al., 2001).
Each allele codes for the creation of amino acids, which are linked together to make proteins. Thus, changes in allele nucleotide sequences result in slightly variable amino acid strings or protein variants.
These proteins code for the development of the organism’s morphological and physiological traits, as well as dictating parts of its behaviour (Harrison et al., 2004).
Plant diversity is part of biological diversity, and it helps to achieve food security, poverty reduction, environmental protection, and sustainable development (Frankel 1984).
It is rapidly eroding in important spice plants and other crops, owing to the replacement of traditional landraces by modern, high yielding cultivars, natural disasters (droughts, floods, fire hazards, etc.), and large-scale destruction and modification of natural habitats harbouring wild species (Frankel 1984, Bramel-Cox and Chritnick, 1998).
Urbanisation threatens the M. myristica population by destroying its natural habitat and causing the majority of trees to be chopped down without replacement. Furthermore, the plant is classified as one of Kew’s problematic seeds due to its difficulty growing outside of its natural habitat (Burkill, 1985).
Genetic variety in traditional landraces and wild species is critical for combating pests and illnesses and developing cultivars that are better suited to continuously changing settings (FAO, 1994).
Molecular tools, such as, have been shown to be more useful and accurate in the study of inter- and intra-species genetic variation in a variety of plants. Randomly amplified polymorphic DNA (RAPD) markers have been effectively used to determine intraspecies genetic variation in numerous plants.
These include Phaseolus vulgaris (Razviet al., 2013), Ocimumspp (Sairkaret al., 2012), Chrysanthemum (Martin et al., 2002), Annonacrassiflora (Cota et al., 2011), Prosopis (Goswami and Ranade, 1999)
date palm (Corniquel and Mercier, 1994), papaya (Stiles et al., 1993), poplars (Bradshaw et al., 1994), and amaranths (Ranade et al. 1997). No such attempt has yet been documented for Monodoramyristica.
1.3RATIONALE
M. myristica is primarily collected from the wild and is severely impacted by wildfires, urbanisation, and the careless and uncontrolled removal of trees for lumber and firewood without replanting.
As a result, breeding strategies for this orphan crop must begin by documenting existing genetic and phenotypic differences. The current paper was created with this in mind, and it should provide a much-needed baseline for future studies.
1.4 Objectives.
The project’s overall goal was to characterise African nutmeg accessions in south-east Nigeria and determine the range and distribution of genetic variability.
The main aims of this work were:
v Determine the level of genetic diversity among 21 accessions of Monodoramyristica using the RAPD approach.
v To compare morphological and yield-related traits among accessions using analysis of variance testing.
v To demonstrate the efficacy of the RAPD approach in genetic diversity investigations of this important plant.
v Identify features that contribute considerably to variance in this species.
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