A Study of Variation in
Chicozapote (Manilkara zapota)
UC Riverside
Dept. of Botany and Plant Sciences
Riverside CA 92521 USA
tel: (909) 787-4686
email: hjheaton@galaxy.ucr.edu
The chicozapote
is an abundant and frequently dominant species of tree found in different
types of tropical forests of the Maya region of Mesoamerica. The tree
has been cultivated or semi-cultivated in the Yucatan Peninsula region
of Mexico since prehistoric times.
It provides many useful products, including
timber, chicle gum (sap), edible fruits, and medicine. In northern Yucatan
and Quintana Roo this tree is found in a wide range of vegetation types,
from semi-deciduous tropical forest to periodically inundated savanna
and tintales.
Over this distribution, the life form
of the tree varies widely. Forest forms are taller and have straight
trunks, large fruits and large seeds. The savanna form is generally
shorter, with a twisted primary trunk that splits into branches very
close to the ground. This form also has smaller leaves, fruits and seeds.
We are studying the genomic DNA of 4
populations of chicozapote to determine if the phenotypic variation
between the different populations is accompanied by genotypic variation.
Genomic DNA has been extracted from desiccated leaf material of these
populations. In order to remove individual variation and only compare
differences between populations, the technique of bulked segregant analysis
is used. In this method, DNA from each member of a population is combined
into a single sample. This results in four samples representing the
total DNA of the four populations. These bulks are amplified using PCR
(polymerase chain reaction) and random primers. When a band difference
is observed between populations with a given primer, DNA from each individual
in the populations is amplified using that primer. Polymorphic loci
are identified and scored for each individual. When a sufficient number
of polymorphic loci have been identified, the data will be statistically
analyzed to determine if there is a significant genetic difference between
the four populations.
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