IMPROVEMENT OF FIELD CROPS THROUGH BIOTECHNOLOGY METHODS

Abstract

The degree of diversity present in a sample of germplasm can be measured in terms
of morphology, pedigree, allelic diversity at marker loci, and allelic at genes determining
target phenotypes. The environment often influences morphological characters and there may
be limited polymorphism in cultivated germplasm. Pedigree information is not available for
wild or crop progenitor germplasm, and even within cultivated germplasm, it can be difficult
to differentiate between closely related accessions because complete pedigree records are not
always available. Allelic diversity based on genes determining key phenotypes currently is
not feasible in most crop plants, although the rapidly expanding EST and SNP databases will
eventually make this feasible in some germplasm, diversity at marker loci is currently the
most feasible strategy for characterizing diversity in wild and cultivated germplasm. Many
types of molecular markers have been used to characterize germplasm, with each method
differing in principle, application, type and amount of polymorphism detected, and cost and
time requirement. These include random amplification of polymorphic DNA (RAPDs),
restriction fragment length polymorphism (RFLPs), amplified fragment length polymorphisms
(AFLPs) and simple sequence repeats (SSRs).