Molecular markers and their application in improvement of vegetable crops

Marker is a tag which is conspicuous or apparent or which helps in identification of traits. There are three different types of markers viz., morphological, biochemical and molecular. Morphological markers have certain constraints i.e. narrow diversity, influenced by environment, problem with epistasis, pleiotropy, incomplete penetrance and variable expressivity. Biochemical markers reveal polymorphism of sequences of certain proteins. It has certain constraints like redundancy of genetic code, incomplete genomic coverage and also sensitive to environmental pressures. Molecular markers directly reveal the polymorphism at the level of DNA. These are tags that can be used to identify specific genes and locate them in relation to other genes.