PROGRESS IN APPLICATION OF MOLECULAR MARKERS TO GENETIC IMPROVEMENT OF HORTICULTURAL CROPS

During the last fifteen years, molecular markers have entered the scene of genetic improvement in a wide range of horticultural crops. Among the major traits targeted for improvement in horticultural breeding programs are, disease resistance, fruit yield and quality, tree shape, floral characteristics, cold hardiness, and dormancy. Today, markers are being used for germplasm characterization, genetic mapping, gene tagging, and gene introgression from exotic species. The most widespread use of markers has been in germplasm characterization. Although genetic maps have been developed for most of our important fruit and vegetable species, and a number of horticulturally important gene loci have been tagged, only a few instances of application of molecular markers for progeny selection have been reported. New, easy to perform allele testing methods are needed to bridge this large gap between marker development and application. Research on tomato provides an elegant example for simultaneous discovery and introgression of quantitative trait loci from wild species with the aid of markers. Molecular markers and genetic maps have not been widely applied to ornamental, medicinal and other horticultural species and only a handful of such species is used in marker development and testing.