Characterization of Pigment and Disease Resistance Genes in Dendrobium Breeding

Abstract

Dendrobiums are economically important cut flowers and potted plants for production in Hawaii. In 2004 Dendrobium was the top selling orchid with a wholesale value of $10.5 million. The crop’s slow growth, limited available gene pool, and unknown genetics make it very difficult to modify certain desirable traits such as flower color or disease resistance. The objectives of this research were to characterize pigment and disease resistance genes for use in Dendrobium breeding. We demonstrated that the Dendrobium dihydroflavonol 4-reductase {Dfr) gene has no substrate specificity and is able to utilize all three colorless dihydroflavonoid substrates; namely dihydrokaempferol (DHK), dihydroquercetin (DHQ), and dihydromyricetin (DHM) in order to produce pelargonidin, cyanidin and delphinidin. We were also able to produce several individual plants resistant to Cymbidium mosaic virus infection by using transgenesis with a mutated movement protein (Mutll). More than half of these plants lack an antibiotic resistance marker gene and thus are particularly desirable for future testing.