Submitted to: International Society of Citriculture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/7/2002
Publication Date: N/A
Technical Abstract: Flavonoids are a widely distributed, diverse group of phytochemicals. In citrus, flavanone disaccharides are the main group of flavonoids that accumulate, and may affect the taste of fruits. Specifically, flavanone neohesperidosides, for instance naringin, cause bitterness in fruit and fruit juice products. This bitterness of the fruit reduces the acceptability of the fresh fruit and juice products in commercial markets. Our main objective is to manipulate the production of flavanone neohesperidosides in citrus using molecular genetics and transformation techniques. As an initial step, we have isolated the cDNAs of chalcone synthase (CHS) and chalcone isomerase (CHI) genes. Sense and antisense constructs of these cDNAs were used to transform grapefruit seedlings to suppress the expression of the target gene or increase the nonbitter flavonoids. To accomplish our goal we also transformed grapefruit with cDNA of a hairpin forming construct of the 1 2 rhamnosyl transferase gene, which catalyzes the last biochemical step in the formation of naringin. The construct was designed to express dsRNA, which interferes with the target gene activity. Transgenic plants are being analyzed by HPLC for their flavonoid composition, and are being characterized for their target gene copy numbers.