Abstract Flavonoids have numeruos biological and pharmacological effects shown by in vitro and in vivo studies. In addition to consumption of flavonoids by diet they are taken as tablets or dry extract capsules to have health benefits especially for their antioxidant and immunostimulant effects. The main goal of the study is to transfer flavonoid pathway genes to Citrus in order to increase the levels of characteristic flavonoid compounds. In this study the second gene, chalcone isomerase (CHI), from the flavonoid pathway was isolated and transferred succesfully to grapefruit plants via Agrobacterium mediated gene transfer method that is one of the biotechnological method. Transgenic plants, which were obtained have elevated flavonoid content compared to control plants. Özet Flavonoitler gerek in vitro gerekse in vivo kanitlanmis sayisiz biyolojik ve farmakolojik aktiviteye sahiplerdir. Flavonoitler diyetle vücuda alinmalari disinda antioksidan ve immunostimulan etkilerinden dolayi tablet veya kuru ekstre kapsülleri seklinde kullanilmaktadir. Çalismanin temel amaci flavonoit yolagindaki genleri narenciye türlerine aktararak narenciye türlerine özgü flavonoit bilesiklerini artirmaktir. Bu çalismada flavonoit yolagindaki ikinci gen, kalkon izomeraz biyoteknolojik metodlardan birisi olan Agrobacterium gen transfer yöntemi kullanilarak basarili bir sekilde greyfurt’a transfer edildi. Kontrol bitkileriyle karsilastirildiklarinda daha yüksek flavonoit miktarina sahip transgenik bitkiler elde edildi.

Keywords: Citrus flavonoids, chalcone isomerase, flavonoid pathway, transformation, gene transfer