A protocol to avoid precocious flowering of sunflower plantlets in vitro

Precocious flowering in in vitro plantlets of sunflower is one of the unfav ourable phenomena when using tissue culture. In this study, additional evid ence is presented on precocious flowering of sunflower regenerants. Three d ay/night cycles (16/8h, 12/12h and 8/16h) and some modifications of media w ere investigated. Under standard conditions (16/8 h day/night, 25 degrees C ) 62% of the plantlets formed flowers, while 55% formed flowers when grown in 12/12h day/night at 20 degrees C and 31% when plantlets were grown under cultivation conditions of 8/16 h day/night at 20 degrees C. According to t he results obtained, precocious flowering of sunflower plantlets in test tu bes depends on culture conditions, nutrition medium and genotype. It was fo und that 20 degrees C and 8/16h day/night was the most favourable condition to reduce precocious flowering of sunflower plantlets in the test tube. Mo dified nutrition media can also help to reduce in vitro flowering.