SUNFLOWER DEVELOPMENT STAGES FOR PHYTOHOR MONES APPLICATION TO CAUSE MALE-STERILITY

This trial was set in Londrina, PR, Brazil, in the crop year 82/83, to study the action of ethrel and gibberellic acid as phytohormones indu cing male sterility in sunflower, applying in different developing sta ges of the flower. The results showed a high induction of male sterili ty on the variety Issanka, and of little expression on the hybrid DK-1 80. Gibberellic acid was less efficient to cause male sterility when a pplied to the flowers with 0.0 to 0.5 cm in diameter. On the other han d, gibberellic acid was more efficient in inducing male esterility on the variety Issanka, when applied to flowers ranging from 0.5 to 2.0 c m. Ethrel did not present gameticide effect.