In Pakistan, the F1 seed production ranks very low in the three-line system. One of the reasons is poor panicle exertion and less out crossing rate in the female lines. Gibbrillic Acid (GA3) increase the seed and improve panicle exertion as well as outcrossing. This study was designed to identify the suitable doses of GA3 application in the seed multiplication block of different CMS lines. The material comprising both the parental lines (cytoplasmic male sterility and maintainer) used in the development of hybrid rice. GA3 powder used in the experiment is 90% concentration in three level concentration that is 0, 100, 200, ppm. The outcomes indicated that GA3 positively increased plant height, stigma exertion, panicle exertion, duration of floret opening, angle of floret opening and panicle length. Increased seed production is 0.3 to 1 t/ha compared to the control (0 ppm GA3). Application of GA3 concentration at the rate of 200ppm gave the best results as compared to the other treatments like control and 100 ppm in all the tested CMS lines increased productivity. So, 200 ppm concentration is recommended in seed multiplication of parental lines used in hybrid rice development.
Key words: Hybrid rice, CMS lines, GA3, seed multiplication.
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