DORMANCY IN PARENTAL LINES OF SUNFLOWER (HELIANTHUS-ANNUUS) SEEDS ANDITS ALLEVIATION

An experiment was conducted on sunflower (Helianthus annuus L.) seed o f autumn crop (harvested in January 1991) to study dormancy in parenta l lines and its alleviation. Nine genotypes including A (male-sterile) , R restorer) and B (maintainer) lines of new hybrids were screened fo r determining seed-dormancy period. Genotypic response for dormancy pe riod was observed with 'RHA 274' (15-30 days); RHA 83R6. 'RHA 297' and '234 B' (31-45 days); '207 B' (46-60 days); 'RHA 6D1' and 'RHA 856' ( 61-75 days) and 'RHA 272' and '86 B 3' (76-90 days). Soaking of the do rmant seeds in water and solution of potassium nitrate (KNO3 200 ppm), thiourea (100, 200 and 500 ppm), ethrel (100. 250 and 500 ppm) and GA 3 (100, 250 and 500 ppm) for 24 hr improved the seed germination by 69 .6-86.6; 66-81.6; 65-80; 70.0-86.6 and 78-95% respectively. Soaking of seeds in GA3 at all concentrations provided the highest germination ( %). However, the minimum germination standard (70%) could be achieved by soaking in water for 24 hr.