Manipulation of source -sink ratio by destruction of capitulum core florets to increase the seed filling, yield and quality in sunflower

The yield of sunflowers is impacted by inadequate source-sink connections. There are no vascular bundles in the center of the capitulum, resulting in low seed setting and filling. It was hypothesized that manipulation of resource availability to peripheral and intermediary seeds by eliminating the predominantly ill-filled seeds of the capitulum core would have an augmenter effect on the filling of seeds in the rest of the two regions. A field experiment was conducted to achieve capitulum core destruction by operating a newly designed hand-held battery-operated ‘capitulum core destructor’, capable of removing the core area to a diameter of 0.8 and 1.5 cm. . Field experiments were conducted to standardize the optimum stage for capitulum core destruction (R5.0- 0% flowering of the capitulum total area (disc florets), R5.1- 10% flowering, R5.4- 40% flowering, R5.8- 80% flowering) and optimum area of core destruction (0.8 and 1.5 cm of inner diameter). The results revealed that the core destructed treatments outperformed the control (T1) in terms of seed yield and seed quality attributes. Amongst the treatments, T5 (1.5 cm core destruction at R5.8 stage) showed a 21% increase in seed yield over the control and registered the highest total number of seeds, total seed weight (48.63 g) and 100-seed weight (g). Additionally, the T5 treatment improved seed recovery percentage (80.23% compared to 70.45% in the control) and reduced rejected seed percentage (19.76% compared to 29.54% in the control). Concomitantly, the resultant seeds of T5 (1.5 cm core destruction at R5.8 stage) also possessed the highest germination potential, speed of germination, seedling growth and vigour index. This study demonstrates a scalable approach for sunflower cultivation globally, offering a practical solution to enhance yield and quality. Therefore, it was concluded that capitulum core destruction optimized resource allocation among the periphery and middle whorls of the capitulum, thereby resulting in a significant augmentation of seed yield and quality potential in sunflower crops.