Seed setting and filling problem in sunflower and its management – A review

Seed setting and filling problem is one of the most important constraints in sunflower production and often considered to be a major reason for low productivity. Besides poor agronomic management, there are several genetic, physiological and environmental factors causing poor seed setting and filling in sunflower. The sporophytic type of self-incompatibility mechanism is one of the genetic reasons for poor seed setting in sunflower. One of the means to alleviate this problem is to identify the self-fertile lines and thus increase seed set and productivity. The physiological mechanisms that regulate seed setting and filling in sunflower are complex. Studies carried out on source-sink relationship and photoassimilate distribution pattern revealed that the photoassimilate supply in the capitulum largely depends on the phyllotaxy of source leaves and the position of sinks in developing inflorescences. A higher proportion of empty achenes (up to 60%), especially in the centre of capitulum result from source limitation. During seed filling, maximum import of photoassimilate appeared in intermediate whorls, while central whorls always exhibited the lowest import leading to poor seed filling. The studies carried out on correlation of the metric traits helped in identifying the characters associated with seed setting and filling. The number of filled seeds per head can be increased up to a certain limit by increasing stem girth and head diameter. Good agronomic practices play an important role in production and productivity of any crop. A crop geometry of 60 cm x 20 cm recorded significantly higher values of growth and yield attributes and seed yield compared to 40 cm x 30 cm (Patel and Thakur, 2003). To get synchronized flowering of male and female plants, sowing of male parent seven days early recorded higher seed setting and filling in RSFH-1 sunflower. Water stress caused by deficit irrigation from early flowering to early seed formation leads to reduced LAI and thus reduces yield attributes. Application of insecticides affects the pollinators visit and pollination thus decreases the seed yield of sunflower. Potential yield of sunflower is highly dependent on environmental conditions during life cycle of the crop. Based on the above mentioned discussion it can be concluded that breeding for the fertile lines, plant physiological manipulations, environmental control and good agronomic management can alleviate up to some extent the problem of seed setting and filling in sunflower.