Weight per grain, oil concentration, and solar radiation intercepted during grain filling in black hull and striped hull sunflower hybrids

The effect of intercepted photosynthetically active radiation (PAR) on weight per grain and oil concentration and their dynamics was investigated in several sunflower (Helianthus annuus L.) striped and black hull hybrids grown in contrasting environments. The study included the previously investigated hybrids Dekalb G-100 and NKT, and two near isohybrids, which differed in the character of the type of hull. The effect of intercepted PAR lower than those studied in previous works was also investigated. Oil concentration was affected by intercepted radiation but striped hull hybrids reached the maximum oil concentration at lower levels of intercepted PAR than black hull hybrids. A decrease in intercepted radiation decreased final oil concentration mainly due to a lower duration of the phase during which oil concentration linearly increases. Despite the hull type, changes in grain oil concentration that were originated by changes in intercepted radiation largely depended on kernel oil concentration. No differences were observed in the response of weight per grain to changes in intercepted radiation among black hull and striped hull hybrids. Low sensitivity of oil concentration to changes in intercepted PAR must be considered for modeling grain quality. Striped hull hybrids could perform as black hull hybrids in environments with low intercepted radiation during grain filling.