The within-panicle flowering sequence of hybrid rice affects seed vigour

摘要

Rice grains located along one panicle do not develop synchronously. Understanding of relationships between upper, middle andbasal portions and flowering positions of rice panicles with grain weight, vigour and morphology is important for high-vigour seedproduction. In this study, four rice F 1 hybrids were used to analyse grain morphology, 1000-grain weight and seed vigour. Theposition of the seed on the panicle had a significant influence on seed vigour, with upper seeds having the highest vigour, followedby middle and basal seeds. The flowering sequence within a given branch affected seed size, 1000-grain weight and seed vigour,with differences in 1000-grain weight, mainly as a function of seed length. In each hybrid, the 1000-grain weight and vigour index ofprimary branches were superior to those of secondary branches. The flowering sequence of the primary grain branch wassignificantly correlated with 1000-grain weight and seed vigour index, with the highest values recorded at second and thirdflowering positions. In secondary branches bearing fewer than four grains, 1000-grain weight and seed vigour index exhibited asignificant linear relationship with flowering sequence, in which the earliest maturing grains had the highest grain weight and vigour.When secondary branches included more than four grains, grain weight and vigour followed the same parabolic trend as in primarybranches. Our findings indicate that 1000-grain weight and seed length can be used as indices of seed vigour.