Abstract
Seed weight is a very important and complex trait in rapeseed (Brassica napus L.). The seed weight of rapeseed shows great variation in its natural germplasm resources; however, the morphological, cytological and genetic causes of this variation have remained unclear. In the present study, nine highly pure inbred rapeseed lines with large seed weight variation and different genetic backgrounds were selected for morphological, cytological and genetic studies on seed weight. The results showed the following: (1) Seed weight showed an extremely significant correlation and coordinated variation with seed size (including seed diameter, seed surface area and seed volume), but it showed no significant correlation with bulk density, which suggests that seed weight is determined by size rather than bulk density. (2) Seed weight showed a higher correlation with the cell numbers of seed coats and cotyledons than the cell sizes of seed coats and cotyledons, which suggests that cell number is more tightly correlated with final seed weight. (3) Seed weight was mainly controlled by the maternal genotype, with little or no xenia and cytoplasmic effects. This is the first report on the morphological and cytological causes of seed weight natural variation in rapeseed. We concluded that the natural variation of seed weight is mainly controlled by maternal genotype. This finding lays a foundation for genetic and breeding studies of seed weight in rapeseed and opens a new field of research on the regulation of seed traits in plants.
Highlights
Seed weight is an important trait with respect to plant evolution and crop improvement
(2) Seed weight showed a higher correlation with the cell numbers of seed coats and cotyledons than the cell sizes of seed coats and cotyledons, which suggests that cell number is more tightly correlated with final seed weight
We concluded that the natural variation of seed weight is mainly controlled by maternal genotype
Summary
Seed weight is an important trait with respect to plant evolution and crop improvement. The relative contributions of maternal and xenia effects are of fundamental interest in genetic and breeding studies [9] These effects have not yet been investigated for seed weight in rapeseed (Brassica napus L.). The weight of seeds shows a large variation (%4-fold) in rapeseed natural germplasm resources [10, 11] Whether this variation is caused by changes in seed volume and/or bulk density as well as changes in cell size and/or cell number remains unexplored. In this present study, the natural variation of seed weight in rapeseed was systematically investigated at the morphological, cytological and genetic levels. The main objectives were to (1) select several representative rapeseed inbred lines for seed weight study, (2) investigate the morphological and cytological causes of the natural variation in seed weight, (3) determine the maternal and xenia effects on the natural variation of seed weight using a subtle experimental design, and (4) estimate the effects of maternal genotype and cytoplasm on seed weight
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