Abstract
Differences in floral morphologies affect pollination behaviour in many flowering plants. In the genus Oryza, several differences in the size of floral organs are known. In this study, we focused on the differences in the size of floral organs between common cultivated rice, Oryza sativa L. and its wild ancestor, O. rufipogon. We compared floral morphologies between cultivated rice O. sativa cv. Nipponbare and O. rufipogon W630. We first evaluated temporal changes in filament and anther lengths. W630 had longer filaments with rapid elongation within 15 min after spikelet opening. W630 also had longer anthers than Nipponbare, and size of anther was consistent throughout all time examined. We also analysed other six floral traits, and found that W630 had higher stigma and style length, as well as lemma and palea length, but lower lemma and palea width. Quantitative trait locus (QTL) analysis was performed to identify the loci controlling these floral traits, using backcross recombinant inbred lines derived from a cross between Nipponbare and W630. A total of 11 significant QTLs were identified. Of these, two pairs of QTLs for lemma and palea length and one pair for lemma and palea width overlapped, suggesting that common genetic factors may be the reason for the differences in these traits. In addition, we performed QTL analysis for grain size, and found that QTLs for grain size coincided with those for lemma and palea size, indicating that grain size is partly controlled by glume capacity. The QTLs identified in this study will be informative for understanding genetic changes associated with rice domestication.
Highlights
Floral morphologies are important factors determining mating systems in many plant species [1]
We focused on the differences in the size of floral organs between common cultivated rice, Oryza sativa L. and its wild ancestor, O. rufipogon
The differences in the size of floral organs between common cultivated rice O. sativa and Asian wild rice O. rufipogon are of interest as the former is known to be domesticated from the latter [7]
Summary
Floral morphologies are important factors determining mating systems in many plant species [1]. The differences in the size of floral organs between common cultivated rice O. sativa and Asian wild rice O. rufipogon are of interest as the former is known to be domesticated from the latter [7]. Wild rice O. rufipogon exhibits outcrossing behaviour, while cultivated rice O. sativa has self-pollination behaviour [8]. This difference in pollination behaviour was likely mediated by the selection of the naturally occurring mutations during rice domestication. An interesting change affecting pollination behaviour in rice is a closed panicle trait, which was selected in the early stages of domestication to increase seed harvesting efficiency [9]. Apart from the differences in panicle shape, distinct characteristics associated with pollination behaviour are observed between wild and cultivated rice. We evaluated the grain size and performed QTL analysis to access whether the loci related to grain size are linked to those controlling floral morphologies
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