Abstract
A pot experiment was conducted to examine the relationship between the basal diameter of the apical dome (AD) at panicle initiation (PI) and the numbers of spikelets, primary rachis-branches (PBs), and secondary rachis-branches (SBs) on the main stems (MS), primary tillers, and secondary tillers, using two rice cultivars (panicle-number type, ‘IR72’; and panicle-weight type, ‘IR65564-44-2-2’). Plants were grown in pots (1 plant / pot) under irrigated conditions. We recorded the order of all tillers and the node at which the tillers emerged, and measured the basal diameter of AD at PI, the numbers of differentiated PBs, spikelets, and so on. In IR72, the basal diameter of AD at PI was largest on MS, whereas in IR65564-44-2-2, not only that on the MS, but also that on primary tiller from the 5 th node of the MS were larger than the others. In both IR72 and IR65564-44-2-2, the number of differentiated PBs was in the following order : MS>primary tiller>secondary tiller. As a result, there were positive correlations between the basal diameter of AD at PI and the number of differentiated PBs in both cultivars. We concluded that the basal diameter of AD at PI is related to the number of differentiated PBs, and therefore, the number of spikelets per panicle is in the following order : MS>primary tiller >secondary tiller.
