Abstract

‘Yunnan’ quince (Cydonia oblongaMill.) is used as the dwarfing rootstock for pear (Pyrusspp.). Here, we reported that the sugar contents in mature ‘Zaosu’ pear fruit grafted on ‘Yunan’ quince (Z/Q) were higher than that in ‘Zaosu’ pear fruit grafted on ‘Duli’ (Pyrus betulifolia) (Z/D). To investigate the underlying mechanism, the leaf photosynthetic capacity and the leaf-to-fruit assimilate transport capacity were initially analyzed. The leaf photosynthetic capacity was similar between Z/Q and Z/D, but the assimilate transport capacity was greater for Z/Q than for Z/D. Sugar transporters mediate the distribution of assimilates; therefore, changes inPbSWEETtranscriptional patterns were examined.PbSWEET6was highly expressed in Z/Q fruit. Thus, thePbSWEET6function related to assimilate transport was further verified. Sucrose and glucose contents increased in transgenic tomato fruit and pear fruit calli overexpressingPbSWEET6. Taken together, these results suggest that ‘Yunnan’ quince positively regulated fruit sugar contents by influencing the flow of PbSWEET6-involved assimilates in the scion.Keywords:graft;PbSWEET6;sugar transport;‘Zaosu’ pear;Cydonia oblonga