Impact of rootstock and interstems on fine root survivorship and seasonal variation in apple

Abstract

Both the production and longevity of fine roots have great impacts on the growth and development of fruit trees. To determine whether different dwarfing rootstocks and interstems could affect fine root longevity, root diameter, and peak-production season, minirhizotrons were used to examine root production, senescence, and mortality over two years in six apple (Malus domestica Borkh.) rootstock/interstem combinations. Fine root longevity was significantly affected by diameter, season of born and rootstock/interstem combinations. Fine roots on three dwarfing rootstock combinations, Dwarfing-Red Fuji/M9, Dwarfing-Red Fuji/SH40, and Dwarfing-Red Fuji/Malus xiaojinensis, had smaller diameters and shorter lifespans than the Vigorous-Red Fuji/Baleng Crab combination. Insertion of a dwarfing interstem in the Red Fuji/M9/Baleng Crab and Red Fuji/SH40/Baleng Crab combinations did not significantly change the diameter or longevity of fine roots. The dwarfing rootstock combination Dwarfing-Red Fuji/SH40 did not have an autumn peak like others. The lifespan of fine roots differed significantly among seasons. Fine roots produced in autumn had longer lifespans regardless of rootstock/interstem combination.