The cell regeneration and connection of grafting between pear and quince trees are defined by the cortex and phloem

Abstract

Pear cultivation in the tropics currently requires the complex use of Pyrus calleryana or Chaenomeles sinensis rootstocks with Cydonia oblonga interstocks. The objective of the present study is to quantify the different proportions of tissues in rootstock-interstock combinations established to obtain saplings. Packham's Triumph pear (scion) was double grafted by cleft grafting onto interstocks of C. oblonga and these combinations were subsequently grafted onto C. sinensis or P. calleryana rootstocks. The sprouting percentage was evaluated passed 150 days. Subsequently, the anatomy of the connections between the scion and interstock and the interstock and rootstock was examined. The following characteristics were evaluated: xylem parenchyma ray area of each grafting component (scion, interstock and rootstock); total connection area; connection areas between xylem-xylem, phloem-phloem, phloem-cortex, and cortex-cortex; percentage of xylem, phloem, and cortex for all materials; rootstock area; interstock area; scion area; rootstock/interstock connection area; interstock/scion connection area; and areas with no connection or with necrosis. The data were subjected to analysis of variance and the Scott-Knott test (P ≤ 0.05), and correlations between tissue percentages and connection areas were calculated and considered significant when R2 ≥ 0.6. Only the tissues composing the cortex and phloem were positively correlated with the connection area. The P. calleryana rootstock has greater compatibility with the interstock due to its greater proportion of cortex. The xylem parenchyma rays do not significantly influence cell regeneration or connection. Therefore, woody species that contain more cortex and phloem in the rootstock and/or scion will have greater potential for grafting success.