Waterlogging tolerance in apple trees grafted on rootstocks from G, CG, and M series

Abstract

This study was performed to evaluate the waterlogging tolerance of Cornell-Geneva (G11, G202, G214, G935, CG4814, and CG5087), M26, and M9 apple rootstocks. After grafting ‘Fuji’ scions on each type of rootstock, grafted trees were planted in 17-L pots and grown in a greenhouse under well-irrigated conditions. Sixteen weeks after planting, grown trees were divided into two groups: one group was drip-irrigated daily with 2 L of water (control treatment, CT), and the other group was waterlogged by repeating flooding and drainage at 1- to 3-day intervals for 4 weeks (waterlogging treatment, WT). After the cessation of flooding, trees were irrigated as in CT for 18 days. Trees grafted on G202, G214, and M9 had markedly lower leaf water potential than CT trees on the 27th day of flooding; predawn leaf water potential was − 1.26 to − 1.45 MPa in WT trees and − 0.30 to − 0.32 MPa in CT trees, and midday leaf water potential was − 2.85 to − 3.03 MPa in WT trees and − 1.83 to − 1.87 MPa in CT trees. This difference persisted until the 18th day after the cessation of flooding. The net photosynthetic rate and stomatal conductance of trees grafted on these rootstocks were also extremely low in WT trees, and they did not recover to the corresponding levels in CT trees until the 18th day after the cessation of flooding. Among WT trees, the height, trunk cross-sectional area, and dry weight of G202, G214, and M9 trees were markedly lower than those of trees grafted on other rootstocks, whereas CG4814 trees showed the least reduction in these parameters. The defoliation percentages of G202, G214, and M9 trees were 22%, 23%, and 35%, respectively, in WT trees, whereas trees grafted on other rootstocks had 4 to 9% defoliation. Thus, G202 and G214 trees showed similar sensitivity levels as M9 trees, whereas CG4814 trees were more resistant to flooding than M26 trees, and G11, G935, and CG5087 trees showed a waterlogging tolerance comparable to M26 trees.