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Phytophthora collar rot of apple: influence of the rootstock on scion variety resistance
Author(s) -
SEWELL G. W. F.,
WILSON J. F.
Publication year - 1973
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1973.tb07735.x
Subject(s) - rootstock , biology , dwarfing , horticulture , botany
SUMMARY In field experiments with young trees great differences were found in the resistance to Phytophthora cactorum of Cox's Orange Pippin apple scions grafted on different clonal rootstocks. The rootstock effect on scion resistance was inversely related to the effect on tree vigour: the rootstocks inducing high resistance were dwarfing (M. 9) or semi‐dwarfing (M. 7, M. 26, MM. 106), and those inducing low resistance were vigorous or very vigorous (M. 25, MM. 104, MM. 109). Mean lesion lengths in Cox on MM. 104 were five to eight times greater than those in Cox on M. 9. The rootstock influence on scion resistance was associated primarily with effects on the rate of lesion extension: during the early stages only of host colonization there appeared to be threshold extension rates below which host resistance factors effectively suppressed a large proportion of infections. The influence of the root‐stock on scion resistance was apparently unrelated to inherent rootstock resistance. On all rootstocks Cox showed diminished resistance to infection during the period from the swelling of buds to the early stages of shoot growth. Although most susceptible during the ‘mouse‐ear’ and ‘pink bud’ stages of development, suscpetibility was not associated with flowering per se. Rootstock type did not affect the resistance of Cox scions to P. syringae , for which the period of susceptibility to infection occurred in the dormant season.