Yield performance of own-rooted 'Chandler' walnut versus 'Chandler' walnut on Paradox rootstock.

摘要

A trial planted in 1991 compares micropropagated ungrafted Chandler to those conventionally grafted onto seedling Paradox rootstock. From 1995 through 1999, own-rooted Chandler had significantly greater trunk circumference and yield than did Chandler on Paradox rootstock. Low vigour and dieback was observed in 1998 on some own-rooted trees. Lesion nematode (Pratylenchus vulnus) was extracted from root samples from the tree with dieback. Pratylenchus vulnus has been detected in soil samples taken from all the trees in the trial with the exception of a single own-rooted tree and on half of the corresponding root samples. Overall, soil nematode populations on own-rooted trees were higher (P=0.05) than on Paradox. Although six trees on Paradox rootstock have crown gall (Agrobacterium tumefaciens), no infections have been found on own-rooted trees. Own-rooted English walnut trees may have potential in areas where commonly used rootstocks (J. hindsii and J. hindsii x J. regia) are undesirable because of hypersensitivity to cherry leaf roll virus. Productivity of micropropagated Chandler suggests the commercial feasibility of growing this English cultivar on its own roots.