In a citrus rootstock trial planted in South Australia in 1997, the combination of Navelina 7.5 (Spanish clone) on C35 citrange started to fail after around 15 years. Of the original 9 trees, 7 have died, and the 2 that are still alive are in poor health. They show a clear crease under the bark at the bud union, indicating incompatibility (see photo).
These are some of the oldest trees of this combination in Australia, but I have been told by some in the industry that reports of a similar problem have emerged from overseas, although I can find no literature to confirm this. Can anyone provide a published paper, or failing that some unpublished information showing this problem happenning elsewhere?
Mark can you supplement some information on nature of soil that is used. the photograph , you have provided is not sufficiently displaying incompatibility , since ratio rootstock -to-scion ratio seems to perfectly alright . Do you feel it is a typical incompatibility issue or any other issue.
Dear Anoop, the soil is sandy loam over sandy clay loam with high pH and the rootzone is a little shallower than recommended, so the soil has been mounded in the tree row.
However, there are 3 scion varieties (all navel orange) and 8 rootstocks in the planting, giving 24 combinations, and most of these are growing strongly and yielding well. As a result I am convinced this is incompatibility, but it is possible that the expression of incompatibility is promoted by the marginal soil conditions, and may not appear, or may be delayed, under better planting conditions.
Significantly, the other 2 navel orange scions are performing quite adequately on C35 so far, with all trees alive and flourishing, whereas 7 of 9 Navelina trees on C35 are dead.
Thankyou for your interest.
Dear Mark
from my reads i notice that this root stock showed symptoms like what you talk about when imperial mandarin budded on this rootstock.It may be due to delayed incompatibility between it and many citrus cultivars belong to many citrus species ,or to something related with soil environment or specific ion toxicity.
best regards
Ali Alhayany
Ali, thankyou for your contribution to this discussion. There certainly are many examples of problems with citrange rootstocks under a range of mandarins.
Regards, Mark
Hi Mark,
In Corsica we recently use C35 Citrange as a rootstock (since 2005-2006) mainly for Clementina. We have a trial with navel oranges but it's less than 10 years old trial. So far, we didn't see any compatybility problem. The only one problem with C35 Citrange is his low true to type ratio, a lot of zygotic trees appear after seedling and must be detected before any trial plantation.
Best regards
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