In March of 2007 a group off scientists and staff from the University of California and the Lindcove Research and Extension Center made an annual inspection of the mother trees in the CCPP Foundation & Evaluation Blocks. This inspection is part of the overall maintenance of the CCPP Foundation collection of budwood source trees. Fruit and trees in the collection are carefully inspected several times annually by scientists and researchers who evaluate each tree for overall health and growth characteristics. Researchers are also looking for growth abnormalities, disease symptoms, and bud sports during this survey.

The inspection team identified abnormal gall growth on the scions of two trees of VI 627 CARTE NOIR CLEMENTINE. These trees are propagated on Carrizo citrange rootstocks and were planted in the Foundation Block in the year 2000. The trees showed good overall growth (Pict. 1) but woody galls were present at the bud-union area and above (Pict. 2).

Picture 1
Photograph by: G. Vidalakis

Picture 2. Photograph by: G. Vidalakis

Closer observation revealed that the galls extend from the bud-union area, where they were clearly above the bud-union while smaller galls were also evident on the main limbs of the scion (Pict. 3). The galls were giving growth to a number of non-trifoliate suckers, supporting the observation that the galls developed on the scion from the bud-union upward (Pict. 4).

Photograph by: G. Vidalakis. Picture3    Picture 4. Photograph by: G. Vidalakis

VI 627 CARTE NOIR CLEMENTINE was received into quarantine at CCPP from INRA-CIRAD, Corsica, France as SRA 646 in March of 1997. This variety tested negative for tristeza, psorosis and citrus viroids upon arrival in quarantine at CCPP. CCPP protocol dictates that all foreign imports undergo thermaltherapy, or heat therapy to eliminate potential pathogens that may be present. In September of 1997 Carte Noir entered thermaltherapy and then in November of 1998 this variety entered the final VI Index. The thermaltherapy treated variety tested negative for all known graft transmissible diseases of citrus (including vein enation/woody gall virus) and was released from State and Federal quarantine in October of 1999. The Foundation Block trees were planted in 2000 and were retested as a condition for CDFA Registration for budwood distribution in 2003. Budwood was first distributed from the two registered Foundation Block trees in January of 2004. Since first being planted in 2000 these trees have continued to test negative for tristeza, psorosis and citrus viroids. A total of 524 buds have been distributed since the first registration date. Other CCPP trees of this variety planted in Riverside and elsewhere have also formed galls.

In order to prevent the spread of any potential unknown graft transmissible agent and to investigate further the cause of the woody galls observed on the scions of CCPP trees of VI 627 the CCPP has taken the following actions:

1. Immediately suspend all distribution of budwood of VI 627 Carte Noir Clementine by the CCPP.
2. Budwood samples have been taken from all CCPP trees of VI 627 and have been reintroduced by CCPP into diagnostic and therapy procedures. This variety will be completely retested.
3. Woody gall samples are now being tested for the presence of fungal pathogens, phytoplasmas and other graft transmissible pathogens known to induce gall formation in citrus.
4. Trees in other CCPP field plots are being investigated for the presence of similar abnormalities.
5. Contact INRA-CIRAD, Corsica, France for additional background information as well as variety status in Corsica plots.
6. Contact other quarantine programs and citrus researchers around the world who grow this variety to see if similar symptoms have developed elsewhere.

The CCPP would like to ask any nursery or grower that maintains VI 627 CARTE NOIR CLEMENTINE as a source tree or trees, or who are growing this specific variety, to observe the bud-union area and main scion limbs above for the presence of woody galls similar to those presented in the pictures here. Please contact the CCPP via phone (951 827 3763 or 951 684 8580) or e-mail (ccpp@ucr.edu) regarding any observations, either positive or negative. Any information of this type will be confidential and will be very useful to us in helping to determine the cause of these galls. The CCPP would like to know the age and condition of trees of this variety, even if the trees are not propagated on Carrizo rootstock. Also, if such galls are found to be present we would like to ask, as a precaution, that further propagation of this variety be discontinued until this situation is resolved by us.

The CCPP will continue to investigate this issue in depth and will keep the citrus community updated with the findings.