Apple proliferation (ApP) is caused by the unculturable, wallless bacterium Candidatus Phytoplasma mali. ApP induces a range of symptoms that are either nonspecific, such as foliar reddening and yellowing, growth suppression, and undersized fruit, or specific, such as witches’-brooms, rosettes, and enlarged stipules. The disease is vectored mainly by the psyllids Cacopsylla picta and C. melanoneura.
The DAS-ELISA reagents (1) consist of monoclonal antibodies, made against an Italian strain of ApP (2) and specifically recognize ApP in apple. Most ApP isolates (from several locations in Italy and Germany) were detected with this reagent. Recently, however, some isolates belonging to the AT-1 subtype, were shown not to be recognized with these antibodies (4).
The concentration of ApP varies during the year. The highest phytoplasma concentration is found in veins of apple leaves late in the growing season; in some favorable (mild winter) climates, good detection might be possible already during summer.
For increased sensitivity, we suggest cutting out the veins from the apple leaves. The veins should then be homogenized at a 1:10 (w/v) ratio in extraction buffer «General» (Art. No. 110120). Cambium from dormant wood of 1-3 years old branches can also serve as sample source. For testing, use either fresh tissue (fresh extracts) or frozen extracts, because the antigenic activity is completely lost during freezing of intact leaves but maintained in frozen extracts (3).
The product was developed in cooperation with the University of Udine, Italy
