DETECTION AND BIODIVERSITY OF CUCUMBER MOSAIC CUCUMOVIRUS CONCLUSIONS FROM A RINGTEST OF EUROPEAN UNION COST 823 NEW TECHNOLOGIES TO IMPROVE PHYTODIAGNOSIS
The detectability and biodiversity of 44 isolates of cucumber mosaic virus (CMV), one isolate of peanut stunt virus (PSV) and one of tomato aspermy virus (TAV), all cucumoviruses, were compared by RT-PCR, variants of ELISA using polyclonal and monoclonal antibodies (Pabs and Mabs) and host plant reactions. The comparisons were made during a Ringtest on zucchini viruses held at the Istituto di Fitovirologia Applicata, CNR, Torino, Italy, in October 1996 in the framework of the European Union action COST-823 «New technologies to improve phytodiagnosis». The isolates originated from 9 European countries, America, Asia and Australia and their natural hosts were mainly cucurbits. Some of the isolates had been characterized previously. RT-PCR with primers specific for CMV RNA 3 followed by digestion with MspI allowed the classification of 19 isolates within subgroup I (S-I) and 13 in subgroup II (S-II). Three distinct and different S-I-like patterns were found for 8 isolates, while 3 isolates displayed a new pattern called S nonI-nonII. PSV, TAV and one isolate were not amplified with this primer set. Three RNA 2-based sets of primers, specific for S-I, SII or both, substantiated the above results. In DAS ELISA Pabs produced against S-I detected most of CMV isolates, but not PSV and TAV, whereas Pabs produced against S-II isolates detected mainly those. In ACP ELISA, two Pabs detected all the cucumoviruses tested. In TAS ELISA, 7 Mabs reacted with most of the isolates and none of them reacted with PSV and TAV. Two Mabs were specific for S-I and two for S-II, confirming the PCR results. The isolates induced symptoms of different severity after inoculation to zucchini, Nicotiana benthamiana, N. clevelandii, N. glutinosa, N. tabacum and Chenopodium quinoa but no correlation was found with subgroup type. Seven S-I isolates and one S-II isolate gave systemic infection on C. quinoa.