Biological properties of some isolate's of Barley mild mosaic virus

Since several years in France, BaMMV variants in high concentration infecti ng ym4 barley cultivars have been detected in TAS-ELISA using monoclonal an tibodies. In 1996, 1997 and 1998, plants with mosaic symptoms from six susc eptible and six resistant cultivars to the common European strain of BaYMV and BaMMV were collected in GO fields from different barley crop areas. In the resistant cvs. 'Express','Labea', 'Maeva', 'Majestic' and 'Rejane', BaM MV is present alone in more than 40 % of infected plants whereas in 'Sunris e' resistant cultivar it is always associated to BaYMV. Forty isolates of BaMMV (29 from susceptible and 11 from the resistant cult ivars), BaMMV-Kal from Japan and Bah IMV-MF, a laboratory isolate from Fran ce, have been mechanically inoculated to the cv. 'Express' and to the susce ptible cv. 'Magie'. None of these BaMMV isolates have been transmitted to c v. 'Express'. Infection to cv. 'Magie' succeeded for only nine BaMMV isolat es, which contaminate naturally both susceptible and resistant cultivars. Stability and multiplication of these isolates have been compared on cv. 'M agie'. Some of the isolates from susceptible or resistant cultivars are pro gressively lost after four successive transmissions whereas BaMMV-Kal and B aMMV-MF are stable. The ability to be repetitively transmitted from both su sceptible and resistant cultivars is only partly dependent on their concent ration in the primary inoculated plants.