Venturia populina, first described on European Populus nigra, has been thought to be the only species of Venturia in Europe and North America to cause leaf and shoot blight of balsam poplars and cottonwoods in Populus sects. Tacamahaca and Aigeiros. The species of Venturia occurring on introduced @entity18033 and native @entity26340 in the Pacific northwest were examined. Venturia populina was consistently found on @entity18033 (i.e. the widespread @entity18033 cv. 'italica') in the region, but V. inopina sp. nov. was present on native @entity26340 and its hybrids. There were neither examples of V. populina on @entity26340 and its hybrids nor of V. inopina on @entity18033 cv. 'italica' (27 collections from 16 sites in Oregon, Washington, and Vancouver Island were made during 1995-2002). In an inoculation study, host-range separation was confirmed in that V. inopina caused sporulating leaf lesions on @entity26340 and its hybrids, but only non-sporulating lesions on @entity18033 cv. 'italica'. These two species of Venturia can readily be distinguished by conidial septation; V. populina is primarily 2-septate, whereas V. inopina is primarily 1-septate. Growth rates on PDA at 15 degrees C, and ITS sequences (2.3% divergence) were also distinct in isolates of these congeners. Conidial shape was of more value in discriminant analysis than conidial length. Venturia inopina is homothallic, given the sexual fertility of cultures of single ascospores that were overwintered under ambient conditions. Its geographic range appears to be restricted even within the Pacific northwest, leaving open the possibility that still other undescribed, native species of Venturia occur elsewhere in North America on sects. Tacamahaca and Aigeiros.

Native Venturia inopina sp. nov., specific to XXXX and its hybrids.

@entity26340 :: ('3694', 'Species') :: ['P. trichocarpa'] @entity18033 :: ('497908', 'Species') :: ['P. nigra']
@entity26340 :: (3694,Species) :: ['Populus trichocarpa']
