Identification, pathogenicity and distribution of Penicillium spp. isolated from garlic in two regions in Argentina

A total of 147 samples of garlic (Allium sativum) bulbs affected by blue mould were obtained from a variety of agroclimatic districts between December 1999 and February 2000. Penicillium species were identified using both morphological and chemotaxonomic characteristics. Penicillium allii was the predominant species isolated (81.8%) in this survey and the only species proven to be pathogenic on garlic. Other species were isolated much less frequently: P. chrysogenum (13.7%), P. brevicompactum (2.8%), P. phoeniceum (0.9%), P. aurantiogriseum (0.6%) and P. flavigenum (0.2%). Colonies of P. allii could be classified into four morphotypes and their distribution seemed to be influenced by seed trade and agricultural practices. Penicillium allii isolates were grouped into three aggressiveness phenotypes (low, medium and high) based on their ability to cause disease during field trials on susceptible (Fuego INTA) and less susceptible (Cassano INTA) garlic cultivars. The number of surviving plants at 191 days after planting and postharvest bulb weight contributed the most towards aggressiveness modelling.