First report of Penicillium allii as a field pathogen of garlic (Allium sativum)

Abstract

Blue mould disease in garlic ( Allium sativum ) is associated worldwide with various Penicillium species, and has been attributed to significant annual crop losses in Argentina; the world's second largest exporter of garlic. To identify the pathogenic Penicillium species responsible, affected plants were sampled in La Consulta station (33 ° 45 ′ S, 69 ° 02 ′ W) and placed in a damp chamber. Characteristic disease symptoms are stunted and chlorotic plants with withered leaves and reduced bulb size. Bulbs are often covered with blue/green conidial masses. Isolations were made from fungal colonies emerging on affected bulbs. Pure cultures (IBT 26466, 26467, 26511 and 26512; CMB collection, BioCentrum-DTU, Denmark) were initially identified by micromorphology as Penicillium allii , and identifications were confirmed by comparing reversed phase-HPLC secondary metabolite profiles with those of P. allii type strains.To confirm pathogenicity, sterilized garlic cloves were injured with a needle and inoculated with 5 µ L P. allii spore suspensions (adjusted to 5 × 10 6 conidia mL − 1 ). Inoculated cloves were planted in a field not previously cultivated with garlic, and the original disease symptoms were produced on inoculated plants while water-inoculated control plants remained healthy. The survival rate of inoculated plants was 68% and P. allii was reisolated from diseased field plants.Penicillium viridicatum was first reported as the causal agent of blue mould of garlic in Argentina (Gatica & Oriolani, 1984) before the characterization of P. allii (Vincent & Pitt, 1989). Penicillium allii is micromorphologically similar to P. viridicatum and both species produce yellow exudates in pure culture. To compare pathogenic ability, standard P. viridicatum strains IBT 16939 and 15053 were inoculated into sterilized garlic cloves and incubated for 12 days. The P. viridicatum strains were not able to sporulate on the garlic cloves.Penicillium hirsutum was recently reported as a pathogen on garlic in Argentina (Cavagnaro et al ., 2005). However, P. allii but not P. hirsutum has been reported as an aggressive pathogen of garlic in comparative pathogenicity trials conducted in damp chambers (Overy et al ., 2005). The results reported here suggest that P. allii , rather than P. hirsutum or P. viridicatum , is the pathogenic species responsible for garlic crop losses due to blue mould rot in Argentina. This is the first report confirming P. allii as a field pathogen of A. sativum.

Pathogenic Fungi in Garlic Seed Cloves from the United States and China, and Efficacy of Fungicides Against Pathogens in Garlic Germplasm in Washington State

“…(2005) found that amongst several isolates in their collection, only those identified as Penicillium allii Vincent & Pitt were strongly pathogenic to garlic, and that isolates bearing the name P. hirsutum were not very aggressive. Valdez et al. (2006) thought the name P. allii preferable to P. hirsutum for those isolates pathogenic to garlic in Argentina.…”

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

“…However, since then P. corymbiferum has been subdivided into several different species contained within the Penicillium series Corymbifera (with synonymy of the original P. corymbiferum characterization aligned with that of P. hirsutum ). In Argentina, P. viridicatum (Gatica & Oriolani, 1984), P. hirsutum (Cavagnaro et al ., 2005) and P. allii (Valdez et al ., 2006) have all been reported as garlic pathogens. Penicillium viridicatum has also been reported from garlic in Japan (Saito & Tsuruta, 1984) and Poland (Machowicz‐Stefaniak et al ., 1998), although in the Polish study pathogenicity of the isolates was not confirmed.…”

“…Penicillium viridicatum has also been reported from garlic in Japan (Saito & Tsuruta, 1984) and Poland (Machowicz‐Stefaniak et al ., 1998), although in the Polish study pathogenicity of the isolates was not confirmed. Recently, doubt has been raised regarding the correct taxonomic identification of the reported P. viridicatum causal agents, as the P. viridicatum strains ATCC 9635 (Smalley & Hansen, 1962), IFO 7736 = CBS 390·48 ex‐type (Saito & Tsuruta, 1984), IBT 15053 = CBS 101034 and IBT 16639 (Valdez et al ., 2006) failed to establish a colony or to sporulate on infected garlic bulbils in damp chambers. As P. allii and P. viridicatum are macro‐ and micromorphologically quite similar, it is possible that the P. viridicatum isolates previously reported as causal agents were in fact P. allii .…”

Metagenomic analysis of soil fungal communities on Ulleungdo and Dokdo Islands

“…genera Chromocleista and Penicillium of the class Eurotiomycetes were higher in the Dongdo sample than in the Ulleungdo and Seodo samples. The genus Penicillium comprises saprophytic, pathogenic, and/or endophytic fungi (da Costa et al, 1998;Khan et al, 2008;Samson et al, 2004;Valdez et al, 2006). Interestingly, the genus Gibberella of the class Sordariomycetes was only detected in the Dongdo and Seodo samples.…”

“…The family Herpotrichiellaceae of the class Eurotiomycetes of Ascomycota was present at high levels only in the Dongdo sample, whereas the family Trichocomaceae comprised greater than 1.0% of all families detected in the Dongdo and Seodo samples. Members of Herpotrichiellaceae have been characterized as human pathogens (de Hoog et al, 2003;Haase et al, 1999), while members of Trichocomaceae maintain saprophytic, pathogenic, and/or endophytic characteristics (da Costa et al, 1998;Khan et al, 2008;Samson et al, 2004;Valdez et al, 2006). The families Clavicipitaceae and Hypocreaceae of the class Sordariomycetes of Ascomycota were slightly more abundant in the Dongdo sample than in the Ulleungdo Fungal classes with a relative abundance greater than 1% in at least one of the three samples are shown.…”