FIELD INVESTIGATION ON GARLIC DRY ROT

Fusarium proliferatum was signalled worldwide since 2002 as the main causal agent of garlic dry rot. According to literature, other Fusarium spp and nematodes (Ditylenchus dipsaci) could contribute to the disease. Moreover, white varieties are reported as more susceptible compared to red ones. Dry rot is considered a postharvest disease, but relevant incidence of symptomatic bulbs at harvest were also reported. The aim of this study was to investigate infection time and agent involved in garlic dry rot from field to table. Field sampling was organised in Piacenza province (north Italy), area of production of white garlic (PGI). Six field units were selected for sampling, 3 of them with an history of relevant dry rot. Soil was sampled before sowing. Garlic plants were collected in three growth stages: BBCH 15 (5th leaf clearly visible), BBCH 45 (50% of the expected bulb diameter reached), BBCH 49 (Leaves dead, bulb top dry; growth complete). With soil, serial dilutions and colony forming units count (CFU) were performed so as nematode counting. Direct isolation from symptomatic and asymptomatic plants was managed, so as the identification at species level for a selected set of fungal strains. PCR was applied to confirm fungi and nematode identification. Ditylenchus dipsaci was not detected in soil in autumn. Regarding fungi, the largely dominant species were F.proliferatum and F.oxysporum, isolated since BBCH 15, increasing in incidence from early growth stages to harvest. F. proliferatum seems confirmed as the candidate most relevant causal agent of dry rot, infecting bulbs early in field.