2º Congreso Argentino De Fitopatología Libro de Resúmenes

2 º Congreso Argentino de Fitopatología
IDENTIFICATION AND PATHOGENICITY OF ARGENTINEAN
SEED-BORNE Fusarium ISOLATES OF ONION SEEDS
J.G. Valdez 1 , P. Caligiore Gei 1,2 , U. Thrane 3 . 1 EEA INTA La Consulta, 2
CONICET, 3 CMB, DTU Systems Biology, Kongens Lyngby, Denmark.
jvaldez@laconsulta.inta.gov.ar
When seeds are contaminated with Fusarium, the fungi are transferred
from seed to soil, infecting subsequent cultures. This work was carried
out to study the identification, distribution and pathogenicity of Fusarium
seed-borne strains. Seed health tests were made on 60 seed samples
and 191 Fusarium strains were isolated. They were characterized by
morphology on PDA and SNA. Pathogenicity trials were conducted to
evaluate damping off (surveyed strains: 134). Cluster analysis was
performed and seven clusters obtained. Three isolates per cluster were
identified using secondary metabolites HPLC profile. Additionally, 55
pathogenic isolates were characterized by microscopic features such
as mono- or poly-phialides, presence or absence of chlamydospores
and disposition of microconidia (in chains or false heads). In total,
62 isolates were identified, 59 as F. proliferatum, 2 as F. oxysporum
and one as F. verticillioides. Isolates were sorted into five pathogenic
classes. The classes were distributed over the whole area. However,
Pocitos and Iglesias in San Juan province, and Maipú and San Carlos
in Mendoza, registered the most aggressive isolates. Fusarium
proliferatum was placed on classes: PC3, 26 isolates, PC4, 23 isolates
and PC5, 2 isolates. PC5 was the most aggressive class. The role
of seeds on the transmission of Fusarium basal rot would be related
only to the species F. proliferatum, while F. oxysporum would play its
principal role after the establishment of the crop. The F. verticillioides
strain resulted non pathogenic in this assay.
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