Journal of Plant Pathology Archive

Abstract:

A two-year survey (2011-2012) was conducted to determine the population composition of Fusarium species on maize (Zea mays L.) in Lombardy (northern Italy). Maize ears exhibiting typical symptoms of Fusarium ear rot (FER) (about 30%), such as white to pink colored mycelia on the tip or scattered all over the ear, were collected at harvest. Rotted kernels were surface sterilized, rinsed in sterile water, dried and placed on potato dextrose agar (PDA) amended with dichloran and antibiotics. Developed Fusarium colonies were single-spore purified and grown on Spezieller Nährstoffarmer agar (Leslie and Summerell, 2006). Based on morphological characteristics, 15 Fusarium spp. strains were identified as Fusarium subglutinans. Colonies on PDA showed a cottony aerial mycelium, initially white, becoming pinkish white. No microconidia chains were detected, conidiophores were erect and terminated in one to three phialides. Macroconidia were falcate, three to five septate, with a slightly beaked apical cell and a barely or distinct footlike basal cell. The translation elongation factor-1α (EF-1α) gene was partially sequenced for all the F. subglutinans strains using primers EF1 and EF2 (Scauflaire et al., 2011). BLASTn analysis showed that the nucleotide sequence (673 bp) of one strain (isolate GV2188, GenBank Accession No. KX156836) shared 100% sequence identity with F. temperatum (HM067689), a recently described species closely related to F. subglutinans (Scauflaire et al., 2011). Using silk channel inoculation method, F. temperatum pathogenicity was assessed on 10 maize ears (LG 32.85 hybrid) under greenhouse conditions. After 30 days, FER symptoms, i.e. whitish pink to lavender fungal growth on kernels, were observed only on inoculated ears and not on water controls. Koch's postulates were fulfilled by re-isolating the fungus from infected kernels. To our knowledge, this is the first report of F. temperatum in Italy associated with FER.