First report of Fusarium andiyazi causing ear rot on maize in Italy

The Fusarium species complexes F. graminearum (FGSC) and F. fujikuroi (FFSC) can cause maize (Zea mays L.) seed decay, seedling blight, root, stalk, kernel, and ear rots. Fusarium infections of maize can result in accumulation of harmful mycotoxins in maize kernels (Leslie and Summerell 2006). A 2-year survey from 2011 to 2012 was conducted to determine the composition of Fusarium species on maize in Lombardy (northern Italy) (Venturini et al. 2015). A total of 1,280 maize ears were collected at harvest; symptoms associated with Fusarium ear rot (FER), white to pink colored mycelia on the tip or scattered all over the ear, were observed on about 30% of the ears. Symptomatic kernels were surface-treated with ethanol (70%) and NaOCl (10%) for 5 min, and rinsed in sterile water. Dry kernels were placed on potato dextrose agar (PDA) amended with dichloran and antibiotics. The plates were incubated at 25°C for 5 days in the dark and microscopically examined to identify Fusarium colonies. Single-spore Fusarium colonies were grown on Spezieller Nährstoffarmer agar (SNA) at 22°C for 7 days under combined visible and ultraviolet light (Leslie and Summerell 2006). Fusarium species were identified based on morphological traits and sequence identity of the translation elongation factor-1α (EF-1α) gene (O’Donnell et al. 2012). Among FFSC isolates (840 strains), the most frequently identified species were F. verticillioides (72%) and F. proliferatum (19%). Moreover, FFSC strains GV2061 and GV2358 were attributed to the species F. andiyazi and were isolated from symptomatic kernels together with F. verticillioides and F. proliferatum. This species, first described on sorghum in Africa and the United States (Marasas et al. 2001), has been recently associated with FER on maize in China and Mexico (Zhang et al. 2014; Leyva-Madrigal et al. 2015). F. andiyazi colonies on PDA showed a floccose to powdery mycelium, initially white, becoming purple with age. Abundant 0-septate microconidia, born in long chains or false heads, were ovoid with a truncate base, size 5.1 to 22.5 ×1.5 to 4.0 μm. Macroconidia were hyaline and straight or slightly curved, mostly 3-septate with a barely curved apical cell, size 28.5 to 61.0 × 1.6 to 4.0 μm. Chlamydospores were absent. BLASTn analysis revealed that strains GV2061 and GV2358 share 100% EF-1α gene sequence identity with F. andiyazi strains (JF270290 and KT257545, respectively). The partial EF-1α gene nucleotide sequences of the strains GV2061 (665 bp) and GV2358 (674 bp) were deposited in GenBank as accession nos. KX982665 and KX982664, respectively. Koch’s postulates were completed for F. andiyazi isolates under greenhouse conditions. Using silk channel inoculation method and a conidial suspension of 106 conidia/ml, F. andiyazi pathogenicity was assessed on 10 maize ears (LG 32.85 hybrid) per isolate. Ten control ears were inoculated with sterile water. After 30 days, FER symptoms, such as whitish pink to lavender fungal growth on kernels, were observed on inoculated ears and no symptoms were observed on water controls. As far as we are aware, this is the first report of F. andiyazi in Italy associated with FER on maize.