PHYLOGENETIC SPECIES OF THE Fusarium graminearum COMPLEX: AGGRESSIVENESS OF STRAINS IN INOCULATION TRIALS ON MAIZE EARS

BELIZAN, MELINA; GALVEZ, CAROLINA ELIZABETH DEL VALLE; CATALÁN, CESAR; SAMPIETRO, DIEGO

Jornada; XXXIV Jornadas Científicas Asociación de Biología de Tucumán; 2017

Fusarium graminearum (Fg) produces rot in maize ears, reducing the yield of grain yield and contaminating it with trichothecenes, mycotoxins that are toxic when ingested at certain doses by humans or animals. In maize crops located in the Argentine Northwestern Region, several phylogenetic species belonging to the F. graminearum morphological species were identified and described. We are not yet aware of their phenotypic behavior, especially as far as their pathogenesis and aggressiveness related to maize is concerned. In this study, pathogenesis and aggressiveness of the Fg complex phylogenetic species on maize genotypes have been studied. Inoculation trials were conducted in CER-INTA Leales plots that had been sown in January (2013/14 and 2014/15 seasons) and in September (2016/17 season). Macroconidial suspensions of the following phylogenetic species strains were prepared and inoculated: F. graminearum sensu stricto (Fgss), F. boothii (Fb) and F. meridionale (Fm). Inoculations were made by injecting 1×105 macroconidia/mL suspensions into the silk channel of female ears. Disease severity was assessed in the physiological maturity stage of the grains by means of a scale based on the percentage of the ear surface covered by rot. The followings severity degrees were observed: >75% (Fgss, 2013/14; 2014/15; Fb, 2013/14), 51-75% (Fgss, 2016/17; Fb, 2014/15; Fm, 2013/14; 2014/15), 26-50% (Fb, 2016/17) and 11-25% (Fm, 2016/17). Our results indicate that the strains of all the phylogenetic species were pathogenic, Fgss being the most aggressive one. Maize ears from the 2013/14 and 2014/15 seasons were more susceptible to the studied species than those of the 2016/17 season.