Effect of phlobaphene accumulation in maize kernel on Fusarium ear rot level in Lombardia

Fusarium ear rot (FER) is one the most serious maize fungal diseases especially in Lombardia, the most important maize producer region in Italy. The main aetiological agents of FER are Fusarium species belonging to Gibberella fujikuroi species complex, in particular F. verticillioides and F. proliferatum. FER usually does not lead to significant yield losses, but its causal agents are well known producers of mycotoxins such as fumonisins. Control measures in Italy consist of one - two treatments against the European corn borer, but additional preventive means are required in order to assure a more effective protection. Breeding efforts have been undertaken to increase resistance to FER and in particular phlobaphenes seem to be able to reduce the fumonisin accumulation in kernels. The aim of this study was to assess the effect of pericarp phlobaphenes on FER rating under field conditions. Two hybrids, one with P1-rr allele providing pigmentation in pericarp and the other carrying P1-wr allele without phlobaphenes accumulation in pericarp, were sown in 2011 and 2012 in four different locations in Lombardia. The frequency and severity of FER, together with the incidence of latent infections caused by G. fujikuroi clade and the fumonisin content, were assessed in each genotype at the four field trials. Significant but not univocal differences in FER frequency and severity between the two genotypes were found only in 2012. Latent infections were significantly more frequent on P1-wr genotype in two fields and on P1-rr in the same location for two years. A similar distribution pattern was also found in the fumonisin level. Statistical analysis showed that FER indexes are positively correlated with both latent infections and fumonisin accumulation and significantly influenced not only by the presence of phlobaphenes, but also by the field location and the year of cultivation