Molecular and chemical charachterization of the pathosystem Fusarium verticillioides-maize.

A 2-year study on the pathosystem F. verticillioides-maize has been developed speculating on both in vitro and in planta perspectives. The former studied the effects of temperature (T) and water activity (aw) on fumonisin B (FBs) production and expression of FUM2 and FUM21 genes in ITEM 10027 and 1744 F. verticillioides strains grown up to 21 days (d). The latter monitored which genes were differentially expressed in resistant and susceptible maize lines after 2-3 d- infection by ITEM 1744. The in vitro study showed that ITEM 10027 was the highest producer of FBs, with predominance of FB1. The maximum level of FB was registered after 21 d in both strains. FUM2 and FUM21 were expressed in all studied conditions, with a 10x difference between the former and the latter. The peak of transcription level was reached after 14 d of incubation for both FUM genes. No data were collected on cultures grown at fixed aw=0.900 because the fungus did not grow at all temperatures tested till 21 d of incubation. The in planta study showed that resistant lines tested were poorly infected by ITEM 1744. Genes differentially expressed were divided into 11 functional categories and nearly 10 % was assigned to the class “cell rescue, defence and virulence”. Most of the pathogenesis-related genes were differentially activated after fungal infection in relation to the resistance level of maize genotypes. In the resistant kernels, defence-related genes provided basal protection against the fungus, while in the susceptible ones, the same genes were induced specifically after pathogen attack.