Evaluation of ear rot (Fusarium verticillioides) resistance and fumonisin accumulation in Italian maize inbred lines

Mycotoxin contamination of maize (Zea mays L.) grain is a global threat to the safety of both human food and animal feed. Hence, the development of maize genotypes with reduced mycotoxin accumulation in grain is of major importance. In order to find maize germplasm sources of resistance to Fusarium ear rot, 34 Italian and six public inbred lines were evaluated by means of artificial inoculation in field experiments during 2009 and 2010. Relationships between ear rot and fumonisin concentration in the ears were investigated. Primary ears were challenged with a mixture of two Fusarium verticillioides isolates from Northern Italy, through kernel inoculation, and ear rot severity was assessed.The average number of visibly infected kernels per ear, after inoculation, ranged from 2 to 68 in 2009 and from 0 to 120 in 2010. Fumonisin concentrations in the inoculated ears were greater than in the experimental controls for both years. Variability was found between the inbred lines: fumonisin accumulation ranged from 0.56 to 240.83 mg kg-1 in 2009 and from 1.09 to 190.60 mg kg-1 in 2010. In both years, six inbred lines showed high fumonisin content (≥100 mg kg-1), while the other genotypes were almost equally split into two groups, low (≤10 mg kg-1) and medium (from 11 to 100 mg kg-1) fumonisin content. The number of infected kernels after artificial inoculation correlated with fumonisin concentration both in 2009 (r = 0.94; P≤0.01) and 2010 (r = 0.67; P≤0.01). Additionally, the percentage of internally infected kernels correlated positively with fumonisin concentration (r = 0.37; P≤0.01) and with the number of infected kernels (r = 0.29; P≤0.05). This research has demonstrated that Italian maize germplasm is a valid source of resistance to Fusarium ear rot. Furthermore, there is a strong association of visible Fusarium symptoms with fumonisin concentration, suggesting that selection in maize for reduced visible moulds should reduce the risk of mycotoxin contamination.