Pathogenicity of Fusarium temperatum and Fusarium subglutinans on maize stalk and ear under artificial inoculation under field conditions

Pathogenicity of Fusarium temperatum, a new species morphologically similar and phylogenetically closely related to F. subglutinans, was observed on stalk and ear of maize (Zea mays L.). In 2010, this species was established in the culture collection of the Maize Research Institute, stored since 2004. Based on interspecies mating compatibility analyses and confirmed with AFLP fingerprint profiles (done by Munaut), two of 20 tested F. subglutinans isolates belonged to the species F. temperatum. These isolates originated from sorghum (Sorghum bicolour (L.) Moench.) grain. In 2011 and 2012, pathogenicity of 20 (2 F. temperatum and 18 F. subglutinans, respectively) and 4 isolates (2 of each F. temperatum F. and F. subglutinans), respectively, was tested on stalk and ear of two maize hybrids. The artificial inoculation of stalk was done by insertion of a Fusarium-inoculated toothpick into the second internode 7 days after silking. Control plants were inoculated with a sterile toothpick. After 6 weeks, disease intensity was evaluated on the stalk longitudinal section by the 0-6 scale (0 - necrosis localised at the inoculation spot; 6 - necrosis spreads to other internodes). Ear inoculation was done with 2-ml spore suspension in silk channels 3-5 days after silking. Control plants were treated with 2 ml sterile water. The disease intensity was assessed on ears immediately prior to harvest, according to the 1-7 scale (1 - no symptoms; 7 - 76-100% infected kernels). There were not statistically significant differences in pathogenicity between isolates of F. temperatum and F. subglutinans, either on stalk or ear. Differences in hybrids responses and symptoms that isolates of fungal species caused on stalks and ears were poorly visible. According to our knowledge, the F. temperaturm occurrence on sorghum seed as well as its pathogenicity on maize ear and stalk are detected for the first time in the world.