Aggressiveness variation of Fusarium graminearum sensu lato isolates from Argentina following point inoculation of field grown wheat spikes

MALBRÁN ISMAEL, MOURELOS CECILIA, MÓNICA AULICINO,PEDRO BALATTI AND GLADYS LORI

CROP PROTECTION

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2012

0261-2194

Aggressiveness variation among isolates of F. graminearum from Argentina was analyzed by following disease development on point inoculated spikes of field grown wheat. Two aspects of the capacity of the isolates to provoke disease were observed: (i) the infection efficiency, reflected by the ability to produce symptoms and evaluated as the number of symptomatic spikes over the inoculated ones; and (ii) the size of the lesion provoked, which is reflected by the number of symptomatic spikelets over the total number .One hundred and twelve isolates were found to provoke significantly different levels of disease severity of head blight, which might be reflecting isolates differences in aggressiveness, a character unrelated with their geographical origin. Differences between isolates were found for the thousand kernel weight and the area under the disease progress curve (AUDPC) and the correlations between disease severity and AUDPC, disease severity and TKW and AUDPC and TKW were highly significant. Based on disease severity, isolates were clustered as low, medium and highly aggressive ones. Both lesion size and infection efficiency were significantly different between these groups. While the disease provoked by representatives from each of the defined groups spreads mainly towards the lower part of the spike; movement towards the upper part seems to be a better indicator of aggressiveness, considering that highly aggressive isolates spread more than the low and medium aggressive ones. Premature ripening of the spike appears to be a function of isolate aggressiveness. Wheat heads inoculated with less aggressive isolates appeared to show less prematurely ripened spikes than the most aggressive ones, which provoked premature ripening sometimes as early as 7 dpi in 2008 Our work confirms that point inoculation is a useful tool to study aggressiveness of large collections of F. graminearum isolates and to analyze FHB development of large numbers of spikes under conditions more similar to those in which this disease naturally occurs.