Zymoseptoria tritici evaluation after a single artificial inoculation at different vegetative stages of a durum wheat cv. in a Northern Italy region,

Septoria tritici blotch (STB) is one of the most damaging disease of wheat caused by Zimoseptoria tritici (formerly known as Mycosphaerella graminicola / Septoria tritici) and worldwide spread. SBT is the most important foliar disease of wheat in America, Asia, Northern, Central Europe and it is a major disease, particularly on durum wheat, in North Africa. In Italy the average severity of STB infection, detected from 2000 up to 2015 on durum wheat varieties, has shown an exponential growth trend, that reached its peak between 2007-2010 with a further peak in 2013 and a slight decline in the last two marketing years. In the plain area environment of Bologna (Emilia Romagna region - North of Italy) the infection is due to Z. tritici with yield losses of 30% in years with high inoculum pressure. The aim of this study has been to evaluate, in the plain of Bologna, in two years field trial, the presence of Z. tritici on the flag leaf in San Carlo, a susceptible Italian durum wheat cultivar, after a single artificial inoculation at different vegetative stages (BBCH 31, 35, 39, 60) with two different inoculum concentration (105 and 106 conidia/ml). Visual assessments (Incidence, Disease severity -DS) and DNA quantification by Real time PCR, using the primer pair ST-rRNA F/R (Guo et al., 2006; Presymptomatic and quantitative detection of Mycosphaerella graminicola development in wheat using Real Time PCR. FEMS Microbiol Lett 262:223-229), were set up. The results demonstrate that the BBCH 39 is the most susceptible stage, independently by the concentration of inoculum and climatic conditions: the year 2012 was characterized by a low infection pressure of the pathogen, while year 2013 was characterized by a high infection pressure. In the 2013 a good correlation between DS and DNA quantity was observed. The results obtained point out that the most suitable period to obtain the best crop protection could be the flag leaf stage, even if Northern Italian farmers perform the fungicide treatment against STB earlier, at BBCH31 in association with the herbicide treatment, because cost-effective.