The use of the area under the disease progress curve (AUDPC) to assess the epidemics of Septoria tritici in winter wheat.

Abstract

Septoria tritici blotch (STB) caused by the ascomycete fungus Mycosphaerella graminicola (anamorph S. tritici) is currently one of the most serious foliar disease of wheat in Europe and other world regions characterized by temperate and wet environment during growing season. Twenty-five wheat genotypes with different resistance levels were evaluated in natural conditions for their reaction to S. tritici attack during 2009-2010 year. The experimental design was a randomized block design with three replications. Disease rating was visually recorded by using the double-digit scale (00-99) in two different times and crop stages (Z53-1/4 head out and Z70-milk development). There were also calculated the Septoria Progress Coefficient (SPC) and Area under Disease Progress Curve (AUDPC) for each wheat genotype evaluated. SPC was low for the higher genotypes comparatively with the shortest ones leading to the conclusion that disease progress is higher as plant height is low (r=-0,8584***). The same aspect was also emphasized by the negative correlation between plants height and disease progress height (r=-0,7241**).The shortest genotypes showed higher necrosis percentage and AUDPC values. There was also a correspondence between genotype susceptibility and AUDPC showing that the most susceptible wheat cultivars recorded higher AUDPC values. Thus, Renan (295), Esential (231), Renesansa (234), Autan (186) recorded the highest AUDPC values while Aztec (45), Meunier (41) and Capo (20) had the best resistance reaction to S. tritici attack. Comparatively with the control Briana cultivar (AUDPC = 153), created to ARDS Simnic, the differences recorded by Renan, Renesansa Esential, Ciprian, Exotic, Cezanne, Aztec, Capo and Meunier were statistically significant. There was also a negative correlation between AUDPC and yield (r=-0,5140). The Area under the Disease Progress Curve (AUDPC) can be an efficient instrument to evaluate the epidemic development of foliar pathogen S. tritici considering each genotype susceptibility and specific architecture.