Confirmation of Stemphylium vesicarium, the causal agent of brown spot of tomato in Germany

Abstract

The tomato is a major crop worldwide and is one of the five most consumed vegetables in Germany. Stemphylium species including S. eturmiunum, S. gracilariae, S. lycii, S. lycopersici, S. rombundicum, S. simmonsii, S. solani, and S. vesicarium have been identified as tomato pathogens in various countries. In Germany, multiple instances of S. lycopersici and S. solani affecting tomato plants have been documented; however, only one incident of S. vesicarium has been reported in 1972. S. vesicarium is known to cause yellowish-brown spots on tomato leaves, which can ultimately lead to defoliation and reduced fruit yield. Therefore, it is crucial to identify the S. vesicarium that cause this disease accurately. In this study, S. vesicarium was isolated from necrotic tomato plants in organic farms located in northern and southern regions of Germany. Single spore isolates were generated and identified as S. vesicarium based on morphological characteristic and molecular analyses using nucleotide sequences of the internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Koch´s postulates were fulfilled and revealed that S. vesicarium is the causal agent of brown spot on the samples adding a new account of the species.