Occurrence of grass bunt in Vojvodina and its influence on wheat seed quality control

Abstract

Causal agents of grass bunt, which infect wild grass hosts in Bromus, Festuca, Ventenata and Vulpia, are Tilletia species whose teliospores could be found in wheat seed samples too. Among them, T. bromi is morphologically similar to those of quarantined T. contraversa, and misidentification of this species could lead to commodity rejection. As a result, monitoring the presence of teliospores of quarantined species in seed samples, and identification of Tilletia species on the basis of morphological characteristics is difficult and in some cases impossible. In order to investigate the presence of grass bunt in seed samples of wheat in Vojvodina, teliospore extraction was carried out by using the size-selective sieving wash method and the OEPP/EPPO diagnostic protocol for Tilletia indica (2007). The analysis of 151 samples of basic, certified and commercial non-processed seed of wheat revealed that 127 samples were contaminated with T. caries, while 12 samples were contaminated with teliospores of Tilletia species which had morphological characteristics that correspond to T. bromi complex or quarantined T. contraversa. These teliospores displayed prominent gelatinous sheath with conspicuous depth of reticulations. Molecular identification of grass bunt teliospores was not possible in this study, because contamination level was too low (1 teliospore per 10 seeds). However, knowing that teliospores of T. bromi often occur in wheat seed samples in very low numbers there is a need for standardization of molecular techniques for the identification of a single teliospore of Tillletia species in order to make plant protection more efficient and reliable