First report of Pseudomonas avellanae causing hazelnut decline in Serbia

Abstract

Grapevine trunk diseases (GTDs) are a group of diseases caused by a large number of fungal phytopathogens that infect and colonize the woody tissue of grapevine, causing chronic or apoplectic decline of plants, and as such posing a serious threat to viticulture. Among the most virulent pathogens are Neofusicoccum parvum, the causal agent of Botryosphaeria dieback, and Fomitiporia mediterranea considered as the main causal agent of grapevine rot within the Esca disease complex. This study aimed to isolate and select potent indigenous bacteria collected from Montenegrin vineyards to serve in the control of GTDs. Isolations were performed from soil samples taken in a zone of grapevine root (Montenegro) on NA after soil was dissolved in water and heating at 80°C for 20 min. A total of 262 isolates were tested for antagonistic activity in a direct in vitro test on PDA. The appearance of a clear zone was checked after fungi development. Results showed that 32 Montenegrin isolates inhibited the growth of N. parvum by 34.0-65.0%, and F. mediterranea by 34.8-71.0%. Neighbourjoining phylogenetic analysis based on the 16S rRNA (primers P0/P6) sequences differentiated those isolates into six clusters but lacked the resolution to differentiate between several species. Six groups were as follows: I (21 isolates: Bacillus amyloliquefaciens/B. velezensis/B. siamensis/B. subtilis), II (2: B. subtilis/B. velezensis/B. tequilensis), III (5: B. halotolerans/B. mojavensis/B. subtilis/B. velezensis/B. tequilensis/B. spizizenii), IV (1: B. licheniformis/B. paralicheniformis), V (2: B. cereus/B. thuringiensis/B. albus/B. anthracis), VI (1: Paenibacillus peoriae/P. polymyxa). Sequencing of housekeeping genes would provide more accurate identification