Diversity and seasonal occurrence of fusaroid species associated with sugar beet roots in Serbia

This study investigated the diversity, seasonal occurrence, and pathogenicity of fusaroid species associated with sugar beet roots and assessed their relationship with infection by 'Candidatus Phytoplasma solani'. Isolates were obtained from roots with root rot, rubbery taproot disease, and asymptomatic roots, including overwintering roots. Based on phylogenetic analyses of the tef1 and rpb2 loci, supported by morphological characterization, seven species were identified: Fusarium oxysporum , F. annulatum , F. verticillioides , Neocosmospora falciformis , N. solani , F. clavum , and F. acuminatum . Fusarium oxysporum was the predominant species and was consistently detected in symptomatic and asymptomatic roots throughout the growing season and in overwintering roots. Species composition varied seasonally, with N. solani and N. falciformis associated mainly with early root rot, whereas other species occurred at low frequencies later in the season and in overwintering roots. Pathogenicity was confirmed for five species, including F. verticillioides isolated from an asymptomatic root. Fusaroid species occurrence and composition were not associated with ' Ca . P. solani' infection. Also, this is the first report of F. verticillioides , F. clavum , and N. falciformis on sugar beet in Serbia. These findings demonstrate diverse and dynamic fusaroid species community in sugar beet and provide new insights into their ecological roles and epidemiological significance.