Phoma Macdonaldi on seed and its importance in etiology of Phoma black stem in sunflower

Abstract

Phoma macdonaldi Boerema, teleomorph Leptosphaeria lindquistii Frezzi, is a widespread pathogen of sunflower. The aim of this research was to identify the presence of fungus P. macdonaldi in seed of different sunflower hybrids, as well as the correlation between seed and field infection. Phoma black stem assessment was performed on three hybrids grown in six localities in Serbia. Untreated and processed seeds of these hybrids were used in the seed health test. Severity of the disease did not differ between localities. Average disease index for hybrids H7, H9 and H19 was 14.01%, 13.25% and 11.83% respectively, and it shows that there are no significant differences in hybrid susceptibility. The index of disease indicates tolerance of these hybrids to Phoma black stem. Seed analysis showed the presence of fungi from the following genera: Phoma, Alternaria, Botrytis, Sclerotinia, Penicillium and Aspergillus. Seed infection with Phoma (of the untreated seeds) per hybrid ranged from 1.2–3.5%. There is no significant correlation between stem and seed infection.

Phoma macdonaldi Boerema; teleomorf Leptosphaeria lindquistii Frezzi jedan je od najraširenijih patogena suncokreta. Cilj ovog istraživanja bio je da se utvrdi prisustvo gljive P. macdonaldi na semenu različitih hibrida suncokreta kao i korelacija između infekcije stabla u polju i infekcije semena. Procena inteziteta bolesti izvršena je na tri hibrida koja su gajena na šest lokaliteta. Za određivanje zdravstvenog stanja korišćeno je netretirano i dorađeno seme hibrida ispitivanih u polju. Intenzitet napada bolesti nije se značajno razlikovao među lokalitetima. Prosečan indeks oboljenja za hibride H7, H9 i H19 bio je 14,01%, 13,25% i 11,83% što pokazuje da ne postoje značajne razlike u osetljivosti hibrida prema crnoj pegavosti. Takođe, dobijeni indeks ukazuje na tolerantnost ispitivanih hibrida prema ovom prouzrokovaču bolesti. Analizom zdravstvenog stanja semena suncokreta utvrđeno je prisustvo gljiva iz sledećih rodova: Phoma, Alternaria, Botrytis, Sclerotinia, Penicillium i Aspergillus. Zaraženost semena gljivom P. macdonaldi utvrđena je na dorađenom i netretiranom semenu i kretala se od 1,2–3,5%. Nije utvrđena statistički značajna korelacija između infekcije stabla i semena u poljskim uslovima. Ovo se može objasniti niskim stepenom napada patogena i prisustvom simptoma samo na stablu, a ne na glavici suncokreta.