Septocyta ruborum: Occurrence and possibility of disease control

Purple blotch of blackberry, the disease caused by Septocyta ruborum (Lib.) Petrark, was described in Serbia in late 1980s (Arsenijevic, 1989), but in last years this disease caused significant losses in blackberry production in Serbia. The characteristic symptoms of purple blotch (red-purple lesions, with black picnidia in the middle, decline of shoots, sometime whole plants) were observed with strong intensity on blackberry plants at the trnavci (Aleksandrovac) locality. The fungus was isolated on PDA medium, from the symptomatic shoots of blackberry, using standard mycological methods. Based on morphological properties (shape and color of colony, appearance and shape of picnidia, shape and size of spores) the isolated fungus was identified as Septocyta ruborum. Total nucleic acid were extractedfrom mycelium of the monosporial culture following the CTAB extraction protocol described by Day and Shattock (1997), dissolved in TE buffer, and maintained at -20 deg C. Polymerase chain reaction (PCR) assay was performed usingITS1/ITS4 primer pair. The obtained amplicon was purified using mi-PCR purification kit (Metabion, Germany) and sequenced. The obtained ITS1/ITS4 sequence (488bp) was deposited in the National Center for Biotechnology Information (NCBI, Bethesda, MD, USA). In order to control the causal agent of purple blotch of blackberry, the effectiveness of ten synthetic fungicides was evaluated during 2007 and 2008 at the locality where the fungus was isolated. The following fungicides were tested: Quadris 0.10% (azoxystrobin, Syngenta), Cabrio top 0.20% (pyraclostrobin + metiram, BASF), Signum 0.20% (boscalid + pyraclostrobin, BASF), Stroby DF 0.02% (kresoxim-methyl, BASF), Topas 100 EC 0.04% (penconazole, Syngenta), Dakoflo 0.30% (chlorothalonil, Galenika Fitofarmacija), Polyram DF 0.25% (metiram, BASF), Funguran OH 0.25% (copper II hydroxide, Hemovet), Cuproxat 0.50% (copper tribasic sulfate, Nufarm) and Bordeaux mixture 100 SC 2% (copper II sulfate + calcium hydroxide, Galenika Fitofarmacija). A complete randomized block design with four replicates per treatment was used in the experiment. Mean percent disease control values were calculated from the evaluations made towards the end of the trials, when differentiation between treatments was the most obvious. Data were analyzed by one-way completely randomized ANOVA and means comparison performed by test by Duncan. In 2007, all fungicides were effective against S. ruborum and there was no significant difference between the efficacies. In 2008, four tested fugicides significantly reduced the diseases severity compared with the untreated plots: Quadris (98.9% and 99.8%), Cabrio top (98.7% and 99.8%), Bordeaux mixture 100 SC (98.5% and 99.2%), and Signum (95.7% and 99.0%). There was significant difference between efficacies of these four fungicides compared to other tested fungicides.