Hlor-dioksid kao dezinficijens za kontrolu Ralstonia solanacearum u vodi, skladištu i opremi

Brown rot or bacterial wilt caused by bacterium Ralstonia solanacearum is the main limiting factor in potato production. Quarantine measures are necessary to avoid spread of disease to disease-free areas. R. solanacearum has been shown to contaminate watercourses from which crop irrigation is then prohibited causing further potential losses in yield and quality. The bacteria also spread via surfaces that diseased seed potatoes come into contact with. This study showed bactericidal activity of chlorine dioxide (CIO2) on R. solanacearum for disinfection of water, surface and equipment. The results showed that CIO2 solution at concentration of 2 ppm at 30 minutes of exposure time had bactericidal effect for disinfection of water. For surface and equipment disinfection, concentration of 50 ppm showed total efficacy at 30 min and 5 sec exposure time, respectively. Results suggest that use of CIO2 as a disinfectant has a potential for control of brown rot pathogen in water, storage and equipment.Mrka trulež ili bakteriozna uvelost krompira prozrokovana bakterijom Ralstonia solanacearum ograničavajući je faktor uspešne proizvodnje krompira. Sprovođenje karantinskih mera zaštite je neophodno kako bi se izbeglo širenje bakterije u regione u kojima bolest nije prisutna. S obzirom da R. solanacearum može kontaminirati vodene tokove i izvore koji služe za navodnjavanje useva, zabrana korišćenja dovodi do dodatnih potencijalnih gubitaka u prinosu i kvalitetu krompira. Bakterija takođe kontaminira površine sa kojima zaraženi semenski krompir dolazi u dodir. U ovom radu prikazana je baktericidna aktivnost hlor-dioksida (CIO2) na bakteriju R. solanacearum u cilju dezinfekcije vode, površine i opreme. Dobijeni rezultati pokazuju da CIO2 ispoljava baktericidni efekat za dezinfekciju vode u koncentraciji od 2 ppm nakon 30 minuta ekspozicije, za dezinfekciju površine u koncentraciji 50 ppm nakon 30 minuta ekspozicije i za dezinfekciju opreme u koncentraciji 50 ppm nakon 5 sekundi ekspozicije. Rezultati dobijeni u ovom radu ukazuju da CIO2 poseduje potencijal kao dezinficijens za kontrolu prouzrokovača mrke truleži krompira u vodi, skladištu i opremi

First Report of a Leaf Spot Disease Caused by Alternaria protenta on the Datura stramonium in Serbia

Datura stramonium L. (jimsonweed) is an invasive and competitive annual weed and a potential reservoir host of pests and pathogens in agricultural fields. During a survey of potato growing fields in the municipality of Maglić, Vojvodina Province, typical Alternaria symptoms on leaves of D. stramonium were observed among the potato plants in September 2016. The incidence of diseased plants ranged from 12 to 70%. The symptoms started as small, round, light brown spots with chlorotic haloes, which gradually enlarged to 0.3 to 2 cm in diameter, becoming irregular and sometimes having a dark brown border. Isolates were obtained by placing small pieces of surface-sterilized infected tissues (immersed in 1% sodium hypochlorite for 1 min and rinsed with sterilized water) on V8 medium for 7 days at 23°C with a 12-h photoperiod. The five isolated colonies were circular, smooth, gray to brownish black, with concentric zones of very intensive sporulation. Conidiophores were branched, solitary or in small groups, brown to olivaceous brown, ranging from 125 to 230 µm. Mature conidia were olivaceous brown, long ovoid or long ellipsoid, 102 to 113 µm long and 16 to 29 µm wide, with five to 12 transverse septa and zero to three longisepta. Beak dimensions were 62 to 98 µm long and 6 µm wide at the base apex to 2 µm on the top of the beak. Two-beak conidia were noticed with a frequency of 28%. Based on morphological characteristics, all isolates were identified as Alternaria protenta Sorauer (Simmons 2007). To further identify the pathogen, PCR was used with the A. solani-specific primer set OAsF7 and OAsR6 (Gannibal et al. 2014). A single unique band of 164 bp was amplified for all five isolates. To confirm the pathogen’s identity, PCR was carried out with isolate JB 46-1 using primers ITS1/ITS4 (White et al. 1990), gpd1/gpd2 (Berbee et al. 1999), and RPB2-5F2/fRPB2-7cR (Woudenberg et al. 2013). The ITS, GAPDH, and RPB2 sequences were deposited in GenBank under accession numbers KY913819, KY913818, and MH454660, respectively, and BLAST analyses showed 100% nucleotide sequence identity with the corresponding gene regions of A. protenta strain CBS 116651 (KC584217, KC584139, and KC584430). A pathogenicity test was carried out with isolates JB 46-1 to JB 46-5 on 20 5-week-old healthy jimsonweed plants grown in a greenhouse at 23 ± 2°C. Inoculation was performed by spraying a conidial suspension (106 spores/ml) prepared from 10-day-old cultures grown on V8 agar plates at 23°C with a 12-h photoperiod. Plants used as controls were sprayed with sterilized distilled water in a similar manner. Inoculated plants were kept in a moist chamber for 2 days with 90 to 100% relative humidity. Leaf spot symptoms, brown lesions with chlorotic halos, similar to those previously observed in naturally infected plants, appeared 5 days postinoculation for all inoculated plants. No symptoms were observed on the inoculated control plants. To fulfill Koch’s postulates, lesions were excised, surface sterilized, and plated on water agar, and the fungus emanating from the infected tissues was identified as previously described. To our knowledge, this is the first report of A. protenta causing leaf spot on D. stramonium in Serbia. According to previous reports, A. protenta can also cause leaf spot disease on potato (Ayad et al. 2017; Landschoot et al. 2017; Woudenberg et al. 2014). The fact that jimsonweed coexists in close proximity with potato plants may have a potentially important economic impact on cultivation of solanaceous crops if left uncontrolled and unmonitored. Therefore, constant management practices are required to control the threat that D. stramonium weed and its diseases might present

First Report of Pectobacterium atrosepticum, Causing Bacterial Soft Rot on Calla Lily in Serbia

In 2015, bacterial soft rot symptoms on calla lily (Zantedeschia aethiopica L.) were found in greenhouse in Kraljevo area, Serbia, with a disease incidence of 20 to 30%. The disease was characterized by water-soaked necrotic lesions on leaves and stems, resulting in collapse of whole plants. Small pieces of leaf tissue, taken from the margin of necrotic lesions, were homogenized and spread onto nutrient agar (NA). After incubation for 48 h at 26°C, single creamy white, round, and convex bacterial colonies were formed. Eight representative isolates (PC1 to PC8), randomly selected for further identification, produced characteristic pits on crystal violet pectate medium (CVP) (Perombelon and Van der Wolf 2002) and showed pectolitic activity by developing rotted tissue on the inoculated potato tuber slices. All isolates were gram-negative, rod shaped, facultative anaerobic, nonfluorescent on King’s B medium; positive for catalase, hypersensitive response on tobacco and nitrate reduction; negative for oxidase reaction, production of levan, arginine dihydrolase, and indole. Differentiation tests among Pectobacterium spp. (Perombelon and Van der Wolf 2002) resulted in negative growth at 37°C, and positive reaction for the production of reducing substances from sucrose. Isolates were further characterized on the basis of sequence analysis of the housekeeping genes gapA and mdh (Ma et al. 2007). Sequences were deposited in the National Center for Biotechnology Information (NCBI) GenBank database for mdh (MF109822–29) and gapA genes (MF109830–37) for the isolates from PC1 to PC8, respectively. BLAST analysis revealed 97% homology (Query coverage 100%; E. value 0.0) with Pectobacterium atrosepticum strains 21A (CP009125) and JG10-08 (CP007744). Pathogenicity was tested on leaf petioles of calla lily plants by injecting with a bacterial suspension (107 to 108 CFU/ml), and incubated at room temperature and 70 to 80% relative humidity (Ni et al. 2010). Three replicates for each isolate were used. After a 24 h period, the inoculated calla lily plants exhibited the rot symptoms, initially presented as light brown lesions at the inoculation sites, which further resulted in dissemination to surrounding tissue, its maceration, and cell death after 3 days. No symptoms were observed on controls inoculated with sterile distilled water. Reisolates produced characteristic pits on the CVP medium. To our knowledge, this is the first report of soft rot caused by P. atrosepticum on calla lily in Serbia. Further research will be performed in order to determine how far the disease is spread to other area or hosts in Serbia