Jelena Poštić

First Report of Cane Blight on Blackberry Caused by Diaporthe eres in Croatia

A cane disease of blackberry (Rubus sp.) cv. Thornfree was observed in May and June 2010 in two growing regions in the eastern part of Slavonia in Croatia. Symptoms consisted of bleached areas between and around cane nodes with some canes showing wilt symptoms. Infected areas were covered with numerous, black pycnidia immersed in the epidermal tissue. Disease occurrence in orchards growing cv. Thornfree ranged between 1 and 15%. Thirty disease samples were collected, disinfected (1 min in 70% ethanol and 2 min in 1% NaOCl), and placed in a moist chamber for 4 days. Fungal sporulating structures were then picked off and placed on potato dextrose agar (PDA). Fungal isolates obtained were identified as a Phomopsis sp., the conidial state of Diaporthe (3), on the basis of cultural and morphological characteristics. Alpha conidia were unicellular, hyaline, fusiform, sometimes tapering toward one or both ends, biguttulate (sometimes with several guttules), and 5.2 to 9.7 × 1.4 to 2.7 μm (average 6.5 × 2.1 μm). Beta conidia were hyaline, aseptate, filiform, hamate, and 16.6 to 28.2 × 0.5 to 1.5 μm (average 24.0 × 1.1 μm). The teleomorph was not observed. Biomolecular analysis was performed to identify the fungal species by sequencing the internal transcribed spacer (ITS) region spanning ITS 1, 5.8S rDNA, and ITS 2 of two isolates (Phk1 and Phk2). The amplified product was sequenced (GenLab-Enea, Rome, Italy) and a BLAST search of the NCBI nucleotide database was performed. Sequences from Phk1 and Phk2 (GenBank Accession Nos. HQ533144 and HQ533143, respectively) were identical to authentic and vouchered Diaporthe eres Nitschke (GenBank DQ491514, BPI 748435, and CBS 109767) ITS sequences in GenBank. Fungal isolates for pathogenicity tests were grown on PDA at 25°C for 7 days (12 h light/dark regimen). Inoculations were made on 30 to 40 cm long green shoots of potted plants of the blackberry cv. Thornfree. One-centimeter long wounds were made with a sterile scalpel and mycelia of D. eres were placed in the wounds. Inoculation sites were covered with a piece of wet cotton wool and aluminum foil to retain moisture. Three replications of 10 plants each were inoculated and these plus 10 control plants (inoculated with plugs of PDA only) were maintained in a growth chamber at 25°C. After 25 days, lesions developed on all 30 inoculated plants that averaged 15 mm long and control plants remained symptomless. D. eres was reisolated from inoculated plants, thus completing Kochs postulates. Phomopsis spp. have previously been reported on blackberry canes in Serbia (1) and Yugoslavia (2,4), however, to our knowledge, this is the first report of the occurrence of D. eres (anamorph P. oblonga) on blackberry in Croatia. References: (1) M. Arsenijevic. Biljni Lekar 34:117, 2006. (2) M. Muntanola-Cvetkovic et al. Zast. Bilja 36:325, 1985. (3) B. C. Sutton. Page 569 in: The Coelomycetes. CMI, Kew, Surrey, UK, 1980. (4) M. Veselic et al. Zast. Bilja 49:76, 1998.

Fusarium species isolated from plant debris in eastern Croatia

Maize (Zea mays L.) genotypes wit It improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha(-1)) and low-N (1100 kg N ha(-1)) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1 in the low-yielding (dry) environment to 55 kg grain kg N-1 under higher yielding environment, When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.Hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) were evaluated as cover crops during two vegetation seasons in the Mediterranean and Continental area of Croatia. Better tolerance to low winter temperatures was observed for crimson clover. Higher plants (10 to 3 1 cm) before winter and in spring (67 to 117 cm) were measured for hairy vetch, while crimson clover had higher yields of fresh biomass (33.7 to 113.1 t ha(-1)). Concentrations of N (1.53 to 3.34%), P2O5 (0.55 to 1.04%) and K2O (2.02 to 5.32%) in plant tissue were higher for hairy vetch. However, due to higher yields of dry matter, crimson clover accumulated more N (105 to 239 kg ha(-1)), P2O5 (28 to 83 kg ha(-1)), and K2O (105 to 440 kg ha(-1)) than hairy vetch. According to our results crimson clover could be recommended as a cover crop in Mediterranean and Continental area of Croatia.