Search Results (4)

During 2021 and 2022, a field investigation was conducted in Istria, Croatia, searching for trees exhibiting signs of Botryosphaeria dieback. Samples of symptomatic trees were collected from 26 different locations and analysed. Isolates that morphologically corresponded to species from the Botryosphaeriaceae family were selected, and detailed morphological characterisation and molecular identification of the isolates were conducted. Based on morphological characteristics and phylogenetic analysis using the internal transcribed spacer (ITS), beta-tubulin (TUB2), and translation elongation factor 1-alpha (TEF1-α) regions, six species of fungi from the Botryosphaeriaceae family were identified: Botryosphaeria dothidea (Moug. ex Fr.) Ces. & De Not.; Diplodia mutila (Fr.) Fr.; Diplodia seriata De Not.; Dothiorella iberica A.J.L. Phillips, J. Luque & A. Alves; Dothiorella sarmentorum (Fr.) A.J.L. Phillips, Alves & Luque; and Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips. This is the first report of D. mutila, Do. sarmentorum, and Do. iberica causing Botryosphaeria dieback on olive trees in Croatia, and the first study investigating the resistance of Croatian olive varieties to species from the Botryosphaeriaceae family. Pathogenicity testing of selected isolates and assessment of variety resistance were conducted on four different olive varieties, namely Buža, Istarska bjelica, Leccino, and Rosinjola, using representative isolates of the mentioned species. The most aggressive species was found to be N. parvum. Olive varieties exhibited differences in susceptibility depending on the fungus they were infected with. Full article

Ginkgo leaf blight, one of the most economically important ginkgo diseases, has become very prevalent in many places in China. Flavonoids and endophytes are both considered important in ginkgo plant functioning. However, little is known about the potential relationships among ginkgo leaf blight pathogens, flavonoid accumulation profiles in infected leaves, and ginkgo leaf endophytes. In this study, the flavonoid accumulation profiles in infected leaves, pathogens of ginkgo leaf blight, and the endophytes of healthy ginkgo leaves were characterized. The levels of total flavonoids in the healthy parts of the infected leaves were significantly higher than those in the healthy leaves. Furthermore, Alternaria tenuissima, Botryosphaeria dothidea, and Dothiorella gregaria were identified as pathogens of ginkgo leaf blight; among them, A. tenuissima was the major pathogen. The in vitro experiments showed that flavonoids (apigenin, luteolin, and kaempferol) could significantly inhibit the growth of one or more pathogens at a concentration of 10 mg/L. Furthermore, fifty-six ginkgo leaf endophytic fungi (GLEF) from healthy ginkgo plants were isolated and characterized. Among them, Alternaria spp. were the most abundant, and GLEF55 shared the same ITS sequence with the pathogen Alternaria tenuissima. Thereafter, four flavonoid-producing endophytes were selected and their effects on the growth of pathogens were evaluated. The extracts of GLEF55 could significantly inhibit the growth of the pathogens B. dothidea and D. gregaria simultaneously in vitro, but not the growth of the pathogen A. tenuissima. Furthermore, the dual cultures of the candidate GLEF and ginkgo leaf blight pathogens revealed that GLEF55 had a similar growth rate to that of A. tenuissima and D. gregaria, but its growth rate was significantly slower than that of B. dothidea. Finally, the GLEF exhibited variable roles when facing pathogens in ginkgo leaves. Among them, GLEF55 showed similar pathogenicity as the pathogen A. tenuissima when they were dually cultured in ginkgo leaves. By contrast, GLEF17 (an uncultured soil fungus) could significantly counteract the pathogenic effects of A. tenuissima and D. gregaria, but it dramatically exacerbated the pathogenic effects of B. dothidea. Larger lesion areas were observed on the side of ginkgo leaves where GLEF39 (Alternaria sp.) or GLEF54 (Aspergillus ruber) and pathogens were simultaneously inoculated, which suggested that the pathogenicity of specific endophytic fungi occurred when plants were wounded. Overall, A. tenuissima, a major pathogen of ginkgo leaf blight, might lurk inside the plants as a friendly endogenous fungus and convert into a hostilely pathogenic mode at a particular time. This study proposed a possible cause of ginkgo leaf blight and provided potential theoretical guidance for its prevention. Full article

Pinus sylvestris bark represents a rich source of active compounds with antifungal, antibacterial, and antioxidant properties. The current study aimed to evaluate the antifungal potential of P. sylvestris bark against Botryosphaeria dothidea, Dothiorella sarmentorum, and Neofusicoccum parvum (Botryosphaeriaceae) through its chemical (water extracts) and biological (Trichoderma spp. isolated from the bark) components. The water bark extracts were prepared at two temperatures (80 and 120 °C) and pH regimes (7 and 9). The presence of bark extracts (30%) caused inhibition of mycelial growth of B. dothidea and D. sarmentorum for 39 to 44% and 53 to 60%, respectively. Moreover, we studied the antagonistic effect of three Trichoderma isolates originating from the pine bark. Trichoderma spp. reduced growth of B. dothidea by 67%–85%, D. sarmentorum by 63%–75% and N. parvum by 55%–62%. Microscopic examination confirmed typical mycoparasitism manifestations (coiling, parallel growth, hook-like structures). The isolates produced cellulase, β-glucosidase and N-acetyl-β-glucosaminidase. The volatile blend detected the emission of several volatile compounds with antimicrobial activity, including nonanoic acid, cubenene, cis-α-bergamotene, hexanedioic acid, and verticillol. The present study confirmed in vitro potential of P. sylvestris bark extracts and Trichoderma spp. against the Botryosphaeriaceae. The study is an important step towards the use of environmentally friendly methods of Botryosphaeriaceae disease control. Full article

Botryosphaeriales represent a diverse order of fungal pathogens of various woody plant species. In Serbia, these fungi are important pathogens of forest, ornamental, and fruit trees causing die-back, cankers, leaf blights, fruit, and root rot. The aim of this study was to evaluate the antifungal activity of Pinus sylvestris bark extracts and Trichoderma spp. against Botryosphaeria dothidea, Dothiorella sarmentorum, and Neofusicoccum parvum (Ascomycota, Botryosphaeriales) isolated from Picea abies, Thuja occidentalis, and Prunus laurocerasus trees planted in urban areas in Serbia. Bark extracts were prepared in water solution at two temperatures (80 and 120 °C). The extracts were tested using two concentrations (20% and 30%). Moreover, two Trichoderma isolates obtained from P. sylvestris bark were tested against Botryosphaeriales and their antagonistic potential was estimated in vitro using a confrontation test. Mycelial growth of B. dothidea and D. sarmentorum was significantly inhibited in the presence of bark extracts, while N. parvum showed no growth inhibition. Botryosphaeria dothidea growth was inhibited by 35 to 39% in the case of 20% extracts and by 39 to 44% in the case of 30% extracts. The growth inhibition of D. sarmentorum was between 48% and 56% in the case of 20% extracts and between 53% and 60% in the case of 30% extracts. The two Trichoderma isolates showed antifungal activity against the selected pathogens. An isolate BKG 4 showed the highest inhibition level, and it inhibited the growth of B. dothidea, D. sarmentorum, and N. parvum by 85%, 75%, and 62%, respectively. Preliminary results suggest that both P. sylvestris bark extracts and Trichoderma spp. could be used as biocontrol agents against B. dothidea, D. sarmentorum, and N. parvum, and this should be a further studied. Full article