In August 2010, a dieback of young olive (Olea europea L.) trees (cvs. Pendolino and Leccino) occurred in two orchards in Istria, Croatia. According to the producers, low temperatures during the winter severely damaged the plants and led to their decline. Distinctive symptoms, assumed fungal infection, were observed in internal tissue of stems and branches. Elongated brown necrosis, sometimes with black streaks, was visible under the bark, therefore Verticillium wilt was suspected. Of 1,086 trees in two orchards (4 ha), 165 (15%) showed symptoms. To isolate the causal agent, surface-sterilized wood chips of symptomatic tissue were placed on potato dextrose agar (PDA). Fungal colonies resembling Botryosphaeriaceae spp. grew from all wood fragments placed on PDA, and from these colonies, monohyphal isolates were obtained. For morphological identification, pycnidial formation was stimulated by growing the isolates on 2% water agar that included stems of plant species Foeniculum vulgare Mill. at room temperature under diffuse light. Pycnidia contained conidia that initially showed as hyaline, becoming light to dark brown as they matured, ovoid with truncated or rounded base and obtuse apex, aseptate, with wall moderately thick, externally smooth, roughened on the inner surface, and 22.8 to 23.5 × 9.6 to 10.5 μm. On the basis of these morphological characters, fungal species Diplodia seriata (teleomorph “Botryosphaeria” obtusa) was suspected (3). For molecular identification, four isolates (MN3, MN4, MN5, and MN6) were used for PCR to amplify the internal transcribed spacer (ITS) region and partial translation elongation factor 1-alpha (EF1-α) gene, using primers ITS4/ITS5 and EF1-728F/EF1-986R, respectively. Sequencing was performed with those amplified genes, then sequences were deposited in GenBank. Comparison of these sequences with GenBank sequences for referent D. seriata isolate CBS 112555 (AY259094 and AY573220) (3) showed 100% homology. On the basis of molecular data, the isolates were confirmed to be species D. seriata De Not. Pathogenicity tests were performed by inoculation of 2-year-old olive plants, six plants per tested cultivar (Pendolino and Leccino). For every cultivar, four plants were wounded and mycelium plugs from D. seriata cultures on PDA were placed on the wounds and sealed with Parafilm. Two control plants per tested cultivar were inoculated with sterile PDA plugs. After 2 months, six of eight inoculated plants wilted completely, and under the bark, brown necrosis was observed. D. seriata was constantly reisolated from the inoculated plants and fulfilled Koch's postulates and confirmed pathogenicity of D. seriata on olive as causal agent of olive dieback. Control plants showed no symptoms of the disease. This fungus has been recognized as the cause of fruit rot of olive (1) and branch canker or dieback in Spain (2). To our knowledge, this is the first report of D. seriata as a pathogen of olive in Croatia. Also, this is one of the first reports of D. seriata as the cause of olive dieback in the world, while Moral et al. (1,2) mostly reported it as the cause of olive fruit rot. Since the same symptoms of olive dieback were observed at other localities in Croatia, the disease could represent a serious threat, particularly for young olive orchards. References: (1) J. Moral et al. Plant Dis. 92:311, 2008. (2) J. Moral et al. Phytopathology 100:1340, 2010. (3) A. J. L. Phillips et al. Fungal Divers. 25:141, 2007.
Strana vrsta Chymomyza amoena (Loew 1862) zabilježena je prvi puta u Hrvatskoj. Ova fitofagna vrsta octene muhe porijeklom iz Sjeverne Amerike otkrivena je u Europi 1975. godine na području nekadašnje Čehoslovačke, a već 1980. godine zabilježena u dvije nama susjedne države (Mađarskoj i Srbiji). Smatra se da se C. amoena proširila uvozom jabuke iz Amerike u Europu, a velik broj dostupnih biljaka domaćina (domaće jabuke, engleski hrast te europski kesten) zaslužan je za široku rasprostranjenost vrste u Europi. U radu se navode biljke domaćini, morfologija i biologija vrste, lokalitet prvog pronalaska, te se prognozira širenje vrste na području Hrvatske. C. amoena razvija se u različitim vrstama orašastih, jezgričavih i koštićavih plodova oštećenim od primarnih štetnika, te se smatra jedinom vrstom octene muhe s ovakvim razvojnim navikama u Sjevernoj Americi i Europi. Poznati domaćini u Europi su šumske vrste (kesten i hrast crnika) te voćne vrste (jabuka, divlja trešnja i šljiva). C. amoena ne pričinjava primarne štete u uzgoju, stoga se ne smatra štetnikom u poljoprivredi i šumarstvu. Dva primjerka vrste pronađena su tijekom 2016. godine u vinogradu na području Međimurske županije okruženim šumom i zapuštenim voćnjakom jabuke. S obzirom da je Međimurska županija poznata voćarska regija, a u relativnoj blizini u okolici Medvednice, Hrvatskom zagorju i Samoborskom gorju nalaze se i kestenove sastojine, pretpostavlja se da bi vrsta mogla biti proširena na području Sjeverozapadne Hrvatske, te na drugim sastojinama pitomog kestena u Hrvatskoj. Rad predstavlja prvi nalaz vrste C. amoena na području Hrvatske, te pruža nove uvide o rasprostranjenosti vrste u Europi.
The invasive alien fruit pest Drosophila suzukii, (Matsumura 1931) causes economic loss in soft‐skinned fruit production across Europe. After its first detection in 2008, the species has successfully expanded to a wide geographic area and invaded new host plants in a relatively short period of time. The aim of the present study was to analyze the connection between food preferences as host specialization and the morphology of D. suzukii. Population morphological variation in wings was investigated in two different host fruits (grape and strawberry) in which economic damage has been recorded. The geometric morphometric results revealed two noticeable wing shape morphotypes in D. suzukii (i.e. vein configuration) between the grape and strawberry fruits. Flies reared in grapes had wider wings, whereas flies grown in strawberries had more narrow wings. These differences in morphotype could be explained by the effects of wing aerodynamics, which affect the strength of the wings in flight. This, in turn, can lead to better dispersion within the associated fruit host. These results confirm that this extremely invasive species, found worldwide, is successful at spreading in part because of its potential to adapt rapidly under different rearing conditions. Therefore, adaptive variations in the wing shape of D. suzukii can be used to differentiate populations based on food preference (e.g. soft fruits) and can serve as an additional tool for detecting different bioecological types of D. suzukii.
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