Kamuran Kaya

Comparison by Sequence-Based and Electron Microscopic Analyses of Fig mosaic virus Isolates Obtained from Field and Experimentally Inoculated Fig Plants

Fig mosaic disease (FMD) and the fig mite, Aceria ficus, are widespread in different fig growing provinces of Turkey. Fig trees (Ficus carica) cv. Bursa siyahı (D1) and an unknown seedling (D2) that showed typical FMD symptoms and was heavily infested by fig mites were used as donor plants for attempted mite transmissions to healthy fig seedlings. Transmission electron microscopy observations of donor plant samples prior to the transmission tests were performed and showed the presence of double membrane bodies (DMBs) in the palisade mesophyll cells. Electron microscopy of all experimentally inoculated fig seedlings showed the same bodies. This result reinforced the suggestion that an agent that elicits the production of DMBs in infected cells is involved in the etiology of FMD. Double-stranded (ds)RNA analyses were also performed from experimentally inoculated plants, and dsRNAs with sizes approximately 1.30 and 1.96 kb were obtained. Reverse transcription-polymerase chain reaction (RT-PCR) products of 468 and 298 bp specific to Fig mosaic virus (FMV) were amplified from both donor and experimentally inoculated plants. BLAST analyses of nucleotide sequences of these fragments showed 90% identity with FMV for the donor plant and 94 to 96% for experimentally inoculated plants. According to these results, FMV is present in both donor and experimentally inoculated plants in Turkey, and this virus is transmissible by A. ficus from fig plant to fig plant.

DETECTION OF FIG MOSAIC VIRUS IN VIRULIFEROUS ERIOPHYID MITE ACERIA FICUS

Fig leaves showing typical fig mosaic symptoms on cv. Bursa siyahi (donor plant) were cut under a stereo microscope into small pieces each hosting 10 putatively viruliferous eriophyid mites (Aceria ficus Cotte) and placed directly on the top leaves of healthy Cucumis sativus, Chenopodium quinoa. C. amaranticolor, Nicotiana occidentalis, Catharanthus roseus, Fraxinus excelsior plants, and fig seedlings. Donor and test plants were analyzed by electron microscopy, RT-PCR and sequencing, whereas the mites (ErMs) underwent molecular assays using Fig mosaic virus (FMV)-specific primers. Mite-infested leaves of fig seedlings and C. roseus showed small yellowish spots after 10 days and 6 weeks, respectively, whereas no symptoms were observed in other test or control plants for three months. Electron microscopy observations showed the occurrence of double membrane bodies (DMBs) in the palisade cells of donor and mite-inoculated fig plants, but not in C. roseus. However, 302 bp RT-PCR products specific to FMV were amplified from donor and inoculated figs, C. roseus and ErMs. Nucleotide identity with the sequence of the FMV isolate in GenBank (accession No. AM941711.6) was 87%, 89% and 87% for donor plant (JQ708183), inoculated fig seedlings (JQ708184) and C. roseus (JQ408437, JQ408438), respectively. The sequences obtained from ErMs (JQ408432, JQ408436) showed 87% and 88% nucleotide identity with the reference FMV isolate, respectively. When dsRNA extracts were analyzed to confirm virus presence in inoculated periwinkles, a complex dsRNA profile was obtained, suggestive of infection by a multipartite virus or by multiple viruses. Sequence from RT-PCR amplicons of dsRNA (JX040436) showed 88% identity with those the reference FMV isolate (AM941716.1) and the donor plant (JQ708183). According to these results, Madagascar periwinkle (C. roseus) can be retained as a new experimental host for FMV and A. ficus appears to be able to transmit FMV from fig to periwinkle plants.

Potential vectors of Plum pox virus in the Eastern Mediterranean Region of Turkey

Although Plum pox virus (PPV) was first detected in Turkey 44 years ago, the virus is present in a rather limited number of trees. Our recent studies on PPV incidence showed that PPV was introduced rapidly in PPV-free regions and that there are no data available about the role of aphid species and Prunus rootstocks on these new infections. In this study the epide- miological aspect of PPV was studied in Antakya-Hatay, located in the Eastern Mediterranean region of Turkey where PPV was first detected in 2011. The susceptibility of different Prunus rootstocks to PPV was evaluated in an established experimental plot next to a PPV-infected nectarine orchard. Aphid populations were monitored in 2011 and 2012 from the last week of April to the middle of June by the sticky-plant method in both the experimental plot (EP) and the surrounding infected nectarine orchard (SNO). Regularly collected plant samples and aphids were individually tested by DASI-ELISA and squash real-time RT-PCR, respectively. The highest aphid population densities were observed at the end of May in both years. The most abundant aphid species were Aphis gossypii and A. spiraecola both in EP and SNO in both years. The percentage of PPV-viruliferous Myzus persicae, A. fabae, A. gosypii, A. spiraecola, Hyalopterus pruni, Macrosiphon euphorbiae and A. craccivora as estimated by squash real- time RT-PCR were 39.47%, 25.00%, 24.56%, 22.60%, 22.22%, 20.00% and 8.00%, respec- tively. The percentages of viruliferous aphids collected from SNO were 12.5% in A. spiraecola, 12.42% in A. gossypii and 11.11% in H. pruni. At the end of 2012, three Myrobolan 29C and two Adesoto 101 rootstocks were found infected by PPV. Molecular characterization studies showed that PPV-M was the strain present in both the originally infected nectarine plot and the Myrobolan 29C rootstocks.

EVALUATION OF THE SUSCEPTIBILITY OF DIFFERENT PRUNUS ROOTSTOCKS TO NATURAL INFECTION OF PLUM POX VIRUS-T

SUMMARY Plum pox virus (PPV) has been observed in Turkey since 1968, but was not widespread except in apricot and plum trees in home gardens and ornamental parks in restricted areas. Susceptibility of six different Prunus rootstocks to strain PPV-T was assessed under natural inoculum pressure in the Izmir-Aegean region during 2010-2011. Aphid populations were monitored from the first week of April to the middle of June by the stickyplant method one year after the rootstock plantation was established. Aphids collected from different rootstocks were tested individually by squash real-time RT-PCR and all rootstocks were regularly tested by DASI-ELISA. The largest aphid populations were observed at the end of May and the most abundant aphid species as averages over the two years were Myzus persicae (20.15%), Hyalopterus pruni (18.64%), Aphis craccivora (9.04%) and Aphis gossypii (8.36%). In 2011, the highest percentage of viruliferous aphids was found in M. persicae (34.78%), followed by H. pruni (32.50%), Macrosiphum euphorbiae (25.00%), A. gossypii (23.80%), A. spiraecola (12.50%) and A. craccivora (10.00%). Of the six Prunus rootstocks tested, only Nemaguard and Myrobalan 29C were infected by PPV-T, infection rate in 2010 being 6.0% (Nemaguard) and 4.0% (Myrobalan 29C). The infection rate increased to 16.0% for Nemaguard and 14.0% for Myrobalan 29C in 2011. However, the other rootstocks, Prunus marianna GF8.1, Docera6, GF677 and Garnem tested negative for PPV-T throughout 2011. PPV isolates obtained from naturally infected apricot trees (inoculum source) and from infected rootstocks in the experimental plot were characterized as PPV-T and had more than 99.5% nucleotide sequence identity.

POTENTIAL PSYLLID VECTORS OF CANDIDATUS PHYTOPLASMA MALI AND CANDIDATUS PHYTOPLASMA PYRI IN TURKEY

Fruit tree diseases caused by phytoplasma have great economic effects on fruit production, especially in Europe. A major phytoplasma is ‘Candidatus Phytoplasma mali’, which causes apple proliferation (AP) disease mainly in cultured and wild forms of apple trees (Seemuller et al., 2011a); however, there has been a report of different hosts, including Prunus avium (L.) L., P. armeniaca L., and P.domestica L. (Mehle et al., 2007). ‘Ca. Phytoplasma pyri’ causes pear decline (PD) disease that is found mainly in cultured and wild forms of pear (Pyrus spp.) and quince (Cydonia oblonga Mill.) (Seemuller et al., 2011b). These phytoplasma are taxonomically classified into the 16SrX group (or AP-group) of phytoplasmas and constitute closely related subgroups (Seemuller and Schneider, 2004). Phytoplasmas are mainly spread by vegetative propagation or the grafting of infected plant material and phloem feeding insects, primarily leafhoppers, planthoppers and psyllids (Weintraub and Beanland, 2006). Only one genus of this last one, Cacopsylla spp., transmit AP-group phytoplasmas to pome and stone fruit trees. In apple orchards, ‘Ca. P. mali’ can be transmitted by two psyllid species. Cacopsylla (Thamnopsylla) picta (Foerster, 1848) (syn. C. costalis) has been reported main vector in Germany (Jarausch et al., 2003, 2011) and northern Italy (Frisinghelli et al., 2000; Carraro et al., 2008), while Cacopsylla (Thamnopsylla) melanoneura (Foerster, 1848) was identified as main vector in Aosta Valley (Tedeschi et al., 2002). C. picta is monophagous on Malus spp. and until now this species have been described only in Europe (Burckhardt, 1994; Ossiannilsson, 1992; Ouvrard, 2014) and Turkey (Klimaszewski and Lodos, 1977, 1979; Drohojowska and Burckhardt, 2014). C. melanoneura has a Palaearctic distribution and is oligophagous on Rosaceae, its principal host plant being a common shrub, hawthorn (Crataegus monogyna L.) (Ouvrard, 2014). In most of studied cases, both psyllid species are present in apple orchards (Jarausch et al., 2003; Delic et al., 2005; Carraro et al., 2008; Mattedi et al., 2008). Two others species living on hawthorn, Cacopsylla peregrina (Foerster, 1848) and Cacopsylla (Thamnopsylla) affinis (Low, 1880), were found able to harbor the phytoplasmas of the AP-group, in particular ‘Ca. P. mali’ (Tedeschi et al., 2009). Their transmission ability was not proven but this result highlights the potential role as vector of these psyllid species. In pear orchards, until recently, two psyllid species were known as vector of ‘Ca. P. pyri’. Cacopsylla (Hepatopsylla) pyricola (Foerster, 1848) has been reported for Great Britain (Davies et al., 1992) and North America (Jensen et al., 1964), while Cacopsylla (Hepatopsylla) pyri (Linne, 1758) was described as the vector in France (Lemoine 1984), Italy (Carraro et al., 1998a) and Spain (Garcia-Chapa et al., 2005). C. pyri is widespread in Europe, in the Caucasus, Georgia, the Middle Asia, including Turkey (Klimaszewski and Lodos, 1979; Burckhardt and Pak. J. Agri. Sci., Vol. 53(2), 383-392; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.3804 http://www.pakjas.com.pk