Stone Fruit Species Research Articles

Worldwide population genetic structure of the oriental fruit moth (Grapholita molesta), a globally invasive pest

BackgroundInvasive pest species have large impacts on agricultural crop yields, and understanding their population dynamics is important for ensuring food security. The oriental fruit moth Grapholita molesta is a cosmopolitan pest of stone and pome fruit species including peach and apple, and historical records indicate that it has invaded North and South America, Europe, Australia and Africa from its putative native range in Asia over the past century.ResultsWe used 13 microsatellite loci, including nine newly developed markers, to characterize global population structure of G. molesta. Approximately 15 individuals from each of 26 globally distributed populations were genotyped. A weak but significant global pattern of isolation-by-distance was found, and G. molesta populations were geographically structured on a continental scale. Evidence does not support that G. molesta was introduced to North America from Japan as previously proposed. However, G. molesta was probably introduced from North America to The Azores, South Africa, and Brazil, and from East Asia to Australia. Shared ancestry was inferred between populations from Western Europe and from Brazil, although it remains unresolved whether an introduction occurred from Europe to Brazil, or vice versa. Both genetic diversity and levels of inbreeding were surprisingly high across the range of G. molesta and were not higher or lower overall in introduced areas compared to native areas. There is little evidence for multiple introductions to each continent (except in the case of South America), or for admixture between populations from different origins.ConclusionsCross-continental introductions of G. molesta appear to be infrequent, which is surprising given its rapid worldwide expansion over the past century. We suggest that area-wide spread via transport of fruits and other plant materials is a major mechanism of ongoing invasion, and management efforts should therefore target local and regional farming communities and distribution networks.

Susceptibility of Prunus rootstocks against Marcus and Dideron isolates of Plum pox virus by graft‐inoculation

AbstractSharka (Plum pox virus, PPV) is one of the most important diseases affecting stone fruits. While there is much information on the reaction of cultivars to PPV infection, details about rootstocks are scarce. In this study, we evaluated 28 stone fruit rootstocks belonging to different Prunus species against the Marcus and Dideron strains of PPV. Rootstocks were evaluated under controlled conditions during two growing seasons using two inoculation methods: direct inoculation of own‐rooted rootstocks and grafting onto PPV‐infected GF305 peach seedlings. Our results showed a generalised susceptibility of the rootstocks evaluated. Evaluating own‐rooted rootstocks was more efficient than the traditional method of grafting onto infected GF305 seedlings. As expected, PPV‐M was found to be more aggressive than PPV‐D, producing symptoms and occurring in a higher number of plants, as shown by ELISA. The most susceptible rootstocks were Myran, Viking, Myro pg Pecher, Julior, Myrobolan 29C, Rubira, Myrobolan B, MrS 2/5, Jaspi and MP8. The least susceptible were GF677, Myrotop, Citation and ZH6. These results highlight the necessity to breed PPV‐resistant rootstocks for the different stone fruit species.

First Report of Hyphodermella rosae Causing Dry Fruit Rot Disease on Plum in Iran.

Plum (Prunus domestica) and peach (P. persica) are widely grown, often in alternate rows with citrus, in the Mazandaran Province of Iran. In June 2011, a dry fruit rot of plum was observed in several production regions in Mazandaran Province (35°47'N, 50°34'E). Initial symptoms at pit-hardening stage appeared as dark brown, circular, necrotic spots from 2 to 5 cm in diameter. They later developed into a dry fruit rot. Severe symptoms occurred during June and July when warm weather (temperature around 28°C) and high relative humidity (RH) (>85%) were present. Marketable yield losses reached 50% to almost 100% in many orchards. To isolate the causal organism, symptomatic fruits were surface disinfested for 1 min in 0.5% active chlorine, washed thoroughly with sterile distilled water, and segments were plated on potato dextrose agar (PDA) amended with 50 mg/liter of streptomycin sulfate and incubated at 25°C for 3 days. The fungus Hyphodermella rosae (Bresadola) Nakasone was consistently isolated (37 isolates from 79 samples) and identified on the basis of morphological characteristics on PDA. Basidiomata were effuse, resupinate, 15 × 10 mm, crustaceous, tubercules small with apical bristles, and light orange to grayish orange. Subhymenium was up to 30 μm thick, composed of vertically arranged, short-celled, nonagglutinated hyphae; subhymenial hyphae were 3 to 4 μm in diameter. Basidiospores were ellipsoid, 7.5 to 8.5 × 4.5 to 5.5 μm (100 determination), and their cell walls were thin, hyaline, and smooth (1). Genomic DNA was extracted from mycelium with a DNA extraction kit (Qiagen, Hilden, Germany) according to the manufacturer's directions and grown on potato dextrose broth for 4 days at 28°C. The rDNA region was amplified with the primers ITS4 (5'-TCCTCCGCTTATTGATATGC-3') and ITS5 (5'- GGAAGTAAAAGTCGTAACAA-3') (4) and the PCR product was sequenced. Nucleotide BLAST analysis of the amplified 627-bp fragment confirmed a 99% similarity with the sequence of H. rosae (GenBank Accession No. JN593086). A pathogenicity test was conducted with isolate MA4099 by placing 5-day-old mycelial plugs grown on PDA at the surface of healthy fruit (n = 6) incubated under >85% RH at 25°C for at least 4 days until the appearance of symptoms, which were similar to those displayed under orchard conditions. Control fruits, inoculated with blocks of PDA plugs, remained intact and symptomless. Reisolation from inoculated fruit samples consistently yielded the inoculated fungus, completing Koch's postulates. The genus Hyphodermella has been reported to be causing wood rot on apricot (2) and sweet and sour cherry (3). To our knowledge, this is the first report of H. rosae causing dry fruit rot on a stone fruit species in the world.

Nutrição e manejo do solo em fruteiras de caroço em regiões de clima temperado

The agronomic techniques adopted for stone fruit trees cultivation should be ecologically and economically sustainable. This implies that production processes, apart from improving fruit yield and quality, mantain or increase the value of natural resources, guaranteeng satisfactory incomes to growers. The paper discusses fertilization and soil management aspects for peach, species largely investigated, and other stone fruit species, with emphasis on the Italian fruit industry.

EVALUATION OF XANTHOMONAS ARBORICOLA pv. PRUNI INOCULATION TECHNIQUES TO SCREEN FOR BACTERIAL SPOT RESISTANCE IN PEACH AND APRICOT

Screening for resistance to bacterial spot of apricot (Prunus armeniaca) and other stone fruit species such as peach (P. persica) and plum (P. domestica), caused by the quarantine bacterium Xanthomonas arboricola pv. pruni requires an inoculation method which is rapid, efficient and which permits to differentiate levels of resistance to this disease. Four inoculation techniques were compared under greenhouse conditions: (i) infiltration in the leaves using a needleless syringe; (ii) injuries caused by a needle; (iii) injuries caused by scissors; (iv) dipping shoots of the plant into the inoculum. All inoculation techniques induced symptoms: infiltration was very efficient and quickly caused severe necrosis and leaf drop; the use of needle was also very efficient but the symptoms were very weak, while the scissors technique was not as efficient as the first two approaches and the symptoms were also very weak. Finally dipping peach shoots into the inoculum was the least efficient in symptom induction, but this technique permitted to obtain more quantitative data suitable for evaluating the level of resistance of a cultivar than all the other techniques (e.g. number of spots per leaf, or damaged surface, calculated disease incidence and resistance index). For this reason, the inoculation technique by immersion was applied to six apricot cultivars to be screened for resistance against bacterial spot. Plants were assessed 15, 28, 38 and 64 days post inoculation for spot number, leaf surface damaged, disease incidence and severity of symptoms. Cv. Orangered was the most resistant, showing low levels of damage to the leaves (10% +/- 3.54) and only a few symptomatic leaves per plant (17.39 +/- 0.56). Cv. Goldbar was the most susceptible with 76.74 +/- 19.39% of symptomatic leaves and high levels of damage per leaf (85 +/- 11.34%). Four other cvs., Bergarouge, Bergeron, Goldrich and Kioto showed intermediate levels of susceptibility to the bacterium. Results of resistance testing were comparable to those observed under field conditions as reported in the literature. This indicates that shoot immersion into the inoculum is an efficient and reliable technique to screen for resistance against bacterial spot of stone fruits under greenhouse conditions.

Development and Evaluation of a 9K SNP Array for Peach by Internationally Coordinated SNP Detection and Validation in Breeding Germplasm

Although a large number of single nucleotide polymorphism (SNP) markers covering the entire genome are needed to enable molecular breeding efforts such as genome wide association studies, fine mapping, genomic selection and marker-assisted selection in peach [Prunus persica (L.) Batsch] and related Prunus species, only a limited number of genetic markers, including simple sequence repeats (SSRs), have been available to date. To address this need, an international consortium (The International Peach SNP Consortium; IPSC) has pursued a coordinated effort to perform genome-scale SNP discovery in peach using next generation sequencing platforms to develop and characterize a high-throughput Illumina Infinium® SNP genotyping array platform. We performed whole genome re-sequencing of 56 peach breeding accessions using the Illumina and Roche/454 sequencing technologies. Polymorphism detection algorithms identified a total of 1,022,354 SNPs. Validation with the Illumina GoldenGate® assay was performed on a subset of the predicted SNPs, verifying ∼75% of genic (exonic and intronic) SNPs, whereas only about a third of intergenic SNPs were verified. Conservative filtering was applied to arrive at a set of 8,144 SNPs that were included on the IPSC peach SNP array v1, distributed over all eight peach chromosomes with an average spacing of 26.7 kb between SNPs. Use of this platform to screen a total of 709 accessions of peach in two separate evaluation panels identified a total of 6,869 (84.3%) polymorphic SNPs.The almost 7,000 SNPs verified as polymorphic through extensive empirical evaluation represent an excellent source of markers for future studies in genetic relatedness, genetic mapping, and dissecting the genetic architecture of complex agricultural traits. The IPSC peach SNP array v1 is commercially available and we expect that it will be used worldwide for genetic studies in peach and related stone fruit and nut species.

Amygdalin content in four stone fruit species at different developmental stages

The amygdalin content of four species of stone fruit trees (apricot, peach, plum, and bitter apricot trees) during different stages was investigated by thin-layer chromatography. The results showed that the amygdalin content in the kernel was much higher than in pulps, roots, shoots, or leaves, and the highest amygdalin occurred in bitter apricot kernels. The patterns of amygdalin content in leaves of the four species consisted of a single peak curve, which increased from 30 April to 30 July, then started to decline reaching a lower level in October. In shoot and root, amygdalin decreased dramatically from 15 March to 15 May, then increased slightly until 15 December and maintained a relatively stable value. The tendency of amygdalin in xylem of stem and root was similarly a double peak curve, originally increasing from 15 March to 15 May, then decreasing to a low level, after that increasing slightly until December. However, the patterns of amygdalin content in shoots phloem was distinct from that of the xylem. The amygdalin decreased in shoot phloem whereas it increased in the stem xylem during the stage from 15 March to 15 July. The amygdalin content in root phloem and root xylem showed a similar trend with stem. Results demonstrated that amygdalin content in pulps and kernels was increased with the increasing in the leaves; the decrease in amygdalin in the phloem is connected with the increased in the xylem in early growth period.

Determination of the pathogenic and non-pathogenic bacteria on stone fruits grown in Northeast Anatolia region of Turkey

In the present study, bacterial flora were isolated from diseased plant samples obtained from stone fruit species (peach, apricot, plum, prune, cherry, sour cherry and almond) grown in the Northeast Anatolia region of Turkey during 2002–2004. All bacterial strains were identified using conventional and molecular techniques, including morphological, physiological and biochemical tests, fatty acid methyl ester (FAME) analysis and carbon utilization profiles. According to FAME analysis, a total of 365 bacterial strains belonging to 39 genera were identified. Among them, 69 strains of two different species of Pseudomonas were demonstrated to be pathogenic based on the hypersensitive test on tobacco and pathogenicity tests on original host plants including peach, apricot and sour cherry. According to Sherlock Microbial Identification System results, the most common pathogenic bacterial strains were Pseudomonas syringae (94.2%) and Pseudomonas fluorescens (5.8%). According to biochemical test results (LOPAT and GATTa), most of the isolated bacterial strains were identified as Pseudomonas syringae pv. syringae.

Genus Monilinia on pome and stone fruit species

Different species of the genus Monilinia are common plant pathogens that endanger pome and stone fruit production worldwide. In Serbia, two species of this genus are widely distributed - M. laxa and M. fructigena, while M. fructicola, which is officially on the A2 EPPO List of quarantine pest organisms in Europe and on the 1A part I List of quarantine pest organisms in Serbia, has so far been detected only on stored apple and nectarine fruits. The most important control measures against these pathogens include chemical control in combination with adequate cultural practices, particularly under favourable conditions for disease development. Concerning that species of this genus can cause significant economic losses, knowledge of the pathogen biology, disease epidemiology and pathogen-host interactions is a necessary prerequisite for stable and profitable production of pome and stone fruits.

First Report of Peach latent mosaic viroid in Peach Trees in Montenegro.

Peach latent mosaic viroid (PLMVd) and Hop stunt viroid (HSVd) are known to infect stone fruit species worldwide. The viroid infection can be latent or induce a variety of disease symptoms. Stone fruit samples were collected in Montenegro for a Plum pox virus (PPV) survey in 2007. Thirteen samples infected with PPV, taken from 12-year-old peach trees (Prunus persica (L.) Batsch, cv. Elegant Lady) in the area of Cemovsko field, were tested for the presence of PLMVd and HSVd by reverse transcription (RT)-PCR. Mild or severe mosaic, chlorotic rings, and fruit deformations were observed on some trees. Total RNA was extracted from all samples with a RNeasy Plant Mini Kit (Qiagen, Chatsworth, CA) and RT-PCR was performed. Samples were tested for HSVd and PLMVd infection using primer pairs RF-43/RF-44 for PLMVd (1) and VP-19/VP-20 for HSVd (2). Amplification products of approximately 348 bp were obtained from nine samples with PLMVd primers. Amplification products from seven samples were successfully cloned into pGEM-T Easy Vector (Promega, Madison, WI) and used for transformation of Escherichia coli. At least four clones of each sample were sequenced. Obtained sequences were 337 and 338 nucleotides long and shared 90.3 to 100% identity. Consensus sequences of each sample were deposited in GenBank under Accession Nos. JF927892-JF927898. They showed 92.6 to 97.9% identity among each other, 94 to 98% identity with the PLMVd isolate G sequence (Accession No. EF591868) and 91.8 to 94.4% identity with PLMVd sequence M83545. HSVd was not detected in analyzed samples. PLMVd infections were found on peach trees in an area where approximately 40% of the peach production is located. Therefore, PLMVd infections can pose a threat to peach production in Montenegro. To our knowledge this is the first report of PLMVd infection of peach in Montenegro.

First Reports of Brown Fruit Rot on Sweet Cherry (Prunus avium) and Plum (P. domestica) and Shoot Blight on Apricot (P. armeniaca), Kwanzan Cherry (P. serrulata), and Sweet Cherry (P. avium) Caused by Monilinia laxa in New York, Rhode Island, and Massachusetts.

In the eastern United States, Monilinia laxa (Aderh. & Ruhl.) Honey has only been reported on tart cherry in New York (NY) (1). As a result of considerable rain in May of 2009 and 2011, an ornamental planting of Kwanzan cherries in Middletown, Rhode Island (RI), a planting of sweet cherry cvs. Ulster, Hedelfingen, Sam, and Lapins in Lanesboro, Massachusetts (MA), and plantings of apricot cvs. Harcot and Hargrande in Albion, Aurora, and Geneva, NY, and Harogem in Lanesboro, MA developed severe shoot blight (>15 to 100% of first-year shoots). Blighted shoots were wilted with the blight encompassing the distal end and often extending into second-year tissue with a distinct sunken margin. Leaves on symptomatic shoots had flushed, but were blighted and light brown. Blossom spurs were often blighted and gummosis was frequently observed at the base. In these same years, sweet cherry cv. Black Gold in Walworth, NY and plum cv. Stanley in Olcott, NY developed severe fruit rot (35 to 70% incidence). Plantings suffering from fruit rot had fruit lesions that began as pale brown, soft lesions with indiscriminant margins that covered 15 to 85% of the fruit surface area. Many blighted spurs, shoot tissues, and infected fruit were sporulating with tan-to-buff colored conidia produced in chains. From each planting with shoot blight, shoot tips were removed for pathogen isolation. Sections of symptomatic shoots (5 cm long) were surface sterilized in 0.6% NaOCl for 1 min and rinsed in sterile dH20. From plantings displaying blighted spurs or fruit rot, isolation was attempted directly from sporulating tissue. Cross sections of sterilized shoot tissue (3 mm thick) or tufts of sporulation from fruit and spurs were placed on potato dextrose agar amended with 50 μg/ml of streptomycin sulfate. After incubation at 24°C for 5 days, colonies with lobed margins, commonly described for M. laxa (4), were obtained. Several colonies resembling M. fructicola were isolated from all locations, but the majority of isolates from spurs and shoots resembled M. laxa. Conidia from both colony morphotypes were lemon shaped, but as expected, those from putative M. laxa isolates were smaller (10.75 × 12.0 μm) compared with those from putative M. fructicola isolates (15.75 × 18.25 μm) (4). Confirmation of M. laxa was further achieved by PCR amplification of the β-tubulin gene using M. laxa-specific primers as previously described (3). Pathogenicity of M. laxa isolates was proven by inoculating fruit of the stone fruit crop from which they were isolated as previously described (2). Fruit inoculated with M. laxa developed brown, soft sporulating lesions identical to the original observations, while those inoculated with water remained healthy. M. laxa was reisolated from symptomatic shoots and spurs, but not from water-inoculated tissues. The presence of M. laxa has been reported on tart cherries in NY (1), but to our knowledge, this is the first instance of economically devastating shoot blight on apricot in NY and MA, ornamental cherry in RI, and sweet cherry in MA and fruit rot on sweet cherry and plum in NY caused by M. laxa. In wet seasons, stone fruit growers may need to revise their chemical management programs to better prepare for M. laxa epidemics on several stone fruit species.

First Report of Plum bark necrosis stem pitting-associated virus in Stone Fruit Trees in China.

Plum bark necrosis and stem pitting disease was first observed on a 'Black Beaut' plum (Prunus salicina Lindl.) in the United States in 1986 and later is several other countries. Plum bark necrosis stem pitting-associated virus (PBNSPaV; genus Ampelovirus, family Closteroviridae), the putative causal agent of the disease, infects many stone fruit species and causes decline, gummosis, flattening of scaffold branches, and stem necrotic pits in some diseased trees (1,3). An investigation of the incidence of PBNSPaV on stone fruit trees in China was conducted during 2009 and 2010. Leaf samples were collected from 47 trees, including peach (P. persica L. Batsch), nectarine (P. persica L. var. nucipersica Schneider), plum (P. domestica L.), ornamental plum (P. cerasifera Ehrb), sweet cherry (P. avium L.), and flowering cherry (P. serrulata L.), grown in Hubei, Henan, and Shandong provinces in central and northern China. Most of sampled trees showed trunk gummosis or stem pitting. The presence of PBNSPaV was tested by reverse transcription (RT)-PCR using primer set PBN195F/PBN195R (5'-CTGGTCTTCCTGCTACTCCTT-3'/5'-AAGCCCACAATCTCAGAGCG-3') designed for the detection of the coat protein (CP) gene of the virus. Total RNA was extracted from leaves using a CTAB protocol reported by Li et al. (2). Products of the expected size of 190 bp were amplified from 20 samples, including seven cultivated peach, four ornamental peach, one nectarine, two plum, one ornamental plum, three sweet cherry, and two flowering cherry samples. All trees positive for PBNSPaV showed stem pitting symptoms on the base of the trunk. To further confirm these results, a 590-base region of the heat shock protein 70 homolog (HSP70h) gene was amplified by RT-PCR using primers HSP-P1/HSP-P2 (5'-GGAATTGACTTCGGTACAAC-3'/5'-TCGAAAGTACCACCACCGAA-3'). Amplicons of the expected size were cloned into the vector pMD18-T (TaKaRa, Dalian, China) and sequenced by Genscript Corp. (Nanjing, China). Sequences of 18 PBNSPaV isolates were deposited in GenBank with Accession Nos. JF810177-JF810194. Sequence comparisons showed that the partial HSP70h gene from the Chinese PBNSPaV isolates shared 82.2 to 100% nucleotide (nt) and 94.0 to 100% amino acid (aa) similarities between them and 83.6 to 99.1% nt and 94 to 100% aa similarities with the corresponding region of the other PBNSPaV isolates deposited in GenBank. In July 2010, peach GF305 seedlings were inoculated by side grafting with budwoods from two PBNSPaV-positive ornamental peach plants. In June 2011, grooving symptom was observed on the stems of the seedlings and the virus was detected by RT-PCR. The results further confirmed PBNSPaV infection in China. These results show that PBNSPaV and the associated disease occur in main cultivated and ornamental Prunus species in China. Given the importance and the devastating symptoms of the disease, it is important to prevent virus spread by using virus-tested propagation materials.

First Report of the Plum Pox Virus Recombinant Strain on Peach in Bulgaria

Plum pox virus (PPV) causes sharka, the most damaging viral disease of stone fruit species. Seven distinct PPV strains are known; PPV-M, PPV-D, and PPV-Rec are the most common (3). PPV-Rec is a unique recombinant (3) between PPV-M and PPV-D and has been reported from plum, apricot, Japanese plum, myrobalan, and blackthorn in eastern and central Europe, but has never been found in peach as a single natural infection (2). A survey was conducted during spring 2009 in eight peach orchards located in the southwest, southeast, and south central regions of Bulgaria to assess the incidence of PPV infection. A total of 98 leaf samples from individual trees showing PPV-like symptoms were collected and analyzed by triple-antibody sandwich (TAS)-ELISA with the universal monoclonal antibody (MAb) 5B (Agritest, Valenzano, Italy). Sixty one samples reacted positive for PPV (optical density 0.161 to 1.267) and these samples were further analyzed with PPV-M (AL) and PPV-D (4DG5) specific MAbs (1). All 61 samples reacted positively with PPV-M specific MAbs. To distinguish PPV-M and PPV-Rec strains, which are serologically identical, immunocapture (IC)-reverse transcription (RT)-PCR was carried out with PPV-M (CIP-M: 5'-GTC GCA GCA TTT GTA GCC CTT GTT-3', CIP-MR: 5'-CCA ACA CGT TAA CGC CAT GCT TCA-3') and PPV-D (CIP-D: 5'-ATG ATG CTG TTT GAC TCG GAG CGA-3', CIP-DR: 5'-TCG CAA CTG CTT GCA CAC ATT CTC-3') specific primers targeting the 6K1-CI genomic region. A PCR fragment of ~880 bp amplified with PPV-M specific primers obtained from 59 samples confirmed that these were PPV-M isolates. However, the remaining two samples (both coming from infected tress located in two different orchards in the southwest region) yielded a 468-bp PCR fragment with PPV-D specific primers, suggesting that these two samples belonged to PPV-Rec strain. These samples together with controls of PPV-M, PPV-D, and PPV-Rec strains were further analyzed by RT-PCR using mD5/mM3 primers spanning the recombination breakpoint (4). Both peach samples and the PPV-Rec strain control produced a single 605-bp PCR product. The two peach amplicons were purified and sequenced directly with the same primers. The nucleotide (nt) sequences obtained were 100% identical to each other. BLAST analysis of the two samples with PPV-Rec (No. AF421118.1) showed maximum nt identity of 98%. Percent maximum nt identity with PPV-M (No. AY324837.1) and PPV-D (No. AB576062.1) were 93 and 87%, respectively. The deduced amino acid sequences of the two isolates were 98% identical to PPV-Rec (No. No. AF421118.1), 93% identical to PPV-M (No. M92280.1), and 84% identical to PPV-D (No. AB576062.1). Analyzed samples were further transmitted from the diseased trees to peach seedlings (GF 305) by chip-budding in a greenhouse during the fall of 2009. Six months later, faint vein clearing on the leaves of inoculated seedlings was observed. The presence of PPV was confirmed by TAS-ELISA and PPV-Rec presence was shown by IC-RT-PCR (mD5/mM3 primers). One of the generated 605-bp products was sequenced and showed 100% nt identity with the isolate used for inoculation. To our knowledge, this is the first identification of PPV-Rec strain in naturally infected peach trees, a finding that calls for further large-scale investigations of PPV-Rec incidence in peach in Bulgaria.

Partial characterisation of a cherry isolate of a newly emerging stone fruit virus: Plum bark necrosis stem pitting associated virus

Plum bark necrosis stem pitting associated virus (PBNSPaV) has occurred globally over the last two decades and is becoming one of the major agricultural issues of stone fruits. The virus was detected for the first time in plums and has been reported in the other stone fruit species. The agent, whose dissemination mode is still unknown, has been first reported in cherries in Turkey grown in Malatya province. In this study, the K1 isolate of PBNSPaV, identified in a sweet cherry plant with severe stem pitting and gumming symptoms on its trunk, was partially characterised. A fragment of Hsp70h gene located on ORF3 of viral genome has been cloned, sequenced and analysed phylogenetically (Accession number. FJ231498). The PBNSPaV-K1 isolate showed 93–96% nucleotide sequence identity to sequences of Italian and American isolates in databases. An RNA probe has been raised for fast and reliable detection of the agent by molecular hybridisation. The studies on development of genome specific primers for the detection of the isolate by one-tube RT-PCR have failed.

Phytoplasma diseases of stone fruit trees in Turkey and their containment

Although fruit tree phytoplasmas were studied since 1999 in Turkey, there have been very limited studies and records on stone fruit tree phytoplasmas. The main symptoms reported on apricot, plum, peach and almond were chlorosis between veins, off season flowering and fruiting as a result of early bud breaking, longitudinal leaf rolling and quick die-back. More than 500 cultivated and wild Prunus plants in or nearby germplasm nurseries and commercial orchards during 2002–2009 were tested by using universal primers P1/P7 and fU5/rU3 in direct and nested PCR assays, respectively. Amplification products were digested with RsaI and SspI restriction enzymes. The average incidence of ‘Candidatus Phytoplasma prunorum’ was detected as 10.19%. The most infected stone fruit species were apricot and plum, followed by almond and peach. No phytoplasma was found in cherries and wild Prunus species.

Comparison of RT-PCR and PCR-RFLP molecular techniques used for the differentiation of isolates belonging to D and M strains of Plum pox virus collected from Cluj region.

Plum pox virus (PPV) is the causal agent of sharka disease, which is responsible for severe damage and important economic losses in the stone fruit industry. The disease mainly affects stone-fruit species, mainly apricot, plum and peach . Sharka is originated from Eastern Europe and was described for the first time around 1915 in Bulgari a (Atanasoff, 1932). In this study we collected thi rty PPV isolates from one experimental orchard belonging to the Fruit Research and Development Station Cluj. Molecular strain differentiation was done with the help of RT-PCR technique by analyzing the genomic region (Cter)CP of the virus by using RFLP analysis we were able to distinguish the two major strains, D and M, based on Rsa I polymorphism located in the genomic region (Cter) CP.

Incidence of Plum Pox Virus in Romanian Plum Orchards

Sharka caused by Plum pox virus (PPV) is the most detrimental viral pathogen of stone fruits. Plum pox virus was identified on the Romanian territory in 1922 by Traian Savulescu, but systematic research on the disease only started in the 1960’s (Minoiu, 1997). Presently, in Romania PPV is spread in all plum growing areas and became one of the significant limiting factors for a profitable plum growing. Romanian fruit crops (stone and pome fruits) include about 158 000 ha of orchards. Stone fruit species cover 87 000 ha (55 %). The plum is the dominant fruit specie in Romania, covering approximately 75 000 ha (48 %) (FAO 2008) and hence is of great economic importance.

Host specialization of Tranzschelia discolor on stone fruits at the uredinial infection stage

The host range specialization of Tranzschelia discolor (Fckl.) Tranz. & Litv. on stone fruits at the uredinial infection stage was investigated. Aeciospore inocula were collected from the alternate host, Anemone coronaria, at ten different locations of Aydin Province in early spring and were separately inoculated to 1–2-year-old nursery stocks of plum, peach, apricot, almond and sweet cherry under growth chamber conditions. Rust pustules developed only on plums, 15–21 days after inoculations, but no infections occurred on the other stone fruits. Urediniospore inocula were collected from naturally infected plums, apricots, peaches and almonds and were inoculated to four host species as well as sweet cherry in a series of cross-inoculations. Rust pustules developed on plants of the respective original host species from which the urediniospore inoculum was collected. No morphological differences were found among teliospores and urediniospores of T. discolor sampled from the different stone fruit species. Results of this study indicate that there is host specialization of T. discolor on stone fruits at the uredinial infection stage. Aecial inoculum from anemones in Aydin Province was infectious only on plums. The alternate host for the other stone fruits in this province was not found.

EPIDEMIOLOGY AND PREDISPOSING FACTORS OF SOME MAJOR BACTERIAL DISEASES OF STONE AND NUT FRUIT TREES SPECIES

Despite the basic importance of studying the epidemiology of bacterial pathogens for their effective control in the field, for many pathogens causing diseases of economic importance there is still a large body of knowledge to acquire. In this minireview the main epidemiological aspects and predisposing factors of some important diseases of stone and nut tree fruit species caused by bacteria are summarized. Apricot (Prunus armeniaca L.), peach (P. persica Batsch.), sweet cherry (P. avium L.), sour or tart cherry (P. cerasus L.) and European plum (P. domestica L.) are the stone fruit trees species that can be severely attacked by two pathovars of Pseudomonas syringae worldwide: P. syringae pv. syringae (Pss) and P. syringae pv. morsprunorum (Psm). The high sensitivity of some recently introduced apricot cultivars would seem a main predisposing factor enhancing the aggressiveness of Pss. Sandy and very clayey soils as well as soils characterized by a low calcium content can also contribute to enhance the sensitivity of apricot and peach trees to Pss. Xanthomonas arboricola pv. pruni is the causative agent of bacterial spot threatening peach, apricot, Japanese plum (P. salicina) and almond (Amygdalus communis L.). This pathogen is present worldwide and is currently spreading in many European countries. A relative humidity of 100% over a period of three days has been shown fundamental for the appearance of the disease in peach leaves. Xanthomonas arboricola pv. juglandis is the causal agent of walnut blight and fruit apical necrosis often severely attacking Juglans regia L. Recent in-depth studies showed that this pathogen starts the infection process at the apex of the fruit. Fungi play a secondary role as saprophytes or opportunistic pathogens in this apical necrosis of fruits. Pseudomonas avellanae is the causal agent of bacterial canker and decline of hazelnut (Corylus avellana L.). So far, this destructive disease has been reported solely from northern Greece and central Italy. Soil of volcanic origin with pH values <5.0 can increase the susceptibility of hazelnut to bacterial canker.

Isotopically-labelled nitrogen uptake and partitioning in sweet cherry as influenced by timing of fertilizer application

Sweet cherry ( Prunus avium L.) is a fruit of increasing economic importance though it is less significant than other stone fruit species such as peach. Cherry has received little attention concerning nitrogen (N) uptake and dynamics in mature trees. The aim of this work was to determine N uptake and partitioning as influenced by the timing of fertilizer application in 7-year-old sweet cherry trees cultivated in a cold region (Los Antiguos, Santa Cruz, Argentina; 71°38′ W, 46°32′ S). Nitrogen (95 kg ha −1) was applied as ammonium nitrate to a soil with ‘Bing’ sweet cherry trees grafted onto Prunus mahaleb rootstocks. Fertilization was split into two equal applications per treatment, involving either the commercial fertilizer ammonium nitrate or the same fertilizer labelled with 15N isotope (10% atom.). Treatments consisted of one early spring (full bloom, October 2005) or one summer (late January 2006, 15 days after harvest) application of 15N ammonium nitrate to three replicate trees. Fruit were harvested in early January and leaves were collected at both full canopy and leaf fall. All trees were excavated in winter (August, 2006). Trees were partitioned into their components: trunk, branches (current-season shoots, 1-year-old and over-1-year-old branches), buds of the same age, small roots (less than 1 mm thick), large roots, leaves (sampled in February and April), and fruit (collected at harvest). Those components were dried and analysed for total N and 15N content. Total N per tree and N content derived from the fertilizer did not differ between treatments. Summer postharvest 15N application partitioned not only to structural components (trunk and roots) but also to buds and leaves. Uptake efficiency was significantly ( p = 0.0113) higher in the spring than in the summer application (65.7% vs. 37.44%). Nevertheless, 52.5% of N applied in spring was lost due to harvest and summer pruning. This emphasizes the importance of the postharvest N fertilization which increases N accumulation in both reserve organs and buds though, according to our data, it is less efficiently used. The extent of nitrogen uptake, efficiency of use and partitioning in the following growing seasons are still open questions that deserve further research.