Pathogenicity and toxigenicity of <Emphasis Type="Italic">Fusarium verticillioides</Emphasis> isolates collected from maize roots,stems and ears in South Africa

Sunflower (Helianthus annuus L.) is an important oilseed crop in South Africa, and is grown in rotation with maize in some parts of North West, Limpopo, Free State, Mpumalanga and Gauteng provinces. Alternaria leaf blight is currently one of the major potential disease threats of sunflower and is capable of causing yield losses in all production regions. Alternaria helianthi was reported as the main cause of Alternaria leaf blight of sunflower in South Africa; however small-spored Alternaria species have been consistently isolated from leaf blight symptoms during recent surveys. The aim of this study was to use morphological and molecular techniques to identify the causal agent(s) of Alternaria blight isolated from South African sunflower production areas. Alternaria helianthi was not recovered from any of the sunflower lesions or seeds, with only Alternaria alternata retrieved from the symptomatic tissue. Molecular identification based on a combined phylogenetic dataset using the partial internal transcribed spacer regions, RNA polymerase second largest subunit, glyceraldehyde-3-phosphate dehydrogenase, translation elongation factor and Alternaria allergen gene regions was done to support the morphological identification based on the three-dimensional sporulation patterns of Alternaria. Furthermore, this study aimed at evaluating the pathogenicity of the recovered Alternaria isolates and their potential as causal agents of Alternaria leaf blight of sunflower. Pathogenicity tests showed that all the Alternaria alternata isolates tested were capable of causing Alternaria leaf blight of sunflower as seen in the field. This is the first report of A. alternata causing leaf blight of sunflower in South Africa.     

Pathogenic variation of Alternaria species associated with leaf blotch and fruit spot of apple in Australia

Four Alternaria species groups (A. longipes, A. arborescens, A. alternata/A. tenuissima and A. tenuissima/A. mali) are associated with leaf blotch and fruit spot of apple in Australia. There is no information on the variability of pathogenicity among the species and isolates within each species causing leaf blotch or fruit spot. We used a detached leaf assay and an in planta fruit inoculation assay to determine the pathogenicity and virulence of the four Alternaria species. Our results showed that isolates within the same species were not specific to either leaf or fruit tissue and showed great variability in pathogenicity and virulence, indicating cross-pathogenicity, which may be isolate dependent rather than species dependent. Generally, virulence of A. tenuissima and A. alternata isolates on leaf and fruit was higher than other species. Isolates of all species groups were pathogenic on leaves of different cultivars, but pathogenicity on fruit of different cultivars varied among isolates and species. Implications of our findings on prevalence of the diseases in different apple-producing regions in Australia and the development of targeted disease management of the diseases are discussed.     

Analysis of genetic and virulence variability of Stemphylium lycopersici associated with leaf spot of vegetable crops

Stemphylium lycopersici (Enjoji) W. Yamam was initially described from tomato and has been reported to infect different hosts worldwide. Sequence analyses of the internal transcribed spacer (ITS) regions 1 and 2, including 5.8S rDNA (ITS-5.8S rDNA) and glyceraldehyde-3-phosphate dehydrogenase (gpd) gene, random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), as well as virulence studies were conducted to analyze 46?S. lycopersici isolates. Stemphylium lycopersici isolates used in this study were obtained from diseased tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), pepper (Capsicum annuum L.) and lettuce (Lactuca sativa L.) from major vegetable growing regions of Malaysia, including the three states of Pahang, Johor and Selangor between 2011 and 2012. Phylogenetic analysis of a combined dataset of the ITS-5.8S rDNA and gpd regions indicated that all isolates were clustered in the sub-cluster that comprised S. lycopersici, and were distinguished from other Stemphylium species. Cluster analyses using the UPGMA method for both RAPD and ISSR markers grouped S. lycopersici isolates into three main clusters with similarity index values of 67 and 68 %. The genetic diversity data confirmed that isolates of S. lycopersici are in concordance to host plants, and not geographical origin of the isolates. All S. lycopersici isolates were pathogenic on their original host plants and showed leaf spot symptoms; however, virulence variability was observed among the isolates. In cross-inoculation assays, the representative isolates were able to cause leaf spot symptoms on eggplant, pepper, lettuce and tomato, but not on cabbage.     

Characterization of Alternaria species associated with potato foliar diseases in China

The population structure of Alternaria species associated with potato foliar diseases in China has not been previously examined thoroughly. Between 2010 and 2013, a total of 511 Alternaria isolates were obtained from diseased potato leaves sampled in 16 provinces, autonomous regions or municipalities of China. Based on morphological traits and molecular characteristics, all the isolates were identified as Alternaria tenuissima, A. alternata or A. solani. Of the three species, A. tenuissima was the most prevalent (75·5%), followed by A. alternata (18·6%) and A. solani (5·9%). Phylogenetic analysis based on sequences of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of representative Alternaria isolates showed that A. solani was distinct from the two small‐spored Alternaria species. Phylogenetic analysis of the partial coding sequence of the histone 3 gene divided the same collection of isolates into three main clades representing A. tenuissima, A. alternata and A. solani, respectively. The pathogenicity of the isolates on detached leaves of potato cv. Favorite did not differ significantly between the three species or between isolates from different geographical origins. The results indicate that the population structure of Alternaria species associated with potato foliar diseases differs from that reported previously in China. This is the first report of A. tenuissima causing potato foliar diseases in China.     

Pathogenicity,Morpho-Species and Mating Types of <Emphasis Type="Italic">Alternaria</Emphasis> spp. causing Alternaria blight in <Emphasis Type="Italic">Pistacia</Emphasis> spp. in Turkey

Alternaria genus includes many plant pathogens on numerous hosts, causing leaf spots, rots and blights. Alternaria blight has been observed as one of the important fungal diseases of pistachio (Pistacia vera L.) as well as its wild relatives (P. terebinthus, P. lentiscus, P. khinjuk, P. atlantica, P. mutica) in Turkey. Alternaria species were sampled from Pistacia spp. hosts from different geographic regions in Turkey during field trips in late spring to early fall of 2013. Alternaria blight symptoms were observed mainly on fruits and rarely on leaves. Four hundred and twenty two of the isolates were morphologically defined as A. alternata, A. tenuissima, A. arborescens and also intermediate morpho-species between A. alternata/A. arborescens. Pathogenicity of the isolates was confirmed with host inoculations on detached fruits. Mating types of 270 isolates of Alternaria spp. from the collection were identified using a PCR-based mating type assay that amplifies either a MAT1-1 or a MAT1-2 fragment from the mating locus. Although a strongly clonal population structure was expected due to the putative asexual reproduction of these fungi, both idiomorphs were detected at equal frequencies at several different spatial scales. The distribution of mating types within each geographic region, within host species as well as in overall collection was not significantly different from 1:1. Amplified fragments of partial idiomorph sequences were obtained for representative isolates. Parsimony trees were depicted based on sequence data of mating type genes for these representative isolates as well as some other Alternaria species obtained by Genebank. Several point mutations presented a few clusters which are supported by high bootsrapped values. The Alternaria blight disease agents both from cultivated and wild hosts were pathogenic on pistachio which may cause difficulties to control the disease because of extensity of pathogen sources. Besides, equal mating type distribution of the pathogen at both geographic and host species levels suggests a potential for sexual reproduction of Alternaria spp. in Turkey.     

Molecular characterization and pathogenicity of <Emphasis Type="Italic">Alternaria</Emphasis> species on wheat and date palms in Oman

This study was conducted to investigate the Alternaria species associated with leaf spot of date palm and wheat in Oman. Out of 98 date palm leaf samples and 146 wheat leaf samples, Alternaria was isolated from 27 and 23% of the samples developing leaf spot symptoms, respectively. Identification of Alternaria isolates using sequences of the internal transcribed spacer region of the ribosomal RNA (ITS rRNA), glyceraldehyde-3-phosphate dehydrogenase (GPDH), translation elongation factor (TEF) and RNA polymerase II subunit (RPB2) genes, showed that the isolates belong to seven Alternaria species or species complexes. A. burnsii - A. tomato and A. arborescens species complexes (58 and 4%, respectively) and A. alternata (38%) were the species recovered from the symptomatic date palm leaves. A. alternata (67%), A. burnsii - A. tomato species complex (15%), A. jacinthicola (3%), A. ventricosa (3%), A. slovaca (6%) and Alternaria caespitosa (6%) were isolated from wheat. Pathogenicity test showed that tested isolates of A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31), A. jacinthicola (WBR4) and A. slovaca (WDK9, WDK7) were pathogenic on date palm, while A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31, WDK11) and A. slovaca (WDK9, WDK7) were pathogenic on wheat. This is the first report of date palm and wheat as new hosts for A. burnsii - A. tomato species complex and the first reports of A. burnsii - A. tomato species complex, A. caespitosa A. slovaca, and A. ventricosa in Oman. The study shows that several species of Alternaria are associated with leaf spot in date palm and wheat in Oman, with some isolates having the ability to cause infection in both hosts.     

Assessing the Belgian potato <Emphasis Type="Italic">Alternaria</Emphasis> population for sensitivity to fungicides with diverse modes of action

Early blight and brown spot, caused by respectively Alternaria solani and Alternaria alternata, can lead to severe yield losses in potato-growing areas. To date, fungicide application is the most effective measure to control the disease. However, in recent years, a reduced sensitivity towards several active ingredients has been reported. To shed light on this issue, Alternaria isolates were collected from different potato fields in Belgium during two growing seasons. Subsequently, the sensitivity of these isolates was assessed using four widely used fungicides with different modes of action. Demethylation inhibitors, quinone outside inhibitors, a dithiocarbamate and a carboxylic acid amide were included in this study. Although all fungicides reduced spore germination and vegetative growth of Alternaria species to some extent, the interspecies sensitivity was very variable. In general, A. solani was more suppressed by the fungicides compared to A. alternata. The effectiveness of the dithiocarbamate mancozeb was high, whereas the quinone outside inhibitor azoxystrobin showed a limited activity, especially towards A. alternata. Therefore, a subset of the A. alternata and A. solani isolates was tested for the presence of, respectively, the G143A substitution and the F129L substitution in the cytochrome b. The frequency of A. alternata isolates bearing the resistant G143A allele (approximately 65%) was comparable in both sampling years, although sensitivity of isolates decreased during the growing season. This finding points to a shift of the population towards resistant isolates. Both the European genotype I and American genotype II were present in the A. solani population, with genotype I being the most prevalent. None of the genotype I isolates carried the F129L substitution, whereas in 83% of the genotype II isolates this substitution was present. Our results demonstrate for the first time that the Belgian Alternaria population on potato comprises a considerable broad spectrum of isolates with different sensitivity to fungicides.     

Multiple Alternaria species groups are associated with leaf blotch and fruit spot diseases of apple in Australia

Leaf blotch and fruit spot of apple caused by Alternaria species occur in apple orchards in Australia. However, there is no information on the identity of the pathogens and whether one or more Alternaria species cause both diseases in Australia. Using DNA sequencing and morphological and cultural characteristics of 51 isolates obtained from apple leaves and fruit with symptoms in Australia, Alternaria species groups associated with leaf blotch and fruit spot of apples were identified. Sequences of Alternaria allergen a1 and endopolygalacturonase gene regions revealed that multiple Alternaria species groups are associated with both diseases. Phylogenetic analysis of concatenated sequences of the two genes resulted in four clades representing A. arborescens and A. arborescens‐like isolates in clade 1, A. tenuissima/A. mali isolates in clade 2, A. alternata/A. tenuissima intermediate isolates in clade 3 and A. longipes and A. longipes‐like isolates in clade 4. The clades formed using sequence information were supported by colony characteristics and sporulation patterns. The source of the isolates in each clade included both the leaf blotch variant and the fruit spot variant of the disease. Alternaria arborescens‐like isolates were the most prevalent (47%) and occurred in all six states of Australia, while A. alternata/A. tenuissima intermediate isolates (14%) and A. tenuissima/A. mali isolates (6%) occurred mostly in Queensland and New South Wales, respectively. Implications of multiple Alternaria species groups on apples in Australia are discussed.     

Characterization of iprodione-resistant Alternaria isolates from pistachio in California

Alternaria late blight caused by Alternaria spp. in the alternata, tenuissima, and arborescens species-groups is one of the most common fungal diseases of pistachio in California. In this study, a field iprodione-resistant (FIR) isolate of the arborescens species-group and a laboratory-induced iprodione-resistant (LIIR) isolate of the alternata species-group were characterized by fungicide and osmotic sensitivity, virulence on detached pistachio leaflets, and sequence of the coiled-coil region (six repeats of approximately 90-amino-acid domain) of the two-component histidine kinase (HK) gene. Both FIR and LIIR isolates were sensitive to azoxystrobin and tebuconazole, and azoxystrobin-resistant isolates were sensitive to iprodione and tebuconazole. The LIIR isolate showed more sensitivity to osmotic stress than its wild-type parent. However, the FIR isolate did not show higher osmotic sensitivity compared to field iprodione-sensitive (FIS) isolates. Laboratory inoculation tests showed that both FIR and LIIR isolates remained highly virulent on pistachio. Analysis of DNA sequences of the HK coiled-coil region showed that there were no differences in deduced amino acid sequence of this region from the LIIR, FIR, and FIS Alternaria isolates from pistachio in California.     

Wilt and root rot of poinsettia caused by three high-temperature-tolerant Pythium species in ebb-and-flow irrigation systems

Poinsettia plants growing in ebb-and-flow irrigation systems developed wilting and root rot during the summer growing seasons of 2010 in Gifu Prefecture and 2011 in Aichi Prefecture. Pythium species were isolated from roots with rot symptoms. The isolates were identified as P. helicoides and P. myriotylum on the basis of morphological characteristics and sequence homologies in the rDNA internal transcribed spacer regions. In pathogenicity tests, these isolates caused severe wilting and root rot. This is the first report of poinsettia root rot disease caused by P. helicoides and P. myriotylum, although P. aphanidermatum was reported as a pathogen of poinsettia root rot. To better understand these diseases, we performed an epidemiological study of three high-temperature-tolerant Pythium species, P. aphanidermatum, P. helicoides and P. myriotylum. Disease incidence as a percentage of diseased plants was greatest at 35 °C for all three species. Disease severity using the rating scale of root rot was also highest at 35 °C, particularly with high zoospore inoculum densities (100.0 zoospores/mL). Although the disease incidence and severity were reduced at lower temperatures, the three Pythium species were able to cause disease at temperatures as low as 20 °C.     

Resistance to azoxystrobin in Alternaria isolates from pistachio in California

Failure to control Alternaria late blight in a few California pistachio orchards was observed after only 3-4 years of consecutive applications of azoxystrobin-based fungicide programs. A total of 72 isolates of Alternaria alternata, Alternaria tenuissima, and Alternaria arborescens, the causal organisms of Alternaria late blight, were collected from pistachio orchards with (58 isolates) and without (14 isolates) a prior history of azoxystrobin applications. The sensitivity to azoxystrobin was determined in conidial germination assays. Isolates from orchards with a history of azoxystrobin applications had EC₅₀ values greater than 100 μg/ml, whereas isolates from orchards without a prior history of azoxystrobin usage had EC₅₀ values ranging from 0.008 to 0.045 μg/ml. Azoxystrobin resistance correlated with a single mutation in the cytochrome b (cyt b) gene causing a change of glycine to alanine at amino acid position 143. A pair of PCR primers AF and AR was developed that amplified a 226-bp DNA fragment of the cyt b gene containing the mutation site from all three Alternaria species but not from 30 other fungal species frequently found on pistachio. PCR-restriction fragment length polymorphism (PCR-RFLP) analysis using the restriction enzyme Fnu4HI allowed differentiation of the PCR fragment of wild type cyt b gene from that of mutated gene. This method will aid in a fast detection of azoxystrobin resistance in these three Alternaria species.     

Monitoring by real-time PCR of three water-borne zoosporic Pythium species in potted flower and tomato greenhouses under hydroponic culture systems

The high-temperature-tolerant Pythium species P. aphanidermatum, P. helicoides, and P. myriotylum cause serious diseases in many crops under hydroponic culture systems in Japan. Control of the diseases is difficult because these zoosporic pathogens spread quickly. In this study, a real-time PCR method was developed for monitoring the spread of zoospores of the three pathogens. Specific primers and TaqMan probes were established using the internal transcribed spacer regions of the rDNA. Specificity was confirmed using known isolates of each species and closely related non-target species. The sensitivity of DNA detection was 10 f. for each pathogen. 10 f. DNA corresponded to 4 P. aphanidermatum, 3 P. myriotylum, and 4 P. helicoides zoospores, respectively. Therefore, this real-time PCR method was used to evaluate and monitor zoospores in the nutrient solutions of ebb-and-flow irrigation systems for potted flower production and closed hydroponic culture systems for tomato production. The results indicated that the pathogens were present in the hydroponic culture systems throughout the year, and spread before disease occurrence.     

<Emphasis Type="Italic">Alternaria alternata</Emphasis>: A new seed-transmitted disease of coriander in South Africa

This is the first report of Alternaria leaf spot disease on coriander (Coriandrum sativum L.) in South Africa. Using the agar plate method, Alternaria alternata was isolated from coriander seed lots together with four other fungal genera, which included Aspergillus, Fusarium, Penicillium and Rhizopus. Standard seed germination tests of coriander seed lots infected with seed-borne mycoflora showed a positive correlation with the number of diseased seedlings (r?=?0.239, p?<?0.01). Pathogenicity tests demonstrated that this seed-borne A. alternata was pathogenic on coriander and symptoms on leaves first appeared as small, dark brown to black, circular lesions (<5 mm diam.) that enlarged and coalesced to form dark brown blotches as time progressed. Leaf spot disease was most severe (64%) on wounded leaves inoculated with A. alternata. Re-isolation of A. alternata from diseased coriander plants satisfied the Koch’s postulates, thus confirming it as the causal agent of Alternaria leaf spot disease. Parsimony analysis based on rpb2 (GenBank Accession No. KT895947), gapdh (KT895949) and tef-1α (KT895945) sequences confirmed identity of the Alternaria isolate, which grouped within the A. alternata clade. Alternaria alternata was shown to be transmitted from infected coriander seed to the developing plants.     

Morphological and molecular characterisation of Trichodorus golestanensis (Nematoda: Trichodoridae), a new species from Iran

Several species of trichodorid nematodes cause economically important disease on plants. Trichodorus comprises most of the trichodorid species. Trichodorus golestanensis n. sp. is described from a forest park in northern Iran. The new species belongs to the T. lusitanicus morpho-species group and is characterized in male by three ventromedian cervical papillae of which two at level of onchiostyle region, three ventromedian precloacal supplements, the posterior one just anterior to retracted spicules and ventrally curved spicules with mid-blade indentation provided with a few bristles. Females are distinguished by well developed triangular vaginal sclerotized pieces in lateral optical view, a rhomboid-shaped vagina and a transverse slit-like vulva in ventral view. Molecular analysis using the sequence of D2-D3 expansion segment of 28S rDNA differentiated the new species and confirmed the relationships of T. golestanensis n. sp. with T. andalusicus and T. asturanus. The sequences of D2-D3 regions were also provided for previous trichodorid records from Iran T. gilanensis, P. teres and N. minor together with discussion of their relationship.     

Control of infection of tomato fruits by <Emphasis Type="Italic">Alternaria</Emphasis> and mycotoxin production using plant extracts

Tomato fruits are susceptible to infection by Alternaria species. In addition, Alternaria species may contaminate the fruits with mycotoxins. There is thus interest in control systems to minimise pathogenicity and control toxin production. The objectives of this study were to examine the effect of plant extracts of Eucalyptus globulus and Calendula officinalis on the growth of strains of Alternaria alternata and A. arborescens, on pathogenicity of tomato fruits and mycotoxin production. The growth bioassays showed that the ethanolic and chloroformic fractions of E. globulus were the most effective in reducing growth of A. alternata (66–74 %) and A. arborescens (86–88 %), respectively at 2500 μg/g. The effects of plant extracts on mycotoxin biosynthesis were variable and strain dependent. The most effective fractions in decreasing mycotoxin accumulation were the ethanolic and chloroformic extracts of E. globulus, which reduced tenuazonic acid by 89 %, alternariol by 75–94 % and almost complete inhibition of alternariol monomethyl ether. All the tested fractions reduced percentage of infected tomato fruits when compared to the controls. The ethanolic and chloroformic fractions of E. globulus completely inhibited growth of A. alternata and A. arborescens on unwounded fruits and reduced the aggressiveness on wounded fruits of strains of both species significantly.     

Identification and characterization of <Emphasis Type="Italic">Alternaria</Emphasis> species causing leaf spot on cabbage,cauliflower, wild and cultivated rocket by using molecular and morphological features and mycotoxin production

Alternaria species are common pathogens of fruit and vegetables able to produce secondary metabolites potentially affecting human health. Twenty-nine isolates obtained from cabbage, cauliflower, wild and cultivated rocket were characterized and identified based on sporulation pattern and virulence; the phylogenetic analysis was based on the β-tubulin gene. Isolates were identified as A. alternata, A. tenuissima, A. arborescens, A. brassicicola and A. japonica. Pathogenicity was evaluated on plants under greenhouse conditions. Two isolates showed low level of virulence on cultivated rocket while the other isolates showed medium or high level of virulence. Isolates were also characterized for their mycotoxin production on a modified Czapek-Dox medium. Production of the five Alternaria toxins, tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene and tentoxin were evaluated. Under these conditions, about 80% of the isolates showed the ability to produce at least one mycotoxin.     

Contrasting species boundaries between sections Alternaria and Porri of the genus Alternaria

The fungal genus Alternaria comprises a large number of asexual taxa with diverse ecological, morphological and biological modes ranging from saprophytes to plant pathogens. Understanding the speciation processes affecting asexual fungi is important for estimating biological diversity, which in turn affects plant disease management and quarantine enforcement. This study included 106 isolates of Alternaria representing five phylogenetically defined clades in two sister sub‐generic groups: section Porri (A. dauci, A. solani and A. limicola) and section Alternaria (A. alternata/tenuissima and A. arborescens). Species in section Porri are host‐specific while species in section Alternaria have wider host ranges. For each isolate, DNA sequences of three genes (Alt a1, ATPase, Calmodulin) were used to estimate phylogenies at the population and species levels. Three multilocus haplotypes were distinguished among A. dauci isolates and only one haplotype among A. solani and A. limicola isolates, revealing low or no differentiation within each taxon and strong clonal structure for taxa in this section. In contrast, 37 multilocus haplotypes were found among A. alternata/tenuissima isolates and 21 multilocus haplotypes among A. arborescens isolates, revealing much higher genotypic diversity and multiple clonal lineages within taxa, which is not typical of asexual reproducing lineages. A species tree was inferred using a Yule Speciation model and a strict molecular clock assumption. Species boundaries were well defined within section Porri. However, species boundaries within section Alternaria were only partially resolved with no well‐defined species boundaries, possibly due to incomplete lineage sorting. Significant association with host specificity seems a driving force for speciation.     

Incidence,pathogenicity and diversity of Alternaria spp. associated with alternaria leaf spot of canola (Brassica napus) in Australia

Studies were undertaken to determine Alternaria spp. associated with leaf spot symptoms on canola (Brassica napus) in two cropping seasons (2015, 2016) across southern Australia. Major allergen Alt a1 and plasma membrane ATPase genes were used to identify Alternaria spp. In 2015, 112 isolates of seven Alternaria spp. were obtained, with A. metachromatica predominating. In 2016, 251 isolates of 12 Alternaria spp. were obtained, with A. infectoria predominating. Alternaria spp. isolates were morphologically and phylogenetically identified and studies to determine their pathogenicity on both B. napus (cv. Thunder TT) and B. juncea (cv. Dune) confirmed 10 species (A. alternata, A. arborescens, A. brassicae, A. ethzedia, A. hordeicola, A. infectoria, A. japonica, A. malvae, A. metachromatica and A. tenuissima) as pathogenic on both Brassica species. Alternaria ethzedia, A. hordeicola and A. malvae were recorded for the first time in Australia on any host and the record of A. arborescens was the first for New South Wales (NSW) and South Australia (SA). Other first records included A. infectoria on B. napus in NSW; A. japonica on B. napus in NSW and Western Australia (WA); A. metachromatica on any host in NSW, Victoria (VIC), WA and SA; and A. tenuissima on B. napus in NSW, SA and WA. It is evident that alternaria leaf spot on canola across southern Australia is not solely caused by A. brassicae, but that a range of other Alternaria spp. are also involved to varying degrees, depending upon the year and the geographic locality.     

Detection and partial molecular characterization of Plum pox virus on almond trees in Turkey

Almond (Prunus dulcis) is one of the well known stone fruit species grown for its unripe fruits and delicious seeds in Turkey. In the Trakya region, however, some prevailing virus infections have reduced almond yields and quality. In ten districts of Trakya, 260 leaf samples were collected from affected almond trees in June 2010. DAS–ELISA assays and RT-PCR tests were employed for the identification of viruses. As a result of these detection studies, five of the 260 leaf samples gathered from symptomatic almond trees had Plum pox virus (PPV), 81 of them had Prunus necrotic ringspot virus (PNRSV), and 11 samples contained Prune dwarf virus (PDV). Only four out of 260 samples had a mixture of these viruses. Partial nucleotide sequences of five almond isolates of PPV were determined and compared with 17 other PPV isolates in databases. Computer analysis of obtained and published nucleotide sequences showed identity ranged from 75.72% to 96.87%. Of the five PPV almond isolates obtained, however, there was a close nucleotide identity of 95.82–96.61% to Turkish isolates. Phylogenetic analysis of nucleotides and amino acids showed that five PPV isolates of almond from the Trakya Region of Turkey were clustered in the same subgroup with PPV-T Turkish isolates in GenBank. Therefore we can consider almond isolates of PPV as PPV-T strain, like the two other isolates from apricot trees in Turkey.     

Identification and species status of the mango biotype of Colletotrichum gloeosporioides in Ghana

Research work was carried out to identify and ascertain the species status of the mango biotype of Colletotrichum gloeosporioides infecting mangoes in Ghana. Forty five isolates of Colletotrichum species were collected from 12 districts in Ghana while five each were obtained from mango fruits from Florida, Mexico and Puerto Rico. The entire internal transcribed spacer region, partial beta-tubulin gene and partial glyceraldehyde-3-phosphate dehydrogenase gene of isolates were sequenced and used in phylogenetic studies. The results of the sequence analysis of the first ribosomal transcribed spacer (ITS 1) region showed that 35 % of the isolates from Ghana and all the five isolates from Mexico were the mango biotype of C. gloeosporioides, while the others were not. Phylogenetic studies showed that the mango biotype of the pathogen was Colletotrichum asianum but not C. gloeosporioides as previously thought. However, the other isolates that were not the mango biotype were identified as Colletotrichum siamense and Colletotrichum species which had probably cross-infected mango from other fruit crops in the field.