Isolates Of Diaporthe Research Articles

A re-evaluation of Diaporthe: refining the boundaries of species and species complexes

Diaporthe is an important plant pathogenic genus, which also occurs as endophytes and saprobes. Many Diaporthe species that are morphologically similar proved to be genetically distinct. The current understanding of Diaporthe taxonomy by applying morphological characters, host associations and multi-gene phylogeny are problematic leading to overestimation/underestimation of species numbers of this significant fungal pathogenic genus. Currently, there are no definite boundaries for the accepted species. Hence, the present study aims to re-structure the genus Diaporthe, based on single gene phylogenies (ITS, tef, tub, cal and his), multi-gene phylogeny justified by applying GCPSR (Genealogical Concordance Phylogenetic Species Recognition) methodology as well as the coalescence-based models (PTP—Poisson Tree Processes and mPTP—multi-rate Poisson Tree Processes). Considering all available type isolates of Diaporthe, the genus is divided into seven sections while boundaries for 13 species and 15 species-complexes are proposed. To support this re-assessment of the genus, 82 Diaporthe isolates obtained from woody hosts in Guizhou Province in China were investigated and revealed the presence of two novel species and 17 previously known species. Synonymies are specified for 31 species based on molecular data and morphological studies. Dividing Diaporthe into several specific sections based on phylogenetic analyses can avoid the construction of lengthy phylogenetic trees of the entire genus in future taxonomic studies. In other words, when one conducts research related to the genus, only species from the appropriate section need to be selected for phylogenetic analysis.

Two new species of Diaporthe (Diaporthaceae, Diaporthales) associated with Camelliaoleifera leaf spot disease in Hainan Province, China.

Tea-oil tree (Camelliaoleifera Abel.) is an important edible oil woody plant with a planting area over 3,800,000 hectares in southern China. Species of Diaporthe inhabit a wide range of plant hosts as plant pathogens, endophytes and saprobes. Here, we conducted an extensive field survey in Hainan Province to identify and characterise Diaporthe species associated with tea-oil leaf spots. As a result, eight isolates of Diaporthe were obtained from symptomatic C.oleifera leaves. These isolates were studied, based on morphological and phylogenetic analyses of partial ITS, cal, his3, tef1 and tub2 gene regions. Two new Diaporthe species (D.hainanensis and D.pseudofoliicola) were proposed and described herein.

Integrative Taxonomy of Novel Diaporthe Species Associated with Medicinal Plants in Thailand.

During our investigations of the microfungi on medicinal plants in Thailand, five isolates of Diaporthe were obtained. These isolates were identified and described using a multiproxy approach, viz. morphology, cultural characteristics, host association, the multiloci phylogeny of ITS, tef1-α, tub2, cal, and his3, and DNA comparisons. Five new species, Diaporthe afzeliae, D. bombacis, D. careyae, D. globoostiolata, and D. samaneae, are introduced as saprobes from the plant hosts, viz. Afzelia xylocarpa, Bombax ceiba, Careya sphaerica, a member of Fagaceae, and Samanea saman. Interestingly, this is the first report of Diaporthe species on these plants, except on the Fagaceae member. The morphological comparison, updated molecular phylogeny, and pairwise homoplasy index (PHI) analysis strongly support the establishment of novel species. Our phylogeny also revealed the close relationship between D. zhaoqingensis and D. chiangmaiensis; however, the evidence from the PHI test and DNA comparison indicated that they are distinct species. These findings improve the existing knowledge of taxonomy and host diversity of Diaporthe species as well as highlight the untapped potential of these medicinal plants for searching for new fungi.

Four new species of Diaporthe (Diaporthaceae, Diaporthales) from forest plants in China.

Species of Diaporthe inhabit a wide range of plant hosts as plant pathogens, endophytes and saprobes. During trips to collect forest pathogens in Beijing, Jiangxi, Shaanxi and Zhejiang Provinces in China, 16 isolates of Diaporthe were obtained from branch cankers and leaf spots. These isolates were studied by applying a polyphasic approach including morphological, cultural data, and phylogenetic analyses of the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef-1α) and β-tubulin (tub2) loci. Results revealed four new taxa, D.celticola, D.meliae, D.quercicola, D.rhodomyrti spp. nov. and two known species, D.eres and D.multiguttulata.

Characterization of Diaporthe species on Camelliaoleifera in Hunan Province, with descriptions of two new species.

Tea-oil tree (Camelliaoleifera Abel.) is an important edible oil woody plant with a planting area over 3,800,000 hectares in southern China. Species of Diaporthe inhabit a wide range of plant hosts as plant pathogens, endophytes and saprobes. At present, relatively little is known about the taxonomy and genetic diversity of Diaporthe on C.oleifera. Here, we conducted an extensive field survey in Hunan Province in China to identify and characterise Diaporthe species associated with tea-oil leaf spots. As a result, eleven isolates of Diaporthe were obtained from symptomatic C.oleifera leaves. These isolates were studied by applying a polyphasic approach including morphological and phylogenetic analyses of partial ITS, cal, his3, tef1 and tub2 gene regions. Two new Diaporthe species (D.camelliae-oleiferae and D.hunanensis) were proposed and described herein, and C.oleifera was revealed to be new host records of D.hubeiensis and D.sojae. This study indicated there is a potential of more undiscovered Diaporthe species from C.oleifera in China.

Diaporthe Seed Decay of Soybean [Glycine max (L.) Merr.] Is Endemic in the United States, But New Fungi Are Involved.

Diaporthe seed decay can compromise seed quality in soybean [Glycine max (L.) Merr.] in the warm and humid production areas of the United States during crop maturation. In the current study, 45 isolates of Diaporthe were recovered from seed sampled from soybean fields affected by Diaporthe-associated diseases in eight U.S. states in 2017. The isolates obtained belonged to 10 species of Diaporthe based on morphology and phylogenetic analyses of the internal transcribed spacer, partial translation elongation factor 1-α, and β-tubulin gene sequences. The associated species included D. aspalathi, D. caulivora, D. kongii, D. longicolla, D. sojae, D. ueckerae, D. unshiuensis, and three novel fungi, D. bacilloides, D. flavescens, and D. insulistroma. One isolate each of the 10 species was examined for pathogenicity on seed of cultivar Sava under controlled conditions. Seven days postinoculation, significant differences in the percentages of decayed seeds and seedling necrosis were observed among the isolates and the noninoculated control (P < 0.0001). While the isolates of D. bacilloides, D. longicolla, and D. ueckerae caused a significantly greater percentage of decayed seeds (P < 0.0001), the isolate of D. aspalathi caused the greatest seedling necrosis (P < 0.0001). The observation of new fungi causing Diaporthe seed decay suggests the need for a more comprehensive survey in U.S. soybean producing areas since members of the genus Diaporthe appear to form a complex that causes seed decay.

Diversity assessment of indigenous and exotic Diaporthe species associated with various crops using ISSR, URP and SRAP markers

Genetic diversity among the isolates representing five Diaporthe (syn: Phomopsis) species isolated from seeds of various crops representing both exotic as well as indigenous collections from India was analyzed using molecular markers, viz., inter-simple sequence repeats (ISSR), universal rice primers (URP) and sequence-related amplified polymorphism (SRAP). The isolates of Diaporthe showed differences among themselves by clustering distinctly which otherwise could not be distinguished with morphological characterization. The total number of polymorphic alleles was 323 with a range of 0.1–3.4 kb in ISSR, 293 with a range of 0.08–3.4 kb in URP and 293 with a range of 0.08–3.4 kb in SRAP. Genetic diversity determining parameters like polymorphic information content, expected heterozygosity, Shannon’s information index, effective multiplex ratio, and marker index was highest in URP markers. Unweighted pair group method with arithmetic average (UPGMA) analysis clustered the isolates into 2 major groups at 61% genetic similarity during combined analysis using these three sets of markers. Among molecular markers, URP markers showed superiority in detecting genetic diversity by differentiating both domestic and exotic isolates representing various species of Diaporthe. Exotic isolates of D. phaseolorum collected from jatropha showed the highest similarity whereas, indigenous isolates of D. phaseolorum isolated from soybean showed the highest level of variation. The isolates did not correspond to agro-ecological regions and the crop origin. This will be helpful in developing species-specific primers for detection of Diaporthe species.

First report of Diaporthe eres causing branch canker on Cinnamomum camphora (camphor tree) in Jiangxi Province, China.

In September 2019, approximately 75 to 90% of camphor trees (Cinnamomum camphora) were observed with cankers and branch dieback symptoms in Anyi (N28°32'54'', E115°37'52'') and Xinyu (N27°37'38'', E114°50'25'') county (Jiangxi Province, China). The symptoms included dark brown to dark, oval-shaped canker lesions, sunken and cracked longitudinally, cracked and evenly swelling, or reddish brown (Figure 1 A-D). Samples were collected from symptomatic branches and were cut into small pieces (ca. 0.5 cm × 0.5 cm × 0.5 cm). Sections were surface sterilized as described by Zhang et al. (2020), then placed on potato dextrose agar amended with 0.01% penicillin and 0.015% streptomycin sulfate and incubated in the laboratory at 25℃ with darkness. After 3 to 5 days, mycelium growing out from tissues were transferred onto PDA medium. In total, 68 fungal isolates including 22 isolates of Diaporthe sp. were obtained from cankers and then were classified into five categories based on morphological characteristics and sequencing of the ITS for morphological representative strains. Pathogenicity tests were conducted in the greenhouse (Figure 1 E-M) and field (Figure 1 N-Q). Branches were surface sterilized and inoculated as described by Prencipe et al. (2017). In the greenhouse, a total of 13 representative isolates (including 6 isolates of Diaporthe sp., 2 isolates of Neofusicoccum sp., 2 isolates of Botryosphaeria sp. and 3 isolates of Colletotrichum sp.) were selected and evaluated using 2-year-old seedlings of camphor tree in pots with 5 replicates per isolate, in which 3 isolates of Collectotrichum sp. had no pathogenicity. Then, two isolates of Diaporthe sp. (Z4 and Z7) were selected for field experiment. In field tests, the same method was used as in the greenhouse. The inoculated and control branches were collected 40 days after inoculation and the fungi were isolated and placed on PDA plates to recover the inoculated fungi and complete Koch's postulates. Both isolates of Diaporthe sp. produced canker symptoms on the branches. Isolate Z4 caused discoloration also on the branch without wounding. Both isolates produced pycnidia scattered in PDA plates supplemented with stems of alfalfa, were dark brown to black, globose to subglobose (Figure 1 T). Alpha conidia were cylindrical, 5.72-9.98 µm (mean 7.64 µm) × 2.15-3.13 µm (mean 2.69 µm) (n = 30) (Figure 1 S, red arrow), while beta conidia were biguttulate, one-celled, hyaline, non-septate, and 16.21-25.52 µm (mean 21.60 µm) × 0.76~1.65 µm (mean 1.14 µm) (n = 30, green arrow) (Figure 1 S). Five isolates (Z4, S-Z4, P-Z4, Z7 and S-Z7) including those used for pathogenicity test were selected for multi-locus phylogenetic analyses of ITS (White et al., 1990), TEF1-α and TUB2 (Glass et al. 1995) gene sequences, which the accession number was MW036358- MW036362 for ITS, MW052267- MW052271 for TEF1- α, MW052276-MW052280 for TUB2. Based on the phylogenetic tree analysis using IQ-TREE 2, all five isolates were identified as D. eres (Figure 2). D. eres has been reported to cause canker on many different woody plants, such as almond (Holland et al. 2020), peach (Prencipe et al. 2017), hazelnut (Wiman et al. 2019), and so on. However, this is the first report worldwide of D. eres causing disease on Cinnamomum camphora in China.

Six Species of Diaporthe Associated with Phomopsis Stem Canker of Sunflower in Southern Pampean Region of Argentina

A survey of 67 commercial fields in 19 locations was conducted in the southern Pampean region of Argentina for Phomopsis stem canker of sunflower (Helianthus annuus L.) between 2014 and 2019. A total of 210 plants having typical symptoms of Phomopsis stem canker were randomly sampled, and fungal isolation was performed. Of the 187 isolates of Diaporthe that were recovered, 94% of the isolates showed morphological characteristics similar to D. helianthi, 3% to D. gulyae, 1% to D. caulivora, 1% to D. sojae, 0.5% to D. kongii, and 0.5% to D. longicolla. Following morphological characterization, the identity of the six morpho-species was confirmed by phylogenetic analyses of β-tubulin, translation elongation factor 1-α, and internal transcribed spacer gene regions. Koch’s postulates were completed for the six fungi by inoculating one susceptible sunflower hybrid with one isolate each of the six species of Diaporthe using the stem-wound inoculation method. Seven days postinoculation, significant differences in disease severity were observed between the six isolates (P &lt; 0.0001), with D. helianthi and D. gulyae isolates causing significantly greater disease severity. To our knowledge, this is the first report of D. kongii, D. longicolla, D. caulivora, and D. sojae associated with Phomopsis stem canker of sunflower in Argentina.

The INFLUENCE OF TEMPERATURE AND FUNGAL COMMUNITY ON GROWTH AND SPORULATION OF Diaporthe FROM FRUIT PLANTS

The purpose of this experiment was to determine the influence of temperature and fungi colonizing fruit plants on Diaporthe, a pathogenic fungus in Poland. The biotic series method was used to test in vitro the effects of the fungi colonizing fruit trees on isolates of Diaporthe. Among the 13 fungal species tested, six inhibited the growth and development of Diaporthe; while another two species were neutral and the rest showed the lack of limiting impact in relation to the pathogen. Fungi present in the shoots of fruit plants was able to limit the growth and development of Diaporthe spp., both in chemically-protected and non-protected orchards. Studies on the effect of temperature indicated that the optimum temperature for vegetative growth of isolates of Diaporthe ranged from 20°C to 30°C, and for conidial sporulation from 25°C to 30°C. However, the ability of Diaporthe sp. to survive at extreme temperature (–20°C and +35°C) enables their vegetative growth in climatic conditions worldwide.

Polyphasic studies of new species of Diaporthe from native forest in Chile, with descriptions of Diaporthe araucanorum sp. nov., Diaporthe foikelawen sp. nov. and Diaporthe patagonica sp. nov.

During a survey of fungi in native forests in Chile, several unidentified isolates of Diaporthe were collected from different hosts. The isolates were characterized based on DNA comparisons, morphology, culture characteristics and host affiliation, in accordance with previous descriptions. Phylogenetic analysis of the ITS region, combined with partial tub2 and tef1 genes, showed that the isolates formed three distinct groups representing three new taxa. The three new species of Diaporthe, Diaporthe araucanorum on Araucaria araucana, Diaporthe foikelawen on Drimys winteri and Diaporthe patagonica on Aristotelia chilensis are described and illustrated in the present study.

Phomopsis husk rot of macadamia in Australia and South Africa caused by novel Diaporthe species

AbstractPhomopsis husk rot (PHR) in macadamia is a disease of economic importance in major commercial production areas in Australia and South Africa. Effective control of PHR is hindered by limited knowledge about its aetiology and epidemiology. The diversity and pathogenicity of more than 50 isolates of Diaporthe associated with PHR in macadamia orchards in Australia and South Africa was assessed. Multilocus phylogenetic analyses of DNA sequences of the ITS, tef1α, and tub2 gene loci revealed four novel clades that are described as Diaporthe australiana sp. nov., D. drenthii sp. nov., D. macadamiae sp. nov., and D. searlei sp. nov. Pathogenicity tests with representative isolates found that all four species caused PHR of varying severity between and within species, as well as between the two macadamia cultivars HAES 344 and HAES 816. The Australian species, D. australiana, was the most aggressive species compared with the three South African species. This study improves our understanding of the aetiology of PHR in macadamia and paves the way for more effective disease management.

Вплив температури на ріст та розвиток гриба Diaporthe (Phomopsis) helianthi M.

The main condition for successful plants cultivation is their ability to adapt to a complex of environment factors. Climatic parameters (temperature, precipitation, humidity of air) takes a significant role in formation of soil processes, since water-air and thermal regimes of the soil, and, accordingly, the direction of biological processes are closely linked with them. In order to successfully grow sunflower Helianthus annuus L. it is necessary to know features of development most dangerous diseases – Phomopsis helianthi Munt , development of which depends on climatic conditions of the region and technology of growing this crop. In this regard, it is relevant to determine the optimal temperatures that contribute to development of Phomopsis helianthi Munt. on sunflower, annually in the Southern region ofUkraine. Under natural conditions, mushrooms are able to adapt to changes in environmental factors. Special effects on growth and development of the fungus are caused by temperature conditions that have a seasonal and daily fluctuation pattern. Therefore, there is a need to determine the most favorable and critical temperatures for development certain types of given pathogen in laboratory conditions in vitro . The aim of study was to determine the effect of temperature on growth and development of Diaporthe (Phomopsis) helianthi M. The isolation of Phomopsis helianthi M. in a pure culture and its identification was carried out at department of the Kherson regional phytosanitary laboratory. Potato glucose agar (PGA) was used in pure culture to isolate Phomopsis helianthi M. For inoculation of substrates, were used 2 weeks age cultures. The mycelium was sown in Petri dishes to the center surface of a dense nutrient agar with a small piece of the inoculum, about 5 ×5 mm in size, always of one density and age. Petri dishes were incubated in a thermostat with temperature of 0 °C; +5; +10; +15; +20; +25; +30 and +35 °C. It has been established that in culture vegetative growth of fungus Diaporthe (Phomopsis) helianthi M. occurs in a wide range of temperatures. Differences in the rate of mycelia growth are determined. The lower limit, which marked the growth of mycelium, is +5 °C, and the higher – + 30 °C. The temperature of 0 and + 35 °C did not reveal a growth of mycelium. In vitro, the least intense growth of the fungus culture was detected under temperature conditions of +5 °C and +10 °C. The beginning of Phomopsis helianthi M. growth occurred at 5 and 4 days, respectively. More intense of mycelium growth was noted for temperature regimes of +15 °C and + 20 °C. It has been shown that optimal temperature for isolates of Diaporthe (Phomopsis) helianthi growth is + 25 °C. Under these conditions, on the 8th day of incubation, complete colonization of the substrate in the Petri dish was recorded. After increasing temperature to + 30 °С, the intensity of growth of mycelium of the fungus decreased. Thus, the average monthly air temperature in the summer (20–23.8 °С) simultaneously with irrigation can contribute development of Diaporthe (Phomopsis) helianthi M. fungus on sunflower plants.

Diversity of fungal latent pathogens and true endophytes associated with fruit trees in Uruguay

AbstractWe have explored the fungal diversity in asymptomatic twigs of apple, peach, pear and blueberry trees, with the objective of discerning between true endophytes and latent pathogens. Several fungal genera containing known bark pathogens were found. Seven Diaporthe species—D. oxe, D. infecunda, D. serafiniae, D. phaseolorum, D. terebinthifolii, D. foeniculina and D. brasiliensis—were identified, along with Botryosphaeria dothidea, Neofusicoccum parvum, Neofusicoccum australe, Cytospora sp., Cytospora acaciae and Pestalotiopsis spp. A pathogenicity trial was undertaken to determine the role of these species on apple, pear, blueberry and peach shoots. Diaporthe brasiliensis, D. foeniculina, Diaporthe inconspicua, D. terebinthifolii, Diaporthe sp.1, Cytospora‐like isolates and Pestalotiopsis spp. isolates produced no lesions on inoculated shoots, suggesting that they could be considered true endophytes on their respective hosts. Meanwhile, some of the isolates of Diaporthe—D. oxe, Diaporthe sp.2, D. infecunda and D. serafiniae, B. dothidea, N. parvum and N. australe could be regarded as latent pathogens in their respective hosts as they produced sunken cankers and necrosis on inoculated shoots. These results demonstrate that apple, pear, blueberry and peach healthy shoots can host many known endophytic fungi along with potential wood disease‐causing fungi that should be regarded as latent pathogens.

Diversity and virulence of Diaporthe species associated with wood disease symptoms in deciduous fruit trees in Uruguay

Several Diaporthe species are recognized as causal agents of many plant disease symptoms, including twig and branch cankers, dieback, shoot blight, and root and fruit rots. In Uruguay, the proximity between apple, pear and peach orchards offers the possibility to study the presence of different Diaporthe spp. associated with wood cankers across different deciduous fruit trees. Symptomatic twigs and branches of these orchard species were sampled, and isolates of Diaporthe were obtained. Selected isolates were used for cross inoculations in the three hosts. Seven Diaporthe spp. were identified, based on the internal transcribed spacer (ITS) region of rDNA and the translation elongation factor 1-alpha gene (EF1-α) phylogenies. The species were: Diaporthe amygdali , D. foeniculina , D. infecunda , D. eres , D. terebinthifolii , D. oxe and D. phaseolorum, while two isolates Diaporthe sp. 1 and Diaporthe sp. 4 could not be assigned to any species. Diaporthe infecunda, D. eres, D. terebinthifolii, D. phaseolorum and D. oxe on Pyrus communis and D. foeniculina on Malus domestica represent new records in these hosts in Uruguay, while D. oxe isolated from Prunus persica is a new record for this species. Diaporthe eres and D. phaseolorum were the most virulent species, posing the greatest risk due to their wide distribution and virulence in apple and peach trees. Although pear trees showed less symptomatic tissues and were less susceptible than peach and apple trees in the pathogenicity tests, they harboured seven of the species, and therefore should be considered as reservoirs of Diaporthe in Uruguayan orchards. Trees of the three hosts could be considered potential reciprocal sources of pathogenic Diaporthe spp.

Identification and Characterization of Diaporthe ambigua, D. australafricana, D. novem, and D. rudis Causing a Postharvest Fruit Rot in Kiwifruit

Diaporthe spp. are important plant pathogens causing wood cankers, blight, dieback, and fruit rot in a wide range of hosts. During surveys conducted during the 2013 and 2014 seasons, a postharvest rot in Hayward kiwifruit (Actinidia deliciosa) was observed in Chile. In order to identify the species of Diaporthe associated with this fruit rot, symptomatic fruit were collected from seven kiwifruit packinghouses located between San Francisco de Mostazal and Curicó (central Chile). Twenty-four isolates of Diaporthe spp. were identified from infected fruit based on morphological and cultural characters and analyses of nucleotides sequences of three loci, including the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), a partial sequences of the β-tubulin, and translation elongation factor 1-α genes. The Diaporthe spp. identified were Diaporthe ambigua, D. australafricana, D. novem, and D. rudis. Multilocus phylogenetic analysis revealed that Chilean isolates were grouped in separate clades with their correspondent ex-types species. All species of Diaporthe were pathogenic on wounded kiwifruit after 30 days at 0°C under normal and controlled-atmosphere (2% O2 and 5% CO2) storage and they were sensitive to benomyl, pyraclostrobin, and tebuconazole fungicides. D. ambigua isolates were the most virulent based on the lesion length measured in inoculated Hayward and Jintao kiwifruit. These findings confirm D. ambigua, D. australafricana, D. novem, and D. rudis as the causal agents of kiwifruit rot during cold storage in Chile. The specie D. actinidiae, a common of Diaporthe sp. found associated with kiwifruit rot, was not identified in the present study.

Morphological and molecular characterisation of Diaporthe species associated with grapevine trunk disease in China

Trunk diseases in grapevine (Vitis spp.) are major problems in the wine and table-grape industries reducing the productivity, quality and longevity of vineyards. Species of Diaporthe are important fungal pathogens of grapevine trunk disease worldwide. A survey of 14 grape vineyards located in different provinces of China was yielded Diaporthe isolates associated with symptomatic grapevine wood. These isolates were identified based on morphology and a combined data matrix of rDNA ITS, partial sequences of translation elongation factor 1-α (EF 1-α), β-tubulin (TUB) and calmodulin (CAL) gene regions. Four species of Diaporthe were identified, which included Diaporthe eres, Diaporthe hongkongensis, Diaporthe phaseolorum and Diaporthe sojae. All isolates of Diaporthe caused disease on detached grape shoots in pathogenicity experiments but differed in virulence. The incidence in local vineyards and the pathogenicity results indicate that D. eres is an important pathogen of grapevine in Chinese vineyards, where it may significantly limit grape production. This is the first detailed report of Diaporthe species associated with grapevine trunk diseases in China with morphology, pathogenicity and molecular data.

Pathogenicity of Diaporthe spp. isolates recovered from soybean (Glycine max) seeds in Paraguay

Phomopsis seed decay (PSD) caused by Diaporthe longicolla has been documented as part of a soybean (Glycine max) fungal disease complex that affects the quality of soybean seed. Soybean-producing countries that have not yet documented the presence of PSD impose soybean seed import restrictions to protect their soybean production. The purpose of this study was to determine the frequency of occurrence of Diaporthe spp. in Paraguay. In 2006, 16 isolates of Diaporthe were recovered for the first time from soybean seed in San Alberto, Paraguay in the south-eastern section of the country. The 16 isolates were used to inoculate mature pods harvested from greenhouse grown PSD-susceptible soybean cultivar ‘Maverick’. Among the16 isolates, six isolates (TN 214, TN 218, TN 224, TN 226, TN 227 and TN 229) caused infection on both pods and seeds within pods. Two groups of isolates were identified based on conidial types: isolates that produced only α conidia and isolates that produced both α and β conidia. The percentage of β conidia ranged from 0 to 95% for all the isolates except for TN 218, TN-222 and TN 223, which only produced α conidia. These results indicate that considerable variability exists in pathogenicity and composition of α and β spores among the 16 Diaporthe spp. isolates recovered from soybean seeds in Paraguay. In addition, these isolates may cause seed quality losses and may spread undetected to soybean production fields in Paraguay and around the world. Although the Diaporthe spp. isolates had three distinct ITS sequence types, none of the three probable species could be identified using currently available information. It is possible that these isolates represent previously unrecognized species, in addition to D. longicolla or D. phaseolorum, but additional data will be required to determine if this is the case.

Stem cankers on sunflower (Helianthus annuus) in Australia reveal a complex of pathogenic Diaporthe (Phomopsis) species

The identification of Diaporthe (anamorph Phomopsis) species associated with stem canker of sunflower (Helianthus annuus) in Australia was studied using morphology, DNA sequence analysis and pathology. Phylogenetic analysis revealed three clades that did not correspond with known taxa, and these are believed to represent novel species. Diaporthe gulyae sp. nov. is described for isolates that caused a severe stem canker, specifically pale brown to dark brown, irregularly shaped lesions centred at the stem nodes with pith deterioration and mid-stem lodging. This pathogenicity of D. gulyae was confirmed by satisfying Koch's Postulates. These symptoms are almost identical to those of sunflower stem canker caused by D. helianthi that can cause yield reductions of up to 40 % in Europe and the USA, although it has not been found in Australia. We show that there has been broad misapplication of the name D. helianthi to many isolates of Diaporthe (Phomopsis) found causing, or associated with, stem cankers on sunflower. In GenBank, a number of isolates had been identified as D. helianthi, which were accommodated in several clades by molecular phylogenetic analysis. Two less damaging species, D. kochmanii sp. nov. and D. kongii sp. nov., are also described from cankers on sunflower in Australia.