• Discrete lineages within Alternaria alternata species group: identification using new highly variable loci and support from morphological characters

      Armitage, A.D.; Barbara, D.J.; Harrison, R.J.; Lane, C.R.; Sreenivasaprasad, Surapareddy; Woodhall, J.W.; Clarkson, J.P. (Elsevier, 2015-07)
      The Alternaria alternata species group is ubiquitous in the environment acting as saprotrophs, human allergens, and plant pathogens. Many morphological species have been described within the group and it is unclear whether these represent re-descriptions of the same species or discrete evolutionary taxa. Evolutionary relationships within the A. alternata species group were established using a phylogenetic approach based on functional genes. Sequencing of five highly variable loci identified three major lineages within the A. alternata species group. These loci included two loci previously shown to be variable within the Alternaria genus (endo-PG, Alt a1) as well as three new phylogenetic loci (TMA22, PGS1, and REV3) identified as highly variable based on publically available genome sequence data for Dothideomycete species. Results indicated that the three lineages have recently diverged and as such were considered as subspecies within a single species A. alternata. Lineages were identified as A. alternata ssp. arborescens, A. alternata ssp. tenuissima, and A. alternata ssp. gaisen in accordance with the placement of reference isolates. The phylogenetic results were supported by morphological analysis, which differentiated strains in A. alternata ssp. arborescens and A. alternata ssp. tenuissima and also aligned with previous morphological species descriptions for A. arborescens and A. tenuissima. However, phylogenetic analysis placed the morphologically described species A. alternata and A. mali within the A. alternata ssp. tenuissima and did not support them as discrete taxa. As A. alternata are of phytosanitary importance, the molecular loci used in this study offer new opportunities for molecular identification of isolates by national plant protection organizations.
    • Virulence diversity of anthracnose pathogens (Colletotrichum acutatum and C. gloeosporioides complexes) on eight olive cultivars commonly grown in Portugal.

      Talhinhas, Pedro; Gonçalves, Elsa; Sreenivasaprasad, Surapareddy; Oliveira, Helena (Springer Link, 2015-05)
      Olive anthracnose, caused by Colletotrichum acutatum and C. gloeosporioides species complexes, is a major disease affecting fruits at maturity, causing significant yield losses, and poor fruit and oil quality. Diverse genetic groups, particularly belonging to C. acutatum s.l. have been reported among the pathogens, with recent research proposing these genetic groups as distinct species. In this work, the virulence diversity of isolates representing different populations of C. acutatum s.l. and C. gloeosporioides s.s. was studied using a set of eight olive cultivars. Higher disease severity was produced by isolates belonging to groups A2 and A5 of C. acutatum s.l. (=C. nymphaeae and C. acutatum s.s., respectively) compared to C. gloeosporioides s.s. isolates as well as isolates of C. acutatum s.l. group A4 (=C. godetiae). Anthracnose severity was higher on the cultivars ‘Cobrançosa’, ‘Maçanilha de Tavira’ and ‘Galega Vulgar’ and lower in ‘Azeitoneira’, ‘Blanqueta’, ‘Negrinha de Freixo’ and ‘Picual’, but results indicate the occurrence of isolate × cultivar interactions. Differences in severity could be related to differences in conidia germination and appressoria formation, suggesting that early host-pathogen recognition events can in part explain disease severity under favourable environmental conditions. Overall results revealed the higher virulence and fitness levels of genotypes belonging to certain genetic groups within C. acutatum suggesting their ability to adapt to diverse agro-climatic conditions including specific hosts.
    • Molecular diversity of anthracnose pathogen populations associated with UK strawberry production suggests multiple introductions of three different Colletotrichum species.

      Baroncelli, Riccardo; Zapparata, Antonio; Sarrocco, Sabrina; Sukno, Serenella A.; Lane, Charles R.; Thon, Michael R.; Vannacci, Giovanni; Holub, Eric; Sreenivasaprasad, Surapareddy (PLoS, 2015-02)
      Fragaria × ananassa (common name: strawberry) is a globally cultivated hybrid species belonging to Rosaceae family. Colletotrichum acutatum sensu lato (s.l.) is considered to be the second most economically important pathogen worldwide affecting strawberries. A collection of 148 Colletotrichum spp. isolates including 67 C. acutatum s.l. isolates associated with the phytosanitary history of UK strawberry production were used to characterize multi-locus genetic variation of this pathogen in the UK, relative to additional reference isolates that represent a worldwide sampling of the diversity of the fungus. The evidence indicates that three different species C. nymphaeae, C. godetiae and C. fioriniae are associated with strawberry production in the UK, which correspond to previously designated genetic groups A2, A4 and A3, respectively. Among these species, 12 distinct haplotypes were identified suggesting multiple introductions into the country. A subset of isolates was also used to compare aggressiveness in causing disease on strawberry plants and fruits. Isolates belonging to C. nymphaeae, C. godetiae and C. fioriniae representative of the UK anthracnose pathogen populations showed variation in their aggressiveness. Among the three species, C. nymphaeae and C. fioriniae appeared to be more aggressive compared to C. godetiae. This study highlights the genetic and pathogenic heterogeneity of the C. acutatum s.l. populations introduced into the UK linked to strawberry production.
    • First report of apple bitter rot caused by Colletotrichum godetiae in the UK

      Baroncelli, Riccardo; Sreenivasaprasad, Surapareddy; Thon, Michael R.; Sukno, Serenella A.; Universidad de Salamanca; University of Warwick (APS, 2014-07)
      Apple is an important crop in United Kingdom, with a total production of 233,750 tonnes in 2011. Symptoms of apple bitter rot were observed on apple fruits (Malus domestica L.) in the Newcastle area, United Kingdom, in October 2008.
    • First report of Colletotrichum acutatum sensu lato (Colletotrichum godetiae) causing anthracnose on grapevine (Vitis vinifera) in the United Kingdom

      Baroncelli, Riccardo; Sreenivasaprasad, Surapareddy; Lane, Charles R.; Thon, Michael R.; Sukno, Serenella A.; University of Warwick; Universidad de Salamanca; University of Bedfordshire; Food and Environment Research Agency (The British Society for Plant Pathology, 2014-06)
      In November 2009, twelve specimens of grapevine (Vitis vinifera) cv. Brant in the area of Penrith, Cumbria in the United Kingdom were showing necrotic black leaf spotting and abundant orange sporulation on the upper leaf surface. Infected plant material was submitted to the FERA (Food and Environment Research Agency) Plant Clinic for diagnosis. The tissue samples were surface sterilised for one minute in 20% sodium hypochlorite and cultured on potato dextrose agar. Monoconidial isolates grown at 25°C with a 12 hour light period had light grey cottony aerial mycelium with colour ranging from whitish to dark grey on the reverse side of the colony. The cultures had orange spores organised in small masses and dark melanised structures similar to acervuli. Disease symptoms and morphology suggested that a member of the genus Colletotrichum caused the disease. Given the fact that strains of Colletotrichum often belong to aggregates of species that can be difficult or impossible to distinguish morphologically, a representative isolate was sent to the University of Warwick for further analysis.
    • Draft genome sequence of Colletotrichum acutatum sensu lato (Colletotrichum fioriniae)

      Baroncelli, Riccardo; Sreenivasaprasad, Surapareddy; Sukno, Serenella A.; Thon, Michael R.; Holub, Eric; University of Warwick; University of Bedfordshire; Universidad de Salamanca (American Society for Microbiology, 2014-04)
      In addition to its economic impact, Colletotrichum acutatum sensu lato is an interesting model for molecular investigations due to the diversity of host-determined specialization and reproductive lifestyles within the species complex. The pathogen Colletotrichum fioriniae forms part of this species complex and causes anthracnose in a wide range of crops and wild plants worldwide. Some members of this species have also been reported to be entomopathogenic. Here, we report the draft genome sequence of a heterothallic reference isolate of C. fioriniae (strain PJ7). This sequence provides a range of new resources that serve as a useful platform for further research in the field.