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Colletotrichum: complex species or species ... - CBS - KNAW

Colletotrichum: complex species or species ... - CBS - KNAW

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The <strong>Colletotrichum</strong> acutatum <strong>species</strong> <strong>complex</strong>Fig. 32. <strong>Colletotrichum</strong> walleri (from ex-holotype strain <strong>CBS</strong> 125472). A–B. Conidiomata. C–H. Conidioph<strong>or</strong>es. I–N. Appress<strong>or</strong>ia. O–P. Conidia. A, C–E, O. from Anthriscus stem.B, F–N, P. from SNA. A–B. DM, C–P. DIC, Scale bars: A = 100 µm, C = 10 µm. Scale bar of A applies to A–B. Scale bar of C applies to C–P.Material examined: Vietnam, Buon Ma Thuot-Dak Lac, from leaf tissue of Coffeaarabica, unknown collection date, H. Nguyen, (<strong>CBS</strong> H-20795 holotype, culture extype<strong>CBS</strong> 125472 = BMT(HL)19).Notes: Species of the C. gloeosp<strong>or</strong>ioides <strong>species</strong> <strong>complex</strong> arewell-known as pathogens of Coffea, especially the African coffeeberry disease pathogen C. kahawae (Waller et al. 1993). AdditionalCoffea-associated components of this <strong>species</strong> <strong>complex</strong> fromVietnam and Thailand have been studied by Nguyen et al. (2009)and Prihastuti et al. (2009); see Weir et al. (2012, this issue) f<strong>or</strong>further review.Masaba & Waller (1992) commented that strains identified asC. acutatum may cause min<strong>or</strong> disease of ripening coffee berries.Kenny et al. (2006) and Nguyen et al. (2010) respectively isolated,in Papua New Guinea and Vietnam, taxa in this <strong>species</strong> <strong>complex</strong>from coffee leaves, twigs and fruits. None of the Vietnameseisolates could infect undamaged coffee berries (Nguyen et al.2010). One of the C. acutatum cultures studied by Nguyen et al.(BMT(HL)19) was sent to <strong>CBS</strong> and a dried sample of this strain ishere designated as holotype of C. walleri. In this study, this is theonly coffee isolate from Asia, while six other isolates from coffee,<strong>or</strong>iginating from Africa and Central America, belong to three other<strong>species</strong> within the C. acutatum <strong>species</strong> <strong>complex</strong> (C. fi<strong>or</strong>iniae, C.acutatum s. str. and C. costaricense). Two of these strains wereincluded in the study by Waller et al. (1993).<strong>Colletotrichum</strong> walleri is separated from other <strong>species</strong> byalmost all genes. It is most easily distinguished using HIS3 and ITSsequences, while sequences of other genes differ by only one bpfrom those of other <strong>species</strong>. The CHS-1 sequence is the same asthat of C. sloanei. The closest TUB2 blastn match f<strong>or</strong> <strong>CBS</strong> 125472(with 99 % identity, 5 bp differences) was GU246633 from isolateR14 from Capsicum annuum from South K<strong>or</strong>ea (Sang et al. 2011).The closest GAPDH match f<strong>or</strong> a sequence covering ± the fullgene length (with 98 % identity, 4 bp differences) was HQ846724from isolate OBP6 from an unnamed plant, probably from India(Chowdappa P, Chethana CS, Madhura S, unpubl. data). The only100 % match with the ITS sequence was FJ968601, the sequenceof the same isolate previously sequenced by Nguyen et al. (2009).DISCUSSION<strong>Colletotrichum</strong> acutatum (in the broad sense) was <strong>or</strong>iginallydistinguished using m<strong>or</strong>phological characteristics. The primarydiagnostic feature was given as the possession of fusif<strong>or</strong>m conidiawith acute ends (Simmonds 1965). M<strong>or</strong>e detailed research hashowever shown that this characteristic is not absolute; while moststrains of <strong>species</strong> within the C. acutatum <strong>complex</strong> have at least aprop<strong>or</strong>tion of conidia with at least one acute end, it is common tofind significant variation in conidial shape within <strong>species</strong> and evenwithin individual strains. Conidia that are m<strong>or</strong>e <strong>or</strong> less cylindricalare frequently encountered. The variation may have multiplecauses; in some circumstances it seems that secondary conidiawww.studiesinmycology.<strong>or</strong>g107

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