Curvularia

Curvularia Boedijn, Bull. Jard. Bot. Buitenzorg, 3 Sér. 13: 123 (1933)

For synonyms see Index Fungorum (2018)

Background

The cosmopolitan Curvularia consists of pathogens and saprobes of various plants, as well as opportunistic pathogens of humans and animals. They are abundantly found as the pathogens of family Poaceae (Hyde et al. 2014). Curvularia lunata, C. trifolii and C. tuberculata can cause leaf spots and leaf blights of some cereal crops such as maize, rice and horticultural crops (Bermuda grasses and turf grasses) (de Luna et al. 2002; Hyde et al. 2014). The most frequent human and animal pathogens within the genus are C. aeria, C. borreriae, C. geniculata, C. inaequalis, C. lunata and C. verrucosa (Hyde et al. 2014). Curvularia is morphologically characterized by its dark mycelium, geniculate conidiophores with sympodial, tretic conidiogenous cells, conidia with smooth to slightly verrucose wall and several false septa (distosepta) (Hyde et al. 2014). The taxonomy of Curvularia has been well studied in recent years, however, the broadly perceived classification was redefined by Manamgoda et al. (2012, 2014) based on the phylogenetic relationships of ex-type strains of Curvularia species and recently collected Curvularia cultures from northern Thailand. See Hyde et al. (2014) and Marin-Felix et al. (2017) for further details.

 

ClassificationDothideomycetes, Pleosporomycetidae, Pleosporales, Pleosporaceae

Type speciesCurvularia lunata (Wakker) Boedijn, Bull. Jard. bot. Buitenz, 3 Sér. 13(1): 127 (1933)

Distribution – Worldwide

Disease Symptoms – Leaf spots and blights, melting out, foot and root rot

The first symptoms to appear on leaves are elliptical brown spots. Gradually the spots enlarge and change colour to brownish black. In melting out disease symptoms on grasses may vary depending on the extent and severity of the attack. The first symptoms are seen as small spots with purple and black specks. Melting out starts as a leaf spot which will expands to the plant base and attacks the roots and crown. Leaf wilts, necrotic roots and plant death can be seen in a foot or root rot (Verma and Gupta 2009; Sunpapao et al. 2014).

Hosts – Mainly found on members of Poaceae. Also occurs on Actinidaceae, Aizoaceae, Caricaceae, Convolvulaceae, Fabaceae, Iridaceae, Lamiaceae, Lythraceae, Oleaceae, Polygonaceae, Rubiaceae and Vitaceae (Farr and Rossman 2018).

Morphological based identification and diversity

Species of Curvularia are traditionally characterized by dark mycelium, geniculate conidiophores with sympodial, tretic conidiogenous cells and elongated conidia. The conidia are smooth to tuberculate-walled, with several false septa (distosepta) and straight or curved due to an enlarged middle cell that is often more pigmented than the other cells (da Cunha et al. 2013). However, taxonomic classification of Curvularia spp. based exclusively on morphological characteristics was insufficient for designating new species because of their phenotypic variability and this has resulted in an inadequate understanding of curvularia-like species. Currently, there are 156 species epithets in Index Fungorum (www.indexfungorum.org; retrieved 24 March 2018) but most of these past records lack molecular data and comprehensive morphological descriptions. In a recent study, Marin-Felix et al. (2017) included 74 accepted Curvularia species to their phylogenetic analyses. Later Hyde et al. (2017) introduced Curvularia palmicola as another species and therefore, we constructed a tree with 75 Curvularia species.

Species delimitation in Curvularia based on morphology only is difficult with overlapping morphological characters among many species (Manamgoda et al. 2014, 2015), as also observed in Bipolaris (see under Bipolaris).

Molecular based identification and diversity

To achieve proper generic and species delimitation, phylogenetic studies using ITS, GAPDH and TEF1-α sequence data were recently performed (Manamgoda et al. 2012, 2014, 2015; Hyde et al. 2014, 2017; Marin-Felix et al. 2017). Phylogenetic studies based on these loci made it possible to reallocate species of Cochliobolus (sexual morph) to either Bipolaris or Curvularia (Marin-Felix et al. 2017). We update the phylogeny of this genus based on a combined ITS GAPDH and TEF1-α sequence data obtained from available ex-epitype, ex-isotype, ex-isolectotype, ex-paratype, ex-syntype and ex-type strains cultures (Table, Fig). The topological structure is in accordance with previous studies.

Recommended genetic markers (genus level) – LSU

Recommended genetic markers (species level) – GDPH

It is recommended to use a combination of ITS GAPDH and TEF (Manamgoda et al. 2015).

 

Accepted number of species: There are 399 species epithets in Index Fungorum (2018) under this genus. However, only 80 are accepted.

References: Sivanesan 1977 (morphology and pathogenicity), Manamgoda et al. 2011 (pathogenicity), Hyde et al. 2014, Marin-Felix et al. 2017 (morphology and phylogeny), Manamgoda et al. 2015 (morphology, pathogenicity and phylogeny).

 

Table Curvularia. Details of the isolates used in the phylogenetic tree

Species Isolate ITS GAPDH TEF1– α
Curvularia aeria CBS 294.61* HE861850 HF565450
C. affinis CBS 154.34* KJ909780 KM230401 KM196566
C. akaii CBS 317.86 KJ909782 KM230402 KM196569
C. akaiiensis BRIP 16080* KJ415539 KJ415407 KJ415453
C. alcornii MFLUCC 10-0703* JX256420 JX276433 JX266589
C. americana UTHSC 08-3414* HE861833 HF565488
C. asiatica MFLUCC 10-0711* JX256424 JX276436 JX266593
C. australiensis BRIP 12044* KJ415540 KJ415406 KJ415452
C. australis BRIP 12521* KJ415541 KJ415405 KJ415451
C. bannonii BRIP 16732* KJ415542 KJ415404 KJ415450
C. borreriae CBS 859.73 HE861848 HF565455
C. bothriochloae BRIP 12522* KJ415543 KJ415403 KJ415449
C. brachyspora CBS 186.50 KJ922372 KM061784 KM230405
C. buchloes CBS 246.49* KJ909765 KM061789 KM196588
C. carica-papayae CBS 135941* HG778984 HG779146
C. chiangmaiensis CPC 28829* MF490814 MF490836 MF490857
C. chlamydospora UTHSC 07-2764* HG779021 HG779151
C. clavata BRIP 61680b KU552205 KU552167 KU552159
C. coicis CBS 192.29* JN192373 JN600962 JN601006
C. crustacea BRIP 13524* KJ415544 KJ415402 KJ415448
C. cymbopogonis CBS 419.78 HG778985 HG779129 HG779163
C. dactyloctenicola CPC 28810* MF490815 MF490837 MF490858
C. dactyloctenii BRIP 12846* KJ415545 KJ415401 KJ415447
C. ellisii CBS 193.62* JN192375 JN600963 JN601007
C. eragrostidis CBS 189.48 HG778986 HG779154 HG779164
C. geniculata CBS 187.50 KJ909781 KM083609 KM230410
C. gladioli CBS 210.79 HG778987 HG779123
C. graminicola BRIP 23186* JN192376 JN600964 JN601008
C. gudauskasii DAOM 165085 AF071338
C. harveyi BRIP 57412* KJ415546 KJ415400 KJ415446
C. hawaiiensis BRIP 11987* KJ415547 KJ415399 KJ415445
C. heteropogonicola BRIP 14579* KJ415548 KJ415398 KJ415444
C. heteropogonis CBS 284.91* JN192379 JN600969 JN601013
C. hominis CBS 136985* HG779011 HG779106
C. homomorpha CBS 156.60* JN192380 JN600970 JN601014
C. inaequalis CBS 102.42* KJ922375 KM061787 KM196574
C. intermedia CBS 334.64 HG778991 HG779155 HG779169
C. ischaemi CBS 630.82* JX256428 JX276440
C. kusanoi CBS 137.29 JN192381 JN601016
C. lunata CBS 730.96* JX256429 JX276441 JX266596
C. malina CBS 131274* JF812154 KP153179 KR493095
C. miyakei CBS 197.29* KJ909770 KM083611 KM196568
C. muehlenbeckiae CBS 144.63* HG779002 HG779108
C. neergaardii BRIP 12919* KJ415550 KJ415397 KJ415443
C. neoindica BRIP 17439 AF081449 AF081406
C. nicotiae CBS 655.74* = BRIP 11983 KJ415551 KJ415396 KJ415442
C. nodosa CPC 28801 MF490817 MF490839 MF490860
C. nodosa CPC 28812 MF490818 MF490840 MF490861
C. nodosa CPC 28800* MF490816 MF490838 MF490859
C. nodulosa CBS 160.58 JN601033 JN600975 JN601019
C. oryzae CBS 169.53* KP400650 KP645344 KM196590
C. ovariicola CBS 470.90* JN192384 JN600976 JN601020
C. pallescens CBS 156.35* KJ922380 KM083606 KM196570
C. palmicola MFLUCC 14-0404* MF621582
C. papendorfii CBS 308.67* KJ909774 KM083617 KM196594
C. perotidis CBS 350.90* JN192385 KJ415394 JN601021
C. pisi CBS 190.48* KY905678 KY905690 KY905697
C. portulacae CBS 239.48* = BRIP 14541 KJ415553 KJ415393 KJ415440
C. prasadii CBS 143.64* KJ922373 KM061785 KM230408
C. protuberata CBS 376.65* KJ922376 KM083605 KM196576
C. pseudobrachyspora CPC 28808* MF490819 MF490841 MF490862
C. pseudolunata UTHSC 09-2092* HE861842 HF565459
C. pseudorobusta UTHSC 08-3458 HE861838 HF565476
C. ravenelii BRIP 13165* JN192386 JN600978 JN601024
C. richardiae BRIP 4371* KJ415555 KJ415391 KJ415438
C. robusta CBS 624.68* KJ909783 KM083613 KM196577
C. ryleyi BRIP 12554* KJ415556 KJ415390 KJ415437
C. senegalensis CBS 149.71 HG779001 HG779128
C. sesuvi Bp-Zj 01 EF175940
C. soli CBS 222.96* KY905679 KY905691 KY905698
C. sorghina BRIP 15900* KJ415558 KJ415388 KJ415435
C. spicifera CBS 274.52 JN192387 JN600979 JN601023
C. subpapendorfii CBS 656.74* KJ909777 KM061791 KM196585
C. trifolii CBS 173.55 HG779023 HG779124
C. tripogonis BRIP 12375* JN192388 JN600980 JN601025
C. tropicalis BRIP 14834* KJ415559 KJ415387 KJ415434
C. tsudae ATCC 44764* KC424596 KC747745 KC503940
C. tuberculata CBS 146.63* JX256433 JX276445 JX266599
C. uncinata CBS 221.52* HG779024 HG779134
C. variabilis CPC 28815* MF490822 MF490844 MF490865
C. variabilis CPC 28813 MF490820 MF490842 MF490863
C. variabilis CPC 28814 MF490821 MF490843 MF490864
C. variabilis CPC 28816 MF490823 MF490845 MF490866
C. verruciformis CBS 537.75 HG779026 HG779133 HG779211
C. verruculosa CBS 150.63 KP400652 KP645346 KP735695
C. verruculosa CPC 28792 MF490825 MF490847 MF490868
C. verruculosa CPC 28809 MF490824 MF490846 MF490867
Bipolaris maydis CBS 137271* AF071325 KM034846 KM093794
B. oryzae MFLUCC 10-0715* JX256416 JX276430 JX266585

 

Figure  Phylogenetic tree generated by maximum likelihood analysis of combined ITS, GAPDH and TEF1- α sequence data of Curvularia species. Related sequences were obtained from GenBank. Eighty-nine strains are included in the analyses, which comprise 1996 characters including gaps. The tree was rooted with Bipolaris maydis (CBS 137271), B. microlaenae (CBS 280.91) and B. oryzae (MFLUCC 10-0715). The best scoring RAxML tree with a final likelihood value of -13720.654431 is presented. The matrix had 716 distinct alignment patterns, with 19.91% of undetermined characters or gaps. Estimated base frequencies were as follows; A = 0.23274, C = 0.300605, G = 0.240654, T = 0.226; substitution rates AC = 0.761255, AG = 2.478832, AT = 0.794435, CG = 0.897227, CT = 5.171218, GT = 1.000000; gamma distribution shape parameter α = 0.790494. RAxML bootstrap support values ≥ 60% (BT) are shown respectively near the nodes. The scale bar indicates 0.02 changes. T, ET, IsoT, IsoLT, IsoPT, LT and NT indicate ex-type, ex-epitype, ex-isotype, ex-isolectotype, ex-isoparatype, ex-lectotype and ex-neotype strains, respectively.

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