Calonectria guahibo N.Q. Pham, Marinc. & M.J. Wingf., 2022

Pham, Nam Q., Marincowitz, Seonju, Chen, ShuaiFei, Rodas, Carlos A. & Wingfield, Michael J., 2022, Soil-borne Calonectria (Hypocreales, Nectriaceae) associated with Eucalyptus plantations in Colombia, MycoKeys 94, pp. 17-35 : 17

Calonectria guahibo N.Q. Pham, Marinc. & M.J. Wingf. sp. nov.

Figs 5 , 6E, F

Etymology.

Name refers to the indigenous people, Guahibo, native to Vichada, Colombia.

Diagnosis.

Closely related to C. gordoniae but differs in having smaller macroconidia.

Type.

Colombia: Vichada, Cumaribo. Soils in Eucalyptus plantation. August 2016. C.A. Rodas. (Holotype PRU(M) 4503, stored in a metabolically inactive state; ex - holotype CMW 49791 , CMW-IA 162). GenBank : OP796480 (ACT) ; OP822350 (CMDA) ; OP822457 (HIS3) ; OP822564 (RPB2) ; OP822243 (TEF1) ; OP822671 (TUB2) .

Description.

Sexual morph not observed. Conidiophores scarce on SNA, composed of conidiogenous apparatus and stipes. Stipes part of conidiogenous apparatus, elongated, septate, 81-223 µm long, 2-5 µm wide near base, tapering towards apex, simple, infrequently branched; vesicles slightly inflated to clavate, 2-5 µm wide. Conidiogenous apparatus hyaline, branched irregularly in 2-3 (-4) tiers; main axis upright, septate, 25-83 × 4-6 µm; branches doliiform to cylindrical, primary branches 11-23 × 4-6 µm, secondary branches 7-16 × 3-5 µm, tertiary branches 9-11 × 3-4 µm. Conidiogenous cells holoblastic, hyaline, discrete, cylindrical to ovoid, tapering towards apex, with perclinal thickening, 6-12 × 2-4 (9.3 ± 1.46 × 3.0 ± 0.52) µm. Macroconidia hyaline, cylindrical with round ends, 1-septate, straight, septum median or sub-median, 26-42 × 3-4 (31.7 ± 3.59 × 3.2 ± 0.19) µm. Chlamydospores present in clumps or in chains. Mega - and microconidia not observed.

Colonies on 2% MEA after 6 d in the dark, growing circular, with fluffy aerial mycelia, above white to pale luteous towards centre, reverse luteous to umber towards centre. Optimal growth temperature at 30 °C reaching 61 mm, followed by 25 °C (57.5 mm), 20 °C (48.3 mm), 15 °C (21.8 mm), and no growth at 5, 10, and 35 °C. Colonies kept at 5, 10, and 35 °C revived after being relocated to 25 °C. Colonies on 2% MEA in the dark for 30 d, with cottony mycelia filled entire Petri dish, above saffron to umber with patches of white, reverse dark brick to sepia.

Distribution.

Colombia.

Material examined.

Colombia: Vichada, Cumaribo. Soils in Eucalyptus sp. plantation. August 2016. C.A. Rodas, CMW 49782 .

Notes.

Calonectria guahibo forms part of the C. pteridis species complex as a sister taxon to C. gordoniae . Calonectria gordoniae was reported from Florida, USA, causing leaf spots and blotches on loblolly bay ( Gordonia lasianthus ) and is known to produce macroconidia (45-81 × 4-6 µm, avg. 61.7 × 5 µm) and microconidia (20-42 × 3-4 µm, avg. 32.5 × 3.6 µm) ( Leahy et al. 2000). Leahy et al. (2000) reported slightly curved conidia which were not observed in C. guahibo . Calonectria guahibo can be distinguished by its smaller conidia (26-42 × 3-4 µm, avg. 31.7 × 3.2 µm) from other closely related species, i.e. C. ovata (50-110 × 4-6 µm, avg. 70 × 5 µm) ( Victor et al. 1997), C. pseudovata (55-50 × 4-7, avg. 69 × 5 µm) ( Alfenas et al. 2015), and C. terricola (40-53 × 3-6 µm, avg. 46 × 4.5 µm) ( Lombard et al. 2016). It can be differentiated from its most closely related species by sequences of ACT, CMDA, HIS3, RPB2, TEF1 and TUB2 gene regions.

Figures

Figure 5. Micrographs of Calonectria guahibo sp. nov. (ex-holotype: CMW 49791 = CMW-IA 162). A conidiophores formed on SNA B stipes and vesicles C conidiogenous apparatus D chlamydospores E conidia (x 400) F conidia (x 1 000). Scale bars: 100 µm (A); 50 µm (D); 25 µm (C, E); 10 µm (B, F).

Figure 6. Culture morphology of Calonectria exiguispora (A-D) at 25 ° C and C. guahibo (E-H) at 30 ° C in the dark for 6 d (A, C, E, G) and 30 d (B, E, F, H) at its optimum temperature A, B CMW 49752 (ex-holotype) C, D CMW 49753 E, F CMW 49791 (ex-holotype) G, H CMW 49782.