Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, Studuies in Mycology 55: 248 (2006).

Basionym: Fusicoccum parvum Pennycook & Samuels, Mycotaxon 24: 455 (1985).

Teleomorph: "Botryosphaeria" parva Pennycook & Samuels Mycotaxon 24: 455 (1985).

 

Ascospores (15–)18–27(–29.5) × (6–)8–11 µm, hyaline, aseptate becoming light brown and 1- or 2-septate.

Conidia (12–)15–20(–24) × (4–)4.5–6(–7.5) µm, hyaline, aseptate, thin walled, becoming darker and 1-or 2-septate before germination, L/W ratio = 3.2±0.4.

 

Ascomata and conidiomata of "Botryosphaeria" parva. Above, on a grapevine stem, below as seen in section.

Characteristics on the host — Ascomata morphologically indistinguishable from those of B. dothidea.  Asci bitunicate with a thick endotunica, clavate, stipitate, 75–145 × 17–20 µm.  Ascospores broadly ellipsoid to fusoid, widest in the middle to upper third, (15–)18–27(–29.5) × (6–)8–11 µm, hyaline, smooth, thin-walled, biseriate. Pseudoparaphyses hyaline, septate, branched, 2–3.5 µm wide.

Conidiomata externally indistinguishable from ascomata, uni- or multilocular, individual or formed on the same stromata as the ascomata, globose and non-papillate to pyriform with a short, acute papilla, opening through a non-periphysate ostiole.  Conidiophores reduced to conidiogenous cells. Conidiogenous cells  hyaline, holoblastic forming conidia at their tips, proliferating internally giving rise to periclinal thickenings, sometimes proliferating percurrently forming one or two annelations,  arising from the inner wall of the locule, and lining the entire locule.  Conidia ellipsoid with subobtuse apex and truncate base, smooth, thin-walled, hyaline, unicellular, (13.5–)15–22.5(–28.5) × 4–7.5 µm; mean and standard deviation of 300 conidia = 18.9 × 5.5 µm.  Length/width ratio of 2.4–4.5, with mean of 3.5.

Characteristics in culture — Colonies on PDA scarcely different from those of B. dothidea. Conidiomata on OA multilocular, non-papillate, and conidia start to ooze from their ostioles after 13–15 days of incubation at 23°C.  Between 35 and 50 conidiomata are  formed on each plate of OA. Conidiophores and conidiogenous cells as found in nature.  Conidia hyaline, guttulate, thin-walled, non-septate, smooth, fusiform to ellipsoidal with a subobtuse  apex and truncate or rounded base, often with a minute basal frill, widest in the middle or upper third with dimensions of (12–)15–20(–24) × (4–)4.5–6(–7.5) µm; mean ± standard deviation of 320 conidia = 17.2 ± 1.6 × 5.6 ± 0.6 µm.  Length/width ratios in the range of (1.8–)2.5–4(–5), and the mean ± standard deviation of 320 conidia = 3.2 ± 0.4.  Conidia frequently become olivaceous or light brown and develop 1 or 2 septa with a darker middle cell.  Microconidia, which are seen in some isolates, are hyaline, smooth, rod-shaped and truncate at either end, 3–5 × 1–1.5 µm.

 

Phialidic conidiogenous cells of
Neofusicoccum parvum. Scale bar = 10 µm.

 Conidia from cultures on oatmeal agar. Scale bar = 10 µm. Aged conidia of Neofusicoccum parvum with brown walls and one or two septa. Scale bar = 10 µm.

Notes – This species is similar to B. dothidea, but it can be distinguished by the shorter, and more ellipsoidal conidia.  In cultures on OA it produces larger and fewer multilocular conidiomata than B. dothidea.  The main feature that distinguishes N. parvum from N. luteum is the absence of a yellow pigment in culture.  Although similar to N. ribis, the conidia of N. parvum frequently become brown and (one or) two septate as they mature and the middle cell is sometimes darker brown.

Specimens:
Holotype: PDD 45438, cultures ex-type PDDCC 8003, ATCC58189

Representative sequences:
ITS: AF243395 (ex-type), AY259098
EF1-alpha: AY236883 (ex-type), AY573221

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Neofusicoccum parvum. Version 04 saved 8 October 2007
Alan J. L. Phillips, alp@fct.unl.pt
Centro de Recursos Microbiológicos, Faculdade de Ciźncias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
Page copyright © 2007 A. J. L. Phillips