Phytophthora gibbosa

Name and publication

Phytophthora gibbosa Jung, Stukely & Burgess (2011)

Jung T, Stukely MJC, Hardy GE StJ, White MD, Paap T, Dunstan WA, and Burgess TI. 2011. Multiple new Phytophthora species from ITS Clade 6 associated with natural ecosystems in Australia: evolutionary and ecological implications. Persoonia 13: 13–39.

Nomenclature

from Jung et al. (2011)

Mycobank

MB518763

Etymology

refers to the gibbous ornamented surface of the oogonia (gibbosa Latin = gibbous, knaggy)

Typification

Type: WESTERN AUSTRALIA, Scott River ironstones, from rhizosphere soil of dying Acacia pycnantha, 2009, VHS, holotype MURU 461 (dried culture on V8A, Herbarium of Murdoch University, Western Australia)

Ex-type: CBS 127951 and VHS 21998

Sequences for ex-type in original manuscript: CBS 127951 = ITS rDNA HQ012933, HSP90 HQ012892, cox1 HQ012846

Ex-type in other collections

CBS 127951 = VHS 21998 = P19586 (WOC/WPC), CPHST BL 65 (Abad), 62B8  (Yang)

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of the ex-type (see Molecular protocols page)

Phytophthora gibbosa isolate CPHST BL 65 (= P19586 WPC) = ITS rDNA MG865499, COI MH136894

Sequences for ex-type in other sources
Position in ITS phylogenetic tree

Clade 6b

Morphological identification

Colonies and cardinal temperatures

Colony morphology is uniform on V8A, CA, MEA, and PDA. Minimum growth temperature 7.5°C, optimum 30°C, and maximum 32.5°C.

Conditions for growth and sporulation

Sporangia are produced in water cultures (soil extract or river water) and not observed in solid media. Oogonia are formed readily in single-strain culture on CA and V8A after about 20 d.

Asexual phase

Sporangia are non-papillate, persistent, and ovoid or ellipsoid in shape. Sporangia average 48.8 ± 9.6 × 30.8 ± 5.4 μm (overall range 24.8–71.1 × 17.4–48.0 μm). Sporangiophores usually in simple sympodia with internal extended proliferation. External proliferation also observed leading to lax sympodia. Hyphal swellings are common. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia are globose with wavy to ornamented gibbous walls turning golden-brown on maturity, average size 38.1 ± 5.4 mm (27.0–49.9 µm). Oospores are aplerotic, globose, with a large ooplast and thick walls, average size 31.4± 4.6 µm (18.9–39.4). Antheridia amphigynous.

Most typical characters

Phytophthora gibbosa can be easily differentiated from all other species from ITS Clade 6 (except Phytophthora ornamentata) by the production of ornamented (gibbous) oogonia in single culture. In addition, it can be separated from Phytophthora gregata and P. taxon raspberry by the lack of nested proliferation of sporangia.

Specimen(s) evaluated

Australia, Western Australia, Scott River ironstones, from rhizosphere soil of dying Acacia pycnantha, 2009, CBS 127951 = VHS 21998; VHS 22007; from dying Xanthorrhoea gracilis, VHS 21999; from a dying Grevillea sp., VHS 22008

CPHST BL 65 = P19586 WPC

Hosts and distribution

Distribution: Australia
Substrate: soil associated with dying plants, roots

Retrieved January 30, 2018 from U.S. National Fungus Collections Nomenclature Database.

Additional info:
Distribution: Western Australia
Substrate: roots, collars, and rhizosphere soil
Disease note: no pathogenicity trials have been conducted
Hosts: Acacia pycnantha, Xanthorrhoea gracilis, Grevillea sp.

Additional references and links

Burgess TI, Webster JL, Ciampini JA, White DW, Hardy GESJ, Stukely MJC. 2009. Re-evaluation of Phytophthora species isolated during 30 years of vegetation health surveys in Western Australia using molecular techniques. Plant Disease 93: 215–223.

Fact sheet authors

Treena Burgess, Ph.D., Centre for Phytophthora Science and Management, School of Biological Sciences and Biotechnology, Murdoch University, Australia; Z. Gloria Abad, Ph.D., USDA-APHIS-PPQ-S&T Beltsville Laboratory, United States of America