Phytophthora phaseoli (to be redescribed 2022)

Name and publication

Phytophthora phaseoli Thaxt. (1889)

Thaxter R. 1889. A new American Phytophthora. Bot. Gaz. 14: 273–274. Phytophthora phaseoli.





from Thaxter (1889)

Type: UNITED STATES OF AMERICA, collected from lima beans (Phaseolus lunatus) in the vicinity of New Haven, Connecticut in September 1889 on pods, stems, and leaves of the lima bean

Ex-type: LOST

Well-authenticated specimen(s) selected by Gloria Abad: 
Selected specimen #1: CPHST BL 28 = P10150 (WPC) from Phaseolus lunatus in Delaware, Race F, UNITED STATES OF AMERICA
Selected specimen #2: CPHST BL 112 = P6609 (WPC) from Phaseolus lunatus in Maryland, Race C, UNITED STATES OF AMERICA

Selected specimen(s) in other collections

CPHST BL 28 (Abad) SE1 = P10150 (WPC)
CPHST BL 112 (Abad) SE2 = P6609 (WPC) = CBS 114106 Tooley 330 Race C

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of selected specimens (see Molecular protocols page)

Phytophthora phaseoli isolate CPHST BL 28 (= P10150 WPC) = ITS rDNA MG865564, COI MH136956

Sequences for selected specimen(s) in other sources
Position in ITS phylogenetic tree

Clade 1c

Morphological identification

Colonies and cardinal temperatures

Colonies after 7 days of growth on V8 agar, potato dextrose agar, and malt extract agar with slow growth and no special pattern. Minimum temperature for growth is 9°C, optimum 15–20°C, and maximum 27°C. 

Conditions for growth and sporulation

Phytophthora phaseoli produces sporangia abundantly on agar; oospores produced abundantly on lima bean agar or in host tissue.

Asexual phase

Sporangia semipapillate; caducous with short pedicels (5–20 µm L); ovoid, ellipsoid, obovoid, or irregular and some with tapered bases (18–54 µm L x 11–27 µm W); nonproliferating; originated in simple sympodial sporangiophores which are slightly swollen at the base of sporangium. Hyphal swellings absent. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled, subspherical (17–36 µm diam.); antheridia predominantly amphigynous, elongated cylindrical, spherical, ellipsoid, or ovoid (7–19 µm L), and sometimes with digitate projections; oospores aplerotic (13–27 µm diam.).

Specimen(s) evaluated

Phytophthora phaseoli CPHST BL 28 SE1 = P10150 (WPC)

Phytophthora phaseoli CPHST BL 112 SE2 = P6609 (WPC)

Hosts and distribution

Distribution: Africa (Congo, Zaire), Asia (Philippines, Sri Lanka, Russia), Europe (Italy, Romania), North America (Mexico, USA), Central America and Caribbean Islands, South America (Brazil)
Substrate: pods. Also on shoots, leaves, petioles. Overwinters in soil or infected plant debris.
Disease note: downy mildew. At least 6 races have been identified. Races D, E, F have recently caused serious outbreaks in the eastern USA (DE, MD).
Host: Phaseolus lunatus (also reported as P. limensis) (lima beans, Fabaceae). Capable of infecting plants from other families after inoculation (Erwin & Ribeiro 1996). Also reported from Phaseolus vulgaris (common bean).

Retrieved February 01, 2018 from U.S. National Fungus Collections Nomenclature Database.

Additional info:
Substrate: foliage/fruits

Additional references and links

Fact sheet author

Z. Gloria Abad, Ph.D., USDA-APHIS-PPQ-S&T Beltsville Laboratory, United States of America