Phytophthora medicaginis

Name and publication

Phytophthora medicaginis Hansen & Maxwell (1991)

Hansen EM and Maxwell DP. 1991. Species of the Phytophthora megasperma-complex. Mycologia 83: 376–381 (pg. 377).


from Hansen and Maxwell (1991)




named for the principal host


Type: UNITED STATES, Oregon, Salem, from Medicago sativa, collected by P. B. Hamm in 1978 [no. AL1 S1 et no. 4 in herbarium at Oregon State University (OSC)]

Ex-type: CBS 119902 (duplicate deposited by Hansen on 12 Oct 1985)

NOTE: According to the original manuscript, cultures of the type were deposited in the American Type Culture Collection. No isolate for AL1 S1 et no. 4 is found in ATCC. E. Hansen confirmed that CBS 119902 is the authentic ex-holotype in e-mail to G. Abad on 7-25-13.

Ex-type in other collections

CBS 119902 (= AL1 S1 et no. 4) = P19830 (WPC), CPHST BL 83 (Abad)

Molecular identification

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

Phytophthora medicaginis isolate CPHST BL 83 (= P19830 WPC) = ITS rDNA MG865532, COI MH136927

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

Clade 8a

Morphological identification

Colonies and cardinal temperatures

Colony morphology after 7 days of growth on potato dextrose agar, V8 agar, and malt extract agar with no distinct pattern. Minimum temperature for growth is 3°C, optimum 27°C, and maximum 33°C. 

Conditions for growth and sporulation

Sporangia and hyphal swellings produced in V-8 agar flooded with 10% soil solution.

Asexual phase

Sporangia nonpapillated; persistent; ellipsoid, ovoid, obpyriform (35–69 L x 20–41 W μm); showing internal proliferation; originated in unbranched sporangiophores; in some cases the sporangiophore broadens towards the sporangium. Hyphal swellings mostly individual subglobose, elongate, irregular or coralloid. Chlamydospores rarely produced; globose or subglobose (20–33 μm diam), intercalary.

Sexual phase

Homothallic. Oogonia smooth-walled, globose (19–40 μm diam), sometimes with tapered bases; antheridia predominantly amphigynous, sometimes with two antheridia, one amphyginous and one paragynous, sometimes with digitate projections; oospores globose (14–32 μm diam) plerotic, aplerotic, or slightly aplerotic.

Most typical characters

Phytophthora medicaginis is characterized by the presence of predominantly amphigynous antheridia in conjunction with paragynous antheridia.

Specimen(s) evaluated

Phytophthora medicaginis ex-type CPHST BL 83, duplicate of P19830 (World Phytophthora Collection), which is a duplicate of CBS 119902

Phytophthora medicaginis selected specimen P7029 (World Phytophthora Collection) (ITSrDNA 100% alignment with ex-type CPHST BL 83)

Hosts and distribution

Distribution: cosmopolitan, throughout the range of the host
Substrate: roots
Disease note: root rot, damping-off of seedlings
Host: Medicago sativa (alfalfa), Onobrychis viciifolia (sainfoin), Cicer arietinum (chickpea) (Fabaceae); also reported on Prunus mahaleb (cherry, Rosaceae)

Retrieved January 31, 2018 from U.S. National Fungus Collections Nomenclature Database.

Additional references and links

Fact sheet author

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