Phytophthora megakarya (to be revalidated 2022)

Name and publication

Phytophthora megakarya Brasier & Griffin (1979)

Brasier CM and Griffin MJ. 1979. Taxonomy of 'Phytophthora palmivora' on cocoa. T. Brit. Mycol. Soc. 72: 111–143 (pg. 137).

Phytophthora L-type (Brasier and Griffin, 1979)

Nomenclature

from Brasier and Griffin 1979

Mycobank

MB320483

Typification

Type: NIGERIA collected from cocoa (Theobroma cacao L.) IMI 182590 A1, and CAMEROON collected from cocoa (Theobroma cacao L.) IMI 202077, A2 (original publication cites two types)

Nomenclature under revision.

Well-authenticated specimen(s) selected by Gloria Abad:
Selected specimen #1: CPHST BL 22 = P1664 (WPC) = IMI 182590: NIGERIA, P38, A1, L, lfusk, Ibadan
Selected specimen #2: CPHST BL 73 = P1672 (WPC) = IMI 202077: CAMEROON, P184, A2, L, ex B. Boccas, no. 36

Selected specimen(s) in other collections

CPHST BL 22 (Abad) = P1664 (WPC), IMI 182590 

CPHST BL 73 (Abad) = P1672 (WPC), CBS 238.83, ATCC 42100, P184, 61J5 (Yang)

Molecular identification

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

Phytophthora megakarya isolate CPHST BL 22 (= P1664 WPC) = ITS rDNA MG865533, COI MH136928

Phytophthora megakarya isolate CPHST BL 73 (= P1672 WPC) = ITS rDNA MG865534, COI MH136929

Sequences for specimen #1 in other sources
Sequences for specimen #2 in other sources
Position in ITS phylogenetic tree

Clade 4

Morphological identification

Colonies and cardinal temperatures

Colony morphology after 7 days of growth on V8 agar and malt extract agar with light chrysanthemum pattern, on potato dextrose agar with no distinct pattern. Minimum temperature for growth is 10°C, optimum 24–26°C, and maximum 30°C.

Conditions for growth and sporulation

Sporangia produced on V-8 agar flooded with 10% soil solution.

Asexual phase

Sporangia papillate (frequently with one papillae, rarely 2 or 3); caducous with medium pedicel (10–30 µm); frequently obpyriform with well-rounded bases, sometimes globose, ovoid or elongate-ovoid, or ellipsoid (20–60 x 13-41 μm). Sporangia originated in loose sympodial sporangiophores. Hyphal swellings absent. Chlamydospores are very rare, but occur both in agar as well as in water cultures and are mostly terminal (20–44 μm diam).

Heterothallic. Oogonia smooth (19–37 μm diam), antheridia amphigynous, situated either well down the oogonial stalk or high up as a collar, depending on the degree of taper of the oogonium (10–16 μm); oospores plerotic (18–34 μm diam).

Most typical characters

Phytophthora megakarya is characterized by the shape of the caducous, globose to ovoid sporangia with medium pedicel and produced in loose sympodial sporangiophores, and also by the shape of the sexual stage.

Specimens evaluated

Specimen #1: Phytophthora megakarya CPHST BL 22 = P1664 (World Phytophthora Collection)

Specimen #2: Phytophthora megakarya CPHST BL 73 = P1672 (World Phytophthora Collection)

Phytophthora megakarya P8516 (World Phytophthora Collection)

Hosts and distribution

Distribution: Africa (Nigeria, Cameroon, Ghana, Fernando Po) (Erwin & Ribeiro 1996)
Substrate: pods, seedlings, bark of trunks, possibly roots
Disease note: pod rot, seedling blight, trunk canker. Inoculum does not survive in mummified pods, but survives in soil up to 18 months, possibly in infected roots (Erwin & Ribeiro 1996).
Host: Theobroma cacao (cacao, Sterculiaceae); also reported from Irvingia sp. (Irvingiaceae)

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

Additional info
Substrate: foliage, fruits, root

Quarantine status

USA: This species was listed as a species of concern during the 2009 Phytophthora prioritization project conducted by USDA APHIS PPQ CPHST PERAL (Schwartzburg et al.).

Additional references and links

Fact sheet author

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