The role of paragynous and amphigynous antheridia in sexual reproduction of Phytophthora cinnamomi

Abstract

The morphology of gametangia was examined in 43 pairs of isolates (mating types A1iA2 ; 11 A1 and 24 A2 isolates ; five isozyme\electrophoretic types) of Phytophthora cinnamomi. An amphigynous antheridium always formed with each oogonium. However, in 41 of the crosses a proportion (39 had 0n2-10 % and two had 30 %) of oogonia also consistently had single or multiple paragynous antheridia. Single or multiple paragynous antheridia formed concurrently with amphigynous ones during the period of gametangial production in paired colonies. Where there were multiple paragynous antheridia associated with an oogonium, sometimes additional antheridia formed after fertilization or even after oospores were visible. Developmental studies showed that when meiosis in amphigynous and paragynous antheridia was simultaneous, fertilization tubes developed synchronously from both. However, cytological examination indicated that either a nucleus from an amphigynous or a paragynous antheridium fertilized the oosphere. Observations of paragynous and amphigynous, and amphigynous-only associations suggested that fertilization from either type of antheridium only occurred when meiosis in the oogonium was nearly synchronous with that of the antheridium. Asynchronous meiosis between oogonia and antheridia may contribute to failed fertilization and aborted oospore development. This appears to be the first description of paragynous antheridia in P. cinnamomi and the second observation of oogonia with both paragynous and amphigynous antheridia in a heterothallic Phytophthora species. Moreover, the development of both paragynous and amphigynous antheridia with an oogonium is rare in Phytophthora, as is the development of multiple antheridia. Antheridial variation is a characteristic to be taken into account in isolate identification. Nuclei from paragynous antheridia appear able to fertilize oospheres and therefore, have a role in sexual reproduction.

Microbial Profiling of Cultural Systems for Suppression of Phytophthora Root Rot in Fraser Fir

“…Trees used in this study were purchased from three suppliers, in order to minimize the likelihood that an infestation in a single lot would affect all study sites. Phytophthora was recovered from 26 of 30 root samples (87%), a rate consistent with expected recovery in culture from known infected samples (29,35,39,53). Seedlings were hand-planted; in mulch treatments, seedlings were placed with the crowns above the soil line to encourage root growth within the mulch.…”

Evidence for the role of synchronicity between host phenology and pathogen activity in the distribution of sudden oak death canker disease

“…Isolate Pr‐102 was found to be moderately pathogenic on oak seedlings (Hüberli et al ., 2006) and it belongs to the most common clonal genotype of P. ramorum , present almost ubiquitously in California forests (Ivors et al ., 2004). Inoculum discs of 5 mm diameter were cut with a sterile cork borer from the margin of 14‐d‐old cultures grown at 20°C on vegetable‐8 juice (Campbell Soup Company) agar (Hüberli et al ., 1997) with omission of β‐sitosterol and CaCO 3 . The isolates are stored in the culture collection of D. Rizzo, University of California, Davis, CA, USA.…”

Is variation in susceptibility to Phytophthora ramorum correlated with population genetic structure in coast live oak (Quercus agrifolia)?

“…data). Inoculum discs, 5 mm diameter, were cut with a sterile cork borer from the margin of 14-d-old cultures grown at 20 ° C on vegetable-8 juice (Campbell Soup Company, Camden, NJ, USA) agar (Hüberli et al ., 1997) with omission of β -sitosterol and CaCO 3 . The isolate is stored in the culture collection of D. Rizzo, University of California, Davis, CA, USA.…”