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Plant-Parasitic Algae (Chlorophyta: Trentepohliales) in American Samoa

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Title:Plant-Parasitic Algae (Chlorophyta: Trentepohliales) in American Samoa
Authors:Brooks, Fred E.
Date Issued:Jul 2004
Publisher:University of Hawai'i Press
Citation:Brooks FE. 2004. Plant-parasitic algae (Chlorophyta: Trentepohliales) in American Samoa. Pac Sci 58(3): 419-428.
Abstract:A survey conducted between June 2000 and May 2002 on the island of
Tutuila, American Samoa, recorded filamentous green algae of the order Trentepohliales
(Chlorophyta) and their plant hosts. Putative pathogenicity of the
parasitic genus Cephaleuros and its lichenized state, Strig;ula, was also investigated.
Three genera and nine species were identified: Cephaleuros (five spp.),
Phycopeltis (two spp.), and Stomatochroon (two spp.). A widely distributed species
of Trentepohlia was not classified. These algae occurred on 146 plant species and
cultivars in 101 genera and 48 families; 90% of the hosts were dicotyledonous
plants. Cephaleuros spp. have aroused worldwide curiosity, confusion, and concern
for over a century. Their hyphaelike filaments, sporangiophores, and associated
plant damage have led unsuspecting plant pathologists to misidentify
them as fungi, and some phycologists question their parasitic ability. Of the five
species of Cephaleuros identified, C. virescens was the most prevalent, followed
by C. parasiticus. Leaf tissue beneath thalli of Cephaleuros spp. on 124 different
hosts was dissected with a scalpel and depth of necrosis evaluated using a fourpoint
scale. No injury was observed beneath thalli on 6% of the hosts, but fullthickness
necrosis occurred on leaves of 43% of hosts. Tissue damage beneath
nonlichenized Cephaleuros thalli was equal to or greater than damage beneath
lichenized thalli (Strigula elegans). In spite of moderate to severe leaf necrosis
caused by Cephaleuros spp., damage was usually confined to older leaves near
the base of plants. Unhealthy, crowded, poorly maintained plants tended to have
the highest percentage of leaf surface area affected by Trentepohliales. Parasitic
algae currently are not a problem in American Samoa because few crops are
affected and premature leaf abscission or stem dieback rarely occur.
Appears in Collections: Pacific Science Volume 58, Number 3, 2004

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