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ARS Home » Pacific West Area » Wenatchee, Washington » Physiology and Pathology of Tree Fruits Research » Research » Publications at this Location » Publication #207163


item Roberts, Rodney

Submitted to: Mycotaxon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2007
Publication Date: 6/1/2007
Citation: Roberts, R.G. 2007. Two new species of alternaria from pear fruit. Mycotaxon. 100:159-167.

Interpretive Summary: Two new species of the fungus Alternaria are described from pear fruit. Alternaria ventricosa was discovered on imported Ya Li pear fruit from China, and A. calycipyricola was discovered growing in the calyx end of European pears that has been in cold storage in the US. Both species are members of the Alternaria infectoria group based upon their appearances in culture and their microscopic characters. Several molecular tests were performed which confirmed that these two new species differ from each other and from other members of the infectoria group.

Technical Abstract: During studies conducted over the past 15 years of various diseases of deciduous tree fruit from around the world, hundreds of Alternaria isolates have been made and characterized using morphological and molecular methods. Two such fungi are newly described here as A. calycipyricola sp. nov. from the calices of fruits of Pyrus communis L. ‘d’Anjou’ grown in Washington State, and A. ventricosa sp nov. from the stem of a fruit of Pyrus bretschneideri Rehd. ‘Ya Li’) grown in Hebei, China. Conidia of both species are fundamentally erostrate, but may produce elongate apical secondary conidiophores from which chain elongation and lateral branching occurs late in the development of individual conidia. The resultant sporulation in culture includes both solitary and catenulate conidia, the latter of which are separated by (usually) elongated secondary conidiophores and produced either in short, relatively unbranched chains or branching chains produced at wide angles from the conidial axis. These characters and the resulting granular visual appearance of the colonies are consistent with diagnostic characters of the A. infectoria group, to which both species belong. A. calycipyricola and A. ventricosa differ from each other in cultural characters, growth rate, and conidial morphology. Combined analyses of RAPD, RAMS and AFLP fingerprints support morphological evidence that A. calycipyricola and A. ventricosa are appropriately placed in the infectoria group sensu Simmons and are distinct from each other and the other species studied within the group.