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United States Department of Agriculture

Agricultural Research Service

Title: Characterization of Aphid Pathogenic Species in the Genus Pandora Using Pcrtechniques and Digital Image Analysis

Authors
item Nielsen, Charlotte - ROYAL VET & AGRI UNIV
item Sommer, Christian - ROYAL VET & AGRI UNIVER
item Hansen, Karen
item Eilenberg, Jorgen - ROYAL VET & AGRI UNIVER
item Humber, Richard

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2001
Publication Date: N/A

Interpretive Summary: PANDORA NEOAPHIDIS is a major, worldwide fungal pathogen of aphids. Because this fungus is so common and affects so many aphids, it has been unsure if this species might not actually represent a complex of similar but taxonomically distinguishable species. Numerous isolates of P. NEOAPHIDIS from a wide range of hosts and locations and related fungi from aphids and other hosts were compared using two different molecular techniques, and the sizes and shapes of their spores were compared statistically by means of digital image analyses. The overall analysis proved that geographic origin was a stronger correlative factor than was host identity among isolates of P. NEOAPHIDIS whereas host identity was most important for distinguishing among other aphid pathogens studied. Combined analyses of host information and spore shapes distinguished species as effectively as did genetic analyses. The overall evidence suggests that P. Neoaphidis is a species complex that can be resolved into separate species better by using the place from which the fungus is collected than by the identity of the host or by the fungus' overall appearance. While this paper does not itself attempt to resolve the P. Neoaphidis species complex, it lays sound bases on which such a taxonomic resolution can be done.

Technical Abstract: Twenty-eight isolates of the insect-pathogenic fungal genus PANDORA Humber derived from various geographical locations and insect hosts were studied in order to examine both genotypic as well as phenotypical variation. I the study 16 PANDORA NEOAPHIDIS, 2 P. NOURYI, 3 P KONDOIENSIS, one P BULLATA and 6 P. DELPHACIS isolates were included. For phenotypical characterization the length and width of the primary conidia were measured and the size and shape of conidia were quantified in digital images. The size of ITS divided P. NEOAPHIDIS, P. NOURYI and P. KONDOIENSIS into the following four groups: (1) all P. NEOAPHIDIS isolates, (2) 2 isolates of P. KONDOIENSIS including the ex neotype, (3) one isolate of P. NOURYI, and (4) one isolate of P. KONDOIENSIS and one isolate of P. NOURYI both sampled from ACYRTHOSIPHON PISUM in Australia. The analysis of RAPD data fully supported the groupings obtained for the ITS lengths. The RAPD technique was able to distinguish between all isolates except those isolated from th same epizootic. It was proven that, among the P. NEOAPHIDIS isolates, a correlation between RAPD-PCR profile and geographical origin of the isolate was present, while no correlation between host species and profile was seen. The analysis of digital images was here employed for the first time for entomopathogenic fungi. The digital image analysis supported at a quantitative level in the original descriptions of P NEOAPHIDIS and P. DELPHACIS primary conidia as ovoid to ellipsoidal whereas the primary conidia of P. NOURYI and P. KONDOIENSIS are ovoid. Within these two clusters information on host insect species is important for distinguishing fungal species. Thus, by combining digital image analysis and information on host insect species the results agreed with the genetic analysis.

Last Modified: 7/12/2014
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