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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #83270
Title: COMPARATIVE HISTOPATHOLOGY OF SIX ISOLATES OF ASCOVIRUS IN EIGHT SPECIES OFLEPIDOPTERA: NOCTUIDAE

Author
item Hamm, John
item STYER, ELOISE - UNIVERSITY OF GEORGIA
item FEDERICI, BRIAN - UNIVERSITY OF CALIFORNIA

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ascoviruses are a recently discovered group of viruses infecting moth larvae of the family Noctuidae which contains many agriculturally important pests including corn earworm, tobacco budworm, fall armyworm and cabbage looper. Six isolates of ascovirus were tested on eight species of noctuid larvae to determine which species were infected and to compare the pathology produced by the different isolates in the different hosts. Two isolates from fall armyworm were the most restricted in host range and in tissues infected; the virus reproduced only in species closely related to fall armyworm and developed only in the fat body. Viral isolates from cabbage looper, corn earworm and tobacco budworm infected all eight species tested. The isolates from cabbage looper and corn earworm developed mostly in the epidermis whereas the isolate from tobacco budworm developed more in the fat body. DNA analysis showed that the isolates from fall armyworm are completely different from the other isolates. However one isolate from corn earworm is related to the isolate from cabbage looper and both isolates from corn earworm and tobacco budworm are related to each other.

Technical Abstract: The histopathologies produced by 6 isolates of Ascovirus in 8 host species (Spodoptera frugiperda, S. ornithogalli, S. exigua, S.eridania, Heliothis zea, H. virescens, A. precationis, and Feltia subterranea) are compared by light microscopy. The 2 isolates from S.frugiperda were the most restricted in both host range and tissue specificity, infecting mainly fat body in S. frugiperda, S. ornithogalli, and S. exigua. They produced aberrant infections which stalled in early stages in some heterologous hosts. Isolates from H. zea, and T. ni infected epidermis in all eight hosts tested and tracheal epithelium in all but S. frugiperda. The isolate from H. zea produced early stages of infection in the fat body in 4 of the hosts while the isolate from T. ni produced early stages of infection in the fat body in 5 species and in S. frugiperda the infection in fat body progressed to produce vesicles. In contrast, the isolate from H. virescens infected only fat body in 6 hosts and showed heavier infections in fat body than in tracheal epithelium or epidermis in the other 2 hosts. The isolate from A. precationis infected 6 of the 8 hosts, infecting fat body in all 6 hosts and varying in infection of epidermis and tracheal epithelium in 3 of the hosts. Aberrant cellular responses to the ascovirus in heterologous hosts described. DNA-DNA dot-blot hybridization indicated the isolate of A. precationis is distinct from previous ascoviruses of T. ni and S.frugiperda Another isolate from H.zea reacted with probes of both A. precationis and T. ni ascovirus indicating either a mixture of viruses or a recombiant virus.