Soybean Aphid, Aphis glycines Matsumura, a New Vector of Potato Virus Y in Potato

American Journal of Potato Research, May/Jun 2005 by Davis, Jeffrey A, Radcliffe, Edward B, Ragsdale, David W

Relative titer levels of PVY strains in the inoculum source used in this study were not measured, so it is not possible to draw conclusions as to relative efficiency of transmission of various strains. However, comparative transmission efficiencies for the PVY^sup O^ and PVY^sup N^ strains in this study were similar to that reported by other authors (Katis and Gibson 1985; Harrington et al. 1986; Fereres et al. 1993), all of whom found that green peach aphid transmitted PVY^sup O^ more efficiently than PVY^sup N^.

If PVY^sup N^ were to become abundant in the North Central region, this could force potato seed certification programs to rely to a much greater extent on serological testing because PVY^sup N^ infections tend to be more difficult to recognize visually. Soybean aphid appeared to transmit PVY^sup N:O^ in preliminary mass inoculation experiments (Davis et al. 2004), but this recombinant was not transmitted in experiments with groups of five or single aphids.

Soybean is not a host of PVY and even when soybean aphid had access to PW inoculum, its efficiency of transmission was less than that of green peach aphid and potato aphid. However, potatoes are frequently rotated with soybean in the North Central region, so this crop is often grown in close proximity to potatoes. Bird cherry-oat aphid (Rhopalosiphum padi (L.)), like soybean aphid, is an inefficient PVY vector (11.5%) compared to M. persicae, but has been implicated as a key vector of that virus in our region (DiFonzo et al. 1997). What soybean aphid lacks in transmission efficiency, it makes up in sheer numbers. In 2003, 2.8 million ha of soybeans in Minnesota were infested with soybean aphid, with nearly 1.4 million ha treated to prevent yield losses. Voegtlin and Onstad (2003) estimated that -400 million soybean aphid alatae emigrated from one 32-ha Illinois soybean field in a single day. Given this aphid's propensity to form alatae, its high fecundity, and relative transmission efficiency, soybean aphid appears to have the potential to be an important vector of PVY. This is the first confirmation of soybean aphid transmitting PVY.

ACKNOWLEDGMENTS

The authors acknowledge Dr. Roger Moon for his statistical advice. We also thank Dr. Philip Berger, USDA-APHIS-PPQ-CPHST, Raleigh, NC, Dr. Jeffrey Wyman, University of Wisconsin, Madison, WI, and anonymous peer reviewers for their constructive comments on a previous draft of this manuscript.

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