Intraspecific variation in zucchini yellow mosaic virus transmission by Myzus persicae and the impact of aphid host plant.

Three isofemale lines of Myzus persicae (Sulzer), two lines collected from and reared on a brassicaceous host, and one line collected from and reared on a malvaceous host, were evaluated for their efficiency of transmitting Zucchini yellow mosaic virus (family Potyviridae, genus Potyvirus, ZYMV). In the first experiment, the transmission efficiencies of two clones from Brassicaceae (B1 and B2) were 52.0 and 60.8%, respectively, and these transmissions were not significantly different. In a second experiment, the transmission efficiencies of the clone on Malvaceae (M1) and clone B2 were significantly different at 35.6 and 55.7%, respectively. Further experiments evaluated host-related mechanisms that may have contributed to the differential transmissions observed between clones M1 and B2. Studies on short-term feeding showed that aphids continuously reared on okra, Abelmoschus esculentus (L.) Moench (malvaceous host), and those that were reared on okra and allowed a 24-h preacquisition feeding period on mustard, Brassica juncea (L.) Czern (brassicaceous host), had significantly lower transmission than aphids continuously maintained on mustard. Aphids reared on mustard and allowed a 24-h preacquisition feeding period on okra had intermediate transmission efficiency. In long-term host association studies, we found that aphids reared on mustard had significantly higher transmission efficiency than those reared on okra, and aphids reared first on okra and then switched to mustard had a transmission efficiency that was intermediate and not significantly different from the other two treatments. Our study reveals the existence of intraspecific variation in the transmission of ZYMV by M. persicae, and it suggests that to accurately assess the transmission capability of ZYMV by this species, multiple clones should be examined. Furthermore, the host plant on which the aphid is reared as well as the host plant on which it feeds just before virus acquisition contribute to ZYMV transmission efficiency of M. persicae.