A survey was conducted for virus-infected potato plants in commercial production fields in Baldwin, Cullman, DeKalb, and Jackson counties in Alabama. Infected plants were assessed visually, i.e., on the basis of occurrence of virus-like symptoms, and by enzyme-linked immunosorbent assay (ELISA). In 1997, potato plants were tested for Cucumber mosaic virus (CMV), Potato virus Y (PVY) and Tobacco etch virus (TEV). PVY was detected from foliar samples collected from Baldwin, Cullman, and Jackson counties. Neither CMV nor TEV were detected in any of the samples. In 1998, potato plants were once again tested for the presence of CMV, PVY, and TEV, with additional analyses for Potato viruse A (PVA), Potato M (PVM), Potato S (PVS), Potato X (PVX), and Potato leafroll virus (PLRV). Four viruses were detected from potato leaf samples collected from Baldwin County: PVS, PVX, PVY, and PLRV. Samples collected from DeKalb and Jackson counties were shown to be infected with CMV, PVA, PVS, PVX, and PVY. Identification of virus infection based on visual assessment was relatively inconsistent with the exception of PLRV-infected potato plants, which had upward curled leaves. The expression of infection by PVA, PVS, PVX, and PVY varied; some infected potato plants were symptomless while others had reddening of leaves that sometimes included a mild mosaic. This is the first report to identify viruses in commercially-grown potato plants in Alabama.

Houtenbos, I.; Bracho, F.; Davenport, V.; Slack, R.; de Ven, C. Van; Killen, R.; Shen, W. P.; Cairo, M.Author Information

Plant viruses face many challenges in agricultural environments. Although crop fields appear to be abundant resources for these pathogens, it may be difficult for viruses to “escape” from crop environments prior to host senescence or harvesting. One way for viruses to increase the odds of persisting outside of agricultural fields across seasons is by evolving traits that increase transmission opportunities between crops and wild plant communities. There is accumulating evidence that some viruses can achieve this by manipulating crop plant phenotypes in ways that enhance transmission by vectors. Putative manipulations occur through alteration of plant cues (color, size, texture, foliar volatiles, in-leaf metabolites, defenses, and leaf cuticles) that mediate vector orientation, feeding, and dispersal behaviors. Virus effects on host phenotypes are not uniform but appear to exhibit convergence depending on virus traits underlying transmission, particularly the duration of probing and feeding required to acquire and inoculate distinct types of plant viruses. This shared congruence in manipulation strategies and mechanisms across divergent virus lineages suggests that such effects may be adaptive. To discern if this is the case, researchers must consider molecular and environmental constraints on virus evolution, including those imposed by insect vectors from organismal to landscape scales. In this review, we synthesize applied research on vector-borne virus transmission in laboratory and field settings to identify the main factors determining transmission opportunities for plant viruses, and thus, selection pressure to evolve manipulative traits. We then examine these outputs in the context of studies reporting putative instances of plant virus manipulation. Our synthesis reveals important disconnects between virus manipulation studies and actual selection pressures imposed by vectors in real-world contexts.

The serological relationships between brome mosaic (BMV), cowpea chlorotic mottle (CCMV), and broad bean mottle (BBMV) viruses, and their coat proteins, were studied by gel precipitin, “rocket immunoelectrophoresis” (RIE), and enzyme-linked immunosorbent assay (ELISA) techniques. Gel precipitin and RIE tests indicated that capsid swelling altered the antigenicity of both BMV and CCMV, as although the coat proteins were serologieally related at both pH 6.0 and pH 7.0, the viruses appeared to be related only when swollen at pH 7.0. Fixation of the viruses with 2% formaldehyde at pH 6.0 appeared to remove the relationship. BBMV was not related by precipitin tests to either BMV or CCMV but was related to both by direct and indirect ELISA at both pH 6.0 and pH 7.4, though less closely than BMV and CCMV were related to each other. Indirect ELISA showed the three coat proteins to be more closely related than the parent viruses. Formalinized BMV and CCMV appeared less related than the native viruses at pH 6.0. Sandwich ELISA proved too strain specific to show any group relationships. The implications of these results and a serological map proposed for the bromoviruses are discussed.