Potato virus Y (PVY), a Potyvirus, is transmitted by aphids in a nonpersistent manner. PVY severely affects potato production worldwide. Single and mixed infections of PVY strains, namely PVY(O), PVY(NTN), and PVY(N:O) are a common occurrence in potato systems. However, information available on the ability of aphids to simultaneously transmit multiple PVY strains, specificity associated with simultaneous transmission, and factors affecting specificity are limited. Aphid-mediated transmission experiments were conducted to test the ability of individual aphids to transmit multiple strains using a PVY indicator host. Preliminary results revealed that aphids can transmit at least two viral strains simultaneously. Subsequently, aphid-mediated transmission of three dual-strain combinations was tested using potato plants. Individual aphids transmitted two viral strains simultaneously for all three dual-strain combinations. In all aphid-mediated dual-strain infections involving PVY(NTN), the rate of PVY(NTN) infection was greater than the infection rates of the second strain and dual-strain combinations, indicating specificity associated with transmission of PVY strains. Results of aphid-mediated transmission experiments were compared with results obtained through mechanical transmission. In general, PVY infection rates from aphid-mediated transmission were lower than the rates obtained through mechanical transmission. Unlike aphid-mediated transmission, component strains in dual-strain inoculations were not eliminated during mechanical transmission. These results suggest that there may also be interference associated with aphid-mediated transmission of closely related PVY strains. Perhaps, the observed specificity and/or interference may explain the increase in the incidence of PVY(NTN) and other necrotic strains in recent years.

PVY causes yield and quality loss in potato. The Ry adg gene from Solanum tuberosum ssp. andigena has been shown to provide extreme resistance to PVY; defined as resistance against all strains. However, Ry adg gene clones have not been screened against PVY N:O , a newly detected North America strain. Three Ry adg -diagnostic molecular markers were tested in tetraploid progeny of a PVY resistant x susceptible cross and in diverse clones/cultivars. Multiple isolates of PVY strains (PVY NTN , PVY N:O , PVY O ) were used for mechanical inoculations of the progeny. In addition, PVY O , PVY N , and PVA were used for graft inoculation on a separate clone/cultivar set. Progeny segregated 1:1 for PVY resistance; fitting a gene model simplex for Ry adg . Marker positive progeny were resistant to all PVY strains, including PVY N:O . Marker presence was also in agreement with PVY resistance in the clones/cultivars. These findings show that these markers can identify resistance to all known PVY strains in North America.Resumen El virus Y de la papa (PVY) causa reducción en la calidad y el rendimiento. Se ha demostrado que el gen Ry adg de Solanum tuberosum ssp. andigena provee resistencia extrema contra el PVY; definida como resistencia contra todas las cepas. Sin embargo, no se ha investigado la resistencia de los clones del gen Ry adg contra PVY N:O , una cepa de Norte América recientemente detectada. Tres marcadores moleculares de diagnostico del gen Ry adg fueron probados en progenie tetraploide de un cruce de PVY resistente x susceptible y en diversos clones/cultivares. Múltiples cepas aisladas de PVY (PVY NTN , PVY N:O , PVY O ) fueron utilizadas para inoculaciones mecánicas de la progenie y PVY O , PVY N y PVA fueron usados para inoculación de injertos en un subconjunto de clones/ cultivares. La progenie segregó 1:1 para resistencia contra PVY; encajando en un modelo genético simplex para Ry adg . Las progenies positivas a los marcadores fueron resistentes a todas las cepas de PVY, incluyendo PVY N:O . La presencia de marcadores tambien concordaba con la resistencia contra PVY en clones/cultivares. Estos hallazgos demuestran que estos marcadores pueden identificar la resistencia a todas las cepas de PVY conocidas en Norte América.

Field studies in citrus were conducted to compare the following as attractants for the Caribbean fruit fly, Anastrepha suspensa (Loew): torula yeast-borax; propylene glycol (10%); a two-component lure consisting of ammonium acetate and putrescine; a two-component lure consisting of ammonium bicarbonate and putrescine; and a three-component lure consisting of ammonium bicarbonate, methylamine hydrochloride, and putrescine. Various combinations of these attractants in glass McPhail, plastic McPhail-type (Multi-Lure), and sticky panel traps were investigated in two replicated studies. In one study on wild flies, the most effective and least complex trap-lure combination tested was the Multi-Lure with propylene glycol baited with ammonium acetate and putrescine. This trap-lure combination captured significantly more female and male flies than the standard glass McPhail baited with torula yeast-borax in water. All of the trap-lure combinations were female biased, with an overall average of 80.8% (SEM 1.4) flies captured being female. A second study on laboratory-reared, irradiated flies indicated no significant differences among these trap-lure combinations with respect to number of flies recaptured, although rankings based on mean number of flies recovered per trap per day supported results of the first study. The percentage of flies recaptured that were female (83.0%, SEM 0.9) was statistically the same as in the first study. Weekly percentage recovery of flies during the second study was low, possibly due to our fly release strategy. Future release/recovery studies with laboratory-reared flies would benefit from some basic research on release strategies by using different trap densities and on relating recapture rates of laboratory-reared flies (nonsterile and sterile) to capture rates of wild flies.

Potato leafroll virus (PLRV) is a major pathogen of potato with worldwide impact on seed and commercial production of potato. In North America, the primary potato cultivars grown by industry are not resistant to PLRV and require the application of insecticides to control the aphid vector of PLRV, so as to prevent PLRV infection of the crop. The Solanum etuberosum-derived dominant gene Rlr etb confers resistance to PLRV and has been mapped to chromosome 4. The previous closest marker to Rlr etb , C2_At1g42990, was mapped 13.6 cM from the gene in a BC 3 population. Cleaved amplified polymorphic sequence markers were developed in the region surrounding C2_At1g42990 and mapped along with Rlr etb in 102 BC 4 progeny. Sixteen markers were identified surrounding Rlr etb , with flanking markers at 2.1 and 9.3 cM. Two markers, 1367-8a and DMB32-11, both 2.1 cM from Rlr etb , are shown to be well suited for marker assisted selection. The development of additional molecular markers more closely linked to Rlr etb will greatly facilitate its use in potato breeding and its continued introgression into cultivated potato for the development of PLRV-resistant cultivars.Resumen El virus del enrollamiento de la hoja de la papa (PLRV) es un patógeno importante de la papa con impacto mundial en la producción de semilla y en la producción comercial de la papa. En Norteamérica, las principales variedades de papa que se cultivan por la industria no son resistentes al PLRV y requieren de la aplicación de insecticidas para control del áfido vector del PLRV, así como para prevenir la infección del cultivo por PLRV. El gen dominante derivado de Solanum etuberosum, Rlretb, confiere resistencia al PLRV y ha sido ubicado en el cromosoma 4. El marcador previo más cercano al Rlretb, C2_At1g42990, fue ubicado a 13.6 cM del gen en una población BC3. Se desarrollaron marcadores fragmentados amplificados de secuencias polimórficas en la región que rodea a C2_At1g42990 y se les hizo un mapa junto con Rlretb en una progenie 102 BC4. Se identificaron 16 marcadores rodeando al Rlretb, con marcadores en los lados a 2.1 y 9.3 cM. Dos marcadores, 1367-8a y DMB32-11, ambos a 2.1 cM de Rlretb, se ha demostrado que son los apropiados para la selección asistida por marcadores. El desarrollo de marcadores moleculares adicionales más cercanamente ligados a Rlretb facilitará grandemente su uso en el mejoramiento de la papa así como su incorporación a papa cultivada para el desarrollo de variedades resistentes al PLRV.