Vectoring of Pepino mosaic virus by bumble‐bees in tomato greenhouses

Abstract

Pepino mosaic virus (PepMV) has become an important viral disease of greenhouse tomatoes worldwide. The ability of bumble-bees (Bombus impatiens), used for pollination, to acquire and transmit PepMV was investigated, and the prevalence of PepMV in plants and bumble-bees in commercial tomato greenhouses was determined. PepMV infection in plants was determined using enzymelinked immunosorbent assay, while in bumble-bees direct real-time PCR was used. In the first experiment, the bumble-bees were exposed for 14 days to PepMV-infected plants. After 14 days, almost all bumble-bees were PepMV positive both in the hive (78.5 AE 17.5%) and in the flowers (96.3 AE 3.6%). In the second experiment, bumble-bees were released into a greenhouse with both PepMV-infected source plants and healthy non-infected target plants for 14 days. At the end of the experiment, 61.0 AE 19.5% of the bees collected from the hive and 83.3 AE 16.7% of the bees sampled from the flowers were PepMV positive. Bumble-bees transmitted PepMV from the infected to the healthy noninfected tomato plants. Two weeks after bumble-bee release, the virus was detected in leaf, fruit and flower samples of formerly healthy plants. After 6 weeks, the percentage of PepMV positive samples from the target plants increased to 52.8 AE 2.8% of the leaves and 80.6 AE 8.4% of the fruits. In the control greenhouse without bumble-bees, the target plants did not become infected. Based on the infection levels in flowers, fruits and leaves, the PepMV infection occurred possibly first in the pollinated flowers, and then spread from the fruit that developed from the flowers to other parts of the plant. In commercial greenhouses where PepMV was present, 92-100% of the plants and 88-100% of the bumble-bees were PepMV positive. No infected plant samples were found in the control commercial greenhouse, but a small number of bumble-bees (10%) tested PepMV positive.

Epidemiología y variabilidad patogénica del virus del mosaico del pepino dulce (Pepino mosaic virus). Nuevas enfermedades asociadas a su presencia (torrao o cribado)

“…Some forms of PepMV transmission associated with its mechanical transmission, such as transmission by Bombus spp., which carried the virions stuck to their bodies and their contact with plants produced the transmission of the virus (Lacasa et al, 2003), or through infected pollen (Shipp et al, 2008), have been studied.…”

“…impatiens (Cresson) (Lacasa et al, 2003;Shipp et al, 2008). En este modo de transmisión, la infección del virus parece producirse en las flores cuando son polinizadas por los abejorros portadores de partículas virales, y de allí se distribuye por el resto de la planta, existiendo dos posibles vías de transmisión.…”

“…La otra posible vía de transmisión se produciría en el momento de la fertilización del óvulo con polen infectado por el virus, que habría sido transportado previamente por los abejorros (Shipp et al, 2008). Aún no se ha demostrado cual de ambas es la que se produce, aunque en los estudios realizados se determinó que tanto los abejorros portadores de polen en sus patas (Lacasa et al, 2003), como aquellos que no presentaban polen adherido fueron positivos al virus, aunque no se sabe si estos últimos son transmisores o no (Shipp et al, 2008).…”

“…La técnica presentó una gran sensibilidad, pudiendo cubrir a priori el diagnóstico de las diferentes cepas descritas, si bien la sonda presentaba un nucleótido de divergencia con el genotipo PE, y debido a que los autores no disponían de ninguna muestra infectada con ese genotipo concreto no pudieron evaluar la eficiencia de la técnica frente a éste . Este sistema Taqman ™ de RT-PCR en tiempo real con una sonda y cebadores específicos de PepMV (de la zona de la polimerasa en este caso), fue empleado con éxito para la detección del virus en abejorros polinizadores (Shipp et al, 2008). En el otro sistema descrito, únicamente se requiere de los cebadores específicos del virus, diseñados en este estudio concreto para amplificar una zona de la CP conservada para todos los aislados, ya que la fluorescencia se emite debido a la adición del fluorocromo SYBR Green que se acopla en la secuencia de DNA.…”

“…Furthermore, bumble bees, such as Bombus terrestris L., B. canariensis Pérez and B. impatiens (Cresson), which are commonly used as pollinators in tomato greenhouses, have also been implicated in the experimental spread of PepMV between tomato plants through the direct injuring of flowers or through fertilization with infected pollen (Lacasa et al, 2003;Shipp et al, 2008). However, long-distance dissemination of this virus possibly occurs by the transfer of young infected plants from the nursery to the grower, through infected grafts, cuttings or fruits, and even through the seed-toseedling transmission .…”