The rhabdoviruses form a large family (Rhabdoviridae) whose host ranges include humans, other vertebrates, invertebrates, and plants. There are at least 90 plant-infecting rhabdoviruses, several of which are economically important pathogens of various crops. All definitive plant-infecting and many vertebrate-infecting rhabdoviruses are persistently transmitted by insect vectors, and a few putative plant rhabdoviruses are transmitted by mites. Plant rhabdoviruses replicate in their plant and arthropod hosts, and transmission by vectors is highly specific, with each virus species transmitted by one or a few related insect species, mainly aphids, leafhoppers, or planthoppers. Here, we provide an overview of plant rhabdovirus interactions with their insect hosts and of how these interactions compare with those of vertebrate-infecting viruses and with the Sigma rhabdovirus that infects Drosophila flies. We focus on cellular and molecular aspects of vector/host specificity, transmission barriers, and virus receptors in the vectors. In addition, we briefly discuss recent advances in understanding rhabdovirus-plant interactions.

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Xylella fastidiosa is a vector-borne, plant-pathogenic bacterium that causes disease in citrus (citrus variegated chlorosis [CVC]) and coffee (coffee leaf scorch [CLS]) plants in Brazil. CVC and CLS occur sympatrically and share leafhopper vectors; thus, determining whether X. fastidiosa isolates can be dispersed from one crop to another and cause disease is of epidemiological importance. We sought to clarify the genetic and biological relationships between CVC-and CLS-causing X. fastidiosa isolates. We used cross-inoculation bioassays and microsatellite and multilocus sequence typing (MLST) approaches to determine the host range and genetic structure of 26 CVC and 20 CLS isolates collected from different regions in Brazil. Our results show that citrus and coffee X. fastidiosa isolates are biologically distinct. Cross-inoculation tests showed that isolates causing CVC and CLS in the field were able to colonize citrus and coffee plants, respectively, but not the other host, indicating biological isolation between the strains. The microsatellite analysis separated most X. fastidiosa populations tested on the basis of the host plant from which they were isolated. However, recombination among isolates was detected and a lack of congruency among phylogenetic trees was observed for the loci used in the MLST scheme. Altogether, our study indicates that CVC and CLS are caused by two biologically distinct strains of X. fastidiosa that have diverged but are genetically homogenized by frequent recombination.

Grapevine leafroll disease is caused by grapevine leafroll-associated viruses (GLRaVs). Within this virus complex, GLRaV-3 is the predominant species in the world. Several GLRaVs have been shown to be transmitted from vine to vine by mealybugs although a detailed characterization of transmission biology is lacking. The introduction of the vine mealybug (Planococcus ficus) in California and other regions of the world may result in increasing disease incidence of established GLRaVs. We studied the characteristics of GLRaV-3 transmission by the vine mealybug. Our results indicate that the vine mealybug transmits GLRaV-3 in a semipersistent manner. First instars were more efficient vectors than adult mealybugs. GLRaV-3 transmission lacked a latent period in the vector. Virus transmission occurred with a 1-h acquisition access period (AAP) and peaked with a 24-h AAP. Mealybugs inoculated GLRaV-3 with a 1-h inoculation access period (IAP), and transmission efficiency increased with longer plant access period up to 24 h, after which transmission rate remained constant. After an AAP of 24 h, mealybugs lost GLRaV-3 and infectivity 4 days after virus acquisition. In addition, GLRaV-3 was not transovarially transmitted from infected females to their progeny as detected by reverse transcription polymerase chain reaction. In summary, we systematically analyzed transmission parameters of GLRaV-3 by the vine mealybug and showed that transmission of this virus occurs in a semipersistent manner. This research fills in important gaps in knowledge of leafroll virus transmission, which is critical for development of leafroll disease management practices.

: AMI complicated with refractory shock remains associated with a high mortality rate, even following ECLS rescue, although ECLS might afford a better chance of survival. The SOFA score can be applied to ECLS condition as a reference point for predicting outcome.