No abstract

Bemisia tabaci has had a colorful nomenclatural past and is now recognized as a species complex. This new species framework has added many new areas of research including adding new insight into the virus transmission specificity of the species in the B. tabaci species complex. There is a wide disparity in what is known about the transmission of plant viruses by different members of the B. tabaci species complex. In this paper, we have synthesized the transmission specificities of the plant viruses transmitted by species belonging to the complex. There are five genera of plant viruses with members that are transmitted by species of the B. tabaci species complex. The transmission of viruses belonging to two of these, Begomovirus and Crinivirus, are well studied and much is known in regards to the relationship between species and transmission and etiology. This is in contrast to viruses of the genera, Torradovirus and Carlavirus, for which very little is known inregards to their transmission. This is the first attempt to integrate viral data within the new B. tabaci species complex framework. It is clear that matching historical transmission data with the current species framework is difficult due to the lack of awareness of the underlying genetic diversity within B. tabaci. We encourage all researchers to determine which species of B. tabaci they are using to facilitate association of phenotypic traits with particular members of the complex.

Tomato plants treated with plant growth-promoting rhizobacteria (PGPR), applied as an industrially formulated seed treatment, a spore preparation mixed with potting medium (referred to as powder), or a combined seed-powder treatment, were evaluated under field conditions for induced resistance to Tomato mottle virus (ToMoV). The PGPR strains used, based on their ability to induce resistance in previous experiments, included Bacillus amyloliquefaciens 937a, B. subtilis 937b, and B. pumilus SE34. Experiments were conducted in the fall of 1997 and the spring and fall of 1998 at the University of Florida's Gulf Coast Research & Education Center, Bradenton. All plants were rated for symptoms and analyzed for the presence of ToMoV DNA at 40 days after transplant (dat). Whitefly densities were determined on individual plants in each trial, and marketable fruit yields were determined at least two times during each trial. The highest level of protection occurred in the fall 1997 trial when, at 40 dat, ToMoV disease severity ratings were significantly less in all PGPR powder-based treatments than in either of the seed or control treatments. Detection of viral DNA using Southern dot blot analyses correlated with symptom severity ratings, as did fruit yields. A reduction in ToMoV symptom severity ratings and incidence of viral DNA were also observed for some PGPR treatments in the spring 1998 trial, although corresponding yield responses were not apparent. Little or no resistance was observed in the fall 1998 trial. No differences in disease severity, detection of ToMoV DNA, or yield occurred among treatments in any of the trials at 80 dat. These data show that up to 40 dat under natural conditions of high levels of vector-virus pressure, some PGPR treatments resulted in reduced ToMoV incidence and disease severity and, in some cases, a corresponding increase in fruit yield. The use of PGPR could become a component of an integrated program for management of this virus in tomato.