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Genetics of Xylella fastidiosa in Texas

Understanding the genetic diversity of Xylella fastidosa isolates is a critical component of the Pierce’s Disease (PD) Research and Education Program in Texas. Texas projects include insect movement, isolate pathogenicity and disease epidemiology. Genetic studies of X. fastidiosa strains will allow scientists in this program to make connections between the movement of the insect, presence of bacterium in plant reservoirs and the subsequent movement of X. fastidiosa across Texas. Additionally, the analysis of genetic differences between strains and the expression of those genes is required to understand the pathogenicity of the ‘grape’ strain in grapes. In other words, to understand X. fastidiosa pathogenicity (and prevent disease spread) we need to know the genes responsible. To meet this goal we have outlined four research objectives over the next four years. First, we will sequence genes of multiple isolates with both conserved genes and less conserved genes in collaboration the Bextine lab (UT Tyler). Strains from Texas will also be compared with California strains using additional genes via the MLST approach in the Nunney lab (UC Riverside). This will allow for analysis of the genetic diversity of X. fastidiosa both within Texas and between Texas and California. Second, we will create DNA fingerprints for multiple X. fastidiosa isolates to monitor the movement patterns of individual isolates (particularly isolates in new infection areas). This technique will allow us to match new infections to the closest previously fingerprinted isolate in the state. Third and forth, we will compare genomes of ‘grape’ and ‘ragweed’ isolates looking for novel virulence genes and we will analyze the expression of particular genes in response to grape sap.

Students Kelly Phillips, Adolfo Lara and Stephen Seidel, summer 2009.
Students Kelly Phillips, Adolfo Lara and Stephen Seidel, summer 2009.


Experimental Vineyard to test PD Resistance

Texas Cooperative Extension has established an experimental vineyard outside Houston (Industry, Texas) under the direction of Jim Kamas. This region of Texas falls within the “PD Hot Zone” of Texas where there is tremendous PD pressure. At this vineyard a collection of varieties will be evaluated for PD tolerance and use as future wine grapes in PD areas. The planting includes historical selections with potential PD resistance and new crosses made by Dr. Lu at Florida Agricultural and Mechanical University and Dr. Walker at University of California, Davis. Data from this vineyard will be compared with a similar experimental vineyard in Fredericksburg, Texas.

Fritz Westover and Dr Lisa Morano at Industry planting, spring 2009.
Fritz Westover and Lisa Morano at Industry planting, spring 2009.
Endophytes of Grapevines

A new and expanding area of microbial ecology is the evaluation of bacterial and fungal endophytes within plants. Endophytes are native “friendly” microbes that take up residence in the plant and may play a role in preventing infection by pathogenic bacteria and fungi. Combining these two observations: First, that endophyte communities might protect plants from infections and Second, European vines and native Vitis differ dramatically in their resistance to Xylella fastidiosa, we are currently investigating the endophyte communities within both old-world and hybrid vines. Specifically, we hypothesize that endophyte communities within the American hybrid varieties will host a microbe or microbe collections which may protect the plants from PD and that these microbes will be absent in the European species.


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Last updated or reviewed on 8/7/09

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