Crown gall of grapevine (Vitis spp.) is a serious and economically important disease caused by the bacterial pathogen Rhizobium vitis, which transforms healthy plant cell genomes leading to hypertrophic and hyperplastic growth of affected plant cells. Recent studies have documented a strong inhibitory effect against Japanese tumorigenic R. vitis isolates by a newly identified non-tumorigenic strain of R. vitis, ARK-1. We conducted co-inoculation assays in tomato (Solanum lycopersicum) and wine grape cultivars (Vitis vinifera) with four tumorigenic isolates of R. vitis from Virginia. These tumorigenic isolates were co-inoculated with ARK-1 in various ratios and resulting gall incidence and gall size were measured. Analysis was conducted with the generalized linear mixed model (GLIMMIX) in SAS (ver. 9.4). ARK-1 significantly reduced both the mean probability of gall formation and the mean gall size (P < 0.05). ARK-1 efficacy against combinations of two or four tumorigenic isolates and up to twice as many cells of tumorigenic isolates was also significant. However, there was an indication of a loss of efficacy when ARK-1 was challenged with four isolates at four times the cell number of ARK-1. Also, the efficacy of ARK-1 was influenced by both the specific isolate and host plant used in the study. Our results suggest that ARK-1 has promising potential as an effective biological control agent for grapevine crown gall in the United States. / MSLFS / Crown gall of grapevine (Vitis species) is a serious and economically important disease to the grape production industry caused by the bacterium Rhizobium vitis. This pathogen alters the genetic material of plant cells leading to cancer-like growth of affected plant cells (tumors); which may lead to the death of a grapevine. Recently, a non-tumor inducing strain of R. vitis (ARK-1) was documented to inhibit gall induction by tumor-inducing R. vitis strains in Japan. To see if ARK-1 would be a good candidate for biological control of the tumor-causing strains of R. vitis in the US, we tested it against four tumor-inducing strains in both tomato (Solanum lycopersicum) and grapevine (Vitis vinifera). The tumor-inducing strains were mixed with ARK-1, injected into plant stems in various ratios, and resulting gall incidence and gall size were measured 42 to 90 days later. ARK-1 significantly reduced both the probability of gall formation and the gall size in both tomatoes and grapevines. ARK-1 was an effective agent against mixtures of one, two, or four tumor-inducing strains and provided control even when outnumbered two to one by cells of tumor-inducing strains. The efficacy of ARK-1 was influenced by the specific strain, relative cell number to tumor-inducing strains, and host plant used in the study. Our results suggest that ARK-1 has promising potential as an effective biological control agent for grapevine crown gall in the United States.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/96598 |
| Date | 06 August 2018 |
| Creators | Wong, Alexander Thomas |
| Contributors | Plant Pathology, Physiology and Weed Science, Nita, Mizuho, Baudoin, Antonius B., Bush, Elizabeth Ann, Vinatzer, Boris A. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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