Current UC Viticulture Research
|Principal Investigator||Kendra Baumgartner|
|Project Title||Identifying Vitis Rootstocks With Resistance To Armillaria Root Disease|
Our goal is to develop a rapid infection assay for the fungal root pathogen Armillaria. Slow and unreliable infection in the greenhouse has been a barrier to Armillaria research. For decades, researchers have relied on an infection assay with a lengthy inoculum-preparation step. Furthermore, datum from the existing infection assay (+/- infection) is qualitative, and does not suit this generalist pathogen with a host range of hundreds of species, which infects most plants it is inoculated to. Accordingly, there is a need to improve every step of the infection assay.
On the day of inoculation, percent root colonization, as measured by confocal microscopy, and fungal biomass, as measured by Q-PCR, was 0 in both rootstocks. Armillaria was detected by microscopy and Q-PCR starting two weeks post-inoculation. At each consecutive harvest interval following inoculation, Freedom had significantly lower root colonization than 3309C. This was consistent in both replications of the experiment. Q-PCR showed similar differences: Freedom had higher fungal biomass than 3309C. We also found a significant positive correlation between percent root colonization and fungal biomass, demonstrating that our two separate methods give similar results. There were no escapes, based on fact that both methods detected the pathogen in all inoculated plants at all four harvests and in both replicate experiments.
The new assay results in faster infection than old assay, based on fact that pathogen was detected at 2 weeks post-inoculation. The new assay equally challenges all inoculated plants; no escapes. Also, the new assay detects differences in host susceptibility, based on our findings that 3309C had higher root colonization and higher fungal biomass at each of 4 harvests and in both replicate experiments. We are currently adapting this infection assay to Prunus crops and Juglans, all of which are more susceptible to Armillaria root disease than grape.
Click to enlarge items below
Figure 2 (includes both photos):
Supplemental Data - Figure of temporal changes in A. mellea biomass.
|Researchers and Cooperators|
Baumgartner K, Coetzee M, Hoffmeister D. 2011. Secrets of the subterranean pathosystem of Armillaria (pdf). Molecular Plant Pathology DOI: 10.1111/J.1364-3703.2010.00693.X. 20pp.
Baumgartner K, Bhat R, Fujiyoshi P. 2010. A rapid infection assay for Armillaria and real-time PCR quantitation of the fungal biomass in planta (pdf). Fungal Biology 114:107-119.
Baumgartner K, Rizzo DM. 2006. Relative Resistance of Grapevine Rootstocks to Armillaria Root Disease. American Journal of Enology and Viticulture 57:4:408-414. Abstract
Baumgartner K, Warnock AE. 2006. A Soil Inoculant Inhibits Armillaria mellea In Vitro and Improves Productivity of Grapevines with Root Disease. Plant Disease 90:439-444.
Baumgartner K. 2004. Root Collar Excavation for Postinfection Control of Armillaria Root Disease of Grapevine (pdf). Plant Disease 88:1235-1240.
Baumgartner K, Rizzo DM. 2002. Spread of Armillaria Root Disease in a California Vineyard. American Journal of Enology and Viticulture 53:3:197-203. Abstract