U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Crops Pathology and Genetics Research: Davis, CA
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    Careers


        


                    Outreach Events
                        UC Davis Picnic Day
                                    Kinders go to College
                                    STEM Girls
                                    Future Scientist Program
                                    Agriculture Future of America
                                    Wallace-Carver Fellowship
                                    Young Scholars Program
                                    Annual Awards Banquet
                    About Us
                        About Us
                                    Our Mission
                                    Principal InvestigatorsSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Pacific West Area Davis, California Crops Pathology and Genetics Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications
- Etiology and Biology of Tree Crop Diseases
- Rice Genetics
- Sustainable Floriculture
- Sustainable Viticulture

Title:   Author  item
                                            Baumgartner, Kendraitem
                                            Fujiyoshi, Phillipitem
                                            Browne, Gregitem
                                            LESLIE, CHUCK - University Of Californiaitem
                                            Kluepfel, Daniel
  Submitted to: HortScience
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 12/10/2012
                                    Publication  Date: 1/15/2013
                                    Citation: Baumgartner, K., Fujiyoshi, P.T., Browne, G.T., Leslie, C., Kluepfel, D.A. 2013. Evaluating paradox walnut rootstocks for resistance to Armillaria root disease. HortScience. 48:68-72.Interpretive Summary: Walnut trees cultivated for the nut crop in California is grafted onto a rootstock  - Paradox - a hybrid between the wild Northern California black walnut and the cultivated English walnut.  Unfortunately, Paradox rootstock is highly susceptible to a fungal root disease, Armillaria root disease.  The resistance of new Paradox rootstocks (AX1, Px1, RR4 11A, RX1, Vlach, and VX211) was evaluated, and compared to Armillaria-resistance exhibited by Northern California black walnut rootstock ‘W17’, English walnut scion ‘Chandler’, and Juglans relative Pterocarya stenoptera ‘WNxW’ (Chinese wingnut).  Plants were grown in a gel-based medium inside small plastic boxes in the laboratory, and the medium was inoculated with three Armillaria mellea strains in three replicate experiments.  At 2 months post-inoculation, the most resistant and most susceptible Paradox rootstocks were AX1 and VX211, respectively, with 9 versus 70% mortality (P < 0.0001, n = 135 plants per rootstock, summed across strains and experiments).  This range of resistance may reflect differences in the genetic background, namely that which originates from the maternal parent, between these two Paradox rootstocks (e.g., J. californica for AX1, J. hindsii for VX211).  Our finding of similar susceptibility of Chandler and W17 (60 and 69% mortality, respectively) is in contrast with some field observations of greater Armillaria-susceptibility of J. regia relative to J. hindsii.  Nonetheless, conflicting reports of the relative resistance of these two species, from trials comparing other genotypes in Armillaria-infected orchards, suggest there is variable resistance within J. regia and J. hindsii.
                                Technical Abstract: The most common Juglans regia (English walnut) rootstock in California is Paradox, a hybrid between J. hindsii (Northern California black walnut) and J. regia.  Unfortuntely, Paradox rootstock is highly susceptible to Armillaria root disease.  The relative resistance of new clonal, Paradox rootstocks (AX1, Px1, RR4 11A, RX1, Vlach, and VX211) was evaluated, and compared to Armillaria-resistance exhibited by Northern California black walnut rootstock ‘W17’, English walnut scion ‘Chandler’, and Juglans relative Pterocarya stenoptera ‘WNxW’ (Chinese wingnut).  Plants were micropropagated in Magenta boxes, and the tissue-culture medium was inoculated with three Armillaria mellea strains in three replicate experiments.  At 2 months post-inoculation, the most resistant and most susceptible Paradox rootstocks were AX1 and VX211, respectively, with 9 versus 70% mortality (P < 0.0001, n = 135 plants per rootstock, summed across strains and experiments).  This range of resistance may reflect the broad genetic background, namely from the maternal parent, between these two Paradox rootstocks (e.g., J. californica for AX1, J. hindsii for VX211).  Our finding of similar susceptibility of Chandler and W17 (60 and 69% mortality, respectively) is in contrast with some field observations of greater Armillaria-susceptibility of J. regia relative to J. hindsii.  Nonetheless, conflicting reports of the relative resistance of these two species, from trials comparing other genotypes in Armillaria-infected orchards, suggest there is variable resistance within J. regia and J. hindsii.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov