Applying crown gall research-based knowledge to orchard management. E. Fichtner, UCCE Tulare County

Transcription

1 Applying crown gall research-based knowledge to orchard management E. Fichtner, UCCE Tulare County

2 Paradox: Juglans hindsii x Juglans regia Crown Gall Common in walnut Paradox rootstock susceptible Less common on black walnut rootstock

3 Crown gall and root gall Photo: Epstein et al. Cal Ag

4 Hairy Root Agrobacterium rhizogenes Photo: E. Fichtner, Fresno Co.

5 Crown Gall Hairy Root Photo: E. Fichtner, Tulare Co.

6 Crown Gall Agrobacterium tumefaciens Gram negative bacterium Soilborne pathogen -fungicides ineffective -bacteriacides limited

7 Agrobacterium tumefaciens Broad host range: dicots only Motile- flagella, chemotaxis ubiquitous soil bacterium biotrophic plant pathogen (keeps the host alive) Long-term soil survival

8 Ubiquitous but chromosome plasmid Not all isolates are pathogenic

9 Tumor inducing plasmid Virulence T DNA Plant Recognition Etc. pti flagella Chromosome Plant Recognition Chemotaxis Attachment

10 plasmid + plasmid

11 The induction of a grown gall is a multi-step process Wound or Natural Opening Transformation of Plant Cells Cell Proliferation

12 Ti Plasmid Well-categorized/sequenced Can be manipulated Used in genetic engineering

13 Scion conventional trans Rootstock

14 Crown Gall Tree Size Irrigation issues Yield Predisposition to other diseases/pests

15 Tree Size

16 Infected Trees overwatered, earlier senescence

17 For every quarter of trunk circumference galled, there was a 12% decrease in cumulative nut yield over the first 4 years of production. (Epstein, et al California Agriculture) Crown Gall Yield Tree size Yield

18 2016: Kings County (Yaghmour, Facundo, Fichtner) Crown Gall No Crown Gall Tree Diameter (In) 26% of the variability of trunk diameter attributed to crown gall

19 WTB

20 Crown Gall Thousand cankers disease Yes No Total Yes No 1 98 Total 42 (25.1%) 125 (74.9%) 68 (40.7%) 99 (59.3%) 167 (Yaghmour, Facundo, Fichtner)

21 # larvae/tree 2010: TLJB/Crown Gall Survey t 0.06 Mapped out crown gall incidence. Randomly selected 8 gall-infected trees. Selected neighboring paired asymptomatic tree. Trenched around trees; counted grubs. Labor intensive; high variability. (Fichtner, 2010)

22 Management Rootstock Selection Q) Are seedlings more susceptible than clones?

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25 Crown gall in rootstock plot Seedling Paradox only Clonal almond rootstock (R. Duncan) RX1-low/moderate resistance?

26 4 rows Tulare County Walnut Rootstock Block Planted in 2016 SCRI Rootstock Block

27 January 2019 Walnut Rootstock Block

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29 Rx1 has J. microcarpa parent

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31 Soilborne History of site monocots/dicots? Prior disease? Sources of inoculum

32 Kern County, clonal rootstock

33 2019: Kern Co. 2016: Tulare Co. Field grafted late; clonal rootstock

34 Possible sources of inoculum: 1) Dirty grafting knife 1) Surface-infested budwood 1) Endophyticbudwood

35 Infestation of budwood

36 Infestation of budwood time

37 Rootstock mother tree J. hindsii; pollinated by J. regia

38 Rootstock mother tree J. hindsii; pollinated by J. regia

39 Experimentally Inoculated seed Crown gall on 94% Paradox seedlings Experimentally Infested soil Crown gall on 93% Paradox seedlings Yakabe, et al. Plant Disease. 2012

40 A. tumefaciens can move systemically in walnut Yakabe, et al. Plant Disease. 2012

41 Endophytic populations may be asymptomatic May be inadvertently transmitted in nurserystock Symptoms may appear much later at wound sites. In this study: 17% of seedlings inoculated as seed developed secondary galls at wound sites. Roots are an inoculum reservoir Yakabe, et al. Plant Disease. 2012

42 Disease Transmission with sequential cuts Paradox Yakabe, L.E. et al, 2012

43 Tool Sanitization Sodium hypochlorite (bleach) Pros Cons Cheap Corrodes tools Eliminates At at 0.5 ppm Phytotoxic Efficacy reduced w/ solids Percent reduction in At populations Total Solids (g/ml) Sodium hypochlorite (0.02 ppm) Yakabe, L.E. et al, 2012

44 Tool Sanitization Cationic surfactants (quarternary ammonium compounds): BC, CTAB, Physan 20 Pros Cons non-corrosive cost Efficacy maintained with particulates Non-phytotoxic Yakabe, L.E. et al, 2012

45 Percent reduction of Agrobacterium tumefaciens Bleach Physan Yakabe, L.E. et al, 2012

46 Tree Removal vs. Gall Removal 1 st leaf trees: Remove and replant 2 nd leaf trees: Remove and replant trees with large galls ( ¼ diameter) Treat those with small galls 3 rd -7 th leaf trees: Treat unless completely girdled 7 th leaf and older: Don t treat. Olson and Buchner, 2001

47 Biological Control Pre-plant/protectant Agrobacterium radiobacter Commercial names: Galltrol A, Norbac 84C, Nogall, or Diegall Efficacy varies based on isolate and environment Post-plant treatment ie. Gallex Phenols Applied to galls or as a disinfectant after gall excision

48 Pre-Plant Treatment Fumigate with Telone C-35 or Telone C-35 followed by chloropicrin in crown gall infested sites. Consider the Biological Vacuum

49 Consider the Biological Vacuum Unfumigated Fumigated

50 Management from nursery to field Consider inoculum: soil, seed, systemic, tools Consider rootstocks: Paradox susceptible (RX1 option) Treatment vs. Replant: Tree age and degree of symptoms