Tomato Rootstock Resistance to Bacterial Wilt as Modulated by Grafting and NC Regional Isolates 1Kressin, Jonathan P.; 2Silverman, Emily J.; 1Panthee, Dilip R.; 2Louws, Frank J.

1Dept. of Horticultural Science, 2Dept. of Plant Pathology; North Carolina State University, Raleigh, NC

Results—Greenhouse 2013-14

Results—Jackson Co. 2013 Summary Bacterial wilt (Ralstonia solanacearum

Smith) is a devastating soil-borne vascular

disease of tomato (Solanum lycopersicum L.)

and many other crops. Endemic in many parts

of the Southeastern US, management with

chemical and cultural methods does not

provide effective season long control. Tomato

resistance is quantitative, and close genetic

associations with small fruit size and

indeterminate growth habit have prevented

development of large-fruited fresh-market

varieties. Host resistance is also known to be

affected by local R. solanacearum strains and

environmental factors (soil and air

temperature, soil moisture, etc.). Vegetable

grafting with bacterial wilt resistant

rootstocks lines can significantly reduce

bacterial wilt incidence in disease infested

fields, allowing for successful harvests, as

well as providing increased vigor to the

commercial scion. Many tomato rootstock

lines have been developed for resistance to

bacterial wilt, but few have been rigorously

tested in NC fields for consistent disease

management and yield. Over-reliance on a

single rootstock may select for new pathogen

strains able to overcome the specific

rootstock resistance.

Conclusions

Acknowledgements

Funding for this research provided by USDA-SCRI

proposal # 2011-01397

Tomato grower collaborators

Seed donations from: BHN Seed and Seminis; Univ.

of FL for open-pollinated varieties

Louws’ lab personnel for field logistical help

Vegetable grafting project graduate students for help

with tomato grafting

NCSU-Mary Anne Fox and Method Road

greenhouse facilities and staff, as well as Liz Meyer

Objectives and Design

Healthy vs. bacterial wilt diseased plants in NC field (top) and greenhouse (right) conditions.

Screen public and private tomato rootstock

germplasm for bacterial wilt resistance in NC

field conditions

Verify the resistance levels of the rootstock

germplasm in greenhouse conditions with

artificial inoculation

Assess rootstock lines for differential

resistance response to R. solanacearum

isolates from contrasting NC environments

Determine if a grafted-management system

affects host resistance levels or marketable

fruit yields

Recommend the best tomato rootstock

germplasm for use in NC

Grafting Process

Soli D

eo G

loria

1

15

2 3 4

5 6 7 8

9 10 11 12

13

14

Grafting seedlings

Healing graft unions

Increasing light Decreasing humidity

Healed graft union

Hardening seedlings

Transplant carefully

Jackson Co. field: Summer 2013, natural

disease pressure, 10 genotypes, non-, self-,

and cross-grafted treatments, and a 91 day

observational period

Wake Co. greenhouse: Winter 2013-14, soil

drench on wounded root ball, 11 genotypes,

two NC isolates, and a 43 day observational

period

Grafting ‘Florida 47’ onto bacterial wilt

resistant rootstocks improved survival rate

No significant differential resistance

responses to NC isolates were detected for

any genotype

Tomato rootstocks recommended for

bacterial wilt management in NC:

- ‘Hawaii 7997’ and ‘Hawaii 7998’ (OP,

public)

- ‘Cheong Gang’ (Seminis)

- ‘RST-04-106-T’ (DP Seeds, = DP106)

- ‘CRA66’ (OP, public)

Total marketable fruit weight, when the

rootstock was ‘Cheong Gang’, ‘RST-04-

106-T’, or ‘CRA66’, was about twice as

great as when the rootstock was the

similarly resistant ‘Hawaii 7997’ or ‘Hawaii

7998’

‘RST-04-105-T’ (DP Seeds, =DP105) is

not expected to be resistant to bacterial wilt

in NC

Heavy rainfall in summer 2013 likely led

to suppressed expression of foliar wilt

symptoms, especially in rootstock canopies

Using fine overhead misting and shad

cloth in a greenhouse environment allows

for efficient and effective production of

grafted tomato seedlings (4 sec. every 4-8

min.)

Extra care is needed for grafted seedlings

when transplanting and managing in field

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