Transcript Medrano and Bell, 2007, Journal of Applied Microbiology

Introduction of an opportunistic
bacterial cotton pathogen into
bolls by the southern green stink
bug (Nezara viridula L.)
E. G. Medrano, J. F. Esquivel, and A. A. Bell
USDA-ARS-SPARC, College Station, TX
Seed Rot of South Carolina Cotton
• Emerging disease
• First reported during 1999 in South
Carolina
• Yield losses from 10 to 15%
• Spread to fields located throughout
southeastern Cotton Belt states
Disease Symptoms
• Disease symptoms manifested inside bolls
• Exterior carpel of immature diseased bolls
are non-symptomatic
• Cross-sections of immature diseased bolls
reveal necrotic seed and discolored fiber
Previous Work
• Role of Pantoea agglomerans in opportunistic
bacterial seed and boll rot of cotton (Gossypium
hirsutum) grown in the field (Medrano and Bell,
2007, Journal of Applied Microbiology- 102, 134-143)
• Transmission of cotton seed and boll rotting
bacteria by the southern green stink bug,
Nezara viridula L. (Heteroptera: Pentatomidae)
(Medrano, Esquivel, and Bell, 2007, Journal of
Applied Microbiology- in press)
Boll inoculated with
r
r
P. agglomerans Rif (PaRif )*
*28-gauge needle simulating insect puncture (Medrano & Bell 2007)
Comparison of diseased
greenhouse* and field cotton
*28-gauge needle simulating insect puncture (Medrano & Bell 2007)
Cotton Insect Pests
• Piercing/sucking mouthparts used for feeding
on developing fruit
• Includes stink bugs, lygus, and cotton
fleahoppers
Insect Transmission Study Method
• Lab-reared southern green stink bugs (SGSB) were
raised on fresh green beans (not sterile) that were
replenished every 2 days.
• Bacterial exposure to insects:
Soaked
2 min in:
PaRif r
Sterilized
Green
Bean
or
H2O
Provided to insect
for 2 days
Insect Transmission Study Method
(cont’d)
• Exposure of cotton bolls to insects:
Harvested
after:
Weeks Post
Anthesis:
2 wks
Caged
2 days
2 wks
• Cotton boll harvesting:
-Evidence of insect feeding was determined after
boll exposure to insects.
-Bolls were surface sterilized and then seed and lint
tissue were aseptically collected, triturated, and then
dilution plated on media with/without Rif.
Cotton bolls exposed to SGSB
PaRif r -
PaRif r +
Cotton bolls exposed to SGSB
PaRif r -
PaRif r +
Cotton bolls exposed to SGSB
r
PaRif +
PaRif r -
Cotton bolls exposed to SGSB
PaRif r -
PaRif r +