Effects of water stress on transmission of ‘Candidatus Liberibacter solanacearum’ pathogen by the vector Bactericera cockerelli

Primary Author: Abigail Cohen

Faculty Sponsor: David Crowder

 

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

 

Abstract:

 

Principle Topic

Both plant pathogens and insects cause damage to crops and be financially ruinous to growers, and do even more damage when a damaging pest transmits the pathogen. However, environmental factors moderate how plant, pest, and pathogen interact with one another. This experiment looks at how water stress alters potato plant defenses when exposed to the pest Bactericera cockerelli, or potato psyllid. The potato psyllid feeds on solanaceous plants, and pierces plant veins to extract phloem sap. This makes it a capable vector for the bacterial pathogen Candidatus Liberibacter solanacearum (Lso), which causes an economically damaging disease known as zebra chip.

Method

To test the effect of water stress on transmission of the Lso pathogen and potato plant defenses, we exposed potato plants with and without water stress to infected B. cockerelli over 3h, 24h, 28h, and 120 h, while stress-free uninfected plants were used as control. Potato psyllids have a wide range and multiple sub-populations, so we ran the experiment twice, first with the Northwestern sub-population, then with Western.

Results/Implications

These results indicate that water stress in the plant has a negative effect on transmission or circulation of the bacterial pathogen through the plant, in both sub-populations. Furthermore, testing the level of defensive hormones in the exposed plants showed that water stress correlates to higher levels of the hormone associated with defense induction, suggesting that stress primes the plant for infection. This indicates that managed water stress may have the potential to reduce Lso infection in potato plants.