Climate change effect on plant – pathogen – beneficial microorganisms interactionin high humidity-promoted tomato diseases
Abstract: Climate change refers to changes in the means and/or variabilities of climateparameters. Plant pathogens have a range of environmental conditions which allows them tosurvive and cause disease. Environmental changes might cause alterations in distribution,survival and plant-pathogen interactions; these changes can increase or decrease epidemicalevents. The suppressive effect of beneficial organisms may also be affected by environmentalconditions. Two humidity promoted polycyclic diseases were studied: i. late blight (Phytophthorainfestans) – a fast developing and destructive disease in tomato and potato plants. A critical factorfor disease epidemic occurrence is 6-8 hours of wetness which allows penetration into the planttissue; ii. grey mould (Botrytis cinerea) – infects many crops including tomato and proliferates athigh humidity, few hours of wetness are a prerequisite for infection. Tomato plants inoculatedwith P. infestans with wetness duration of 4, 6, 8, 12 and 24 hours showed decrease in diseasefrequency and severity under 8 and 12h wetness as compared with 24h. B. cinerea infectionseverity was different between 4 and 10h wetness duration. Spraying the plants with two yeast,three bacterium isolates and Trichoderma followed inoculation with P. infestans under wetnessdurations of 8 and 24h, revealed an effect of wetness duration on biocontrol activity; 24h wetnessduration less disease control was observed. When treating with the microorganisma at pre- andpost-inoculation, the same disease suppression was obtained for 8 and 24h wetting periods. Twoof the BCAs decrease sporangia formation. No interaction in grey mould supression wasobserved between biocontrol agents and wetness duration. It seems that environmental conditionswhich decrease late blight intensity allow better activity of the introduced biocontrol agents.Climate change is expected to affect rain quantity and frequency and as a result the duration ofwetness may be affected. This in turn, in some cases as demonstrated in the present work, mayaffect the ability of beneficial organisms to suppress diseases.