Detection of ultra-weak photon emission in sunflower (Helianthus annuus L.) infested by two spotted-spider mite, Tetranychus urticae Koch-research note

Sunflower production plays an important role in global industrial oil production. Two-spotted spider mite, Tetranychus urticae, is a dangerous, polyphagous arthropod pest with a cosmopolitan distribution, which can endanger the economic features of global sunflower production. It is widely known that pests trigger various reactions in host plants. Among these, detection of ultra-weak photon emission (UPE) enhanced upon infestation is a novel, non-invasive method suitable for the visualisation and monitoring of both biotic and abiotic stress in living tissues. In the present study, the increase in ultra-weak UPE triggered by biotic stress caused by T. urticae in Helianthus annuus was measured. UPE response of injured plants differed from that of the control plants, which was reflected by a difference in bioluminescence intensity. In leaves attacked by T. urticae the onset value of average photon count detected by the sensor and expressed in cps (counts per second) was one order of magnitude higher on average as compared to that revealed by uninjured leaves. Furthermore, UPE emission in infested leaves resulted in an abrupt decrease in the ultra-weak photon emission intensity when assayed as a function of time. The use of this non-invasive imaging technique has allowed the detection of the injury induced by T. urticae, as a biotic stressor.