Morphological, Physiological, and Metabolite Responses of Potato to Infestation by the Fall Armyworm (Spodoptera frugiperda) and the Potato Scab Bacterium (Streptomyces resiliuntiscabiei)

The effect of the fall armyworm (FAW) (Spodoptera frugiperda) and the pathogenic bacterium Streptomyces resiliuntiscabiei, in combination or singly, on the morphological and physiological (growth, yield, and gas exchange), and metabolite responses of potato plants were studied. Potato seedlings were exposed to these two biotic stressors and morphology, physiology and metabolomic indices were captured at 13, 34, and 83 days after exposing the plants to the organisms. The FAW did not affect the growth, yield and physiological parameters, namely, photosynthesis rate, stomatal conductance, transpiration efficiency, the ratio of intercellular CO2 to ambient CO2, and water use efficiency. However, when the pest was administered with S. resiliuntiscabiei, the rate of photosynthesis, stomatal conductance, and transpiration efficiency of the potato leaves surged (to about three times the control) 13 days post exposure to the pest and the bacterium. Singly, the pathogen did not affect the physiological parameters. Both organisms, individually or combined did not affect the growth and the yield of the plant. Metabolite profiling performed using liquid chromatography – mass spectrometry followed by chemometric analysis of the metabolites data showed that the pest and the bacterium induced metabolomic changes in the pest and pathogen-treated leaves. Correlation analysis of the morphological and physiological parameters revealed association between some of the physiological measurements. In conclusion, the pest and the bacterium induce metabolomic reprogramming in the leaves while having a limited effect on plant morphology and physiology. However, further and more comprehensive studies are necessary to concretize the findings of the current study. At step 1, the plants were infested with Spodoptera frugiperda and inoculated with Streptomyces resiliuntiscabiei. At step 2, photosynthesis measurements were taken, and growth, photosynthesis measurements and metabolite analysis were conducted at step 3. Finally, the plants were harvested at step 4 and for each plant the tubers were weighed and counted.