Variety dependent tomato physiological status and volatile organic compounds signaling modulate Spodoptera exigua...

Insect herbivores induce direct and indirect defenses in crops while also altering the physiological parameters that reciprocally affect their performance. However, the relationship between crop physiology and indirect defenses is less understood. In this study, physiology, volatile emission, and herbivore performance were tested on five commercially grown tomato (Solanum lycopersicum L.) varieties: Amish Paste Organic (Amish), Big Beef F1 (BB), Celebrity Plus F1 (Celeb), Nepal Organic (NoG), and Super Sweet 100 F1 (SS). Herbivory by fourth-instar beet armyworm (BAW), Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), was imposed during the vegetative stage of tomato (3-week old), and data on net photosynthesis rate, transpiration rate, stomatal conductance, and VOCs emission were collected and assessed. BAW performance was assessed based on larval mass gain, pre-pupal and pupal weight, and adult survival, along with damage scale on each variety. Results revealed that SS variety had the significant lowest physiological parameters (photosynthesis rate, stomatal conductance, transpiration rate, and intercellular CO2) and least emission of VOCs. Consequently, BAW performance was the poorest on the SS variety, with the lowest survival, larval mass gain, pre-pupal, and pupal mass. The damage scale data and behavioral assay of BAW also showed that SS was the least preferred variety, while Amish and NoG were the most preferred. The findings from this study can be used to understand the interrelationship between crop physiology and defense traits related to different crop varieties, which are of critical importance in developing tomato varieties resistant to insect herbivores.