Drought and Herbivory Have Selective Transgenerational Effects on Soybean Eco-Physiology, Defence and Fitness

Soybeans, one of the most important legumes, face multiple stresses including drought and herbivory. But the potential transfer of the interactive effects of these stressors onto the transgenerational plants has not been understood. We hypothesised that progeny from stressed parents will have enhanced ecophysiology and defence traits through priming, affecting fitness. Experimental plants were derived from seeds of drought (D), drought and herbivory interaction (D × H), herbivory (H) and well-watered (WW) treatments imposed on parental generation. The findings revealed significant transgenerational effects of D, D × H, H and WW treatments; D × H treatment had negative impacts on seed germination and seedling vigour. The percent change in leaf and root nitrogen and protein content in seedling roots and leaves in D × H compared to D revealed possible remobilisation of nutrients in transgenerational seedlings. The transgenerational effects due to D × H persisted throughout the growing period reducing physiological parameters including net photosynthesis rate and stomatal conductance. But the trichomes were significantly induced indicating potential tradeoff for strengthened defences confirmed by soybean looper bioassays. And the tradeoff between defence and morpho-physiology also led to negative effects on yield and fitness. Taken together, transgenerational induction, offers opportunities for developing resilient crops under multiple stressors like drought and herbivory.