ABSTRACT
This study aimed to characterize the quantitative and qualitative damage caused by Deois flexuosa (Walker) (Hemiptera: Cercopidae) adults in Axonopus catharinensis cv. SCS 315 Catarina and Cynodon dactylon (Tifton 85 and Jiggs cultivars) under different infestation densities and, consequently, the expression of tolerance-type resistance. For this purpose, potted plants were infested with different insect densities (0, 5, 10, 20, and 40 adults m-2). The impact of the infestation levels was assessed in the first growth cycle (10-day coexistence period) and in the regrowth (40 days after the first cut, without infestation) based on crop yield and chemical-bromatological composition as well as on photosynthetic pigments and hydrogen peroxide content. The principal component analysis relating infestation density and chemical-bromatological parameters showed a positive correlation between infestation density of D. flexuosa and the contents of neutral detergent fiber, acid detergent fiber, and the dry matter (DM). On the other hand, infestation density inversely correlated with the tillering rate, photosynthetic pigments (chlorophyll a and b, carotenoids), and iron content. In general, the impacts on DM production and chemical-bromatological composition were lower in A. catharinensis cv. SCS 315 Catarina when compared to the Cynodon species, possibly because A. catharinensis has higher tillering capacity and does not show a reduction in the photosynthetic pigments, which may act as compensating factors to D. flexuosa damage. Our results demonstrate that the A. catharinensis cultivar expresses tolerance-type resistance to D. flexuosa and constitutes an interesting option for pasturelands formation and diversification where this spittlebug species is an emerging pest.
Subject(s)
Hemiptera , Animals , Carotenoids , Chlorophyll A , Detergents , Hydrogen Peroxide , Iron , PoaceaeABSTRACT
BACKGROUND: In studies of plant stress signaling, a major challenge is the lack of non-invasive methods to detect physiological plant responses and to characterize plant-plant communication over time and space. RESULTS: We acquired time series of phytocompound and hyperspectral imaging data from maize plants from the following treatments: (1) individual non-infested plants, (2) individual plants experimentally subjected to herbivory by green belly stink bug (no visible symptoms of insect herbivory), (3) one plant subjected to insect herbivory and one control plant in a separate pot but inside the same cage, and (4) one plant subjected to insect herbivory and one control plant together in the same pot. Individual phytocompounds (except indole-3acetic acid) or spectral bands were not reliable indicators of neither insect herbivory nor plant-plant communication. However, using a linear discrimination classification method based on combinations of either phytocompounds or spectral bands, we found clear evidence of maize plant responses. CONCLUSIONS: We have provided initial evidence of how hyperspectral imaging may be considered a powerful non-invasive method to increase our current understanding of both direct plant responses to biotic stressors but also to the multiple ways plant communities are able to communicate. We are unaware of any published studies, in which comprehensive phytocompound data have been shown to correlate with leaf reflectance. In addition, we are unaware of published studies, in which plant-plant communication was studied based on leaf reflectance.
