Epifluorescence and stereomicroscopy of trichomes associated with resistant and susceptible host plant genotypes of the Asian citrus psyllid (Hemiptera: Liviidae), vector of citrus greening disease bacterium

Authors: Hall, David; AMMAR, DESOUKY - Former ARS Employee; Bowman, Kim; Stover, Eddie

Submitted to: Journal of Microscopy and Ultrastructure
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2017
Publication Date: 5/8/2017
Citation: Hall, D.G., Ammar, D., Bowman, K.D., Stover, E.W. 2017. Epifluorescence and stereomicroscopy of trichomes associated with resistant and susceptible host plant genotypes of the Asian citrus psyllid (Hemiptera: Liviidae). Journal of Microscopy and Ultrastructure. Available: http://www.sciencedirect.com/science/article/pii/S2213879X17300020.

Interpretive Summary: Epifluorescence, light and stereo-microscopy were used to characterize foliar trichomes associated with young flush leaves and stems of six plant genotypes that are hosts of the Asian citrus psyllid, Diaphorina citri, vector of the economically important citrus greening disease. These genotypes included five highly susceptible to colinization by the psyllid (lemon, Citrus jambhiri; grapefruit, Citrus paradisi; sweet orange, Citrus sinensis; curry leaf, Bergera koenigii; and orange jasmine, Murraya paniculata) and a sixth genotype regarded as resistant (trifoliate orange, Poncirus trifoliata). Simple unicellular trichomes were observed at moderate to large densities on young leaves and stems of each genotype except lemon and sweet orange, which had considerably fewer trichomes. Trichomes ere generally most abundant on young leaves of curry leaf and orange jasmne, two genotypes that are often heavily colonized by the psyllid. Although we did not quantify oviposition rates, we observed that psyllid females deposited eggs on young leaves, buds and stems regardless of the density of trichomes present, sometimes directly within or close to a dense bed of trichomes. While trichomes were moderately abundant on young leaves of trifoliate orange, our observations suggest that these trichomes may play little or no role in reduced colonization by the psyllid on this host, at least at the trichome densities and lengths we observed. Finally, the epifluorescence method we used here to study trichomes, exploiting their blue autofluorescence, is a very simple and promising technique to study the structure and density of trichomes on young leaves and shoots of various plants.

Technical Abstract: Epifluorescence, light and stereo-microscopy were used to characterize foliar trichomes associated with young flush leaves and stems of six plant genotypes that are hosts of the Asian citrus psyllid, Diaphorina citri, vector of the economically important citrus greening disease. These genotypes included five highly susceptible to colinization by the psyllid (lemon, Citrus jambhiri; grapefruit, Citrus paradisi; sweet orange, Citrus sinensis; curry leaf, Bergera koenigii; and orange jasmine, Murraya paniculata) and a sixth genotype regarded as resistant (trifoliate orange, Poncirus trifoliata). Simple unicellular trichomes were observed at moderate to large densities on young leaves and stems of each genotype except lemon and sweet orange, which had considerably fewer trichomes. Trichomes ere generally most abundant on young leaves of curry leaf and orange jasmne, two genotypes that are often heavily colonized by the psyllid. Although we did not quantify oviposition rates, we observed that psyllid females deposited eggs on young leaves, buds and stems regardless of the density of trichomes present, sometimes directly within or close to a dense bed of trichomes. While trichomes were moderately abundant on young leaves of trifoliate orange, our observations suggest that these trichomes may play little or no role in reduced colonization by the psyllid on this host, at least at the trichome densities and lengths we observed. Finally, the epifluorescence method we used here to study trichomes, exploiting their blue autofluorescence, is a very simple and promising technique to study the structure and density of trichomes on young leaves and shoots of various plants.