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Article

Maize Bushy Stunt Phytoplasma Favors Its Spread by Changing Host Preference of the Insect Vector

Departamento de Entomologia e Acarologia, Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ), Universidade de São Paulo (USP), Avenida Padua Dias, 11, Piracicaba 13418-900, Brazil
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Insects 2020, 11(9), 600; https://doi.org/10.3390/insects11090600
Received: 3 August 2020 / Revised: 30 August 2020 / Accepted: 3 September 2020 / Published: 5 September 2020
(This article belongs to the Special Issue Insect Vectors of Plant Pathogens)
Phytopathogenic bacteria such as phytoplasmas induce physiological changes in their host plants that may modulate the behavior of an insect vector in favor of their own spread. In this study we investigate changes in the host selection behavior of the leafhopper vector, Dalbulus maidis (DeLong and Wolcott), in choice tests between healthy vs. maize bushy stunt phytoplasma (MBSP)-infected maize leaves (Zea mays L.), for insects previously exposed to infected plants (named “bacteriliferous”) or not (naive). The results showed that males and naive females of D. maids did not distinguish the treatments when infected leaves were still asymptomatic, whereas bacteriliferous females prefer to settle on healthy leaves, a behavior that favors pathogen inoculation and primary spread at early crop stages. During the symptomatic phase of maize infection, naive males and females were initially attracted to infected leaves, favoring pathogen acquisition; interestingly, the females tend to move towards healthy leaves a few hours later, a behavioral shift that promotes secondary spread. Overall, this study presents evidences that MBSP optimizes its spread in maize crops by influencing the host selection behavior of the leafhopper vector.
Plant pathogenic bacteria may influence vector behavior by inducing physiological changes in host plants, with implications for their spread. Here, we studied the effects of maize bushy stunt phytoplasma (MBSP) on the host selection behavior of the leafhopper vector, Dalbulus maidis (DeLong and Wolcott). Choice assays contrasting leaves of healthy (mock-inoculated) vs. infected maize (Zea mays L.) were conducted during the asymptomatic and symptomatic phases of plant infection, with leafhopper males or females previously exposed to infected plants (bacteriliferous insects) or not. In each assay, 40 adults were released in choice arenas where only the leaves of two plants from each treatment were offered and visible, and the insects landed on the leaves were counted 1, 2, 3, 5, 7, 9, 11 and 23 h after release. During the asymptomatic phase of plant infection, an effect was observed only on bacteriliferous females, who preferred leaves of healthy plants 5 h after release or later. The symptomatic phase triggered a pull–push effect on non-bacteriliferous females, who were first attracted to symptomatic leaves but hours later moved to healthy leaves. Non-bacteriliferous males initially preferred symptomatic leaves (up to 5 h after release) and later became equally distributed between treatments. Bacteriliferous males and females initially did not discriminate between healthy and symptomatic leaves, but only the females tended to move to healthy leaves 9 h after release. Oviposition was drastically reduced on symptomatic leaves. The changes in vector behavior induced by MBSP favor its primary spread, since bacteriliferous females prefer healthy leaves at early (asymptomatic) stages of the crop. At later stages, secondary spread may be favored because non-bacteriliferous females are initially attracted to infected (symptomatic) leaves, allowing pathogen acquisition and subsequent transmission as they move to healthy plants. View Full-Text
Keywords: corn leafhopper; corn stunt; phytopathogenic mollicute; vector manipulation corn leafhopper; corn stunt; phytopathogenic mollicute; vector manipulation
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    Link: https://zenodo.org/record/3971068#.XyhUKSij_IU
    Description: Figure S1 – Free-choice arena 30 x 30 x 30 cm. A – Side view. B – Side view with (a) side opening (4 x 20 cm) sealed with 'voile' fabric for ventilation. C – Top view with (b) openings (4 x 20 cm) for ventilation and (c) ‘Falcon’ tube where the insects were released. D – Internal side view showing the openings throw which the leaves were inserted (d) 1.5 x 6.0 cm (e) 1.5 x 7.0 cm.
MDPI and ACS Style

Ramos, A.; Esteves, M.B.; Cortés, M.T.B.; Lopes, J.R.S. Maize Bushy Stunt Phytoplasma Favors Its Spread by Changing Host Preference of the Insect Vector. Insects 2020, 11, 600. https://doi.org/10.3390/insects11090600

AMA Style

Ramos A, Esteves MB, Cortés MTB, Lopes JRS. Maize Bushy Stunt Phytoplasma Favors Its Spread by Changing Host Preference of the Insect Vector. Insects. 2020; 11(9):600. https://doi.org/10.3390/insects11090600

Chicago/Turabian Style

Ramos, Anderson, Mariana B. Esteves, Mayerli T.B. Cortés, and João R.S. Lopes 2020. "Maize Bushy Stunt Phytoplasma Favors Its Spread by Changing Host Preference of the Insect Vector" Insects 11, no. 9: 600. https://doi.org/10.3390/insects11090600

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