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. 2014 Sep 25;9(9):e108242.
doi: 10.1371/journal.pone.0108242. eCollection 2014.

Colonization of onions by endophytic fungi and their impacts on the biology of Thrips tabaci

Alexander M Muvea  1 , Rainer Meyhöfer  2 , Sevgan Subramanian  3 , Hans-Michael Poehling  2 , Sunday Ekesi  3 , Nguya K Maniania  3
Affiliations

Colonization of onions by endophytic fungi and their impacts on the biology of Thrips tabaci

Alexander M Muvea et al. PLoS One. .

Abstract

Endophytic fungi, which live within host plant tissues without causing any visible symptom of infection, are important mutualists that mediate plant-herbivore interactions. Thrips tabaci (Lindeman) is one of the key pests of onion, Allium cepa L., an economically important agricultural crop cultivated worldwide. However, information on endophyte colonization of onions, and their impacts on the biology of thrips feeding on them, is lacking. We tested the colonization of onion plants by selected fungal endophyte isolates using two inoculation methods. The effects of inoculated endophytes on T. tabaci infesting onion were also examined. Seven fungal endophytes used in our study were able to colonize onion plants either by the seed or seedling inoculation methods. Seed inoculation resulted in 1.47 times higher mean percentage post-inoculation recovery of all the endophytes tested as compared to seedling inoculation. Fewer thrips were observed on plants inoculated with Clonostachys rosea ICIPE 707, Trichoderma asperellum M2RT4, Trichoderma atroviride ICIPE 710, Trichoderma harzianum 709, Hypocrea lixii F3ST1 and Fusarium sp. ICIPE 712 isolates as compared to those inoculated with Fusarium sp. ICIPE 717 and the control treatments. Onion plants colonized by C. rosea ICIPE 707, T. asperellum M2RT4, T. atroviride ICIPE 710 and H. lixii F3ST1 had significantly lower feeding punctures as compared to the other treatments. Among the isolates tested, the lowest numbers of eggs were laid by T. tabaci on H. lixii F3ST1 and C. rosea ICIPE 707 inoculated plants. These results extend the knowledge on colonization of onions by fungal endophytes and their effects on Thrips tabaci.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Endophytic colonization of onion seeds.
Percentage colonization of onion plant parts (root, stem and leaves) by different fungal endophytes through seed inoculation. Data are percentage mean ± SE. (P≤0.05).
Figure 2
Figure 2. Endophytic colonization of onion seedlings.
Percentage colonization of onion plant parts (root, stem and leaves) by different fungal endophytes through seedling inoculation. Data are mean ± SE. (P≤0.05).
Figure 3
Figure 3. Effect of endophytically colonized onion plants on proportion of adult Thrips tabaci.
An evaluation of fungal endophytes for their effect on proportion of thrips settling on inoculated onion plants after 72 h. Bars indicate means ± SE at 95% CI. Means followed by the same letter indicate no significant differences between treatments.
Figure 4
Figure 4. Effect of endophytically colonized onion plants on feeding punctures by adult Thrips tabaci.
The figure quantifies mean feeding activity by Thrips tabaci exposed for 72 h on onion plants inoculated with different fungal endophytes. Bars indicate means ± SE at 95% CI. Means followed by the same letter indicate no significant differences between treatments.
Figure 5
Figure 5. Effect of endophytically colonized onion plants on oviposition by adult Thrips tabaci.
The figure shows the mean number of eggs laid by Thrips tabaci on onion plants endophytically colonized by different fungal isolates. Bars indicate means ± SE at 95% CI. Means followed by the same letter indicate no significant differences between treatments.
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Publication types

Grants and funding

This study was funded by the BMZ (The German Federal Ministry for Economic Cooperation and Development) through GIZ (Deutsche Gesellschaft für Internationale Zusammenarbeit) through a project grant entitled “Implementation of integrated thrips and tospovirus management strategies in small-holder vegetable cropping systems of Eastern Africa“ (Project number: 11.7860.7-001.00, Contract number: 81141840) to which we are grateful. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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