Abstract
The olive fruit fly, Bactrocera oleae, the most serious pest of olives, requires the endosymbiotic bacteria Candidatus Erwinia dacicola in order to complete its development in unripe green olives. Hence a better understanding of the symbiosis of Ca. E. dacicola and its insect host may lead to new strategies for reduction of B. oleae and thus minimize its economic impact on olive production. Studies of this symbiosis are hampered as the bacterium cannot be grown in vitro and the established B. oleae laboratory populations, raised on artificial diets, are devoid of this bacterium. Here, we sought to develop a method to transfer the bacteria from wild samples to laboratory populations. We tested several strategies. Cohabitation of flies from the field with the laboratory line did not result in a stable transfer of bacteria. We provided the bacteria directly to the egg and also in the food of the larvae but neither approach was successful. However, a robust method for transfer of Ca. E. dacicola from wild larvae or adults to uninfected flies by transplantation to females was established. Single female lines were set up and the bacteria were successfully transmitted for at least three generations. These results open up the possibilities to study the interaction between the symbiont and the host under controlled conditions, in view of both understanding the molecular underpinnings of an exciting, unique in nature symbiotic relationship, as well as developing novel, innovative control approaches.
Highlights
The olive fruit fly Bactrocera oleae (Rossi) (Diptera, Tephritidae) causes enormous losses in olive production and is present in the great majority of olive orchards in the world
Current control measures against olive fly rely on the use of chemical insecticides; primarily bait applications targeting the adult fly
Third instar larvae were sampled from infested green olives collected from olive orchards in Prefecture of Heraklion, Crete, Greece; 35°18′18.47′′N 25°04′25.9′′E, 82 m above sea level, FORTH campus and 35°19′19.8′′N 25°09′26.0′′E, 79 m above sea level, Agios Ioannis, both located within Heraklion municipality, Greece in September 2015
Summary
The olive fruit fly Bactrocera oleae (Rossi) (Diptera, Tephritidae) causes enormous losses in olive production and is present in the great majority of olive orchards in the world. The total loss in olive production has been estimated to up to 30% of the production (Bueno and Jones, 2002; Kampouraki et al, 2018). Current control measures against olive fly rely on the use of chemical insecticides; primarily bait applications targeting the adult fly. Insecticide resistance substantially affects the efficiency of control applications in some regions (Vontas et al, 2011; Kampouraki et al, 2018). Alternative control methods have been developed and/or tried such as biological control, the Sterile Insect Technique (SIT), mass trapping and the use of genetics-enhanced SIT They have not produced very encouraging results due to either their higher cost and/or their low effectiveness against high infestations (Raspi et al, 2007; Daane and Johnson, 2010; Ant et al, 2012; Nestel et al, 2016)
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