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|Title:||Development of a continuous small-rearing technique on natural host for the olive fruit fly Bactrocera oleae (Rossi) and study on volatile organic compounds (VOCs) emitted by Olea europaea L. as potential host allelochemics||Other Titles:||Messa a punto di un metodo di allevamento in continuo su piccola scala per la mosca delle olive Bactrocera oleae (Rossi) e studio su composti organici volatili (VOCs) emessi da Olea europaea L. come potenziali allelochimici||Authors:||Baratella, Valentina||Keywords:||Olive fly;Bactrocera oleae;VOCs;Allelochemics;Mosca olivo;Allelochimici;AGR/11||Issue Date:||2-Feb-2011||Publisher:||Università degli studi della Tuscia - Viterbo||Series/Report no.:||Tesi di dottorato di ricerca. 23. ciclo||Abstract:||
The olive fruit flies Bactrocera oleae (Rossi), as most of the Tephritidae species (“true fruit flies”), is a pest of great economic importance. It’s among the most serious pests of Olea europaea L. in the Mediterranean Basin and in olive growing regions worldwide.
Longstanding control programmes as well as current research efforts emphasize the development of long-term management practices, focusing on classical biological control for sustainable management. As part of a classical biological control programme, several attempts have been done in the past in order to rear olive fly ex-situ. Undue efforts are often directed toward producing the largest possible number of flies at the least possible cost, but the flies produced on artificial diets or on factitious hosts may not be effective in carrying out the mission for which they were intended. In the case of B. oleae, genetic changes seem to occur when olive flies are reared on artificial diet causing adverse effect on their performances and fitness if compared to wild individuals. For this reason, researchers are now oriented to obtain laboratory colonies maintaining them on their natural host: developing rearing protocols for olive fruit fly on its natural host would allow bioecological and behavioural studies and successful field-releases of olive fruit fly biological control agents.
The present study establishes fundamental guidelines for a small-scale and cost-effective rearing of B. oleae, for the first time successfully culturing year-round the olive fruit fly on its natural host basing upon the continual availability of fresh olive fruits, suitable to oviposit.
In line with IPM and biological management purposes, ending the use of non-selective long-lasting poisons and beginning the use of insects attractants, not just pheromones, could potentially become a powerful management tool, interfering with plant and insects at vulnerable steps. At this regard, the second purpose of the present study was the characterization of the broadest possible range of volatile compounds and to investigate the possible changing trends of biological volatile emissions during development stages. The return of feral olive fly populations to the olive groves after the first abundant summer rains it must certainly be due to volatile compounds emitted by the plants and active on the olive fly. These results involve that host-plant odours play the fundamental ecological role of olfactory attractants and oviposition stimulants interacting with B. oleae.
Olea europaea L., the common olive, is considered to be a low emitting species: its terpenoids emissions are generally found to be zero or close to zero. A number of authors have already attempted the identification of volatile components deriving from various parts of the olive plant or dissolved in the oil, by means of distillations, solvent extractions or head-space samples from plant detached portions, mainly focusing on the compounds bioactivity against pathogens and entomo-pathogens. At this regard there is a confuse variety of roles attributed to the plant compounds.
During the last few decades, much has been done in order to understand chemical communications in insect-insect interactions and about the insect responses to specific volatiles compounds. Research emphasis is now directed towards insect-plants interactions: it needs to properly investigate and recognize the volatiles released by living plants first of all, testing bioactive aspects of such compounds and correlating insect responses in the second place.
The present study reports on the original results of VOCs detection from whole, living olive trees (Olea europaea L.). For the first time, an early comparison of the volatile organic compounds emitted from plants in different phenological stages (vegetative and fruiting stage) was performed.
The method developed appears to be functional for a true detection of biogenic compounds from whole olive trees, monitoring the changing trend of volatile profile characteristics during time and obtaining the corresponding volatile profile characteristic for the different phases. For the first time, an early comparison of the volatile organic compounds emitted from plants in different phenological stages (vegetative and fruiting stage) was performed.
Despite the usual low emission rates of the specie, the variations of VOCs emission between different phenological stages of Olea europaea L. were clearly displayed and a broad range of emitted volatile compounds were successfully characterized.
The information accumulated forms overall an excellent base of knowledge for studying plant-insect interactions and are likely to improve the current strategies against the olive fruit fly Bactrocera oleae Rossi, for the first time enabling its continuous lab-rearing on the natural host and better clarifying natural occurrence and the ecological role of host allelochemicals, i.e. attractants of the pest.
Dottorato di ricerca in Protezione delle piante
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checked on Oct 30, 2020
checked on Oct 30, 2020
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