## 6 Genetics and Biotechnology in the Service of IPM
Other genetic markers, such as olfactory receptors, have also been studied to make genetically modified organisms more reluctant to reproduce. When released, they interfere with the mating behaviours and reproductive potentials of the flies, helping to control the pests [290]. Likewise, in 2012, a British company presented an initiative to Spanish MAPA and the Autonomous Government of Catalonia to test, in a controlled way, in 48 olive trees in Tarragona, a genetically modified strain of _Bactrocera oleae_ whose females died at the larvae and early pupal stages. That could help to fight against this olive pest. In 2013, the company withdrew the application, overwhelmed by political and social obstacles. Several scientists, most of them from the company, demonstrated that the modified strain was effective in combating the pest [291]. As said, gene drive hasseveral potential opportunities for pest control but also several uncertainties surrounding its employment in agricultural crops [291, 292]. The knowledge of the nature of the genetic variation in olive pests at the intra- and inter- population levels is relevant for the design of IPMs and their success. The advance and cheapening of genetic techniques are providing us with new and more sensitive tools for genetic analysis, showing relevant data about the unequivocal species identifications, genetic diversities, structures, and gene flows of these damaging pests. The use of microsatellite markers (very short DNA sequences--two to seven nucleotides--repeated many times, found in thousands of the location in the whole genome of an organism) has allowed researchers to determine the geographical origin, relatedness, and reproduction of _B. oleae_ as well as to assess the impact of the sterile insect technique (SIT) on wild populations [293, 294]. The resistance to pesticides is another important area where genetics can provide valuable information. Agricultural pest control relies mostly on synthetic insecticides, such as organophosphates (OPs) and pyrethroids (PYs), but the effectiveness of many pesticides is recurrently compromised by the evolution of resistances that have become major concerns. The intensive use of OPs to control the olive fruit fly led to an increase in resistance in field populations. Hence, a dramatic increase in the resistance to PYs such as alpha-Cypermethrin has been observed in _B. oleae_ populations in Greece, especially in Crete [295, 55]. Spanish olive fruit fly populations also have high frequencies of alleles conferring resistance to organophosphate insecticides, as determined by studying mutations at the _ace_ gene [56]. All of this information helps farmers to make better decisions about when to carry out insecticide interventions, as well as the most appropriate ones. This information is not only used to programme chemical insecticide interventions but is also used for compounds in IPM. For example, a resistance to spinosad has already been detected, although it remains low in most populations [296]. The analysis via PCR and the sequencing of a fragment of the mitochondrial gene of cytochrome oxidase subunit I (COI) have addressed the genetic diversity, population structure, and gene flow of _B. oleae_ in different regions of the Mediterranean. The data revealed that _olf_ populations, in general, hold high to moderate levels of genetic diversity and have been long established in the Mediterranean Basin with two main genetic groups. Gene flow seems to be the main process in shaping this genetic structure as well as the fly's colonisation routes that have paralleled those of the olive tree. This genetic marker was sensitive to identify the source of origin of new infestations, making global collaboration easier [32, 297, 298, 300, 301, 302, 303]. The COI mitochondrial gene is also a useful and reliable taxonomic tool since it is the universal barcode for animal species identification. This trait makes it possible to identify olive pests at early stages, which is essential in the prompt detection and control of pests.