New strains and proteins from Bacillus thuringiensis bacteria

The use of Bacillus thuringiensis as a biological control agent is an alternative to chemical methods, safe for the environment and compatible with beneficial fauna. The durability of the set of its available proteins and of the ones being discovered, will depend on the use we make of them. This is why the strategies designed for the management of resistances are of vital importance. This was one of the conclusions of Iñigo Ruiz de Escudero Fuentemilla, lecturer at the Public University of Navarre, while defending his PhD thesis recently. The research characterised new strains and proteins having insecticide properties from the Bacillus thuringiensis bacteria, the bioinsecticide most used as a biological control agent with crop pests. The title of the thesis is “Bacillus thuringiensis toxins for the control of lepidopteran pests”. Biological control of pests The biological control of pests and diseases uses nature’s natural enemies or competitors of the pests or pathogens for the control of the same. It involves an age-old technique used by cultures such as the Chinese in the III century AD. Nevertheless, this type of control has lost favour over the past seven decades with the generalised worldwide use of chemical synthetic insecticides to control insect pests. But the indiscriminate, systematic and practically exclusive use of these has given rise to toxic pesticide waste in the environment and in trophic chains, and which have caused serious human health and environmental problems. Moreover, populations of insects resistant to various chemical pesticides have been created. This situation has inspired the development of what are known as Integrated Pest Management Programmes (IPM) that, through the combination of various control techniques with the monitoring of populations, as the PhD researcher explains, have been shown to be highly efficient and sustainable, both economically and ecologically. Amongst these alternative methods of control there are entomopathogenic micro-organisms – being the bioinsecticides based on the bacteria Bacillus thuringiensis the most employed, given that their wide specificity means that they are toxic for the phytophagic insects that are required to be controlled, without affecting beneficial fauna at the same time. It is within this field that Iñigo Ruiz de Escudero’s PhD has been set, the overall aim of which is “the search for new useful strains and proteins from Bacillus thuringiensis for the control of lepidopteran pests”. The main pest in European vineyards To this end, Iñigo Ruiz de Escudero isolated and characterised a series of B. thuringiensis (Bt) from earth samples from the Canary Islands, obtaining 684 strains of Bt and some of which showed activity against Lepidoptera. Moreover, the research arose from the search for new proteins, within other collections belonging to the Laboratory for the Agricultural Entomology and Pathology of Insects (LEAPI) of the Public University of Navarre, and the study of a group of toxins of B. thuringiensis for the control of a specific pest. Iñigo Ruiz de Escudero carried out the characterisation of a strain, the HU4-2 with activity for dipterans and, above all, against a series of Lepidoptera species which are not all well controlled.together by the same commercial strain but are so by this HU4-2. Thus, this strain, subject to a patent, has a great commercial future. The researchers also discovered a new gene that codes for a new Cry protein with activity against Lepidoptea E. insulana, L. Botrana and P. xylostella and against the Chrysomelida L. decemlineata in such a way that this protein can be used jointly with others or, alternatively, in the control of these pests. Finally, the insecticide potential of the toxins B. thuringiensis against Lobesia botrana – Vine Moth – has been determined, indicating that these proteins are susceptible to being used jointly or, alternatively, in the control of this pest, making the possible selection of resistant biotypes more difficult. The importance of this finding lies in the fact that Vine Moth, L. botrana, is the species that causes the most important damage in European vineyards. In this way, argues the researcher, although the control of L. botrana to date has been efficiently undertaken with a series of commercial strains such as Dipel®, Delfín® or Xentari®, this can be improved by introducing third-generation strains or products that have Cry9C or Cry2Ab proteins, the individual toxicities of which are greater than any of the proteins making up the active material of these commercial strains. Source:[ http://www.basqueresearch.com/berria_irakurri.asp?Gelaxka=1_1&Berri_Kod=991&hizk=I]

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