Ecology and molecular characterization of Neozygites tanajoae (Entomophthorales: Neozygitaceae) a fungal pathogen of the cassava green mite
··· lezzter Preis 15.20 ··· 9783867279239 ··· 10361170039 ··· For the biological control of the cassava green mite (Mononychellus tanajoa, Bondar),Brazilian strains of the entomopathogen Neozygites tanajoae were recently introduced intoAfrica to improve the control achieved by predatory mites. In order to monitor theestablishment of the Brazilian strains two PCR primer pairs, NEOSSU_F / NEOSSU_R and8DDC_F / 8DDC_R were tested on N. tanajoae strains collected from several locations inBrazil and from three countries in Africa, Benin, Ghana and Tanzania. The first primer pairenabled the species-specific detection of N. tanajoae, while the second differentiated theBrazilian isolates from those of other geographical origin. The results confirmed that the twoprimer pairs tested are suitable for the detection of N. tanajoae and the differentialidentification of Brazilian and African strains. PCR can therefore be used to monitor theestablishment and spread of the Brazilian strains in Benin and in other African countrieswhere they have been introduced recently in order to improve cassava green mite (CGM)control.In this work the establishment and spread of Brazilian strains of N. tanajoae were followedin a countrywide survey in Benin in which a total of 141 cassava fields were inspected.Samples of M. tanajoa suspected of being infected by N. tanajoae were found in 60 fieldsdistributed between the coastal Southern Forest Mosaic (SFM) and the Northern GuineaSavannah (NGS) zones. PCR analysis of DNA samples extracted from samples from thesefields revealed that N. tanajoae is well distributed in Benin and that Brazilian strains wereeffectively established and have spread throughout the country. However, the highest rates ofinfection due to Brazilian strains were observed in the sub-humid and humid savannah zonesof the country.Identification of N. tanajoae strains using molecular tools, however, is very costly. Hence,development of alternative techniques is desirable. Therefore, the difference in biocontrolperformance and in host ranges was compared to discriminate between African and Brazilianstrains of N. tanajoae. The results suggest that the biocontrol potential and the host rangesbioassays are suitable for evaluating the infectiveness of N. tanajoae on cassava green mite.However, those methods were not suitable for differentiating among different origins ofstrains of the entomopathogenic fungus.The establishment of N. tanajoae in Benin after its introduction for the control of cassavagreen mite resulted in co-occurrence with the predatory mite Typhlodromalus aripo in cassavafields. However, little is known on the interaction of the two antagonists and on the biologicalcontrol potential of M. tanajoa. In a series of greenhouse experiments, effects of single andcombined releases of N. tanajoae and T. aripo on their respective population dynamics and onthe suppression of M. tanajoa populations were evaluated. In order to complement thegreenhouse experiments, laboratory experiments were conducted to evaluate the feeding,oviposition and longevity of T. aripo fed with healthy or N. tanajoae-infected M. tanajoa. Theresults showed that simultaneous release of T. aripo and N. tanajoae in the same cassava fieldmay be detrimental to the biological control of the cassava green mite. It is thereforepreferable to release in each area only the antagonist species known to be well adapted to theprevailing environmental conditions.In conclusion, this thesis shows that molecular techniques are the most suitable methods todetect infection of CGM by N. tanajoae and to differentiate among strains. Moleculartechniques are also useful for monitoring the establishment and dispersal of introduced N.tanajoae species in the field. Furthermore, this study increased our knowledge on theperformance and host ranges of the African and Brazilian strains of N. tanajoae. It alsoimproves our understanding of the interaction between N. tanajoae and the most effectivepredatory mite T. aripo as both biocontrol agents are sharing the same habitats.Future research should focus on in vitro production and cryopreservation of African strainsof N. tanajoae in order to develop specific primers for detecting African isolates.Furthermore, studies of the genetic diversity of N. tanajoae populations in the cassava fieldsusing molecular techniques could strongly improve our understanding of the interactionbetween exotic and native fungi in the cassava ecosystem. Further investigations are requiredon the interaction between the predatory mite T.aripo and the pathogen N. tanajoae at a largerspatial scale and under natural conditions, and on factors affecting the loss in biocontrolpotential of exotic species of N. tanajoae when introduced in their new environment. Hersteller: Cuvillier Verlag Marke: Cuvillier Verlag EAN: 9783867279239 Kat: Lieferzeit: Sofort lieferbar Versandkosten: Ab 20¤ Versandkostenfrei in Deutschland Icon: https://www.inforius-bilder.de/bild/?I=pBwZ6%2FZguE66kOi%2BHMwStFv92dhFjUnxpPAM53d6%2Bls%3D Bild:
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