Abstract Description

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the Natal fruit fly, Ceratitis rosa (Karsch); and the oriental fruit fly, Bactrocera dorsalis (Hendel) are pests of phytosanitary concern on citrus in South Africa. These pests can also cause direct damage to the fruit, making them non-marketable. The bait application technique (BAT) is the main method for control of these pests in South Africa. BAT is a method that uses a combination of a protein-based attractant and an insecticide to target the adult stages of the pests. Currently only a limited range of protein attractants is available for use in BAT and those that are available are not equally effective across all fruit fly pests. Previous studies have documented how yeasts play a role in larval development and influence the behaviour of fruit fly species. This study aims to isolate, identify, and characterise yeast strains associated with three fruit flies for a better understanding of the behaviour of these pests. The isolation and characterisation of these yeast strains could lead to the development of potential species-specific attractants to better control these pests in the field. For this study, wild fruit flies were collected from orchards in Addo (Eastern Cape) and Mbombela (Mpumalanga). Additionally, adult fruit flies were also collected from laboratory cultures of C. capitata, C. rosa, and B. dorsalis, maintained in Mbombela. Fruit flies were homogenised and streaked onto yeast peptone dextrose (YPD) agar plates containing chloramphenicol and grown at 25 °C for 48 hours. Single colonies were selected and grown in YPD broth, and genomic DNA was extracted using the YeaStar™ or Purelink™ Genomic DNA kit. Currently, forty yeast species from thirteen genera, such as Kodamaea, Meyerozyma, Saccharomycetales, Candida, Starmerella, Rhodotorula, Debaryomyces, Sporobolomyces, Filobasidium, Papiliotrema, Cystofilobasidium, Diutina, and Wickerhamomyces have been identified using PCR amplification and sequencing of the ITS region. The current work in progress involves identifying additional yeasts that have been isolated and then investigating whether any of these isolated yeasts influence the foraging behaviour of adults of C. capitata, C. rosa, or B. dorsalis. Preliminary results from behavioural assays conducted in a laboratory indicate that female C. capitata flies are attracted to a Wickerhamomyces spp. yeast culture. Future work will include metabarcoding analysis of yeasts associated with C. capitata, C. rosa, and B. dorsalis.