Cryopreservation of the Mediterranean fruit fly (Diptera: Tephritidae) VIENNA 8 genetic sexing strain: No effect on large scale production of high quality sterile males for SIT applications.

Ihsan Ul Haq,Carlos Cáceres,Jose Salvador Meza,Adly Abd-Alla,Ulysses Sto Tomas,Kostas Bourtzis,David A Lightfoot

doi:10.1371/journal.pone.0211259

Abstract

The sterile insect technique (SIT) integrated in area-wide integrated pest management (AW-IPM) programmes is being used for the successful management of the Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) which is a horticultural pest of economic importance in tropical and subtropical countries. All programmes with an SIT component are using the VIENNA genetic sexing strains (GSS), mainly the VIENNA 8 GSS, which have been developed by applying classical genetic approaches. The VIENNA 8 GSS carries two selectable markers, the white pupae and the temperature sensitive lethal genes, which allows the production and release of only males thus increasing the biological efficiency and cost effectiveness of SIT applications. However, mass rearing may affect quality traits of the GSS, in which case replenishment of the colony with wild flies is recommended, a process which is tedious and time consuming. We previously reported the development of a cryopreservation protocol for the VIENNA 8D53+ strain. In the present study, we report on the evaluation of the cryopreserved strain VIENNA 8D53+/Cryo-228L, reared under semi mass rearing conditions, for production parameters, quality control indices and mating competitiveness of males, in a comparative way with the non-cryopreserved VIENNA 8D53+ strain, against wild type males. The VIENNA 8D53+ and VIENNA 8D53+/Cryo-228L strains were similar for production parameters viz. egg production, pupal production, pupal recovery, and quality control indices like fly emergence, sex ratio and flight ability. Males from both strains were equally competitive with males of the wild type strain in achieving mating with wild type females under field cage conditions. Results are discussed in the context of cryopreservation as a potential backup strategy for refreshing the mass rearing colony with biological material from a cryopreserved stock.

Highlights

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the most destructive pests in the world, causing extensive direct damages to horticultural produces and indirect losses by impeding the international trade [1,2]
Two main factors have made the sterile insect technique (SIT) for the Mediterranean fruit fly more cost-effective: first, the technological developments that enabled the production of flies on a large scale i.e. more than 4000 million sterile pupae per week are produced in different facilities world-wide [10] and second, the development of genetic sexing strains (GSS) [9] which allowed the separation of sexes early in development
The VIENNA 8D53+ and VIENNA 8D53+/Cryo-228L strains were similar in egg production, pupal production, pupal recovery as well as in quality control indices such as fly emergence, sex ratio, and flight ability

Summary

Introduction

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the most destructive pests in the world, causing extensive direct damages to horticultural produces and indirect losses by impeding the international trade [1,2]. The GSS carrying the mutations in the wp and tsl genes allows the production and release of males only This improves the cost effectiveness and the biological efficiency of the SIT application due to the following reasons: (i) male-only releases eliminated the assortative mating between sterile males and sterile females, making the SIT component much more effective [14], (ii) dispersal of the sterile males to find wild females for mating is higher which enabled them to transfer their sterile sperms to more wild females and (iii) male-only releases reduced the cost of releasing sterile males [15,16]. Despite the fact that GSS are performing very well in small scale rearing environments, they may be vulnerable to break down, due to recombination phenomena, under large scale mass rearing conditions [19] To overcome this potential problem, the colony management practice i.e. filter rearing system (FRS) was introduced. An additional step for preventing recombination-related problems was the integration of an inversion, known as D53, on some versions of the VIENNA 8 GSS [13,18]

Methods

Results

Conclusion