Genetic variation in host discrimination ability in Diachasmimorpha longicaudata (Hymenoptera: Braconidae) attacking Ceratitis capitata (Diptera: Tephritidae)

DEVESCOVI, FRANCISCO; NUSSENBAUM, ANA L; BACHMANN, GUILLERMO; LANZAVECCHIA, SILVIA B.; CLADERA, JORGE L; SEGURA DIEGO F.

Tapachula

Simposio; 10th International Symposium on Fruit lies of Economic Importance.; 2018

Background: Diachasmimorpha longicaudata is a solitary parasitoid which attacks late instars Ceratitis capitata larvae, among other fruit fly pest species. Superparasitism -the oviposition in already parasitized larvae by the same or other females- is a frequent phenomenon observed in artificial rearings. In such cases, supernumerary eggs do not complete development and are eliminated through competition, therefore reducing the efficiency of the production process and quality of the emerged adults. If genetic variability and heritability in the ability to discriminate previously parasitized hosts (i.e. host discrimination ability) could be demonstrated, further artificial selection could aid in reducing the incidence of superparasitism in mass rearing yields. Methods: We first determined the variability among 50 virgin females in their host discrimination ability using an indirect method, in which healthy host larvae were exposed for 4 h to a single female. After 48 h, we dissected the pupae and compared the observed frequency distribution of the number of eggs/host with the Poisson frequency distribution (i.e. random distribution). Then, we selected 12 females and established isolines. For each isoline, between 4 to 8 F1 female offspring were tested as their mothers. We estimated the heritability in the broad (H2) and narrow (h2) senses using family analyses and parent-offspring regressions, representing the amount of phenotypic variation explained by the total genetic and additive variation, respectively. Results: 38% of the parental females showed a non random egg distribution, though a continuum degree in the expression of host discrimination ability was observed. Heritability (H2 nor h2) was not statistically significant neither using an estimator of superparasitism intensity (i.e. mean number of eggs/host = λ) or the Poisson dispersion index (variance/λ) as variables. Conclusions: Host discrimination ability was confirmed in D. longicaudata. Although considerable variability for this behavior exists in our experimental rearing, such variation seems largely environmental rather that genetic.