Cross-breeding of Tenebrio molitor strains from a large-scale perspective

To meet the increased future needs in insect Processed Animal Proteins PAPs, insect sector has to optimize the mass rearing of insects. That being the case, a means to tackle this growing demand for insects is to invest in breeding strategies aiming for the production of hybrids with improved economically and biologically valuable traits. In this framework, the objective of the present study was to evaluate the mating compatibility among four strains of the yellow mealworm, Tenebrio molitor, from different geographical areas (Greece, Belgium, Italy and USA) and to assess and compare the performance of the produced inbred and partially outbred lines. All trials were performed in crates of the size (40 × 60 cm) typically used in industrial rearing of mealworm. Adults of T. molitor were placed in the crates and were left to mate and oviposit. To assess mating compatibility, the amount of oviposited eggs (g) as well as the larval hatching rate were recorded. For the assessment of larval performance of inbred and partially outbred lines, two to three weeks old larvae were placed in crates together with Insectus as feeding substrate. The results showed that all crossed lines demonstrated compatibility, and certain combinations outperformed others as suggested by the high cumulative number of eggs and the larval hatch rates for both inbred and partially outbred lines produced. For hatched larvae, there were significant differences among the inbred and partially outbred lines. The highest hatch rates recorded for the Italian-Italian, Belgian-Italian, and Belgian-USA lines. Concerning offspring performance, all crosses followed a similar pattern in terms of final larval weight. The present study aims to draw the attention of the scientific community and insect producing companies to cross-breeding practices to start unfolding its potential for the genetical improvement of commercially farmed insects.