An Estimate of Cytoplasmic Incompatibility and its Use in the Control of a Storage Pest, Tribolium castaneum (Herbst)

Abstract

Using purebred and hybrid crosses involving four indigenous (viz. CHI, DHA, KHU and RAJ) and four exotic (viz. BLA, CTC, FSS and KAN) strains of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera:Tenebrionidae), cytoplasmic incompatibility (Cl) relationships between the strains have been established. An analysis of the observed incompatibility, where the percentage of egg-hatch data was considered as· an index, demonstrate that of 52 crosses, 34 (65.38%) were compatible, 12 (23.08%) were partially incompatible and 6 ( 11.54%) were incompatible. The results suggest that two of the indigettous strains viz. KHU and RAJ and three of the exotic strains viz. CTC, FSS and KAN might be infected with RMO (rickettsia-like microorganisms). Backcross data, on the other hand, indicate th:at the two indigenous (KHU and RAJ) and one exotic (BLA) strains clre perhaps uninfected. Effect of tetracycline treatment in the food medium and its consequence on the expression of Cl in T. castaneum demonstrate that when males reared on untreated· food are mated with the females reared on a similar medium, all the infected strains show compatibility. But when untreated males are paired with females reared on tetracycline-treated food, all the crosses exhibit incompatibility. Alternatively, when males reared on treated medium are crossed to females reared either on untreated or treated medium, all the cross-matings become compatible. This indicated that the tetracycline treatment might have 'cured' the infected males from the RMO, if any. Apparently fecundity of the experimental insects was not affected by the tetracycline treatment.