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During mass rearing, adaptation of biological control agents to the rearing environment is a potential problem. Using the parasitoid wasp Trichogramma pretiosum, the performance of 26 highly inbred lines, five composite ‘populations’ (created from the inbred lines) and one insectary-reared population was compared using fertility life tables. Of the composite populations, three were created with maximal and identical genetic variation as a mixture of all 26 inbred lines, but these were then reared for a different number of generations (2, 6 or 17) before their performance was measured. The remaining two composite populations were created based on the performance of the individual inbred lines: one was a combination of two inbred lines with a high intrinsic rate of natural increase (rm), ‘high rm’; and the other was a combination of two lines with a ‘low rm’. High and low rm populations were reared for two generations prior to testing. Parameters measured were fertility, longevity and sex ratio. We found no difference between the maximally variable population reared for two generations and the ‘high rm’ population (rm = 0.285 and 0.282, respectively). ‘Low rm’ was the population with the lower performance (rm = 0.255). Genetically variable population reared for two generations for 48 h produced significantly more offspring than the populations reared for 6 and 17 generations. Hybrid population derived from the high-rm lines did significantly better than that derived from the low-rm lines. Low-performance populations become more male based than high performance at 48 h. The potential benefits to improve population's performance using inbred lines for mass rearing are discussed.

Molecular taxonomy of trichogrammatids has made impressive beginning in the last two decades. Several workers have employed RFLP, RAPD, AFLP and PCR techniques. In India, a modest beginning has been made in using the internal transcribed spacer (ITS) region especially ITS-2. By the use of specific primers, it is possible to confirm the identity among thelytokous populations/species, thus overcoming the limitation to use males in conventional taxonomy. Examples of molecular key for Trichogramma species based on PCR product size and response to chosen enzymes (like Eco RI, Mse I, Pvu I and Nru I) are provided. Scope exists for evolving multiplex PCR, involving both species-specific primers and a complementary universal primer for ITS-2 region. Potential for application of molecular techniques exists in quality control for commercial units against contamination by other species. Strain identification is possible with microsatellite markers and ISSR (inter-simple sequence repeat) technique. Enzymatic analysis, especially with EST, MDH and SOD, can be employed as complementary means of distinguishing morphologically close relatives. The targets of analysis include mitochondrial DNA and ribosomal RNA. Analysis and alignments of DNA sequences are also discussed. Software packages providing additional information are also listed.

Species of parasitic Hymenoptera are used extensively in biological control as agents for permanent suppression of a pest or as insectary-reared, augmentative agents for seasonal suppression of a pest. Both approaches require the agent to be cultured but the methods used to culture them often affect their quality, especially that of females. Poorly producing cultures frequently manifest detrimental sex-ratio changes, occasionally becoming entirely male with the consequent extinction of the culture. These sex-ratio changes arise from the interactions among conditions within the culture and factors such as sex determination, sex allocation, haplodiploidy, sex-ratio distorting elements, or unusual life histories of the parasitoids. In addition to the interaction between inbreeding and the sex-determining mechanisms, sex-ratio distortion due to several other factors that alter offspring sex ratios have been detected in Hymenoptera. Some of them have the potential to extirpate a culture or to reduce its productivity. Sex-ratio distorters in these cases involve heritable elements either within the genome or the cytoplasm and include such factors as sperm morphology, the paternal sex-ratio (PSR) element, primary male syndrome, maternal sex ratio, son-killer trait, nonreciprocal cross-incompatibilities, and thelytoky.