Identificação molecular de Trichospilus diatraeae, Palmistichus elaeisis, Tri chogramma pretiosum e caracterização de imaturos de Tetrastichus howardi (Hymenoptera: Chalcidoidea)

Abstract

Parasitoid wasps play a fundamental role in biological control. The pupal endoparasitoids Trichospilus diatraeae Cherian & Margabandhu, 1942, Palmistichus elaeisis Delvare & LaSalle, 1993, Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae), and the egg parasitoid Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) are widely used for the population control of lepidopteran pests. Differentiation among parasitoid strains may result in significant biological variations, such as changes in the life cycle and immature development. However, their morphological identification may be limited due to their small size and the high morphological similarity among species. Therefore, molecular approaches stand out as complementary tools for rapid and accurate identification, ensuring the safe and effective release of these biological control agents in the field. Our objective was to identify species-specific genomic variants of the target species T. diatraeae, P. elaeisis, T. howardi, and T. pretiosum through whole-genome sequencing, as well as to describe the larval development of two strains of T. howardi. Parasitoids were collected from their hosts and established in the laboratory after adult emergence. Samples of each species were sent to the Department of Biological Sciences at the Federal University of Espírito Santo (UFES) and to the Oscar Monte Entomophagous Insect Collection for morphological identification. Subsequently, samples composed of females of each parasitoid species were preserved in absolute ethanol and sent to Agropartners Consulting Company. DNA was extracted, quantified, and sequenced on the Illumina NovaSeq 6000 platform. Bioinformatic tools were used for data quality control, detection of species-specific genomic variants, principal component analysis (PCA), and support vector machine (SVM) classification. Genomic sequencing generated high quality data for the analyzed parasitoids, allowing the identification of four specific vari ants for T. diatraeae, four for P. elaeisis, two for T. howardi, and five for T. pretiosum. Additionally, the DO (Dourados) and LA (Ladário) strains of T. howardi were established under laboratory conditions, and females were exposed to Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) pupae for 24 h. Over a period of 20 days, parasitized pupae were collected daily, preserved, dissected, and photographed. Larval instars were determined through morphometric measurements of head capsule width, body length, and body width, followed by principal component analysis. Both strains exhibited three larval instars, with differences in immature developmental time. This study significantly contributes to the biological and molecular knowledge of parasitoids used in biological control programs by facilitating species identification in future collections and supporting the planning and monitoring of field populations.