Life history of Dactylopius opuntiae (Hemiptera: Dactylopiidae) on Moroccan resistant cactus germplasm

The important damages caused by Dactylopius opuntiae (Hemiptera: Dactylopiidae) to cactus crops around the world require an integrated pest management (IPM) approach, based on the combination of several techniques (varietal resistance, biological, chemical methods, etc). In this sense, this study evaluated the resistance of 10 Moroccan cactus genotypes to D. opuntiae in order to characterize the expression of antixenosis and/or antibiosis. Antixenosis was accessed in the greenhouse and in the laboratory (26±2ºC) using choice and non-choice tests with 1 st instar nymphs. Aakria and Cherratia showed a strong antixenosis effect towards D. opuntiae (0-0.3 D. opuntiae alive 30 after infestation). For antibiosis assessment, 30 1 st instar nymphs were confined on cladodes of the 10 selected genotypes under the same laboratory conditions to allow their development, as well as the life cycle performance and behavior of D. opuntiae on the 10 selected cactus genotypes, were evaluated under greenhouse conditions. No influence of genotypes on insect oviposition was observed, indicating that the mealybug does not prefer any genotypes over the others for oviposition. The mealybug failed to develop on genotypes Aakria and Cherratia and did not grow beyond the young female stage on all other resistant genotypes tested. Similarly, first instar nymphs fed on genotypes Marjana, Melk Zhar, and A200 died without reaching the second instar nymph stage. In addition, all genotypes tested had a negative effect on nymph viability (<24%), indicating resistance (antibiosis and/or antixenosis) to the cactus scale. These cactus genotypes may all be useful in breeding programs focused on cactus resistance to mealybugs.

Research Progress on Oviposition-Related Genes in Insects

Oviposition-related genes have remained a consistent focus of insect molecular biology. Previous research has gradually clarified our mechanistic understanding of oviposition-related genes, including those related to oviposition-gland-related genes, oogenesis-related genes, oviposition-site-selection-related genes, and genes related to ovulation and hatching. Moreover, some of this research has revealed how the expression of single oviposition-related genes affects the expression of related genes, and more importantly, how individual node genes function to link the expression of upstream and downstream genes. However, the research to date is not sufficient to completely explain the overall interactions among the genes of the insect oviposition system. Through a literature review of a large number of studies, this review provides references for future research on oviposition-related genes in insects and the use of RNAi or CRISPR/Cas9 technology to verify the functions of oviposition-related genes and to prevent and control harmful insects.