Submitted to: Journal of Insect Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2010
Publication Date: 5/1/2011
Citation: Yocum, G.D., Rinehart, J.P., Larson, M.L. 2011. Monitoring diapause development in the Colorado potato beetle, Leptinotarsa decemlineata, under field conditions using molecular biomarkers. Journal of Insect Physiology. 57(5):645-652. Interpretive Summary: The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is the major defoliator of potato and also feeds on tomato and eggplant. The CPB is endemic in most of the potato growing regions worldwide. The plasticity of the CPB’s diapause response played a key role in its range expansion. Dormancy in the form of diapause or quiescence enables insects to survive and synchronize their life cycles to the abiotic and biotic factors needed for development and reproduction. Counter to the orderly sequence of diapause development seen under laboratory conditions, L. decemlineata diapause response under field conditions presents a more complex picture. At any given time there is normally a wide range of diapause disposition of individual beetles in the wild. We developed a molecular technique to monitor diapause disposition in real time under field conditions. This technique was employed to monitor CPB in potato plots in the Red River Valley of North Dakota and Minnesota for three consecutive years. The results clearly demonstrated that the dynamic diapause composition of a field population of L. decemlineata can be monitored over the course of the growing season using molecular biomarkers.
Technical Abstract: A multiplex PCR protocol was developed using five diapause-regulated genes to monitor diapause development of the Colorado potato beetle under field conditions. A total of 870 beetles from the Red River Valley of North Dakota and Minnesota, USA, were screened for three consecutive years. Out of the 32 possible expression profiles, eight could be arranged in chronological order of diapause development. These eight profiles account for over 92% of the beetles surveyed. Intra-population variation in diapause phenotypes was observed in the field. Some beetles were already in the diapause initiation phase in June when the day length was greater than 17 hours. Inter-seasonal variation in the timing of diapause development was also noted. The greatest differences were before the day length decreased to less than 15 hours. Anomalies in the results, e.g., the presence of the diapause maintenance phase profiles in beetles collected on the potato plants, argue that laboratory results are not always equivalent with what is observed under field conditions.