An Integrated Morphometric-Molecular Framework for High-Fidelity Instar Identification in the Safflower Aphid Uroleucon gobonis (Matsumura)

Abstract Accurately identifying pest developmental stages is a key prerequisite for developing efficient prevention and control strategies. This study integrated morphometric and molecular biology techniques to establish a multi-dimensional instar identification system for the safflower aphid. The method first systematically evaluated the identification efficiency of eight morphological indicators of Uroleucon gobonis (Matsumura) ( U. gobonis ), and found that the body length can effectively distinguish the aphids from the first instar (1st instar) to the fourth instar (4th instar), abdominal tube length can distinguish the third instar (3rd instar) and later instar, and antennal length can clearly distinguish between the second instar (2nd instar) and 3rd instar, and between the 3rd and 4th instars; the other five indicators show overlap. To overcome the inherent limitations of traditional morphological identification methods, this study analyzed the five developmental stages of U. gobonis using six candidate genes identified from transcriptome data. The expression level of DN1098 peaked at the 3rd instar aphid stage; DN136 showed the highest expression at the adult stage; DN1031, DN1019, and DN1093 were highly expressed at the 1st instar aphid stage; and DN1068 remained highly expressed from the 2nd to the 4th instar aphid stages. The multi-gene expression “fingerprint” identification system, constructed based on these characteristics, can accurately distinguish all target developmental stages. For the first time, this study provides a comprehensive instar identification framework for U. gobonis , spanning rapid preliminary morphological screening to precise molecular confirmation, thereby providing important technical support for population monitoring.