Genetic diversity and genetic differentiation pattern of Tuta absoluta across China

Tuta absoluta (Meyrick) is a cosmopolitan invader and one of the most serious pests of tomato. This pest has expanded rapidly in China since it initially invaded Xinjiang in the northwest in 2017 and Yunnan in the south in early 2018. More complete knowledge of the migration patterns and genetic structure of this pest is important for implementing effective management strategies. To fill this knowledge gap, the COI gene of T. absoluta was sequenced based on nationwide routine monitoring. This study showed a new invasion into Gansu and Inner Mongolia, indicating ongoing expansion of this pest. Most populations of T. absoluta, both in China and worldwide, have high genetic homogeneity. Nevertheless, some degree of genetic variability was found in populations in southern China, especially in Yunnan. Two distinct haplogroups were distinguished, and clade A was predominant at the global level. The high level of sequence divergence indicated the possible existence of cryptic species. Furthermore, FST and analysis of molecular variance (AMOVA) revealed weak but significant differentiation between the Xinjiang northwestern group and southern group/subgroups and provides compelling evidence of the different dispersal avenues of T. absoluta in northwestern and southern China. T. absoluta likely established bridgehead populations in Yunnan and then spread rapidly throughout this province and neighboring territories in southern China. Knowledge regarding genetic diversity, population structure and dispersal pattern is valuable for improving management guidelines for this pest. Strict plant quarantines, local eradication and practical control measures are needed to solve the problem caused by T. absoluta.