Degradation dynamics of cotton DNA in adult Harmonia axyridis feeding on cotton aphid or cotton pollen

Author of the article:BAO Wei-Fang1, 2** WANG Qian2 FAN Dong1*** LU Yan-Hui2***

Author's Workplace：1. College of Agriculture, Northeast Agriculture University, Harbin 150030, China; 2. State Key Laboratory of Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China

Key Words：Harmonia axyridis, Aphis gossypii, cotton plant DNA, PCR, gut content analysis, food composition

Abstract： [Objectives] Predatory ladybird beetles consume plant DNA indirectly by preying on herbivorous insect pests, but also directly by ingesting plant foods such as pollen . We assessed the degradation of plant DNA consumed by ladybird beetles via both these routes. [Methods] A tritrophic system, Harmonia axyridis - Aphis gossypii - Gossypium hirsutum, was used for this study. Cotton plant DNA in ladybird beetles was detected using PCR technology after feeding on A. gossypii on cotton leaves, or on cotton pollen, and the effects of digestion time on the DNA detection rate was analyzed. [Results] The maximum detection rate of cotton DNA in H. axyridis adults that had fed on A. gossypii was 16.7% 4 h after feeding. Cotton DNA could not be detected after 8 h. Detection rates of cotton DNA in H. axyridis that had fed on cotton pollen were 70.4% after 4 h, 51.9% after 12 h, and 39.3% after 16 h and 0% after 20 h. [Conclusion]  Cotton DNA was detectable for longer in H. axyridis that had fed on cotton pollen than in those that had fed on A. gossypii.