Structural characterization and applications of ITS2 from rice leaffolders Cnaphalocrocis medinalis and Marasmia patnalis (Lepidoptera: Pyralidae)

Abstract

Cnaphalocrocis medinalis and Marasmia patnalis are important rice insect pests in Asia and have similar morphologic features and same feeding patterns. Understanding the molecular difference of the two leaffolders is helpful to their identification and clarification of their phylogenetic class in the Pyraloidea. In this study, we determined and analyzed the nucleotide sequences of nuclear rDNA internal transcribed spacer 2 (ITS2) in the two rice leaffolders from 9 populations (six C. medinalis populations collected from China, Philippine, Thailand, and Vietnam, and three M. patnalis populations from Philippine, Thailand, and Vietnam) and compared interspecies variation of IST2 among different geographic populations and intraspecies variation of ITS2 from Pyraloidea. Phylogenetic trees were constructed on the two leaffolders and other Pyraloidea species using Maximum Parsimony method. Results showed that the ITS2 sequences differed in the two leaffolders. Compared to C. medinalis, ITS2 of M. patnalis had small deletion at the sites of 41, 72, 81, 304 and an insertion at the site of 337. Interspecies variation results showed that three C. medinalis populations from Southeast Asia (VN, PH, and TH) are with small divergence compared to NJ and HZ, and small divergence was observed among three M. patnalis populations (VN, PH, and TH). Intraspecies variation results showed that two leaffolders were with close relationship compared to the other Pyraloidea. Phylogenetic trees showed that two leaffolders were grouped together with Maruca vitrata. These results indicated that the ITS2 sequences differed in the two leaffolders could potentially be used in the distinguishing of the two rice leaffolders and the determination on the phylogeny of species.