Evaluation of molecular markers for genetic diversity studies of western tarnished plant bug (Lygus hesperus Knight)

Western tarnished plant bug (Lygus hesperus Knight) is an important cotton pest in the Texas High Plains. Lygus hesperus genetic diversity in the region is yet to be fully understood. This is mainly due to a lack of suitable molecular markers. Further, only a few Simple Sequence Repeat (SSR) markers have been published, and genome sequence information is unavailable for this species. Four common molecular marker types, Random Amplified Polymorphic DNA (RAPD), Simple Sequence Repeat (SSR), Inter-Simple Sequence Repeat (ISSR), and Amplified Fragment Length Polymorphism (AFLP); were evaluated for polymorphism, repeatability, and cost/time efficiency. Lygus hesperus samples (n=32) were collected from four geographical populations in the Texas High Plains and were genotyped using fifteen selected primers from each molecular marker type. While initially difficult to develop, SSR markers were observed to be the most reliable of those evaluated. RAPD and ISSR markers had low reputability but they were relatively economical and easy to develop. AFLP markers demonstrated higher repeatability, but the high DNA quality requirement and information loss from DNA fragments with sizes exceeding 600 base pairs during capillary electrophoresis using CEQ 8000 were major drawbacks of this type of marker. The results of this study will be valuable in genetic diversity studies of Lygus hesperus as well as other closely related Lygus species.