Chloroplast DNA analysis of the invasive weed, Himalayan balsam (Impatiens glandulifera), in the British Isles

Daisuke Kurose,Kathryn M Pollard,Carol A Ellison

doi:10.1038/s41598-020-67871-0

Abstract

Impatiens glandulifera or Himalayan balsam (HB), is an invasive alien weed throughout the British Isles (BI). Classical biological control of HB in the BI using a rust fungus from the Himalayan native range was implemented in 2014. However, not all HB populations are susceptible to the two rust strains currently released. Additional strains are needed that infect resistant populations in order to achieve successful control. These are best sourced from the historical collecting sites. A molecular analysis was conducted using six chloroplast DNA sequences from leaf material from across the BI and the native range. Herbarium samples collected in the Himalayas between 1881 and 1956 were also included. Phylogenetic analyses resulted in the separation of two distinct groups, one containing samples from the BI and the native range, and the other from the BI only; suggesting that HB was introduced into the BI on at least two occasions. The former group is composed of two subgroups, indicating a third introduction. Ten and 15 haplotypes were found in the introduced and native range respectively, and with two of these found in both regions. Results show where to focus future surveys in the native range to find more compatible rust strains.

Highlights

Impatiens glandulifera or Himalayan balsam (HB), is an invasive alien weed throughout the British Isles (BI)
Phylogenetic analyses resulted in the separation of two distinct groups, one containing samples from the BI and the native range, and the other from the BI only; suggesting that HB was introduced into the BI on at least two occasions
Our preliminary work showed that variability in the internal transcribed spacer regions, including the 5.8S rDNA was very low, which is consistent with the previous research[30]

Summary

Introduction

Impatiens glandulifera or Himalayan balsam (HB), is an invasive alien weed throughout the British Isles (BI). The ability to gain insight into the introduction of a species—including information on where introductions originated from, how many times the species was introduced, and the distribution and occurrence of specific genotypes (genetic diversity)—is an invaluable tool which can reduce both the time and costs associated with identifying, matching and prioritising natural enemies for such projects[20, 21] These molecular techniques are widely used as a tool in CBC programmes against invasive, non-native or alien weeds, where both herbivores and pathogens have been exploited as biological control agents[22,23,24,25]. The typical maternal inheritance of cpDNA in angiosperms means that any genetic structure that was present in the original introductions may be retained, in comparison to nuclear markers that are subject to gene flow via both pollen and s eed[22]

Methods

Results

Conclusion