Establishment of Lolium species resistant to acetolactate synthase‐inhibiting herbicide in and around grain‐importation ports in Japan

Abstract

Compared with natural seed dispersal, human-mediated seed dispersal could spread herbicide resistance genes on a much larger scale. Herbicide-resistant weed seeds have been reported as contaminants in commercial grain. We investigated the contamination of seeds of Lolium species with target-site mutations conferring resistance to acetolactate synthase (ALS)-inhibiting herbicides in wheat imported from the USA, Canada and Australia into Japan. We also investigated the establishment of ALS-inhibiting herbicide-resistant Lolium species in 12 seaports in Japan that are major entry points for international commodities. We found herbicide-resistant Lolium spp. seeds from all classes of wheat samples. Resistant individuals became established at six of eight ports where more than 50 kt of imported wheat is unloaded every year. The establishment of resistant Lolium spp. individuals was common at major grain landing ports. Monitoring over 3 years at one port revealed that the frequency of resistant individuals did not fluctuate between years. Many resistant individuals were distributed in front of the entrance of a fodder company, but a few resistant individuals were found in areas 2 km away from the port. The results indicate that gene flow is rare through pollen or seed movement from resistant plants to peripheral populations. Further extensive and longterm monitoring is necessary to perform a comprehensive risk assessment of herbicide-resistant plants entering Japan through major commercial ports.

Derived Polymorphic Amplified Cleaved Sequence (dPACS): A Novel PCR-RFLP Procedure for Detecting Known Single Nucleotide and Deletion–Insertion Polymorphisms

“…The same approach was employed for the rapid diagnosis of neonatal sepsis in India [51] and to determine the magnitude of drug resistance in Mycobacterium tuberculosis in Central Punjab, Pakistan [52]. Other recent examples of the use of dCAPS markers abound in phylogeny [53], map-based cloning [54], gene flow [55,56] and population genetics studies [57].…”

Population Genomics of Herbicide Resistance: Adaptation via Evolutionary Rescue

“…Anecdotally, cases in which highly problematic resistant weeds become more widespread across a range are often attributed to humanmediated gene flow via seed dispersal, such as for glyphosate-resistant Amaranthus palmeri across the United States (28) or the introduction of Amaranthus tuberculatus into Ontario, Canada (35). Similarly, three 20-kg Japanese imports of wheat from the United States, Canada, and Australia contained between 2,931 and 4,673 seeds of Lolium spp., with frequencies of ALS resistance ranging from 28.6% to 84.6% encoded by seven unique TSR substitutions (155). Anecdotal cases such as this suggest that the spread of genetic variation for resistance via seed dispersal may be of primary importance for long-range establishment of resistance.…”

The Expansion Route of Ryegrasses (Lolium spp.) into Sandy Coasts in Japan

“…Japan imports 99% of its wheat from the United States, Canada, and Australia (Ministry of Finance, Japan 2014). According to Shimono et al (2015), Australian wheat contains greater than 30-fold the quantity of Lolium seeds compared with the same amount of wheat from other countries. Therefore, more seeds derived from Australian wheat fields will spill out around seaports.…”