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Echinochloa crus-galli (L.) Pal. Beauv. is one of the most noxious weeds in maize cultivation and has evolved target-site resistance to ALS-inhibiting herbicides. Due to the hexaploid nature of E. crus-galli, resistance inducing mutations can be harbored by multiple gene copies, but up to now, studies did not include an analysis of the ALS gene copies conferring resistance. Investigations on E. crus-galli populations from different countries in Central Europe revealed the presence of several point mutations conferring resistance and occurring independently at the positions Ala-122, Pro-197 and Trp-574. Moreover, an Asp-376-Glu mutation in the ALS gene in E. crus-galli and a Ser-653-Tyr amino acid change in the ALS protein of a weed were detected for the first time. Additionally, the study revealed the first case of an ALS-resistant population (Trp-574-Leu) in the Czech Republic. The detection of mutations is relevant to the evolution and management of herbicide resistance. Dose–response experiments showed different effects depending on the population and the individual active ingredients and mixtures. Due to the genetic variability of E. crus-galli, results were highly variable. Overall, the populations showed a high level of resistance. For the prevailing mutated positions, i.e., Ala-122, Pro-197 and Trp-574, gene copies were examined separately using molecular genetic methods. A single mutation in at least one out of three ALS gene copies was sufficient to confer resistance at the positions Pro-197 and Trp-574. At Ala-122, point mutations co-occurring in the ALS 1, ALS 2 and ALS 3 gene copy were identified. The study provides a starting point for differentiation of the resistance mechanisms in polyploid E. crus-galli. [ABSTRACT FROM AUTHOR]

Highlights • Southeastern Europe and Anatolia were the source for recolonisation of Central Europe after the most recent glacial period. • Northwestern Europe was re-colonised from refugia in southwestern France. • Human activity might have caused the postglacial migrations of Microthlaspi to southern Sweden. • Pleistocene glacial refugia were in all of the Mediterranean peninsulas, southwestern France, Transcaucasia and Central Asia. Abstract Quaternary climatic oscillations had strong effects on Palearctic biodiversity. Although Transcaucasia is hypothesised to be a centre of diversity for many taxa, relatively few studies have investigated its potential role as such, or as a Pleistocene refugium. Using AFLP and sequence data (ITS, mat K, trn L-F) from samples collected across the entire range of Microthlaspi perfoliatum , from the Iberian peninsula to Kazakhstan, and including the Mediterranean Basin and Central Europe, in this study it is examined how the interplay of Pleistocene climatic oscillations and historical demography may have shaped the current genetic structure of the species. The results of this study provide evidence that M. perfoliatum survived Pleistocene glaciation in five major refugia, Iberia, southwestern France, Italy, the Balkans and Anatolia/Transcaucasia and a sixth, unknown refugium in the disjunct distribution area in Central Asia. Our analyses support an ancient colonisation of M. perfoliatum towards the western and central Palearctic, perhaps, during the early Pleistocene or late Pliocene, likely starting from Transcaucasia. However, postglacial recolonisation of western and Central Europe has taken place from two distinct refugia, namely southwestern France/northern Italy, and Anatolia/Southern Balkans, respectively. The Iberian populations apparently did not contribute to postglacial recolonisation of Europe, perhaps because the Pyrenees acted as a significant barrier to dispersal. It is also conceivable that a rapidly expanding population from southwestern France and the southeastern part of the range effectively blocked the establishment of latecomers. The present study thus reveals a complex pattern of colonisation of Europe from Transcaucasia, with an interplay of climate and physical geography as main factors shaping the present-day genetic structure of M. perfoliatum. [ABSTRACT FROM AUTHOR]