Genetic diversity and population structure of a global invader Mayweed chamomile (Anthemis cotula): management implications

Abstract

Mayweed chamomile (Anthemis cotula L.) is a globally invasive, troublesome annual weed but knowledge of its genetic diversity, population structure in invaded regions, and invasion patterns remains unstudied. Therefore, germplasm from 19 A. cotula populations (sites) from three geographically distinct invaded regions: the Walla Walla Basin (located in southern Washington) and the Palouse (located in both northern Idaho and eastern Washington), Pacific Northwest, USA and Kashmir Valley, India were grown in the greenhouse for DNA extraction and sequencing. A total of 18,829 SNPs were called and filtered for each of 89 samples. Pairwise-FST , Nei’s genetic distance, heterozygosity, Wright’s inbreeding coefficient (F), and self-fertilization rates were estimated for populations within and among the three regions with a total of 19 populations comprised of 89 individuals. Overall measurements of genetic variation were low but significant among regions, populations, and individuals. Despite the weak genetic structure, two main genetic clusters were evident, one comprised of populations from Palouse and Kashmir Valley, the other comprised of populations from the Walla Walla Basin. Significant selfing was observed in populations from the Walla Walla Basin and Palouse but not from Kashmir Valley, indicating that Mayweed chamomile in the Pacific Northwest USA could persist with low pollinator or pollen donor densities. Although FST values between the regions indicate Palouse populations are more closely related to Kashmir Valley than to Walla Walla Basin populations. Based on Migrate-n analysis, panmixis was the most likely model, suggesting an unrestricted gene flow among all three regions. Our study indicated that Kashmir Valley populations either originated from or shared the origin with the Palouse populations, suggesting human-mediated migration of A. cotula between regions.

Weak population differentiation and high diversity in Salsola tragus in the inland Pacific Northwest, USA

“…J.D. Sauer, 69,80 and Anthemis cotula L. 87 Finally, although specific adaptive variation is not necessarily well predicted by overall genetic diversity, 90 higher levels of total genetic variability have been associated with higher potential for populations to successfully adapt to changing environments, particularly at the shorter time-scales most relevant to agroecosystem management. [91][92][93]…”

“…Weed managers should expect that future herbicide-resistance traits will likely spread across the region with similar rapidity, and be prepared to adjust herbicide programs and other relevant management inputs with equal speed, regardless of their proximity to the point of initial origin. Low acrossrange differentiation, usually in combination with high levels of genetic diversity, has also been suggested as a shared trait among problematic and adaptable weeds, 79 with examples in a range of arable 67,69,[80][81][82][83][84][85][86][87] and invasive 88,89 weeds. This pattern appears to be emerging with particular regularity in outcrossing dicot weeds with widespread herbicide resistance, including Bassia scoparia, 67,85,86 Amaranthus palmeri S. Watson, 83,85 Amaranthus tuberculatus (Moq.)…”

Uncovering the secret weapons of an invasive plant: The endophytic microbes of Anthemis cotula

“…We choose A. cotula for two reasons: one that it is very widespread and abundant in Kashmir Himalaya [ 20 ] and second, its leaves emit pungent smell because of which it is commonly called as ‘stinking chamomile’ [ 21 ]. While studying the role of morpho-physiological [ 22 ], and reproductive [ 23 ] traits in the invasiveness of this species it has emerged that the leachate of pungent smelling leaves of A. cotula show allelopathic activity [ 23 , 24 ], thus making leaves as an organ of interest to us for studying the diversity and role of endophytes. We focussed on three aspects: (1) Diversity of bacterial and fungal endophytes in the leaves of A. cotula, (2) Plant growth promoting activities of endophytes, such as Indole acetic acid (IAA) production, phosphate solubilization, ammonia production, and (3) Biocontrol activity of endophytes against two phytopathogens, namely Fusarium oxysporum (a common soil pathogen) and Botrytis cinerea (enemy of A. cotula in its native range).…”