Genetically Based Trait Differentiation but Lack of Trade-offs between Stress Tolerance and Performance in Introduced Canada Thistle

Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations. Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions (nutrient stress, shading, simulated herbivory, drought, and mowing), to evaluate whether native and introduced individuals differ in performance or stress tolerance. An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse. Introduced populations tended to be larger in size, but no trade-off of stress tolerance with performance was detected; introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens. We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments, consistent with recent climate adaptation within the introduced range. Our results are consistent with rapid adaptation of introduced populations, but, contrary to predictions, the evolution of invasive traits did not come at the cost of reduced stress tolerance.

Saving threatened plant species: Reintroduction of Hill's thistle (Cirsium hillii. (Canby) Fernald) to its natural habitat

Hill’s thistle (Cirsium hillii (Canby) Fernald) is a perennial plant endemic to the Great Lakes region of North America. Hill’s thistle is listed as threatened in Ontario and Canada where it is found in globally rare alvar habitats. The main objective of this study was ex-situ conservation of Hill’s thistle using in vitro culture techniques and reintroduction of micropropagated plants back to their natural habitat in Bruce Peninsula National Park, Ontario, Canada. Two out of twenty-nine available seeds were successfully germinated under in vitro condition. An efficient micropropagation protocol was optimized with 100% survival during acclimatization of plantlets in the greenhouse. Three hundred micropropagated plants were reintroduced to twelve different sites within Bruce Peninsula National Park in June and July 2017. Plants were monitored for survival, rosette growth, and flowering on all sites from 2017–2019. After four months of planting, 67 to 99% of the plants were alive in different sites and 90 to 99% of them survived over winter. In the following years, shoot regeneration and flowering were observed on most sites. This study further confirms the benefit of plant tissue culture techniques to ensure revival of Hill’s thistle ecological biodiversity through the reintroduction of micropropagated plants. This approach consisting of the components of conservation, propagation, and reintroduction (CPR) may potentially serve as a model for saving and enriching other species at risk.

Antifungal and Herbicidal Effects of Fruit Essential Oils of Four Myrtus communis Genotypes

The chemical composition of the essential oils isolated by hydrodistillation from the fruits of four selected Myrtus communis L. genotypes from Turkey was characterized by GC-FID and GC/MS analyses. 1,8-Cineole (29.20-31.40%), linalool (15.67-19.13%), α-terpineol (8.40-18.43%), α-pinene (6.04-20.71%), and geranyl acetate (3.98-7.54%) were found to be the major constituents of the fruit essential oils of all M. communis genotypes investigated. The oils were characterized by high amounts of oxygenated monoterpenes, representing 73.02-83.83% of the total oil compositions. The results of the fungal growth inhibition assays showed that the oils inhibited the growth of 19 phytopathogenic fungi. However, their antifungal activity was generally lower than that of the commercial pesticide benomyl. The herbicidal effects of the oils on the seed germination and seedling growth of Amaranthus retroflexus L., Chenopodium album L., Cirsium arvense (L.) Scop., Lactuca serriola L., and Rumex crispus L. were also determined. The oils completely or partly inhibited the seed germinations and seedling growths of the plants. The findings of the present study suggest that the M. communis essential oils might have potential to be used as natural herbicides as well as fungicides.

Predicting Developmental Timing for Immature Canada Thistle Stem-Mining Weevils, Hadroplontus litura (Coleoptera: Curculionidae)

Predictions of phenological development for insect biological control agents may facilitate post-release monitoring efforts by allowing land managers to optimize the timing of monitoring activities. A logistic thermal time model was tested to predict phenology of immature stem-mining weevils, Hadroplontus litura F. (Coleoptera: Curculionidae), a biological control agent for Canada thistle, Cirsium arvense L. (Asterales: Asteraceae). Weevil eggs and larvae were collected weekly from Canada thistle stems in eastern North Dakota from May through July during 2010 and 2011. Head capsule widths of sampled larvae were measured at the widest point and plotted on a frequency histogram to establish ranges of head capsule widths associated with each instar. We found head capsule width ranges for first-, second-, and third-instar H. litura larvae were 165-324 µm, 346-490 µm, and 506-736 µm, respectively. Logistic regression models were developed to estimate the proportions of H. litura eggs, first-, and second-instar larvae in the weevil population as a function of thermal time. Model estimates of median development time for eggs, first instars, and second instars ranged from 219 ± 23 degree-days (DD) to 255 ± 27 DD, 556 ± 77 DD to 595 ± 81 DD, and 595 ± 109 DD to 653 ± 108 DD, respectively. Based on model validation statistics, model estimates for development timing were the most accurate for eggs and first instars and somewhat less accurate for second instars. These model predictions will help biological control practitioners obtain more accurate estimates of weevil population densities during post-release monitoring.

Effects of apical meristem mining on plant fitness, architecture, and flowering phenology in Cirsium altissimum (Asteraceae)

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PREMISE OF THE STUDY

Interactions that limit lifetime seed production have the potential to limit plant population sizes and drive adaptation through natural selection. Effects of insect herbivory to apical meristems (apical meristem mining) on lifetime seed production rarely have been quantified experimentally. We studied Cirsium altissimum (tall thistle), whose meristems are mined by Platyptilia carduidactyla (artichoke plume moth), to determine how apical damage affects plant maternal fitness and evaluate both direct and indirect mechanisms underlying these effects.•

METHODS

In restored prairie, apical mining was manipulated on tall thistles by applying insecticide, water, or no spray to apical meristems. We quantified effects on lifetime seed production, plant architecture, and flowering phenology. Seed germinability and seedling mass were evaluated in a greenhouse.•

KEY RESULTS

Apical meristem miners decreased lifetime seed production of C. altissimum, but not seed quality. Higher mortality rates of damaged plants contributed to reduced seed production. Apical damage reduced plant height and increased the proportion of blooming flower heads in axial positions on branches. Apical damage delayed flowering and shortened flowering duration.•

CONCLUSIONS

Apical meristem mining reduced plant maternal fitness. The shift in the identity of blooming flower heads from terminal to axial positions contributed to this reduction because axial heads are less fecund. Shorter, meristem-mined plants may have been more susceptible to competition, and this susceptibility may explain their higher mortality rates. The kinds of changes in architecture and phenology that resulted from apical damage to C. altissimum have been shown to affect floral visitation in other plant species.

Stagonolides G-I and modiolide A, nonenolides produced by Stagonospora cirsii, a potential mycoherbicide for Cirsium arvense

Stagonospora cirsii Davis, a fungal pathogen isolated from Cirsium arvense (commonly called Canada thistle) and proposed as a potential mycoherbicide of this perennial noxious weed, produces phytotoxic metabolites in liquid and solid cultures. Stagonolide, the main phytotoxic metabolite, and five new related nonenolides, named stagonolides B-F, were isolated from the fungus. When grown on solid culture, nonenolide yields increased. A further four nonenolides were isolated and characterized by spectroscopy. Three were new compounds and named stagonolides G-I, and the fourth was identified as modiolide A, previously isolated from Paraphaeosphaeria sp., a fungus separated from the horse mussel. Leaf disk-puncture assays at 1 mg/mL of stagonolides H-I and modiolide A were phytotoxic to C. arvense. Only stagonolide H inhibited chicory seedling root growth. The most potent toxin, stagonolide H, indicated selectivity when tested on leaves of eight different plants: Canada thistle was most sensitive to the compound.

Nonenolides and cytochalasins with phytotoxic activity against Cirsium arvense and Sonchus arvensis: a structure-activity relationships study

A structure-activity relationships study was conducted assaying 15 natural analogues and derivatives belonging to two groups of organic compounds, nonenolides and cytochalasins, for their toxicity against the composite perennial weeds Cirsium arvense and Sonchus arvensis occurring through the temperate region of world. The toxic nonenolides (stagonolide, putaminoxin, pinolidoxin) and cytochalasins (deoxaphomin, cytochalasins A, B, F, T, Z2 and Z3) were isolated from phytopathogenic Stagonospora, Phoma and Ascochyta spp. The pinolidoxin (7,8-O,O'-diacetyl- and 7,8-O,O'-isopropylidene-pinolidoxin) and cytochalasins B (21,22-dihydro-, 7-O-acetyl- and 7,20-O,O'-diacetyl-cytochalasin B) derivatives were obtained by chemical modifications of the corresponding toxins. Among the 15 compounds tested, stagonolide and deoxaphomin proved to be the most phytotoxic to C. arvense and S. arvensis leaves, respectively. The tested phytotoxic nonenolides were stronger inhibitors of photosynthesis in C. arvense leaves than cytochalasines A and B. Stagonolide had less effect on membrane permeability in C. arvense leaves than cytochalasin B. Significant changes of light absorption by C. arvense leaves in visible and infrared spectra were caused by stagonolide. The functional groups and the conformational freedom of the ring, appear to be important structural features for the nonenolides toxicity, whereas and the presence of the hydroxy group at C-7, the functional group at C-20 and the conformational freedom of the macrocyclic ring are important for the cytochalasins toxicity.

Herbicidal potential of stagonolide, a new phytotoxic nonenolide from Stagonospora cirsii

Stagonospora cirsii is a pathogen of Cirsium arvense, causing necrotic lesions on leaves of this noxious weed. The fungus produced toxic metabolites when grown in liquid culture. A new phytotoxin, named stagonolide, was isolated and characterized as (8R,9R)-8-hydroxy-7-oxo-9-propyl-5-nonen-9-olide by spectroscopic methods. Stagonolide was shown to be a nonhost-specific but selective phytotoxin. Leaves of C. arvense were most sensitive and leaves of tomato and pepper (both Solanaceae) were less sensitive to stagonolide, which was assayed at 5 x 10(-3) M, than other plants. Stagonolide assayed at 5 x 10(-6) M was demonstrated to be a strong inhibitor of root growth in seedlings of C. arvense and some other Asteraceae species. Seedlings growth in wheat and radish was much less affected by the toxin, and seedlings of cucumber were insensitive to it.

Changes in nutrient content of Cirsium arvense (L.) Scop. during the vegetation period

Cirsium arvense /L/ Scop. nowadays is popular in all territory of Hungary, it can be found almost on every soil types. Cirsium arvense is one of the most difficulty eradicated weed of the fields, the ruderals, and also the roadsides. On the base of IV. Hungarian Weed Survey 1996-1997, it takes the fifth place in the dominance sequence of the weeds, with 1.8% average covering. In the interest of effective weed control we can know the biological characteristics of the weeds in detail. In our experiments we followed the nutrient uptake and its changing in Cirsium arvense plants. Nitrogen concentration of shoots altered between 1.5-3.6%. We established that plants can uptake potassium in a great quantity. Roots and shoots contained potassium in high concentration between 2.2-5.9%. The maximum of shoot production from the adventitious buds of the roots was in October and the minimum was in April and May.