César Núñez

Palmer Amaranth (Amaranthus palmeri) Identification and Documentation of ALS-Resistance in Argentina

Abstract Palmer amaranth has greatly disrupted agricultural practices in the United States with its rapid growth and rapid evolution of herbicide resistance. This weed species is now suspected in Argentina. To document whether the suspected plant populations are indeed Palmer amaranth, molecular comparisons to known standards were conducted. Additionally, these same plant populations were screened for possible herbicide resistance to several acetolactate synthase (ALS)-inhibiting herbicides. Sequencing data confirmed that suspected populations (A2, A3, A4) were indeed Palmer amaranth. Another population (A1) was tested to determine whether hybridization had occurred between Palmer amaranth and mucronate amaranth the native amaranth species of the region. Tests confirmed that no hybridization had occurred and that A1 was simply a unique phenotype of mucronate amaranth. Each population was screened for resistance to imazapic, nicosulfuron, and diclosulam. All Palmer amaranth populations from Argentina were shown to be resistant to at least one ALS-inhibiting herbicide. The populations were then subjected to further testing to identify the mutation responsible for the observed ALS resistance. All mucronate amaranth populations exhibited a mutation previously documented to confer ALS resistance (S653N). No known resistance-conferring mutations were found in Palmer amaranth. Nomenclature: Diclosulam; glyphosate; imazapic; nicosulfuron; mucronate amaranth; Amaranthus quitensis L; Palmer amaranth; Amaranthus palmeri S. Wats.

Halophytic Flora of Argentina: A Checklist and an Analysis of its Diversity

Saline terrestrial areas represent 3.32 % (92,600 km2) of the Argentine continental territory. Halophytic vegetation is recognized in these regions like edaphic or azonal depending on its association with saline or alkaline soils, not on the ecoregion’s climates. The aims of this contribution are: (1) to provide the first preliminary checklist of native vascular plants growing and completing their life cycle for saline continental areas of Argentina, and (2) to determine its endemism’s, life forms and the ecoregions where these halophytes have been collected. A total of 673 halophytic taxa within 291 genera and 64 families of vascular plants were recorded in the various saline habitats of Argentina, 23.17 % of them are endemics. The halophytic flora represents 6.49 % of the total vascular flora of Argentina. Diversity shows a decreasing tendency from those geosystems that are less affected by hydrohalomorphic processes to those physically characterized by the maximum expression of the flooding-salinization processes. Historical factors along with occupational factors may have contributed in defining the current floristic pattern. Temporal fluctuations in depth, electrical conductivity and ionic composition of groundwater, are the main environmental factors determining the compositional variation of the saline vegetation of the country. Nearly all halophytes are flowering plants, only 0.30 % correspond to Ferns. Dicots comprised 67.31 % of the total (453 taxa in 48 families), while the remainder consisted of 216 taxa of Monocots (14 families), and only two Gymnosperm species. The family with the highest number of genera was: Asteraceae (53) followed by Poaceae (50), Fabaceae (21), Amaranthaceae (13), Solanaceae and Cactaceae (11), and Verbenaceae (10). The most represented genera are Atriplex (19), Lycium (18 taxa), Senecio (16), Chloris (12), Baccharis (12), Deyeuxia and Hordeum (11), Heliotropium (10), Gomphrena, Sporobolus, Solanum and Prosopis (9), Grindelia (8), Distichlis, Junellia, Glandularia (7) and Euphorbia, Aristida, Eragrostis and Festuca with 6 species. Regarding the life-form forms spectra, Hemicryptophytes are the predominant life-form and constitute 52.9 % of all recorded species, followed by Chamaephytes (21.84 %), Therophytes (10.10 %), Phanerophytes (7.13 %), Geophytes (5.79 %), Succulents (2.08 %), and Parasites (0.15 %). In the study area, the largest number of taxa was found in the Dry Chaco (26.95 %) followed by Espinal (18.31 %), Pampa (11.97 %), Patagonian Steppe (8.01 %), Puna (6.97 %), Monte of Plains and Plateaus (9.69 %), Humid Chaco (4.57 %), High Andes (4.06 %), Monte of Hills and Valleys (3.12 %), Ibera Marshes (2.81 %), Parana Flooded Savanna (2.71 %), and Mesopotamian Savanna (0.83 %). When comparing the distribution of total endemics between the different ecoregions, Dry Chaco (33.65 %), appeared with the highest values followed Monte of Plains and Plateaus (18.27 %), Espinal (16.35 %); Patagonian Steppe (12.02 %), Puna (8 %) and Pampa (7.2 %). Surprisingly the number of halophytic taxa that grows in Argentina is very high, representing nearly 22 % of the total number cited for the world.