Transgenic crops: Engineering a more sustainable agriculture?

Transgenic crops currently available foruse potentially provide environmental benefits, suchas reduction in insecticide use and substitution ofless toxic for more toxic herbicides. These benefitsare contingent on a host of factors, such as thepotential for development of resistant pests,out-crossing to weedy relatives, and transgenic cropmanagement regimes. Three scenarios are used toexamine the potential sustainability of transgeniccrop technologies. These scenarios demonstrate thatexisting transgenic varieties, while potentiallyimproving the sustainability of agriculture relativeto existing chemical based production systems, fail inenabling a fully sustainable agriculture. Genetictraits that have a higher potential for promoting asustainable agriculture have been precluded fromdevelopment for a number of reasons. These include thelack of EPA and USDA regulatory policies thatexplicitly promote sustainable traits; the structureof the agricultural biotechnology industry, which isdominated by agricultural chemical companies; andpatent law and industry policies that proscribe farmhouseholds from saving transgenic seed and tailoringtransgenic crops to their local environmentalconditions – ecological, social, and economic.     

Migrations and movements of Atlantic tarpon revealed by two decades of satellite tagging

Understanding large‐scale migratory behaviours, local movement patterns and population connectivity are critical to determining the natural processes and anthropogenic stressors that influence population dynamics and for developing effective conservation plans. Atlantic tarpon occur over a broad geographic range in the Atlantic Ocean where they support valuable subsistence, commercial and recreational fisheries. From 2001 through 2018, we deployed 292 satellite telemetry tags on Atlantic tarpon in coastal waters off three continents to document: (a) seasonal migrations and regional population connectivity; (b) freshwater and estuarine habitat utilization; (c) spawning locations; and (d) shark predation across the south‐eastern United States, Gulf of Mexico and northern Caribbean Sea. These results showed that some mature tarpon make long seasonal migrations over thousands of kilometres crossing state and national jurisdictional borders. Others showed more local movements and habitat use. The tag data also revealed potential spawning locations consistent with those inferred in other studies from observations of early life stage tarpon leptocephalus larvae. Our analyses indicated that shark predation mortality on released tarpon is higher than previously estimated, especially at ocean passes, river mouths and inlets to bays. To date, there has been no formal stock assessment of Atlantic tarpon, and regional fishery management plans do not exist. Our findings will provide critical input to these important efforts and assist the multinational community in the development of a stock‐wide management information system to support informed decision‐making for sustaining Atlantic tarpon fisheries.     

Nitrogen requirements for deficit-irrigated bermudagrass (Cynodon spp.) fairways in South Florida

Several new bermudagrass cultivars are available and commonly used on golf course fairways. However, little is known about their cultural requirements or how these cultivars perform under lower inputs regimes. A 2-year study was conducted at University of Florida, Fort Lauderdale Research and Education Center, to assess performance of four hybrid bermudagrass [Cynodon dactylon L. Pers. X Cynodon transvaalensis (Burtt-Davy)] cultivars (‘Latitude 36’, ‘Tifway 419’, ‘TifGrand’ and ‘TifTuf’), and 2 common bermudagrass (Cynodon dactylon L. Pers.) cultivars (‘Bimini’ and ‘Celebration’) irrigated at either 50% or 80% reference evapotranspiration (ET_o) and fertilised at either 0, 146, 244, or 342 kg N ha⁻¹ year⁻¹. Plots were evaluated monthly for turfgrass quality, dark green colour index (DGCI), normalised difference vegetation index (NDVI), and Chlorophyll Index, and seasonally for N tissue content. Plots watered at 80% ET_o enhanced bermudagrass quality compared to 50% ET_o, DGCI and NDVI only in two months out of 24. Latitude 36 and Celebration were the top-rated cultivars, and their quality was not affected by no N fertilisation. Conversely, TifGrand, TifTuf and Tifway that received no N fertilisation resulted in insufficient quality during the second year of the study. Insufficient quality may be linked to reduced N metabolization compared to the highest rated cultivars. Results show that new cultivars such as Latitude 36 and Bimini could be maintained at sufficient quality levels with reduced water and N inputs in South Florida.