Thursday, February 26, 2015
Wednesday, February 25, 2015
In the U.S. we may often forget that other countries have their own issues with invasive species. the yellow sugarcane aphid (Sipha flava) was recently found in northeast Spain in two different municipalities, La Selva del Camp (province of Tarragona) and Blanes (province of Girona) and is believed to have come to Spain by way of north Africa. While surgarcane is not a major crop in Europe, the aphid is known to feed on other species of grasses and it is not known what the impact may be on other important grass crops in Europe, such as rice and corn.
For more information on the find: Yellow Sugarcane Aphid Detected in Continental Europe
|Sipha flava by Kansas Department of Agriculture Archive, Bugwood.org|
For more information on the find: Yellow Sugarcane Aphid Detected in Continental Europe
Tuesday, February 24, 2015
For the first time, University of Georgia researchers have successfully cryogenically frozen germplasm from hemlock trees being wiped out across the eastern U.S. by an invasive insect. They've also unlocked a new way to clone the few hemlock trees apparently fighting off the hemlock woolly adelgid, which could potentially lead to a solution for the pest.
In a new paper published in Trees-Structure and Function, researchers in UGA's Warnell School of Forestry and Natural Resources outline how they were able to generate hemlock tissue cultures, cryogenically store them and then grow plants from the cultures after thawing them several months later-the first to successfully do so.
As part of their efforts to freeze the germplasm, they also developed a method that will allow them to clone hemlocks, particularly important as they seek to propagate trees naturally resistant to the insect that has destroyed millions of hemlocks in 18 states since it was accidently introduced into the eastern U.S.
There are only two native hemlock species in the eastern U.S.-eastern and Carolina-and both are in terrible danger from an insect that first appeared in Virginia in the 1950s. The hemlock woolly adelgid, a pest native to East Asia, kills hemlocks possibly by injecting a toxin into the trees while feeding on sap. It has spread from Virginia and virtually exploded in the Appalachians, said Warnell professor Scott Merkle.
"It looks like a bomb went off where there were once pure hemlocks," Merkle explained. "It's just dead trees because there doesn't seem to be much natural resistance."
Merkle, who is also Warnell's associate dean of research, was lead author on the paper and worked with Warnell researchers Paul Montello, Hannah Reece and Lisheng Kong.
Hemlocks protect stream banks from erosion, provide food and shelter for deer and other wildlife and keep trout streams cool with their shade. Because of its importance to forest ecosystems, researchers say it is vital that the tree be preserved.
One 2009 study by the U.S. Forest Service said woolly adelgids could kill most of the hemlocks in the Appalachian region in a matter of years if the insect remains unchecked. Unfortunately, researchers are not yet sure how the insect is even killing hemlocks. They believe that it is inserting its stylet-a sharp, pointed nose-under the leaf, through the base and into the tissue that carries sugar around the tree. The tree then essentially shuts down, loses needles and eventually dies.
A number of researchers are studying ways to fight the infestation, including the possibility of introducing some sort of biocontrol or predator to eat the adelgids. Merkle is looking at ways to not only introduce natural resistance to newly planted hemlocks, but also to successfully store hemlock germplasm cryogenically to conserve it in case a solution isn't found before they are wiped out.
Long-term storage of hemlock germplasm has been hindered because seeds from the trees have lost viability after being stored under refrigeration after two to four years, meaning that once planted, they won't germinate and grow into thriving plants. The U.S. Forest Service is growing collections of hemlocks outside the range of the adelgid to conserve their germplasm, but this approach requires maintenance of the trees in areas where hemlocks are not found naturally.
Merkle and his research team took a different approach to standard storage methods: Using seeds from surviving hemlocks collected by cooperators at the Alliance for Saving Threatened Forests and North Carolina State University, they created in vitro cultures of a number of eastern and Carolina hemlocks that they then froze in liquid nitrogen at minus 196 degrees Celsius-something no one else had successfully done. The researchers cryofroze several samples from different hemlock lines from around the Southeast for several months, then thawed them out, allowed them to regrow and began to produce trees from them. Of the five hemlock lines they tested, all samples of three Carolina lines and one eastern hemlock line regrew after coming out of cryostorage.
Merkle says the ability to cryostore and recover hemlock cultures, followed by production of new trees from them, provides a practical approach for storing the germplasm of a large number of trees indefinitely, so that the species can be repopulated once a system to deal with the adelgid is in place.
Being able to grow them after they're thawed won't make them resistant to the woolly adelgid, Merkle said, but it does mean that if need be, researchers might be able to save samples of the hemlocks from extinction. These cultures also allow the researchers to assist with testing other methods of introducing resistance to the insect, including trying to create clones of hybrids with Asian hemlocks that do have a natural resistance to the woolly adelgids.
Some individual hemlock trees in the U.S. appear to be naturally resistant, Merkle said, so he and his team are working on ways to determine if the resistance is genetically based. They'll do that by collecting seeds from these trees that have survived the insect infestation and creating embryogenic cultures that they can then use to clone single trees. Because these surviving trees are all genetically different, researchers can't really tell what key factor makes them resistant to the woolly adelgid.
But if 20 trees are planted that are all members of the same clone, clonal testing can be done to try to narrow down why particular trees can fight the pest. And once a genetic line is identified that is resistant, Merkle said, "You can then hand seedlings out to people to start planting."
The study is available online at http://link.springer.com/article/10.1007/s00468-014-1084-0.
Glyphosate resistant kochia (Kochia scoparia) was first confirmed in Kansas in 2007 (http://www.weedscience.org/). Since then, it has been found in South Dakota, North Dakota, Montana, Colorado, Oklahoma, Nebraska, Oregon, Idaho, Wyoming, Alberta (Can), Manitoba (Can), and Saskatchewan (Can). In fact, in Montana and the three Canadian provinces, there have been populations of kochia with multiple herbicide resistance (resistance to more than one site of action) found; kochia resistant to glyphosate and another type of herbicide. Discovering how a species evolves resistance to a herbicide can aid researchers in not only learning about the plants, their genetic make-up, and how they are able to withstand stressful conditions, but also may help the researchers to figure out ways to work around the mechanism causing the resistance.
Mostly, instances of glyphosate resistance in other species have been via:
- Reduced translocation - i.e. herbicide is absorbed by the plant, but not moved within the plant to where it has an effect (target site), or
- Mutations in the target site - change within the plant at the target site which prevents the herbicide from interacting or binding (ex: the plant changes the "locks" (target site) in its "house" (entire plant) and so the "key" (herbicide) can't get in.)
A recent paper by Jugulam et al. (Tandem amplification of a chromosomal segment harboring 5-enolpyruvylshikimate-3-phosphate synthase locus confers glyphosate resistance in Kochia scoparia, 2014) evaluated how some kochia populations are now resistant to glyphosate. They found that the type of resistance displayed by the kochia populations they observed was amplification of the genes which produce EPSPS (the target for glyphosate). Resistant populations were found to have 9-16 copies of the gene, whereas sensitive populations have only 2 copies. Having more copies of the gene means that more of the target (EPSP) can be produced than the recommended amount of glyphosate will be able to bind up and so the plants can survive when sprayed. This is the first reported instance of gene amplification on a single chromosome conferring field-evolved herbicide resistance in weeds.
|Kochia scoparia. Leslie J. Mehrhoff, University of Connecticut, Bugwood.org|
For more on the discovery: Invasive weed Kochia's resistance to well-known herbicide stems from increase in gene copies
European Union Regulation on the prevention and management of the introduction and spread of invasive alien species
Regulation No 1143/2014 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
of 22 October 2014 went in force January 1, 2015.
Invasive Alien Species are animals and plants that are introduced accidentally or deliberately into a natural environment where they are not normally found, with serious negative consequences for their new environment. They represent a major threat to native plants and animals in Europe, causing damage worth millions of euros every year.
The new European Union Regulation on invasive alien species was published in the Official Journal on 4 November 2014. It went into force on 1 January 2015. The new regulation seeks to address the problem of invasive alien species in a comprehensive manner so as to protect native biodiversity and ecosystem services, as well as to minimize and mitigate the human health or economic impacts that these species can have.
The regulation foresees three types of interventions; prevention, early warning and rapid response, and management. A list of invasive alien species of Union concern will be drawn up and managed with Member States using risk assessments and scientific evidence.
Click here for the Regulation on Invasive Alien Species
For background information and The EU Commission Communication click Towards an EU Strategy on Invasive Species.