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October 13, 2011
· Weed control taking a step backwards
· Brazil’s GM bean stirs political stew
· EU moves to ‘green’ its farm reform
· Soil testing to reduce nitrogen pollution
· So one yeast cell says to the other …
Weed control taking a step backwards
(University
of Illinois via ScienceDaily.com) – 2,4-D is
coming back. What many might consider a "dinosaur" may be the best
solution for growers fighting weed resistance today, said Dean Riechers,
"Farmers can't imagine going back to 2,4-D or other auxin herbicides," Riechers said. "But herbicide resistance is bad enough that companies are willing to bring it back. That illustrates how severe this problem is."
In a recently published article in Weed Science, Riechers and his team of research colleagues suggest that tank-mixing auxinic herbicides with glyphosate may be the best short-term option available to farmers interested in broad-spectrum, postemergence weed control.
"Resistance has become a big problem," Riechers said. "In 1997, researchers predicted that glyphosate resistance would not be a big issue in Round-Up Ready crops. For the most part, they were right. But they underestimated a few weed species and resistance mechanisms."
Since the 1950s, 29 auxin-resistant weed species have been discovered worldwide. In comparison, 21 glyphosate-resistant weed species have been discovered since 1996 when Round-Up Ready soybeans were commercialized. And interestingly enough, two of the most problematic weeds in Round-Up Ready soybean and cotton -- common waterhemp and Palmer amaranth -- are not yet on the list of auxin-resistant weeds, Riechers said.
Ideally, chemical companies would come up with a new herbicide to fight these resistant weeds. But new herbicide development is expensive and time-consuming. Riechers said he does not know of any new compounds on the horizon.
"If we don't find completely novel and new herbicides,
our next best bet is to mix glyphosate and another herbicide with relatively
minor resistance problems," Riechers said.
"Auxin resistance is not considered a huge
problem in the
Why have the auxinic herbicides escaped the resistance problems of the more modern herbicides used today?
Riechers said there are three major reasons that help explain why resistance to auxin herbicides has not become a big problem yet. First, the auxin family of herbicides has a very complicated mode of action. In theory, a weed would have to develop a very complicated resistance method to overcome it. Riechers said the auxin herbicide family is very unusual because it has multiple target sites, which were only recently discovered.
"In addition, resistance to these compounds is rare because a plant that evolves resistance may have a fitness cost," he said. "The resistance mechanism that overcomes the herbicide could have a negative consequence to the plant in absence of the herbicide. Basically, for auxin herbicides there may be a 'penalty' to having resistance."
The third explanation is that auxin herbicides have rarely been relied on by themselves and are normally mixed with other herbicides. A good example is the frequent use of several auxinic herbicides in tank mixes for weed control in home lawncare and golf course applications.
Some farmers are concerned about going back to 2,4-D and other auxin herbicides because they are considered old compounds that tend to drift and move off-target to sensitive plants. Riechers said Monsanto and Dow AgroSciences have announced that they are working on new formulations to reduce drift, and agricultural engineers are exploring spray application technology to reduce the problems, too.
"This is a risk/reward decision," Riechers said. "If you have a huge resistance problem in your field and are concerned about losing yield, this may be your best solution for now. The alternative is to give up and do nothing. For some growers, this technology may be worth the risk because they have no other choices."
So the question remains. How long will it take for plants to form resistance to the combination of auxin herbicides and glyphosate?
"We are trying to predict the future, but all we can do at this point is speculate," Riechers said. "However, we can use the past to help us make wise choices for the future. We have resistance to almost all herbicide families now. Tank-mixing auxin herbicides with glyphosate may work for the short term, but I expect that auxin resistance will likely increase over time. Nature always finds a way."
Until the next novel herbicide comes out, Riechers said you only have to look back at what happened with glyphosate to see how important it is to be a good steward by using herbicides in a sustainable, beneficial way.
Brazil
(naturenews) – Paired with rice
or steeped in feijoada stew, beans are an essential
feature of Brazilian cuisine. So great is
Approved on 15 September by the Brazilian National Technical Commission on Biosafety (CTNBio), the transgenic bean uses RNA interference to shut down replication of the virus (K. Bonfim et al. Mol. Plant Microbe Interact. 20, 717–726; 2007). A product of more than a decade of home-grown research, the bean could begin appearing on tables across the country as early as 2014.
"It is an extremely important crop for our small
farmers," says Francisco Aragăo, a plant
geneticist who led the work for the Brazilian Agricultural Research Corporation
(EMBRAPA), the research arm of the Ministry of Agriculture, based in
The biosafety commission has taken
a favourable position towards biotechnology in past
years, helping
Environmental groups and a presidential advisory panel, the
National Council for Food Security and Nutrition, have called for more
transparency in biotechnology science and decision-making, and increased research
to rule out health risks stemming from the bean. Nodari,
a former member of CTNBio who has long questioned
transgenic crops, says that the commission improperly granted EMBRAPA's request for confidentiality regarding key aspects
of the genetic engineering. "We don't know what we will be eating tomorrow
in
Current members of the commission have aggressively defended their decision. In a media interview after the decision last month, Edilson Paiva, president of CTNBio, said that Nodari and other opponents of genetic engineering are taking an ideological position aimed at "promoting fear and uncertainty" as they demand that scientists provide the impossible: guarantees of absolute safety.
EMBRAPA says that it must keep core information about genetic insertions confidential, to allow it to patent the work. The details will help the agency to develop bean varieties that are resistant to the golden mosaic and similar viruses, says Aragăo, who is a member of CTNBio but abstained from the decision on the beans.
Aragăo notes that safety analyses
showed no reason for concern regarding the beans. He says that whereas some
other GM crops produce unfamiliar proteins that could in theory cause an
allergic reaction when eaten, the GM pinto bean produces only small snippets of
RNA, tailored to react with and neutralize RNA from any invading virus. Herve Vanderschuren, a
biotechnologist at the Swiss Federal Institute of Technology in
With approval secured, EMBRAPA must now conduct a further
round of field trials to ensure that the transgenic bean produces yields comparable
to those of existing varieties. Aragăo hopes that the
strain will not only boost yields, but also enable planting on as much as
200,000 hectares of land on which the golden mosaic virus is so prevalent that
farmers cannot grow beans at all at present.
"The best part of this story is that the bean was
developed in
EMBRAPA is already looking to develop other virus-resistant beans, including common black beans and the popular carioca bean. "It's very easy to transfer this gene to any other variety," says Aragăo. "That's the next step."
EU moves to ‘green’ its farm reform
(AFP via Yahoo!) – The EU called for a greener, fairer farm policy on Wednesday as it moved to radically overhaul its Common Agricultural Policy (CAP) by capping subsidies and tying them to environmental concerns.
"The CAP must be redefined," EU Agriculture Commissioner Dacian Ciolos told the European Parliament, outlining a sweeping plan to reform the EU's controversial farming subsidies from 2014 -- a plan set to trigger months of heated debate.
There was immediate criticism of the proposals from
Among proposals to rethink the CAP, which traditionally accounts for about 40 percent of the bloc's annual spending of nearly 140 billion euros, is a call for 30 percent of EU direct farm subisidies to be conditional on respect for the environment.
The measures include crop diversity, maintaining permanent pastures and creating ecological fallows that are havens for plants, animals and insects on at least seven percent of arable land.
Ciolos said the reforms would lead
to an agricultural U-turn, putting
To even out subsidies in the interests of fairness, Ciolos wants to cap payouts to farmers at 300,000 euros ($424,000) per year. In addition, levies would be applied progressively on all payments exceeding 150,000 euros.
While highly-mechanised large farms would be hit, those using a large number of workers could win exemptions.
In a response,
But she said "overall we're disappointed" by proposals that "actually take us backwards".
In
He said the new environmental measures would entail "more spending for companies and entail a huge bureaucracy without bringing real benefits."
Also in the interests of the environment, Ciolos is proposing to gradually favour extensive rather than intensive farming by progressively calculating subsidies per hectare (acre) from 2014 to 2019, rather than basing payments on production, as has often been the case.
The proposals are intended also to address squabbling between member states on their respective quotas, with newer members from eastern Europe complaining more money goes to founder states.
However, while France, currently the top beneficiary, would see a 1.5 percent fall in the 2014-2019, it would remain the largest recipient.
"Politics, especially at the European level, is the art of what is possible," Ciolos said. "The most important thing is to launch movement in the right direction."
Responding to criticism from the EU's Court of Auditors, the commission proposals also seek to ensure subsidies go only to "active farmers" -- rather than to airports or golf-clubs, as has sometimes been the case.
The reform proposals will have to be approved by both the parliament and all member states before taking effect.
In other criticism, Europe's leading farmers' organisation Copa-Cogeca said
that "at a time when the Chinese are massively purchasing land in
Bio-innovation leader Novozymes meanwhile said the proposals failed to go far enough.
"A bio-based economy can foster the transition of
Soil testing to reduce nitrogen pollution
(CBCnews) – The P.E.I. Department of Agriculture is
hoping new research can help keep
The department is sponsoring research into how to determine exactly how much nitrogen fertilizer a field requires.
"We want to get it down to a little finer detail now, especially in a system where all our drinking water is derived from groundwater," departmental research director Barry Thompson told CBC News Tuesday.
Thompson said farmers have to estimate the amount of nitrogen fertilizer they need, and that can lead to too much nitrogen being sprayed on crops. That excess nitrogen can end up in groundwater and people's wells.
Thompson believes a new soil test should offer more accurate information.
David Burton, a soil scientist at
"Our hope is that it would allow the producer to
produce their crop more profitably, but also reduce any impacts on the
environment," said
Some research plots have used up to 50 per cent less
nitrogen, said
P.E.I. potato farmer Bertha Campbell has some doubts that there will be big savings for her in using the tool. It might provide more accurate readings, she said, but she and other farmers are already using as a little fertilizer as possible because of the high cost.
"You don't want to put too much on cause it costs too much," she said.
"You want to be bang on."
Refining the tool for use by farmers will take another few years.
The nitrogen testing tool is part of a larger program being developed call AgriLogic, which tracks farm inputs with the aim of reducing the impact on local waterways.
So one yeast cell says to the other …
(Discover) – This single-celled fungus–for which we should give thanks for bread, beer, and wine–can reproduce in several ways. Most of the time, it produces buds that eventually split off as free-living cells of their own. Its daughters are identical to itself, carrying the same two sets of chromosomes.
Sometimes, however, life gets rough for yeast, and they respond by making spores, each with only one set of chromosomes. Later, when times get better, the spores can germinate. In some cases the yeast cells that emerge just grow and divide. But they can also have sex. One yeast cell merges with another one, combining their DNA to produce a new yeast cell with two sets of chromosomes.
What makes yeast sex especially interesting is that the cells communicate with each other first. A yeast cell produces a pheromone that can cause another cell to stop dividing and start crawling towards the source of the signal. These pheromones divide yeasts into two groups. Yeast cells carry one of two genes for making pheromones and will only mate with yeast cells that produce the opposite type.
But if you surround a yeast cell with a ring of pheromone producers, the yeast will not just pick a partner at random. It will exercise a choice. The cell will measure the pheromones coming from each suitor, and it will creep its way to the strongest source.
Some scientists have suggested that natural selection favors this choice because it lets yeast be efficient about sex. Rather than creep a long way to find a mate, a yeast cell can just love the one it’s with. But there are some problems with this explanation.
First off, yeast make a lot of pheromones–much more than they would need simply to be detected. For another thing, yeast cells vary in how much pheromone they make. A strong pheromone maker will be more likely to attract a mate than a weak one that’s closer. What’s more, when a pheromone-producing yeast cell detects a signal from the opposite mating type, it cranks up its own signal. If you didn’t know better, you might think yeast cells were trying to get some attention.
In fact, some scientists think that yeast are doing exactly that. They argue that yeast cells release pheromones like a love song, in order to attract mates.
Carl Smith and Duncan Grieg, two evolutionary biologists at University College London, wondered if the same pressures drove the evolution of yeast pheromones that have driven the evolution of more familiar kinds of sexual displays, like peacock tails, frog croaks, and elk horns. According to one particularly influential hypothesis, the Handicap Principle, females could benefit from being choosy about mates if that choice led them to have more success reproducing. Of course, a male frog can’t offer a female frog a DNA test documenting his good genes. So he needs some way of advertising his quality. A song or a horn or a fragrance are all possible ways to send this signal.
The problem with this sort of communication is that it can be hacked. A weak male can, in theory, channel some extra energy into building a false sexual display. If some males start to cheat, females who are choosy will end up with no advantage over other females. Female choice will disappear, and male displays will vanish as well.
Honesty is thus crucial to the evolution of sexual displays. And one way for displays to be honest is for them to be expensive. A weak male with fewer resources will have a harder time producing an expensive display than a strong one. In effect, a long-tailed widowbird is saying, “I’ve got so much to offer that I can waste a lot of energy on these magnificent tail feathers.”
To see if yeast were wooing each other with expensive signals, Smith and Grieg disabled the genes in some cells so that they could not make pheromones. Then they compared how fast healthy and engineered yeast cells reproduced asexually. The quiet yeast grew far faster, the scientists found, presumably because they no longer had to use up a lot of energy making pheromones. This result confirmed a key prediction of the handicap principle: a signal has to be costly. In fact, yeasts can suffer a 30% drop in their viability by making pheromones.
But some yeast pay a bigger price than others. Some strains of yeast Smith and Grieg studied carried mutations that caused them to grow relatively slowly, while other cells could grow faster. Smith and Grieg found that when they disabled pheromone genes in low-quality yeast, the cells enjoyed a much bigger boost than high-quality yeast. In other words, making pheromones is a bigger sacrifice for low-quality cells than for high-quality ones. That difference could help ensure that pheromones remain an honest signal.
Finally, the scientists compared how much pheromones each kind of yeast produced. They found that yeast of higher quality churned out more pheromones than yeast of lower quality. So a yeast that chooses to mate with a strong pheromone producer will be endowing its offspring with good genes.
Smith and Grieg’s experiment makes me think about the yeast
in a glass of wine in a different way: I now imagine an ocean of love songs.
But it also makes me appreciate just how far-reaching
End Transmission