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Archive for the ‘Biotechnology’ Category

Study identifies ways to encourage ‘refuge’ planting, slowing resistance to Bt crops

April 3, 2017 by Matt Shipman

Study identifies ways to encourage ‘refuge’ planting, slowing resistance to Bt crops
Credit: Alexander Steinhof

A new study from North Carolina State University finds a significant shortfall in the amount of “refuge” cropland being planted in North Carolina – likely increasing the rate at which crop pests will evolve the ability to safely devour genetically engineered Bt crops. However, the study also identified actions that may make farmers more likely to plant refuge crops in the future.

For about 20 years, have made use of Bt to limit crop damage from pests. Bt crops, including corn, are genetically engineered to produce proteins from the Bacillus thuringiensis (Bt) bacterium. These proteins are harmless to vertebrates, but toxic to a specific class of invertebrate crop pests.

To date, these Bt crops have been remarkably successful. However, insect pests have shown the ability to evolve resistance to Bt proteins. In order to slow down the development of Bt resistance, farmers who plant Bt crops are urged to plant a certain percentage of their fields with non-Bt crops – called refuge crops. In fact, in the case of Bt corn, farmers are required to plant a section of their fields with refuge crops.

That’s because refuge crops provide fodder for insect pests that are not resistant to Bt proteins. These pests are then able to breed with their Bt-resistant counterparts, diluting Bt resistance in the overall population.

But compliance with planting refuge crops is variable. Some growers plant too little of their fields with Bt crops, and some don’t plant refuge crops at all.

This raised some interesting questions for Dominic Reisig, an associate professor of entomology at NC State and an extension specialist at the Vernon James Research & Extension Center in eastern North Carolina. Reisig divides his time between conducting research and helping farmers deal with problems related to insect . Recently, Reisig began to wonder: How many growers aren’t planting sufficient refuge crops? Do growers understand the rationale behind refuge crops? What can influence whether growers plant refuge crops? And what factors affect a grower’s willingness to plant refuge crops?

To address these questions, Reisig talked with several hundred corn growers in more than a dozen counties in eastern North Carolina.

Reisig found that approximately 40 percent of corn growers who used Bt corn would not plant refuge crops in the next growing season, while another 25 percent weren’t sure. However, a majority of growers did understand the value of refuge crops – and felt they should be planting them.

Reisig also found that there was a high correlation between how much land was devoted to corn, cotton and soybeans in a county, and how likely farmers in that county were to plant refuge crops. The more land being devoted to crops, the more likely farmers were to plant refuge.

“Some of the resistance to planting refuge may be due to a lack of understanding about how important refuge crops are,” Reisig says. “But it’s also likely to be a function of the fact that many of the farms in counties with low refuge crop compliance are smaller operations. Growers may simply be trying to get more crop yield from their acreage – though there is little evidence of short-term benefit, and ample evidence of long-term risk from Bt-resistant pests.”

Reisig also found that better enforcement and peer pressure from other farmers weren’t seen as making farmers more likely to plant refuge crops. Instead, growers said that financial incentives – such as rebates on non-Bt seed – would make them more likely to plant crops, as would the availability of high-yield non-Bt seed.

“This study is really a starting point,” Reisig says. “We know this is a problem. I’m looking for partners in the social sciences to help me figure out how we can help growers make informed decisions and protect the long-term viability of their crops.”

Explore further: Armyworms develop resistance to Bt corn

More information: Dominic D. Reisig. Factors Associated With Willingness to Plant Non-Bt Maize Refuge and Suggestions for Increasing Refuge Compliance, Journal of Integrated Pest Management (2017). DOI: 10.1093/jipm/pmx002

Read more at: https://phys.org/news/2017-04-ways-refuge-resistance-bt-crops.html#jCp

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PHYS ORG

March 23, 2017

Novel virus breaks barriers between incompatible fungi
SsMYRV4-mediated enhancement of horizontal transmission between different VCGs effectively prevents and controls Sclerotinia diseases. Credit: Wu S, et al. (2017)

Scientists have identified a virus that can weaken the ability of a fungus to avoid pairing with other incompatible fungi, according to new research published in PLOS Pathogens. By promoting fungal pairing, the virus could aid transmission of additional unrelated viruses between fungi.

Fungi, like all other organisms, can recognize foreign substances; such non-self recognition can help protect against pathogens. Some also use non-self recognition to avoid pairing and sharing genetic material with incompatible strains. The fungus Sclerotinia sclerotiorum, which infects hundreds of plant species worldwide, employs this strategy, which is known as vegetative incompatibility.

While studying S. sclerotiorum, Jiatao Xie of Huazhong Agricultural University, China, and colleagues discovered a they named Sclerotinia sclerotiorum mycoreovirus 4 (SsMYRV4). To better understand this novel virus, they grew infected S. sclerotiorum alongside other vegetatively incompatible strains and investigated the molecular effects.

The researchers found that SsMYRV4 decreased expression of S. sclerotiorum genes that promote vegetative incompatibility. Vegetative incompatibility is a molecular process that normally causes when two incompatible strains touch each other; in this study, Xie’s team found a reduction in the amount of cell death that normally occurs in intermingled colonies of incompatible strains.

S. sclerotiorum infected with SsMYRV4 successfully made connections with incompatible by fusing filamentous structures known as hyphae. To investigate the consequences, the scientists grew SsMYRV4-infected fungi alongside fungi infected with other unrelated viruses. They found that the unrelated viruses were able to pass through the fused hyphae, crossing between fungal pairs.

Vegetative is considered a significant obstacle to using viruses to effectively control fungal diseases. These new findings could point to a new strategy that uses SsMYRV4 to weaken barriers between fungi. They could also improve understanding of virus ecology and evolution.

Explore further: Potential biological control agents found for fungal diseases of soybean

More information: Wu S, Cheng J, Fu Y, Chen T, Jiang D, Ghabrial SA, et al. (2017) Virus-mediated suppression of host non-self recognition facilitates horizontal transmission of heterologous viruses. PLoS Pathog 13(3): e1006234. DOI: 10.1371/journal.ppat.1006234

Read more at: https://phys.org/news/2017-03-virus-barriers-incompatible-fungi.html#jCp

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US EPA Approves Three Varieties of GE Potatoes

The U.S. Environmental Protection Agency approved the planting of three types of genetically engineered potatoes that resist the pathogen that caused the Irish potato famine. According to EPA, the GE potatoes are safe for the environment and safe to eat.

The GE potatoes were developed by J.R. Simplot Co. According to Simplot, the GE potatoes only contain potato genes and that the resistance to late blight trait originated from an Argentine potato variety that naturally exhibited defense against the pathogen.

The decision by EPA is consistent with the safety clearance given by Food and Drug Administration in January 2017.

Read more from AP. View the notices (for Y9 and X17) from the EPA website.

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CropBiotechUpdate
http://www.isaaa.org/kc/cropbiotechupdate/article/default.asp?ID=15083

Researchers Discover Off-Switch to CRISPR-Cas9 Gene Editing System

Researchers from the University of California, San Francisco have found a way to switch off the CRISPR-Cas9 gene editing system using newly identified anti-CRISPR proteins that are produced by bacterial viruses. The newly discovered anti-CRISPR proteins could enable more precise control in CRISPR applications, but also provide a fail-safe to quickly block any potentially harmful uses of the technology.

To find an anti-CRISPR protein that would work against the CRISPR-Cas9 system used in most labs which depends on a protein called SpyCas9 as its targeted DNA clippers, the researchers thought that they should be able to identify bacteria with inactivated CRISPR systems. This can be conducted by looking for evidence of so-called “self-targeting” – bacterial strains where some virus had successfully gotten through the Cas9 blockade and inserted its genes into the bacterial genome.

The research team examined nearly 300 strains of Listeria, and found that 3 percent of strains exhibited “self-targeting.” Further investigation isolated four distinct anti-CRISPR proteins that proved capable of blocking the activity of the Listeria Cas9 protein, which is very similar to SpyCas9.

Further research showed that two of the four anti-CRISPR proteins, called AcrIIA2 and AcrIIA4 by the researchers, worked to inhibit the ability of the commonly used SpyCas9 to target specific genes in other bacteria, as well as in engineered human cells. Together, the results suggest that AcrIIA proteins are potent inhibitors of the CRISPR-Cas9 gene editing system as it has been adopted in labs around the world.

For more details, read the news release from UC San Francisco.

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Australian researchers say they have developed a sustainable way to protect crops from pests and diseases, by spraying them with a special clay.

The discovery could also help the rural sector in the fight against pesticide resistance in certain crops.

The spray is known as ‘BioClay’ and was developed by the Queensland Alliance for Agriculture and Food Innovation (QAAFI) and the Australian Institute for Bioengineering and Nanotechnology (AIBN).

“It will produce huge benefits for agriculture in the next several decades, and the applications will expand into a much wider field of primary agricultural production,” Professor Xu from AIBN said.

Agricultural biotechnologist and research leader, Neena Mitter, said the clay spray contained molecules that helped protect crops from invading pathogens.

“BioClay is a beautiful combination of biology and nanotechnology,” she said.

“Once it is applied, the plant thinks it is being attacked by a disease or pest insect and responds by protecting itself from the targeted pest or disease.

“It is a [pest] control measure, which is environmentally sustainable, ecologically safe, stable, and easy to be adopted by farmers to protect their crop from diseases.”

In the trials the researchers were able to protect a crop of tobacco from invading diseases for up to 20 days using the BioClay spray.

The team also trialled the spray on cowpeas and capsicums, and think it could also work for cotton and a range of other crops.

Chemical companies and researchers around the world, including Monsanto, are in a race to develop and commercialise similar technology.

However, the QAAFI and AIBN team is the first to produce long-lasting results, and to have the findings published.

Professor Mitter said she hoped to have a commercial product on the shelves in three to five years.

“There is a lot of work going on in using gene silencing in a spray, but I think we are fairly progressed in our own BioClay product,” she said.

How it works

The clay contains molecules of double-stranded ribonucleic acid (RNA), a sibling of DNA, which can switch off gene expression and prevent plants from being susceptible to a virus.

The clay helps the molecules stick to the plant, and then peels off over time.

This means once a virus comes into contact with the RNA on the plant, the plant will kill the pathogen.

Using RNA as a defence against disease is not a new concept, and researchers have applied it to crops before.

However, the new aspect is Professor Mitter’s invention of the spray on clay to help bind the RNA molecules to the plant.

RNA is traditionally used to silence genes in the genetic modification process.

However, Professor Mitter said her BioClay process did not genetically modify plants, because the process involved collecting RNA from a virus and turning it against itself, rather than changing the genome of a plant.

“We are using that RNA to silence a gene in the pathogen and that RNA has nothing to do with the plant, and has no similarity to the crop,” she said.

“We are not modifying the genome of the plant, we are not doing genetic modification; we are just spraying it with RNA.”

The researchers hope BioClay can be used as an alternative to traditional chemicals, to prevent crops from building up pesticide resistance.

“If you use a chemical, pathogens are clever and can adapt, but with BioClay we use RNA from the pathogen to kill the pathogen itself.” Professor Mitter said.

“So we are strongly placed in terms of addressing the issue of pesticide resistance.”

Can farmers afford it?

Finding a cost-effective way of applying RNA pesticides to plants has been difficult until now.

A criticism of using RNA to protect crops in the past has been that the technology was too expensive, but Professor Mitter said it was becoming cheaper and farmers would be able to afford it.

“The aim is to make it affordable because the clay part is cheap to manufacture,” she said.

“The production of RNA could be expensive but companies around the globe are working on mass producing RNA at a very cheap scale.

“I’m hoping this product will be commercially viable.”

Topics: pest-managementruralpestsenvironmentcrop-harvestingagricultural-cropsvegetablesfruit,brisbane-4000

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Grahame Jackson
24 Alt street
Queens Park
NSW 2022
Australia

Phone: +612 9387 8030
Mobile: +61 412 994 206
Skype: gvhjackson

www.pestnet.org
www.ediblearoids.org
www.terracircle.org.au

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Eldana saccharina stem borer

Eldana saccharina

By Josh Lancette

When using Bt crops, a constant concern is preventing insect pests from becoming resistant. According to a paper published in the Journal of Economic Entomology that contains new analysis of previous studies, a common tactic to prevent resistance in Africa might not be working as hoped.

Bt crops are plants that have been genetically modified to express a protein produced by the bacterium Bacillus thuringiensis. This protein is toxic to some insects, so when an insect feeds on the plant, it ingests the protein and dies. These crops are useful because they can provide an alternative to pesticides, which benefits the environment, other beneficial insects, humans that would otherwise come in contact with pesticides, and operators of farms who don’t have the means for large-scale pesticide applications. Furthermore, Bt crops typically are considered safe for consumption by humans and other non-target animals.

Josh Lancette

Josh Lancette

However, while Bt crops have benefits, one risk is that insect populations can grow resistant to them if effective management strategies are not used.

A strategy to prevent insects from becoming resistant to Bt crops is to plant a “refuge” non-Bt crop around the main Bt crop. The idea is that the refuge crop produces non-resistant insects, which then mate with any resistant insects in the main crop, producing mostly non-resistant offspring. So, the non-resistant insects on the main crop die, and the resistant insects that don’t die produce mostly non-resistant offspring that will die.

In parts of Africa dominated by small crops and farms rather than large industrial agricultural operations, wild plants are commonly used as refuge crops. However, the evidence suggests they aren’t working in regards to lepidopteran stem borer pests of corn.

“Recent studies from East and Southern Africa have … started questioning the contribution that wild host plants could make as reservoirs for stem borer pest infestation,” writes Dr. Johnnie Van den Berg, the author of the paper and a professor at North-West University in South Africa. “While these plants may have the characteristics of refuge crops … the fact that they do not produce sufficient numbers of high-quality moths make them unsuitable as refuge crops. This poor suitability of wild grasses as a refuge for lepidopteran stem borers became evident from field studies conducted throughout Africa over the last decade.”

Van den Berg argues that wild plants have been used, even though they don’t work, because of faulty information given to farmers.

“The use of unstructured refugia and wild host plants as refuges is not approved as an IRM [insect resistance management] strategy of African stem borers, but it is often suggested as a possible solution,” writes Van den Berg. “This continuous erroneous reporting on the importance of wild hosts over the years created the perception that stem borers were present in high numbers in wild host plants, that these plants were abundant, and that they could serve as refugia for stem borers and be part of an IRM strategy for Bt maize.”

Moving forward, Van den Berg thinks that new strategies for managing insect resistance need to be developed.

“Current IRM strategies and reliance on wild host plants as refuge in most of the developing world is not appropriate to small farming systems,” writes Van den Berg. “Previous experience has shown that compliance to requirements of structured refuge approaches will be low, necessitating novel approaches to address this problem. It is therefore necessary to have a new look at integrated pest management strategies that may serve to reduce selection pressure for resistance evolution.”

While IRM strategies need to work from a biological perspective, they also need to work from a sociological perspective, as not all strategies can or would be used by farmers.

“To be accepted by farmers, IRM strategies must be compatible with the existing cropping systems and normal farming practices,” Van den Berg writes. “If other crops are planted as refugia, these must be economically viable, socially acceptable and easy to implement by those making the management decisions at the farm level.”

Read more: “Insect Resistance Management in Bt Maize: Wild Host Plants of Stem Borers Do Not Serve as Refuges in Africa,” Journal of Economic Entomology


Josh Lancette is manager of publications at the Entomological Society of America.

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