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Archive for the ‘Host plant resistance’ Category

basmati-farmer

A farmer in Jind, Haryana in his  basmati paddy field. (Express photo: Renuka Puri)

Pesticide residues are an issue, more so when it concerns products such as basmati rice, fetching the country annual export revenues ranging from $ 3.23 billion in 2016-17 to $ 4.52 billion in 2014-15. The burden of consignments being rejected ultimately falls on the farmer, who has to, then, use new-generation pesticides that are safer, but costlier and very often proprietary/patented molecules.

The most recent example is of Tricyclazole. A single 120-gram spray of this common fungicide, against leaf and neck blast disease in paddy, hardly costs Rs 150-170 per acre. But with the European Union (EU) deciding not to allow import of any rice having Tricyclazole levels above 0.01 parts per million (ppm) from January 1, farmers would find it difficult to spray the generic chemical sold under assorted brands like ‘Sivic’, ‘Baan’ and ‘Beam’. The existing tolerance limit stipulated by the EU (which accounts for about 3.5 lakh tonnes of India’s total annual basmati shipments of 40 lakh tonnes) for Tricyclazole is one ppm or 1 mg/kg; 0.01 ppm will make it 1mg/100 kg!

With Tricyclazole ruled out, farmers may, henceforth, have to go for fungicides that are considered environmentally friendlier, though costing ten times more. These include Azoxystrobin (a single 200-ml spray, sold under the Swiss company Syngenta’s ‘Amistar’ brand, costs around Rs 900 per acre) and Picoxystrobin (the cost of a single 400-ml spray of this formulation, sold under DuPont’s ‘Galileo’ brand, comes to Rs 1,300 per acre). No less expensive is ‘Nativo’. This combination fungicide of Bayer CropScience, containing Tebuconazole and Trifloxystrobin, costs Rs 1,000 for a single 160-gram spray per acre.

However, an alternative approach to pesticide application — necessary, especially keeping in view basmati’s premium quality attributes and huge export market — is to “breed for disease resistance”. This involves transfer of specific disease-resistance genes, from both traditional landrace cultivars and wild relatives of paddy, into existing high-yielding basmati varieties. That is what scientists at the Indian Agricultural Research Institute (IARI) have sought to do.

The New Delhi-based institute — under a collaborative project with the Indian Council of Agricultural Research’s National Research Centre on Plant Biotechnology — has transferred the ‘Pi9’ gene into its popular Pusa Basmati-1 variety. This gene, sourced from Oryza minuta (a wild relative of Oryza sativa, which is the normal cultivated paddy), provides “very high resistance” against leaf blast and “moderate resistance” against neck blast fungus.

The resultant variety, which is called Pusa Basmati-1637, combines Pusa Basmati-1’s high-yielding trait with resistance against a fungus that infests the leaf and neck nodes of the rice plant’s main stem, from where the grain-bearing earheads (panicles) emerge. Blast disease affecting the leaf basically damages the chlorophyll, thereby impeding photosynthesis that involves absorption of sunlight and using its energy to synthesise carbohydrates. Neck blast, if severe, can cause the stem to even break. If the panicles at that point have only partially formed grains, in their early milky stage, the yield losses can be huge.

Rajeev Kharb, a farmer from Tito Kheri village in Safidon tehsil of Haryana’s Jind district, has grown Pusa Basmati-1637 in five out of his total 80-acre holding. The latter includes 28 acres of own and 52 acres of leased land. High temperatures and humidity levels this time round has resulted in the bulk of his planted area – mainly under Pusa Basmati-1401, Pusa Basmati-1 and Pusa Basmati-1509 – suffering gardan-marod (the local term for blast, whose literal translation is “curling of the neck”) to the extent of 10-20 per cent.

“But nothing has happened to my Pusa Basmati-1637 field. This, even without spraying any Tricyclazole,” says Kharb. A loss of 10-20 per cent isn’t small. Taking per-acre yields of 22-25 quintals for Pusa Basmati-1, 25-28 quintals for Pusa Basmati-1509 and 28-30 quintals for Pusa Basmati-1401, and current average price realisations of Rs 2,800/quintal, it works out to anywhere from Rs 7,000 to Rs 14,000 per acre.

“We will continue to have to spray for other diseases (bacterial blight and sheath blight fungus) and pests (brown plant hopper and stem borer). But with this new variety, there is still significant savings from not using Tricyclazole or other expensive fungicides against blast,” points out Pritam Singh Hanjra, a progressive farmer from Urlana Khurd village in Madlauda tehsil of Panipat district.

Hanjra, who has sown Pusa Basmati-1637 in five out of his 105-acre holding (30 acres own and the rest leased), estimates expenses on crop protection chemicals at Rs 3,000-4,000 out of the total cultivation costs of Rs 20,000-22,000 per acre for paddy. “It can go up, depending on the extent of pest and disease incidence. Either way, this is the second biggest expenditure head after manual harvesting-and-threshing (Rs 4,500-5,000), and more than fertilizers (Rs 2,100-2,200),” he claims.

A K Singh, head of IARI’s Division of Genetics, notes that Indian breeders have, over a period, managed to raise crop yields. The traditional tall basmati cultivars, for instance, gave barely 8-10 quintals of paddy per acre. With improved dwarf high-yielding basmati varieties, these have gone up to 25 quintals or so. “Our challenge now is to protect these yields and preferably through breeding for resistance, as opposed to pesticide application,” he adds.

IARI is, in fact, working on transferring other blast resistance genes as well — such as ‘Pi54’, ‘Pi25’, ‘Pi2’ and ‘Pib’, all from wild relatives and land races of rice — to high-yielding basmati varieties.

“We want to do pyramiding of these genes (combining two or more of them), in order to impart more durable resistance against blast. Besides, we have already developed and released two new varieties, Pusa Basmati-1718 and Pusa Basmati-1728, both of them incorporating the Xa21 and xa13 genes that confer resistance to the bacterial blight pathogen. The first variety is basically Pusa Basmati-1121 and the second one Pusa Basmati-1401, containing both these genes obtained from Oryza longistaminata (another wild relative of paddy) and BJ1 (a traditional land race), respectively,” informs Singh.

 

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Growing Produce

Silicon: a Biocontrol Agent that Boosts Plant Immunity

Quality and profitability are two important factors that drive our agricultural markets. We have fine-tuned our cultivation processes over centuries to obtain higher yields with lower inputs to protect both our environment and our bodies.

The biocontrol market contains a diverse set of less-toxic alternatives to aid in the overall goal of environmental stewardship. One set of materials contain a bioavailable form of silicon, important for enhancing the plant’s natural immune system.

Silicon is an essential trace element important for animal and human health. It also has an important role in plant health.

Silicon Protects Against Some Disease And Insect Pests
Studies show that adding silicon to the growing media significantly reduces the presence of powdery mildew in a variety of plants, including cucumber, tomatoes, strawberries, grapes, melons, and lettuce. This nutrient also protects against bacterial and viral infections in certain plants.

Not only does silicon protect against disease, it also reduces the population of insects and mites feeding on silicon-treated plants.

For many years, it was thought that silicon provided a physical barrier associated with the plant cuticle, making it harder for insects to penetrate.

While this process is involved, recent studies show that arthropods feeding on silicon-treated plants produce fewer offspring, suggesting that silicon is altering some aspect of the plant material ingested by these menaces. Combining silicon with other biocontrol agents may lead to better protection and control over infestations.

Tips on Gaining Nutrition from Silicon
There are many forms of silicon that can be taken up by plants.

Commercially available products include:
■ Solid materials for media incorporation that come from mined rocks (wollastonite and ignimbrite)
■ Recycled slag from the steel industry (also containing additional micronutrients and used as alternative liming agents)
■ Recycled glass (used as solid substrate in hydroponics or aquaponics)
■ Plant material (including rice hulls, coir, and biochar produced from plant material).
■ Liquid materials that can be applied as a media drench or foliar spray (including potassium-, sodium-, and calcium-silicates).

These materials have unique characteristics and release varying amounts of plant-available silicon. It is important to match the material with your growing system.

The amount of silicon required to enhance growth and stress resistance varies greatly by plant type and even variety. There are no current recommendations for silicon concentrations in plant tissue.

As a general rule of thumb, many of the grasses and grains need large amounts (and can take up to 100,000 ppm or higher silicon), while dicots range in their foliar concentrations from 10,000 ppm (in cucumber) to 100 ppm (in onion). It is important to note that silicon protects both cucumber and onion in various stress responses, showing that foliar concentration does not predict protection.

Silicon fits in as a biocontrol because it enhances the plant’s own immune response, allowing for a faster and more robust response to invading pathogens or herbivores. By providing plants with this nutrient prior to the onset of disease or early in the detection of nuisance arthropods, we can help our photosynthetic friends maintain their quality and yield, even in the presence of stress.

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Diamondback-moth

CAAS Scientists Develop GE Cabbage Resistant to Diamondback Moth

Chinese Academy of Agricultural Sciences researchers successfully incorporated a Bt gene into cabbage plants to improve resistance to destructive pest, diamondback moth (Plutella xylostella). The results of their study are published in Scientia Horticulturae.

The researchers used Agrobacterium tumefaciens-mediated transformation to develop transgenic cabbage plants with Bacillus thuringiensis cry1Ia8 gene. The resulting transgenic plants were able to control both susceptible and Cry1Ac-resistant diamondback moth larvae.Then they analyzed the expression and inheritance of the Bt gene in four single-copy lineages and their sexually derived progenies.

Results of the analyses showed that the transgene was successfully inserted in the genome of cabbage and the inheritance of the gene in the progenies followed the Mendelian segregation pattern. These results imply that the transgenic lines exhibiting stable inheritance can be used as donor in breeding programs for cabbage.

Read the research article for more information.

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FTF logo

Field days show Ugandan farmers hope in disease-resistant varieties

By Allison Floyd
University of Georgia, Peanut & Mycotoxin Innovation Lab

Planting an unimproved variety of peanut in Uganda was a recipe for disaster this year. Groundnut rosette disease (GRD), an aphid-borne virus that causes mottling and affects much of sub-Saharan Africa, took 80% to 100% of the yield in some fields planted with a traditional variety.

The difficult season made farmers even more interested in two recent field-day events held in Uganda, where they could see the results coming from fields planted with improved varieties resistant to GRD.

Farmers check out peanut-growing guides at one of two recent Field Day trainings in Uganda.

One woman, a farmer named Adong Christine borrowed $7,000 from a bank and planted 20 acres with a local variety. At the end of the season, she harvested just two bags of peanuts (from a potential 400 bags) and could not repay the loan.

“There had been an outcry of big losses as most of the capital were borrowed from loan institutions. This event showcasing improved groundnut varieties therefore was timely as it restored hopes and enhanced adoption,” organizers said.

David Okello, the head of Uganda’s national groundnut research program and a leading scientist on PMIL’s breeding project, is behind many of the varieties. Based at the National Semi-Arid Resources Research Institute (NaSARRI) in Serere District, Okello works to create varieties that are high yielding, resistant to drought and GRD, and to educate farmers about practices that will give them more success with their peanut crop.

Peanuts are a traditional crop in Uganda and much of sub-Saharan Africa, are high-protein and valuable as a cash crop. Still, GRD is a persistent problem that stunts the growth of otherwise healthy plants and can destroy a crop if the disease strikes early enough in the season before flowering.

A woman farmer picks up some bags of seed at Field Days in the Nwoya District of Uganda. At the end of a particularly bad season for disease, many farmers made the investment to buy small bags of improved seed.

At one of two field days, 61 farmers, researchers and representatives of local government visited a 5.6-acre plot planted with three varieties bred for their resistance to GRD and leaf-spot, Serenut 9T (Aber), Serenut 14R and Serenut 5R. While participants could see for themselves the success of the varieties, farmers in the Loyo Kwo group, who are using the new varieties, explained their agronomic practices, where they get seed and how NaSARRI trainings helped improve their results.

“Heart breaking and sad testimonies came from the farmers growing local varieties,” Okello said. “The Loyo Kwo group members, on the other hand, were boasting of bumper harvests, higher income and improved livelihoods that they are experiencing from adopting the improved groundnut varieties,” Okello  said

Uganda Field DaysLeoora Okidi (centre) shows her approval of the high yield of Serenut 11T, an improved variety during a Field Day in August 2017 in the Kiteny Pader District of Uganda.

 

Farmers were able to buy small packs of .5 kg to 3 kg., and the NaSARRI team delivered 45 kgs of Serenut 8R (Achieng), a large-seeded red variety that had been previously promised.

In a second field day, farmers spent part of a religious holiday – the Assumption of the Virgin Mary to Heaven – visiting test plots, learning about improved production practices and visiting a farm where the owner planted Serenut 5R and Serenut 11T alongside the local Red Beauty variety.

Uganda Field Days crowdA crowd of farmers fan out over a field at a recent Field Days event comparing the yield and disease resistance of improved lines and varieties over the traditional, unimproved types, which have been ravaged by rosette disease this year.

 

The farmer, Leonora Okidi, planted 2 of her 5 acres with an improved variety, and the other 3 acres with the local variety. She abandoned the local variety after the first weeding since most of the plants had been severely attacked by the rosette virus.

In a good year, she is able to feed and educate her 11 own children and support 25 others from her groundnut operation, which is part of a women-led group called Pur Lonyo or “Farming is Wealth,” she said.

Okidi first connected with Okello through her son, who he mentored in his diploma and bachelor’s degree studies and still supervises in his current master’s degree studies. She offered land to host demonstration plots and participatory variety trials and co-funded the operations using her family labour.

“The superiority of our improved lines and varieties over her local varieties caught her attention and (Okidi) quickly adopted these improved varieties and has become a model research farmer in the village,” Okello said. “Through this effort our improved varieties adoption rates has increased and we are closely working with her women group to upscale these successes, improve their livelihoods and increase varieties adoption.”

– Published Sept. 1, 2017

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SE farm press

 

Randy Gardner Dilip Panthee Tomatoes Dee Shore/North Carolina State University
North Carolina State University tomato breeders Dilip Panthee and Randy Gardner.

Breeding a better tomato

North Carolina State University scientists are breeding flavorful and disease-resistant tomatoes for farmers and home gardeners.

Dee Shore | Aug 22, 2017

With some 700 varieties grown around the world, tomatoes come in an array of colors, shapes and sizes. To take advantage of that variety, two North Carolina  State University scientists are breeding more flavorful and disease-resistant types for farmers and home gardeners alike.

NC State’s tomato breeding program focuses on developing tomatoes especially suited for North Carolina’s growing conditions, from the mountains to the coast. Based at the Mountain Horticultural Crops Research and Extension Center near Asheville, the program has yielded more than 30 hybrids, including some of the most widely grown types in the eastern United States.

The breeders, Randy Gardner and Dilip Panthee, have even more varieties on the way.

Panthee’s efforts focus on developing better commercial varieties for the fresh market, while Gardner is producing new breeding lines and hybrid varieties derived from heirloom tomatoes – ones that are open-pollinated, with seeds passed down from one generation to the next. They are prized for their flavor and come in a wide variety of fruit colors, sizes and shapes.

Gardner founded the breeding program in 1976, as North Carolina tomato producers struggled to deal with a devastating disease known as verticillium wilt. Nearly every variety he has developed has resistance to that disease, and some have resistance to multiple viral and fungal diseases that have popped up over the years.

Gardner, now a professor emeritus in NC State’s Department of Horticultural Science, retired in 2008, but he hasn’t stopped breeding tomatoes.

“I plan soon to release several hybrids of different fruit colors in the heirloom-type tomatoes. These are ones bred primarily for late-blight resistance. Most people are familiar with red tomatoes, and a lot of people won’t eat a tomato unless it’s red, but there are other colors, many with their own distinct flavor profiles and fruit texture,” he said, pointing to yellow, orange, pink, purple, and even striped tomatoes he’s grown in a research station greenhouse and tested in research station and grower trials.

Since 2008, Gardner has worked side by side with Panthee in the greenhouse. Like Gardner, Panthee has had success with breeding varieties resistant to a range of diseases. He’s also focused on traits such as flavor and levels of lycopene, an antioxidant that appears to have health benefits.

Panthee came to NC State with a passion for tomatoes that he gained during the early part of his career as a breeder in Nepal. He also brought experience in molecular marker-assisted breeding, a technique that can cut the amount of time it takes to produce a new hybrid. It involves looking for sequences of nucleotides, or markers, that make up a segment of DNA near the genes of interest; if a young plant doesn’t have that DNA segment, the breeder can discard the plant, focusing only on those that do have the genes.

In the breeding pipeline, Panthee has several hybrids with multiple disease resistance that he’s close to releasing. While farmers could rely on chemicals for disease control, that raises their production costs. Having resistant varieties is also important to home gardeners and others interested in growing tomatoes organically.

North Carolina is the nation’s fourth-leading state when it comes to fresh market tomato production, and one of Panthee’s goals is to continue developing varieties that will make the industry even more competitive.

“I see a very good potential to exploit the geographical and climatic variation that exists in North Carolina,” he said. “We have to grab the market that exists here in North Carolina and niches in other states, as well.”

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EurekAlert

Public Release: 10-Aug-2017

Blocking pathogens in rice

Düsseldorf plant researchers funded by Bill & Melinda Gates Foundation

Heinrich-Heine University Duesseldorf

IMAGE
IMAGE: Rice plants; the research group led by Wolf B. Frommer wants to make rice resistant to the harmful rice blight that endangers rice harvests in Africa and South-East Asia. view more 

Credit: Wolf B. Frommer

What is known as “rice blight” is a dreaded plant disease that endangers rice harvests throughout the whole of South-East Asia, especially India, as well as large parts of Africa and can thus lead to great hardship amongst the local population. The disease is caused by the bacterial pathogen Xanthomonas oryzae oryzae.

Professor Wolf B. Frommer, plant researcher at the Institute of Mo-lecular Physiology at HHU, has assembled an international research group to fight rice blight. The team includes scientists from Iowa State University and the University of Florida in the USA, the Institut de Recherche pour le Développement in Montpellier, France, Colombia’s International Centre for Tropical Agriculture and the International Rice Research Institute in the Philippines. The researchers have found a way to make plants resistant to the pathogen.

Frommer is an expert on transport processes in plants. The sugar transporters known as SWEET identified by his research group play a key role in resistance. Plants need these transporters to bring the sugar produced during photosynthesis in the leaves to the seeds. And it is precisely this transport mechanism that the pathogens re-programme for their own purposes.

In independent studies, US-American researchers Professor Bing Yang and Professor Frank White (now at Iowa State University and the University of Florida) discovered that a protein (which later transpired to be SWEET) is responsible for plants’ resistance to rice blight. Joint trials then revealed that the bacteria systematically activate the transporters in the rice cells and in so doing gain access to nutrients. If such activation is prevented, the bacteria cannot multiply.

Wolf B. Frommer says: “This surprising discovery has provided us with a strategy for our joint research project: We cut off the pathogens’ route to their larder – the plants’ sugar stores – and starve them out.”

The research project “Transformative Strategy for Controlling Rice Disease in Developing Countries” began on 1 August 2017. The project is supported by a four-year grant from the Bill & Melinda Gates Foundation. In the framework of the project, Frommer will concentrate especially on the production of elite varieties for India and Africa. He will mostly conduct his research work within the working group led by Dr. Joon Seob Eom at the Max Planck Institute for Plant Breeding Research in Cologne.

The research results can prove valuable beyond the specific topic of rice blight. Wolf B. Frommer: “Our discovery might be just the tip of the iceberg. We could use the same approach to try and combat other plant diseases and in that way hopefully make a small contribution to protecting the world’s food supply.” And that would also be good for the climate and the environment, since if plant diseases can be combatted effectively, less pesticides and fertilisers would be needed worldwide to ensure sufficient harvests.

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Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Phys.org News

Researchers find corn gene conferring resistance to multiple plant leaf diseases

July 24, 2017 by Mick Kulikowski

Researchers find corn gene conferring resistance to multiple plant leaf diseases
Credit: North Carolina State University

Researchers at North Carolina State University have found a specific gene in corn that appears to be associated with resistance to two and possibly three different plant leaf diseases.

In a paper published this week in Nature Genetics, NC State researchers pinpoint the gene – caffeoyl-CoA O-methyltransferase – that seems to confer partial to Southern blight and gray leaf spot, and possibly to Northern leaf blight, a trio of diseases that cripple worldwide.

Finding out more about the mechanisms behind complex traits like has the potential to help plant breeders build the best traits into tomorrow’s plants, says paper corresponding author Peter Balint-Kurti, a research plant pathologist and geneticist for the U.S. Department of Agriculture-Agriculture Research Service (USDA-ARS) who is housed at NC State.

Balint-Kurti’s group and colleagues identified several regions of the genome where genetic variation had a significant effect on variation in resistance to multiple diseases.

“There were hundreds of genes in this region and identifying the specific genes affecting resistance was a challenge,” Balint-Kurti said. “It’s like looking for a particular restaurant in a city – without Google to assist you.”

Using an approach called fine mapping, NC State postdoctoral researcher Qin Yang winnowed the region down to a small segment of DNA carrying just four genes, and then with a number of collaborators from NC State, Iowa State University, the University of Delaware, Texas A&M University, the University of North Carolina at Chapel Hill, Cornell University and the USDA Agricultural Research Service she performed more tests to narrow those four genes down to one.

“It’s interesting that this gene also seems to be involved in lignin production,” Yang said. “Generally, more lignin production seems to be linked to more robust disease resistance in plants.”

Balint-Kurti says the gene appears to confer a small but important disease-resistance effect.

“It’s difficult to see these small effects, but it is also difficult for pathogens to adapt to counter them,” Balint-Kurti said. “Much of the resistance to Southern leaf blight and gray leaf spot is conferred by multiple that each have small effects.”

Southern corn leaf blight is a moderate problem in the southeastern United States, Balint-Kurti says, and can be a significant problem in Southeast Asia, southern Europe and parts of Africa. Prevalent in hot, humid climates around the globe, it causes small brown spots on leaves. The spots get larger and eventually spread to the whole plant. Severe infections can cause major corn yield losses. Gray leaf spot – which produces an eponymous effect – is found both in the U.S. Midwest and Southeast and is also an important corn disease in Africa. Northern can be found in the Midwestern corn belt and in the Northeast; it causes cigar-shaped lesions on leaves. All three are so-called necrotrophic pathogens that derive much of their nutrition from dead host tissue.

“This gene is also involved in suppressing programmed cell death,” Balint-Kurti says, “which, perhaps counter-intuitively, can be a good defense mechanism against necrotrophic fungi like these three diseases.”

Explore further: Study shows corn gene provides resistance to multiple diseases

More information: A gene encoding maize caffeoyl-CoA O-methyltransferase confers quantitative resistance to multiple pathogens, Nature Genetics (2017). DOI: 10.1038/ng.3919

Read more at: https://phys.org/news/2017-07-corn-gene-conferring-resistance-multiple.html#jCp

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