Archive for the ‘Plant breeding’ Category

JULY 20, 2020

Returning to farming’s roots in the battle against the ‘billion-dollar beetle’

by University of Arizona

Returning to farming's roots in the battle against the 'billion-dollar beetle'
Western corn rootworm larvae can devour the tips of corn roots, robbing the plants of nutrients and making them susceptible to falling over. Credit: Cyril Hertz, Lingfei Hu and Matthias Erb, University of Bern, Switzerland

Nicknamed the “billion-dollar beetle” for its enormous economic costs to growers in the United States each year, the western corn rootworm is one of the most devastating pests farmers face.https://3777ec3032f89ac36b1a5fe5c7568749.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

“They are quite insidious. They’re in the soil gnawing away at the roots and cutting off the terminal ends of the roots—the lifeblood of corn,” said Bruce Tabashnik, Regents Professor and head of the University of Arizona Department of Entomology. “And if they’re damaging enough, the corn plants actually fall over.”

Genetically modified crops have been an important tool in the battle against pests such as these, increasing yields while reducing farmers’ reliance on broad-spectrum insecticides that can be harmful to people and the environment.

Corn was genetically engineered to produce proteins from the bacterium Bacillus thuringiensis, or Bt, that kill rootworm larvae but are not toxic to humans or wildlife. The technology was introduced in 2003 and has helped keep the corn rootworm at bay, but the pest has begun to evolve resistance.

“So, now the efficacy of this technology is threatened and if farmers were to lose Bt corn, the western corn rootworm would become a billion-dollar pest again,” said Yves Carrière, a professor of entomology in the College of Agriculture and Life Sciences.

Crop Rotation in Mitigating Pest Resistance

Carrière is lead author of a study to be published in PNAS that evaluated the effectiveness of crop rotation in mitigating the damage caused by resistant corn rootworms. Tabashnik and colleagues from North Carolina State University, the University of California-Davis, McGill University and Stockholm University coauthored the study.

Crop rotation, the practice of growing different crops in the same field across seasons, has long been used for pest control. In 2016, the U.S. Environmental Protection Agency mandated crop rotation as a primary means of reducing the damage to Bt corn fields caused by resistant corn rootworms, but there have been limited scientific studies to support the efficacy of this tactic.https://googleads.g.doubleclick.net/pagead/ads?client=ca-pub-0536483524803400&output=html&h=280&slotname=5350699939&adk=2265749427&adf=625945176&w=750&fwrn=4&fwrnh=100&lmt=1595996918&rafmt=1&psa=1&guci=×280&url=https%3A%2F%2Fphys.org%2Fnews%2F2020-07-farming-roots-billion-dollar-beetle.html&flash=0&fwr=0&rpe=1&resp_fmts=3&wgl=1&dt=1595996918602&bpp=11&bdt=88&idt=147&shv=r20200727&cbv=r20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3Dfd49ee1f356c7aad-2230268791c20026%3AT%3D1595996908%3AS%3DALNI_MZ__AIkhsEMsw1AjrlZUCXlh_wvFw&correlator=2622896222429&frm=20&pv=2&ga_vid=683244895.1595996911&ga_sid=1595996919&ga_hid=1573871060&ga_fc=0&iag=0&icsg=2271232&dssz=26&mdo=0&mso=0&u_tz=-300&u_his=2&u_java=0&u_h=1080&u_w=1920&u_ah=1040&u_aw=1920&u_cd=24&u_nplug=3&u_nmime=4&adx=447&ady=2184&biw=1903&bih=969&scr_x=0&scr_y=0&oid=3&pvsid=1003068873479674&pem=0&rx=0&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1920%2C0%2C1920%2C1040%2C1920%2C969&vis=1&rsz=%7C%7CpeEbr%7C&abl=CS&pfx=0&fu=8320&bc=31&ifi=1&uci=a!1&btvi=1&fsb=1&xpc=7ptrOeJu1R&p=https%3A//phys.org&dtd=154

Carrière and his team rigorously tested this approach by analyzing six years of field data from 25 crop reporting districts in Illinois, Iowa and Minnesota—three states facing some of the most severe rootworm damage to Bt cornfields.

The results show that rotation works. By cycling different types of Bt corn and rotating corn with other crops, farmers greatly reduced rootworm damage.

Most notably, crop rotation was effective even in areas of Illinois and Iowa where rootworm resistance to corn and soybean rotation had been previously reported.

According to the study, crop rotation provides several other benefits as well, including increased yield, reductions in fertilizer use and better pest control across the board.

“Farmers have to diversify their Bt crops and rotate,” Carrière said. “Diversify the landscape and the use of pest control methods. No one technology is the silver bullet.”

Returning to farming's roots in the battle against the 'billion-dollar beetle'
Western corn rootworm beetle on corn tassels. Credit: Joseph L. Spencer, Illinois Natural History Survey, University of Illinois at Urbana-Champaign

A Multipronged Approach

Tabashnik relates the research back to UArizona’s work with the pink bollworm, in which researchers spearheaded a management program to suppress the pink bollworm’s resistance to Bt cotton.

“The key to eradicating pink bollworm in the U.S. was integrating Bt cotton with other control tactics,” Tabashnik said. “We succeeded, whereas this voracious invasive pest rapidly evolved resistance to Bt cotton in India, where the genetically engineered crop was used alone.”

In collaboration with cotton growers, UArizona scientists sustained the efficacy of Bt cotton against pink bollworm by establishing the “refuge strategy,” in which non-Bt crops are planted near Bt crops to allow survival of susceptible insects. The strategy has become the primary approach used worldwide to delay the adaptation of insect pests to genetically engineered crops.

Although farmers have used refuges to thwart the rootworm’s resistance to Bt corn, this strategy alone has proven insufficient against the pest.

“During the last decade, we have learned that refuges are often not sufficient to delay resistance in pests like the corn rootworm,” Carrière said. “It would be wise to diversify management tactics before such pests evolve resistance. This approach, called integrated pest management, is vital for preserving the benefits of biotechnology.”

Returning to Agricultural Roots

In many ways, the study reaffirms traditional agricultural knowledge.

“People have been rotating crops since the dawn of farming. The new agricultural technology we develop can only be sustained if we put it in the context of things we’ve known for thousands of years,” Tabashnik said. “If we just put it out there and forget what we’ve learned in terms of rotating crops, it won’t last.”

The authors emphasize that increasing crop rotation is essential for sustaining the economic and environmental benefits provided by rootworm-active Bt corn. During the six years of the study, the average percentage of corn rotated to other crops per state ranged from about 55-75%.

“This is one of the most important applications of Bt crops in the United States,” Carrière said. “If we lose this technology and we start using soil insecticides again, it’s going to have a big negative environmental impact.”

Explore furtherScientists offer recommendations for delaying resistance to Bt corn in western corn rootworm

More information: Crop rotation mitigates impacts of corn rootworm resistance to transgenic Bt corn, PNAS (2020). DOI: 10.1073/pnas.2003604117Journal information:Proceedings of the National Academy of SciencesProvided by University of Arizona

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CGIAR – Gender and breeding intiatives

Plant breeders produce new varieties for their customers: farmers. To predict what kinds of new varieties are likely to offer significant benefits to farmers, breeders may turn to their customers to evaluate which characteristics might make a new variety more acceptable. A comprehensive review of many such evaluations suggests that if breeders were to pay more attention to what women need, it could increase the usefulness of new varieties in many ways.

[Gender and Farmer Preferences for Varietal Traits: Evidence and Issues for Crop Improvement], published in Plant Breeding Reviews, came out of a workshop of the Gender and Breeding Initiative, led by the CGIAR Research Program on Roots, Tubers and Bananas (RTB). The authors scanned the published literature looking for research that addressed plant breeding, seed selection, trait evaluation and similar ideas and that specifically reported data from women about their varietal preferences. The paper describes their analysis.

Although 39 papers met the criteria, the authors say that none of them focused on gender differences for trait preferences as a primary objective. Women evaluated traits and varieties, but understanding their preferences was never the primary reason for any of the studies. The studies covered a wide variety of crops, countries and agricultural production and food systems. Despite the high diversity and specificity of these cases, the authors identified some trends and patterns.

Security versus productivity

Women and men sometimes have diametrically opposed views about what matters in a plant variety. Women mention traits related to their family’s food security, such as earliness, multiple harvests and pest and disease resistance, more often than men. Men, by contrast, mention varieties with market appeal — high yields, low labor requirements — more often than women.

“Women preferred traits conferring stability or the capacity to produce under stressful conditions,” said Jacqueline Ashby, one of the study authors and Senior Advisor on Gender Research at the CGIAR System Office at the time of the research.

There are differences after the harvest too. Women are more likely to be concerned about traits such as ease of processing and lower processing losses or medicinal properties, reflecting their concern with food quality, while men focus on storage life and marketability.

“Women tend to be responsible for food preparation, and thus have more detailed knowledge about what a good variety should bring to the table,” said Eva Weltzien of the University of Wisconsin and another of the paper’s authors. “If women cannot prepare more food from grain produced by a higher yielding variety, because losses during food preparation are higher than the yield advantages from the new variety, they will not adopt the new variety and will discourage the men from doing so.”

Women are responsible for ensuring that their family is well-fed, and that influences their preferences. In Ethiopia, for example, women say that they are the ones who have to maintain early and drought-tolerant sorghum varieties because “they are the first to hear a starving child cry”.

Same crop, different needs

Many crops are grown by women and men, albeit under different circumstances and sometimes with diverse goals. Very often, women prefer traits that will deliver an assured harvest from the poorer conditions of their plots. In West Africa, the fields on which women grow sorghum are low in fertility because they are allocated those fields at the end of the rotation and they do not have access to manure. They prefer early and tall sorghum varieties, which make the most of poor conditions.

This example, and several others, show that, as the authors note, “even within the same agro‐ecology and village, women and men may be cultivating the same crop under contrasting conditions and thus will have different trait preferences”.

Women tend to value characteristics of crop varieties differently from men when they have different roles and responsibilities during the crop production cycle. For example, when women are primarily responsible for weeding, harvesting or threshing, they will appreciate variety traits that reduce weeding and their workload.

It is also common that women use specific parts of plants that men are less interested in, and ignoring their preferences can block the uptake of an otherwise better variety. In Ethiopia, for example, women objected to more productive short-strawed sorghum varieties partly because they would increase their work, but also because they would reduce the income women earn by selling the sorghum stalks as fuel.

Let women decide

Some crops are seen as “women’s crops,” among them groundnut and Bambara groundnut in West Africa, finger millet in East Africa and traditional vegetables across Africa and Asia. The literature contained no research on gendered trait preferences for these women’s crops which, the authors note, “warrants further research”.

“In fact,” said Jacqueline Ashby, “the idea that some crops are ‘women’s crops’ is questionable. More to the point, whenever women grow any crop for home consumption using rudimentary technology, their opinions about what would improve the crop have been largely ignored by modern breeding.”

GBI and the Excellence in Breeding CGIAR platform have already teamed up to pilot a more systematic approach to ensuring that women’s trait preferences are included in the product profiles that guide the work of plant breeders.

Should the aim be to produce separate varieties for women and men? Probably not.

“It is costly and difficult to develop new varieties,” Eva Weltzien explained. “In most cases it will be better to combine the traits that women and men prefer. For example, there may be no real yield disadvantage for taller sorghum plants.”

Better, Weltzien said, to ensure that women’s preferences are being met. In Ethiopia, a new sorghum variety that is tall and high-yielding improves the likelihood that the improved variety might be adopted, because women and men will want it.

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