Posts Tagged ‘Susanne Dreisigacker’

A fresh look at the genes behind grain weight in spring bread wheat

New study provides an extensive field-test validation of existing genetic markers for thousand grain weight; finds both surprises and promising results

To meet the demand for wheat from a rising and quickly urbanizing population, wheat yields in farmers’ fields must increase by an estimated 1.5% each year through 2030. 

Of all the factors that influence yield, grain weight is the trait that is most stable and heritable for use in breeding improved wheat varieties.  Breeders measure this by thousand grain weight (TGW).

Over the years, molecular scientists have made efforts to identify genes related to increased TGW, in order to speed up breeding through marker-assisted selection (MAS). Using MAS, breeders can select parents that contain genes related to the traits they are looking for, increasing the likelihood they will be passed on and incorporated in a new variety. 

Guillermo Garcia Barrios, a co-author of the study and student at Colegio de Postgraduados in Montecillo, Mexico with a PHERAstar machine used to validate genetic markers.
Photo: Marcia MacNeil/CIMMYT

There have been some limited successes in these efforts: in the past years, a few genes related to increased TGW have been cloned, and a set of genetic markers have been determined to be used for MAS. However, the effects of most of these candidate genes (CGs) have not yet been validated in diverse sets of wheat germplasm throughout the world that represent the full range of global wheat growing environments.

A group of wheat geneticists and molecular breeders from the International Maize and Wheat Improvement Center (CIMMYT) has recently conducted a thorough study to confirm the effects of the favorable alleles reported for these genes on TGW in CIMMYT wheat,   — and to identify new genetic determinants of this desired trait.

They found some good news and some bad.

First, the good news:  focusing on more than 4000 lines of CIMMYT wheat germplasm they found 15 haplotype blocks significantly associated with TGW.  Four haplotype blocks associated with TGW were also associated with grain yield – a grand prize for breeders, because in general the positive association of grain yield with TGW is less profound and sometimes even negative. However, of the 14 genes that had been previously reported to increase TGW, only one in CIMMYT’s 2015-2016 Elite Yield Trial and two in Wheat Associative Mapping Initiative panel were shown to have significant TGW associations.

The scientists also found that the alleles — pairs of genes on a chromosome that determine heredity – that were supposedly favorable to TGW actually decreased it.   These candidate genes also appear to vary in their TGW effects with genetic background and/or environment.

Thus, these findings also provide a foundation for more detailed investigations, opening the door for more studies on the genetic background dependence and environment sensitivity of the known candidate genes for TGW. 

Thousand Gain Weight is measured in this machine at CIMMYT’s administrative headquarters at El Batan, Mexico.
Photo: Marcia MacNeil/CIMMYT

 “Our findings indicate that it will be challenging to use MAS based on these existing markers across individual breeding programs,” said Deepmala Sehgal, CIMMYT wheat geneticist and the primary author of the study.

However, efforts to identify new genetic determinants of TGW were promising.  The authors’ study of CIMMYT germplasm found one locus on chromosome 6A that showed increases of up to 2.60 grams in TGW and up to 258 kilograms per hectare in grain yield.

This discovery expands opportunities for developing diagnostic markers to assist in multi-gene pyramiding – a process that can derive new and complementary allele combinations for enhanced wheat TGW and grain yield.

Most of all, the study highlights the strong need for better and more validation of the genes related to this and other traits, so that breeders can be sure they are using material that is confirmed to increase wheat grain weight and genetic yield.

“Our findings are very promising for future efforts to efficiently develop more productive wheat in both grain weight and grain yield,” said Sehgal. “This ultimately means more bread on household tables throughout the world.”

 “Validation of Candidate Gene-Based Markers and Identification of Novel Loci for Thousand-Grain Weight in Spring Bread Wheat” in Frontiers in Plant Science by Deepmala Sehgal, Suchismita Mondal, Carlos Guzman, Guillermo Garcia Barrios, Carolina Franco, Ravi Singh and Susanne Dreisigacker was supported by funding from the CGIAR Research Program on Wheat (WHEAT), the Delivering Genetic Gain in Wheat (DGGW) project funded by the Bill & Melinda Gates Foundation and the UK Department for International Development (DFID), and the US Agency for International Development (USAID) Feed the Future Innovation Lab for Applied Wheat Genomics.

Read the full article here: https://doi.org/10.3389/fpls.2019.01189


Wheat grains prepared for placement in TGW machine. Photo: Marcia MacNeil/CIMMYT

Scientists use DNA fingerprinting to gauge the spread of modern wheat in Afghanistan

New study finds that wheat farmers often do not accurately identify their varieties.

Wheat is Afghanistan’s number-one staple crop, but the country does not grow enough and must import millions of tons of grain each year to satisfy domestic demand.

Despite the severe social and political unrest that constrain agriculture in Afghanistan, many farmers are growing high-yielding, disease resistant varieties developed through international, science-based breeding and made available to farmers as part of partnerships with national wheat experts and seed producers.

These and other findings have emerged from the first-ever large-scale use of DNA fingerprinting to assess Afghanistan farmers’ adoption of improved wheat varieties, which are replacing less productive local varieties and landraces, according to a paper published yesterday in the science journal BMC Genomics.

The study is part of an activity supported between 2003 and 2018 by the Australian Department of Foreign Affairs and Trade, through which the Agricultural Research Institute of Afghanistan and the International Maize and Wheat Improvement Center (CIMMYT) introduced, tested, and released improved wheat varieties.

“As part of our study, we established a ‘reference library’ of released varieties, elite breeding lines, and Afghan wheat landraces, confirming the genetic diversity of the landraces and their value as a genetic resource,” said Susanne Dreisigacker, wheat molecular breeder at CIMMYT and lead author of the new paper.

“We then compared wheat collected on farmers’ fields with the reference library. Of the 560 wheat samples collected in 4 provinces during 2015-16, farmers misidentified more than 40%, saying they were of a different variety from that which our DNA analyses later identified.”

Wheat is the most important staple crop in Afghanistan — more than 20 million of the country’s rural inhabitants depend on it — but wheat production is unstable and Afghanistan has been importing between 2 and 3 million tons of grain each year to meet demand.

Over half of the population lives below the poverty line, with high rates of malnutrition. A key development aim in Afghanistan is to foster improved agronomic practices and the use of high quality seed of improved wheat varieties, which together can raise yields by over 50%.

“Fungal diseases, particularly yellow rust and stem rust, pose grave threats to wheat in the country,” said Eric Huttner, research program manager for crops at the Australian Centre for International Agricultural Research (ACIAR) and co-author of the present paper. “It’s crucial to know which wheat varieties are being grown where, in order to replace the susceptible ones with high-performing, disease resistant varieties.”

Varietal adoption studies typically rely on questionnaires completed by breeders, extension services, seed producers, seed suppliers, and farmers, but such surveys are complicated, expensive, and often inaccurate.

“DNA fingerprinting resolves uncertainties regarding adoption and improves related socioeconomic research and farm policies,” Huttner explained, adding that for plant breeding this technology has been used mostly to protect intellectual property, such as registered breeding lines and varieties in more developed economies.

This new study was commissioned by ACIAR as a response to a request from the Government of Afghanistan for assistance in characterizing the Afghan wheat gene bank, according to Huttner.

“This provided the reference library against which farmers’ samples could be compared,” he explained. “Accurately identifying the varieties that farmers grow is key evidence on the impact of introducing improved varieties and will shape our future research

Joint research and development efforts involving CIMMYT, ACIAR, the Food and Agriculture Organization (FAO) of the United Nations, the International Centre of Agricultural Research in Dry Areas (ICARDA), French Cooperation, and Afghanistan’s Ministry of Agriculture, Irrigation and Livestock (MAIL) and Agricultural Research Institute (ARIA) have introduced more than 400 modern, disease-resistant wheat varieties over the last two decades. Nearly 75% of the wheat grown in the areas surveyed for this study comes from these improved varieties.

“New gene sequencing technologies are increasingly affordable and their cost will continue to fall,” said Dreisigacker. “Expanded use of DNA fingerprinting can easily and accurately identify the wheat cultivars in farmers’ fields, thus helping to target breeding, agronomy, and development efforts for better food security and farmer livelihoods.”


For more information, or to arrange interviews with the researchers, please contact:

Marcia MacNeil, Wheat Communications Officer, CIMMYT
M.MacNeil@cgiar.org, +52 (55) 5804 2004, ext. 2070

Rodrigo Ordóñez, Communications Manager, CIMMYT
r.ordonez@cgiar.org, +52 (55) 5804 2004, ext. 1167

About CIMMYT
The International Maize and Wheat Improvement Center (CIMMYT) is the global leader in publicly funded maize and wheat research and related farming systems. Headquartered near Mexico City, CIMMYT works with hundreds of partners throughout the developing world to sustainably increase the productivity of maize and wheat cropping systems, thus improving global food security and reducing poverty. CIMMYT is a member of CGIAR and leads the CGIAR Research Programs on Maize and Wheat, and the Excellence in Breeding Platform. The center receives support from national governments, foundations, development banks and other public and private agencies.

About ACIAR
As Australia’s specialist international agricultural research for development agency, the Australian Centre for International Agricultural Research (ACIAR) brokers and funds research partnerships between Australian scientists and their counterparts in developing countries. Since 1982, ACIAR has supported research projects in eastern and southern Africa, East Asia, South and West Asia and the Pacific, focusing on crops, agribusiness, horticulture, forestry, livestock, fisheries, water and climate, social sciences, and soil and land management. ACIAR has commissioned and managed more than 1,500 research projects in 36 countries, partnering with 150 institutions along with more than 50 Australian research organizations.

About Afghanistan’s Ministry of Agriculture, Irrigation and Livestock
The Ministry of Agriculture, Irrigation and Livestock (MAIL) of the Islamic Republic of Afghanistan works on the development and modernization of agriculture, livestock and horticulture. The ministry launches programs to support the farmers, manage natural resources, and strengthen agricultural economics. Its programs include the promotion and introduction of higher-value economic crops, strengthening traditional products, identifying and publishing farm-tailored land technologies, boosting cooperative programs, agricultural economics, and export with marketing.