University of California scientists have discovered genetic data that will help food crops like tomatoes and rice survive longer, more intense periods of drought on our warming planet.
Over the course of the last decade, the research team sought to create a molecular atlas of crop roots, where plants first detect the effects of drought and other environmental threats. In so doing, they uncovered genes that scientists can use to protect the plants from these stresses.
Their work, published today in the journal Cell, achieved a high degree of understanding of the root functions because it combined genetic data from different cells of tomato roots grown both indoors and outside.
"Frequently, researchers do lab and greenhouse experiments, but farmers grow things in the field, and this data looks at field samples too," said Neelima Sinha, a UC Davis professor of plant biology and the paper's co-author.
The data yielded information about genes that tell the plant to make three key things.
Xylem are hollow, pipe-like vessels that transport water and nutrients from the roots all the way up to the shoots. Without transport in xylem, the plant cannot create its own food via photosynthesis.
"Xylem are very important to shore up plants against drought as well as salt and other stresses," said lead study author Siobhan Brady, a professor of plant biology at UC Davis.
In turn, without plant mineral transport in xylem, humans and other animals would have fewer vitamins and nutrients essential for our survival. In addition to some typical players needed to form the xylem, new and surprising genes were found.
UC Riverside
The second key set of genes are those that direct an outer layer of the root to produce lignin and suberin. Suberin is the key substance in cork and it surrounds plant cells in a thick layer, holding in water during drought.
Crops like tomatoes and rice have suberin in the roots. Apple fruits have suberin surrounding their outer cells. Anywhere it occurs, it prevents the plant from losing water. Lignin also waterproofs cells and provides mechanical support.
"Suberin and lignin are natural forms of drought protection, and now that the genes that encode for them in this very specific layer of cells have been identified, these compounds can be enhanced," said study co-author Julia Bailey-Serres, a UC Riverside professor of genetics.
"I'm excited we've learned so much about the genes regulating this moisture barrier layer. It is so important for being able to improve drought tolerance for crops," she said.
Genes that encode for a plant's root meristem also turned out to be remarkably similar between tomato, rice, and Arabidopsis, a weed-like model plant. The meristem is the growing tip of each root, and it's the source of all the cells that make up the root.
"It's the region that's going to make the rest of the root, and serves as its stem cell niche," said Bailey-Serres. "It dictates the properties of the roots themselves, such as how big they get. Having knowledge of it can help us develop better root systems."
Brady explained that when farmers are interested in a particular crop, they select plants that have features they can see, such as bigger, more attractive fruits. Much more difficult is for breeders to select plants with properties below ground they can't see.
"The 'hidden half' of a plant, below ground, is critical for breeders to consider if they want to grow a plant successfully," Brady said. "Being able to modify the meristem of a plant's roots will help us engineer crops with more desirable properties."
Though this study analyzed only three plants, the team believes the findings can be applied more broadly.
"Tomato and rice are separated by more than 125 million years of evolution, yet we still see similarities between the genes that control key characteristics," said Bailey-Serres. "It's likely these similarities hold true for other crops too."
IMAGE: Tomatoes grown in Davis, CA and sampled to obtain genetic material for this research. view more
Not many of us see Model T cars on the road today. This 1920's era car made car travel accessible for the middle class, but its last production was in 1927. Yet, some of the engineering that went into the Model T still has an impact on today's cars.
In the same way, older varieties of crops, now much-improved, may today occupy very few acres of land. Where they once were the major variety of the day, their impact is on the history – and genetics – of their specie.
Some of the engineering that went into the Model T still has an impact on today's cars. Source: Hemmings.com
A type of wheat called Madsen, is one of those varieties not widely produced today. But its impact on today's wheat, and future generations, is undeniable. Released in 1988 for production in the Pacific Northwest, Madsen is a soft white winter wheat. It has a high yield potential. But, newer, higher producing cultivars are now more popular, but that doesn't negate the importance Madsen has in the success of today's wheat cultivars.
Madsen's legacy has gone far beyond commercial production. Madsen has been the parent of over 45 released cultivars, many of which were the lines that replaced it in commercial production. It is used as a parent mainly because of the excellent disease resistance it has to common diseases of the PNW. Madsen has also been used in research projects to identify disease resistance genes. In some cases, Madsen was found to be carrying resistance genes the breeder was not aware of but were discovered later in research or field screenings.
The variety of wheat called Madsen was released in 1988 for production in the Pacific Northwest. It is a soft white winter wheat. Credit: Arron Carter
A plant breeder's goal is to release cultivars that are commercially economical and environmentally sustainable. The premise is that new cultivars released are superior to those that are currently available. Through multiple years of testing in small-plot trials, released cultivars and new breeding lines are evaluated for many agronomic traits such as heading date, plant height, yield potential, etc. Furthermore, new breeding lines are subjected to different biotic stress conditions to evaluate pest and disease resistance traits. They may even be subjected to different abiotic stress conditions, either under field or controlled conditions, such as cold temperatures, drought, or low pH soils. After multiple years of testing, breeding lines that have better performance than currently grown cultivars are released for commercial production. Although plant breeders have multiple years of data supporting the performance of the new cultivar, there is no true indicator of how it will perform as a new cultivar until it is released and growers cultivate it on large acreage under commercial production systems.
Madsen wheat has been the parent of over 45 released cultivars, many of which were the lines that replaced it in commercial production. Credit: Arron Carter
During its development, Madsen showed very effective resistance to Pacific Northwest races of the stripe rust fungus and to leaf and stem rust. This disease resistance is important, as fungal diseases spread easily and reduce yields. In fact, Madsen was originally developed to be resistant to a different disease, eyespot foot rot.
Commercial Production
Once Madsen was released as a cultivar, it became widely grown in only a few years. At one time, 20% of the wheat produced in the Pacific Northwest was Madsen. It remained the most widely grown cultivar in the PNW for almost 13 years. Madsen has also been blended and planted with other cultivars in the same field to manage pests because of its excellent disease resistance. This production history has been an impressive 30-year life of a cultivar!
Breeding value
Approximately 45 cultivars have been released in the Pacific Northwest containing Madsen as a direct parent or somewhere within the pedigree. Six of these have been the leading cultivars in either Oregon or Washington for multiple years based on planted hectares.
Agronomic value
If you have ever driven by a field of beautiful wheat and see some of it laying on the ground (versus upright), that is called lodging. Lodging can hurt the value of wheat. Madsen has a lower rate of lodging than other wheats, which could be because its stems are strong. In addition, its resistance to fungal diseases may also help.
Consumer value
No cultivar of crop will remain on the market long if its end-users do not buy it. In addition to how well Madsen performs in the field, it also has excellent baking properties.
Answered by Arron Carter, Washington State University
Fun fact: did you know that many cultivars are named after people? Madsen was named in honor of Dr. Louis L. Madsen, Dean of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University from 1965 to 1973. Dr. Madsen was an effective advocate of wheat research at the university, and a strong supporter of the collaboration between the USDA units and the College on campus.
About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world's food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.
Most plant-based foods we eat today are a product of innovative plant breeding programs. Careful choice of plant parents is followed by a multitude of intentional, hand-pollinated blooms. These result in thousands of unique seeds. This is just the start of a long process to create better crops.
In a paper we published recently in Crop Science, we outline a very critical issue: U.S. public investment in plant breeding programs has fallen. The current funding model of short-term grants (1-, 2- or sometimes 5-year awards) is particularly challenging for breeding programs which require typically a 7- to 12-year process, or far longer.
Crop breeders are not just looking for characteristics like drought tolerance or disease resistance in their breeding programs. They also must create new crops with these characteristics that taste good!
Breeders select plant parents based on desirable characteristics. These could be taste, size, cooking ability, yield, disease resistance and more.
They then cross-pollinate, growing seeds that are hybrids of the parents. They are the “children.”
These “child” seeds are germinated, nurtured, and then meticulously evaluated. Many inferior seedlings are ultimately discarded, with only a few of them advancing to a new round of parenting.
Crops go through many such cycles of newly-created diversity and intentional selection. Eventually, the plant breeder may become satisfied that an elite seedling has what it takes to become a successful new variety. This practice is a long-term endeavor. Some crops can be brought to market in a few years, but crops like apples can take well over a decade.
The benefits of public plant breeding programs
As a result of plant breeding, yields and quality have increased, resulting in remarkable improvements in agricultural production systems. Related species have been used as parents to give important crop plants tolerance to biological and physical stressors. New varieties are adapted to withstand harsh growing conditions or potentially devastating invasive pests or diseases. As climate conditions and ecosystems change, plant breeding is an essential tool to address our long-term food security.
Both private and public institutions have crop breeders working to improve our food supply. Public plant breeding programs often focus on crops that are important to society but may be less profitable than crops that drive the bottom line for large businesses. These crops may have long generation times or otherwise be challenging to breed. They may be the focus of regional cultural specialties or beloved niche markets. Private breeding programs usually must focus on large multinational commodity markets with a potential to generate large, near-term financial returns on private investment. Given these pressures, private companies may find it difficult or impossible to address smaller national or regional markets or longer-term needs.
Public plant breeding programs frequently target such longer-term goals, many of which address food security issues. For example, “pre-breeding” enriches our agricultural base with diverse plant characteristics from crop wild relatives or other related plants. This requires a lot of research, and significant risk that some efforts won't pan out. But these trials can create new, superior seedlings which make it possible for public breeding programs and private breeding companies to produce important new crop varieties.
Public plant breeding programs also play a key role in educating the next generation of plant breeders and plant scientists for both public and private programs.
Varieties of apple that don't brown quickly once sliced, or perform better when cooked, take years of crop breeding to develop.Credit: Getty Images Pro/Canva
Funding issues cause problems
Several studies over the past 30 years have looked at the status of breeding programs. Each showed that U.S. plant breeding capacity is at risk. Budgets and personnel availability continue to decline, despite the development of new plant breeding technologies.
Our most recent survey cited above, in 2018, updated this information. The data indicates a significant reduction in public breeding program personnel over the last 5 years, and aging program leaders. Many programs report that budget shortfalls and uncertainty endanger or constrain their ability to support key personnel, maintain core infrastructure and operations, and make use of current technology.
Many surveyed said that when funding is reduced or sporadic, they focus on sustaining the most basic core operations of the program. These are items like fixing the greenhouse roof and watering the fields. Applying new scientific advances or continuing graduate student and postgraduate training opportunities are typically the first losses. This impacts not only the public program's advanced goals but also development of a long-term social resource: the next generation of plant breeders.
The bottom line is that the struggle to maintain adequate funding hampers public breeding programs. The timeline to bring new crops to market exceeds the time period of most funding sources by years. This requires program leaders to devote much of their time to the constant search for more funding, rather than focusing on their actual work. One solution is to create longer-term grant programs. Otherwise, advances in important crops that are not global commodities could start to decline.
Produce variety has increased over the past few decades thanks to crop breeding programs. Unfortunately, the breeding and funding processes of this research are out of sync. Credit: Morguefile
Our study shows public plant breeding programs are at risk of disappearing. They need reinvigorated, stable, long-term access to funding, technology, knowledge, and expertise.
U.S. plant breeding capacity as a whole (both public and private) and, more broadly, U.S. food security, natural resource resilience, and public health will erode if the trajectory of declining budgets and reduced staffing and expertise in public plant breeding programs is allowed to continue.
Public plant breeding programs are easy to overlook, but their loss would be a devastating blow to our food system.
Floyd Zaiger a world famous fruit breeder has just passed. Luther Burbank created such creations as the Russet Burbank Potato, the Shasta daisy and the ‘Santa Rosa” plum. This was all done through traditional breeding practices. Floyd Zaiger carried the breeding process to a more intense level for fruit trees, crossing plums and apricots to get ‘Pluots' and ‘Apriums' and a range of other crosses between species – interspecifics. He worked to create low-chill cherries, such as ‘Minnie Roya', ‘Royal Lee' an ‘Riyal Crimson' that are more adapted to Southern California growing conditions than traditional cherries. He and his company Zaiger Genetics were able to create new varieties by the sheer number of crosses that are done every year, thousands. Part of the success has been the use of moveable containers that allow them to create environments that are more conducive to crosses that would not normally occur because of different flowering times. The Zaiger family continues with the family business and we can expect to see many more new Zaiger fruits, nuts and rootstocks in the future.
New selections currently under development include:
varieties with low winter chilling requirements,
dwarf and semi-dwarf varieties,
dwarfing rootstocks and extremely vigorous semi-dwarfing rootstocks,
nematode and disease-resistant rootstocks,
extra-early and extra-late-ripening varieties,
low acid/high flavor white-fleshed peaches and nectarines,
And we do have UC breeders of all manner of fruits – strawberries, walnuts, pistachios, citrus amongst many other crops. A couple of avocado breeders are Mary Lu Arpaia and Patty Manoslava
The U.C. Cooperative Extension Farm Advisors have combined to publish this quarterly combined newsletter. It will emphasize citrus and avocado, but will also discuss the minor subtropicals.
University of California Cooperative Extension Ventura County 669 County Square Drive, Suite 100 Ventura, CA 93003 Phone: 805.645.1451 Fax: 805.645.1474
Facebook
X (Twitter)
Reddit
Pinterest
Tumblr
LinkedIn
