Peanut Grower November 2018 NPB Research Review

R E S E AR CH RE V IE W:

The Future Of Peanut Breeding

Sponsored by National Peanut Board

R ES EA R C H R E V I E W:

The Future Of Peanut B THE GOAL: PRECISION PEANUT BREEDING Precision agriculture, at least in some form, has been widely adopted in peanut farming.

For most, it came through using auto steer as a navigation aid to help plant and dig peanuts more accurately. The use of global positioning system receivers helped producers stay on the row and increased digging efficiency greatly. While it was an improvement over human eyesight, it still offered too much room for error. With producers wanting and needing passto-pass accuracy down to the sub-inch, the use of GPS signal correction using Real Time Kinematic (RTK) technology came about. This more advanced technology improved the accuracy of auto steer even further.

But auto steer is only one tool in your tool box. Would you go back to planting and digging without it? Probably not. But it takes many tools to produce a crop. Any time you can add a tool that improves efficiency over an old tool, that’s what you should do.

YOUR BOLD MOVE And that’s what you did for peanut breeding. Along with shellers and manufacturers, peanut producers, through producer organizations and with the Peanut Foundation taking the reins, initiated a bold research project to map the peanut’s genetic code.

Until that time, peanut breeders were making selections using techniques of crossing various lines that showed promise and were successful in moving the industry forward through improved varieties. These conventional breeding techniques made it possible to overcome diseases such as Tomato Spotted Wilt Virus and increase average yields by more than 1,000 pounds. Since 1969, 105 peanut cultivars were registered. But the truth is, peanuts were behind in advanced variety development technology by as much as 10 years.

While there is the need to increase disease resistance or overcome the allergy issue for peanut farmers and the peanut industry as a whole, there is also the pressing need to expand all of agriculture worldwide in order to feed 11 billion people by 2050. Peanuts are the third most important oilseed in the world, and production of all agricultural crops must increase by more than 70 percent to meet this future need. That’s why moving toward precision peanut breeding is so critical.

USING BETTER TOOLS Precision breeding, simply put, is a group of tools and methods used to develop new varieties more precisely and rapidly. Now that we know the genetic sequence of the peanut, we can look into what those specific genes do. However, it needs to be noted that knowing and being able to select traits beneficial to our needs of pest resistance or drought response doesn’t mean breeders are moving away from conventional breeding techniques toward genetic modification.

Your use of RTK GPS doesn’t mean you don’t use the tractor any more. You still need the tractor. Being able to identify and select traits makes conventional breeding faster and more efficient — but it is still conventional breeding. Genetic modification is another potential tool, but is not the direction the peanut industry is moving. Thanks to the completion of the Peanut Genomic Initiative and tools that are being developed and will continue to be developed, peanut breeders have advanced techniques that will work to improve conventional breeding for at least 25 to 30 years. The tools are available to move toward precise peanut breeding.

12 /

THE PE ANUT GROWER • NOVEMBER 2018

Where Are We Now? •

Precision agriculture coupled with precision breeding could allow the available food supply to keep up with the growing world population.

•

Molecular peanut breeding will reduce the time and effort required to develop improved cultivars.

•

Future peanut breeders should be (and must be) well-trained in molecular and traditional breeding methods.

•

Extensive phenotyping of genotyped material is essential to develop a collection of trait-associated markers for peanut.

•

For peanut breeders to use marker assisted selection in their programs, it is imperative that the sampling cost be affordable.

•

With the use of marker assisted breeding, peanut breeding by design can become a reality!

Source: Kelly Chamberlin, USDA ARS, Stillwater, Oklahoma

GRAPHICS BY VECTEEZY.COM

ut Breeding THE LAUNCH: PROPELLING THE SCIENCE FORWARD Rockets launch because they burn a great amount of fuel at once but in a manner to propel the craft forward and not have it explode. In reality, the launch is not caused by a single ignition and thrust. That would only get it so far. Space shuttles are hurled into space because of multiple thrusts provided by two solid rocket boosters and three main engines.

The solid rocket boosters are the heavy lifters on the shuttle and provide most of the initial thrust, but only burn for about two minutes, after which the solid rocket booster fuel tanks separate from the shuttle and fall back to Earth. The engines burn and propel the craft further into space, but only for about eight minutes each. It takes all these various bursts of energy and momentum to launch the space craft, which weighs about 4.4 million pounds, at a speed of thousands of miles per hour needed to get through our atmosphere and beyond the reach of Earth’s gravitational pull.

A GIANT LEAP The advancement of peanut breeding, and all plant breeding for that matter, can be thought of in a similar way. At one time, it was only the farmers saving seed selected from their best performing plants. As science progressed, more was known about the biology of the plant and better plant breeding could take place. Each breakthrough in plant breed-

ing thrust it further. Completion of the Peanut Genomic Initiative was a big boost forward for peanut plant breeding and the peanut industry that depends on these varieties.

These discoveries offer new capabilities to find beneficial genes in cultivated and wild peanut species.

But the PGI project brought more than mapping the peanut genome. Additional capabilities were discovered. One of those is the ability to move genes from wild peanut species, which are diploid, meaning they have two sets of chromosomes, to cultivated peanut species, which are tetraploid and have four sets of chromosomes. As simple as that sounds in one sentence, the feat was huge in the peanut breeding world.

AN EXCITING FUTURE Now, both the wild species and cultivated species, which were collected by some of our early peanut breeding researchers and make up the USDA peanut core collection in Griffin, Georgia, can be combed through for desirable traits.

Finding some of these traits and narrowing down the collection to a more manageable mini-core collection has already been accomplished. All of these achievements propel peanut breeding forward and bring an exciting future to the peanut industry. As we dig deeper into the specific genes looking for those desirable traits, the future of peanut plant breeding will happen on this molecular level.

NOVEMBER 2018 • THE PE ANUT GROWER /

13

Constraints In Molecular Breeding Very few molecular markers

Very few molecular markers

No genetic map or maps with low marker density

No genetic map or maps with low marker density

No genome sequence

No genome sequence

No available appropriate germplasm, mapping populations and/or phenotyping data

No available appropriate germplasm, mapping populations and/or phenotyping data

No trait-associated markers Capacity and skills of breeders due to lack of molecular background/training

Peanut Genome Is Sequenced!

Cost prohibitive

No trait-associated markers Capacity and skills of breeders due to lack of molecular background/training Cost prohibitive

Source: Kelly Chamberlin, USDA ARS, Stillwater, Oklahoma

THE MASTERPIECE: OUR FUTURE VARIETIES Can you look at a piece of sheet music with hundreds, if not thousands, of notes and know what it sounds like? Perhaps you can read music. Breaking down that sheet of music, you find the specific notes, an A, a B, middle C, a G. The notes will be in the natural key or one that is flat or sharp. You can know the number of beats per measure by looking at the timing signature and determine whether it is fast or slow. Symbols tell you where to rest, where to repeat and where to skip ahead. You can read all of that, but do you know what it sounds like?

That’s where peanut breeding is today. Determining what the notes sound like. We have the specific genetic sequence that makes up the peanut. Now it’s a matter of taking that genetic map and digging into those specific regions of the map, called markers, to determine their function or what specific trait it offers. The genetic map is the sheet music. The markers are the notes. The sound is what that trait actually does in the peanut plant.

DIGGING EVEN DEEPER The differences that distinguish one plant from another are encoded in the plant’s genetic material, the DNA. DNA is packaged in chromosome pairs or strands of genetic material, one coming from each parent. The genes, which control a plant’s characteristics, are located on specific segments of each chromosome. All of a plant’s genes, together, make up its genome. That’s where we are with the peanut. We know this genome.

Some traits, like flower color, may be controlled by only one gene. Other more complex characteristics, like crop yield or oil content, may be influenced by many genes. Traditionally, plant breeders selected plants based on their visible or measurable traits.

This process is slow and costly, and as we now know, is outdated.

QUICKER, MORE EFFICIENT BREEDING A quicker way and the direction future peanut breeding is moving is the use of marker-assisted selection to help identify specific genes. The markers are a string or sequence of nucleic acid that makes up a segment of DNA. The markers are located near the DNA sequence of the desired gene. Since the markers and the genes are close together on the same chromosome, they tend to stay together as each generation of plants is produced. This is what helps researchers predict whether a 14 /

THE PE ANUT GROWER • NOVEMBER 2018

plant will have a desired gene. If researchers can find the marker for the gene, it means the desired gene itself is present.

Work is being done to find the specific markers for many traits in peanut, such as leaf spot. In order to find markers associated with specific traits, both genetic and phenotypic (visual or measurable data) must be gathered and correlated. In a test set of plants designed specifically for identifying markers associated with a certain trait, DNA is taken from each plant and analyzed. The same plants are examined for the specific trait in the field for a period of years. This is called phenotyping and is necessary to determine which markers correlate to what trait. When the specific markers are always present in leaf spot resistant plants, breeders can use those markers to select those peanut plants in their breeding programs. Whatever it is that the peanut plant or peanut kernel can exhibit – disease resistance, drought tolerance, reduced skin slippage, improved blanchability — there is a marker for it. The bottleneck, if you will, for molecular peanut breeding is effective marker-trait associations or phenotyping markers to determine the traits.

REAL WORLD APPLICATION With the PGI project completed last year, the Peanut Foundation has shifted its focus to more applied problem-solving tools for the industry. The four problems they are working towards are leaf spot, aflatoxin, drought tolerance and flavor/quality issues.

Building on the mechanisms created by nature, the latest innovations in plant breeding methods will result in the breeding of peanut varieties in less time and with greater precision.

What was learned through the PGI adds greatly to plant breeders’ ability to get to that level. When it all comes together, it will be the masterpiece of new and better peanut varieties that lead to reduced production costs, less disease pressure, greater yields, improved processing traits, increased nutritional content and better flavor. Worldwide, U.S. peanut producers will be more competitive. An exciting future for peanut breeding and the peanut industry is just ahead. RR