May 14, 2021

Varietal Research: Still a Laborious Effort…Albeit on a Faster Track

By Tim Linden

Building that better variety is a time-consuming endeavor, but over the years seed breeders have developed techniques to target desirable traits and speed up the process. Though these efforts can shave several years off a successful launch of a new variety, development is still measured in years with five years appearing to be a typical average for a new variety to survive the trial period and be offered to the grower community.

“As a rule, it still takes a relatively long time to bring a new variety to market,” said Jeff Zischke, senior director of research and development, Sakata Seed America, Salinas, CA. “But there are techniques that have been developed that make a difference.”

Marcio Pais de Arruda, a tomato breeder for HM. Clause in Davis, CA, made a similar point during an interview covering many different aspects of varietal research. “The way we make hybrids hasn’t dramatically changed,” he said, “but we have developed innovative techniques and processes that allow us go faster and help us to be more precise.”

He said not too long ago, the normal time to develop a new variety and bring it to market was about seven years. Now he says it can be done as quickly as three to five years, especially if the effort involves adding a new trait to an existing variety.

Zischke estimated that it typically takes five to six years in today’s environment. While some have lamented that more advanced techniques involving gene editing are not yet available, the Sakata researcher does not fret about it. “I am a big believer in conventional plant breeding,” he said. “Plant breeders continue to make steady improvements using these techniques.”

He has no doubt that gene editing will eventually be utilized in varietal development but it is essential that we gain the public’s trust. Zischke said breeders have done very well in utilizing time-saving and trait-targeting techniques to speed up the process and reduce the misses.

He discussed a number of those processes in detail which will only be briefly discussed in this report.

He said one technique researchers now use is “breeding pools,” which are used to generate parental groups with common characteristics. Zischke said if you are looking to transfer a specific trait from one parent to another in the same pool, you don’t have to start from scratch. Most of the characteristics of a line are common within the pool. Crosses between pools is generally a proven formula for making potential products. This, of course, depends on how disciplined the breeder is with his pools and how well they complement each other.

Zischke said another time-saving technique is the use of tissue culture technology to generate dihaploid plants. A single plant will generate a finished and genetically fixed inbred line. This is not possible with all species and not all dihaploid plants yield useful lines, but when successful, it can dramatically speed up the process of inbred or parental line development.

Marker assisted selection is another area where advances can help in the development of new varieties. Linked markers can easily identify which plants carry specific traits and allow breeders to more rapidly use these traits in the breeding effort.

Pais de Arruda agreed that the way vegetable breeders make a hybrid has not changed dramatically, but he said new, innovative techniques and processes do make the work easier and quicker. He said geneticists and breeders have developed new ways of using markers that help them in many ways.

For example, he said breeding using information across the genome of the plants allows for more predictability. A breeder does not necessarily need to go through extensive field testing of a larger number of combinations to determine how they will all react under known circumstances. Some combinations can be eliminated before they are even made, based on DNA information. They can also follow genes/traits of interests with molecular markers to add them to a line, which allows for faster development of a new variety with added value.

The HM. Clause tomato breeder said there have also been many advances that speed up the process on the front end. Multiple generations can be developed in a year’s time as new processes and technology allow for moving through generations without growing out an entire crop.

Pais de Arruda said breeding programs now include experts in other disciplines to help analyze winners and losers at a molecular level and again decrease the number of crosses that must be grown out in the field. He has been in the HM. Clause tomato breeding program for five years and he said within that short time the number of scientists involved (plant pathologists, genetics and biometrics support) has increased, with much more work being done on the gene level.

“Predictive breeding” is becoming a common practice with breeders running thousands of molecular markers and then they can predict, with some degree of certainty, how the plant will perform in the field without actually planting it. Of course, these materials are planted and checked and their predictive models are adjusted when necessary. Pais de Arruda said this technique allows a breeder to be more focused and better use the resources available to them.

There will continue to be advances in how new varieties are developed, but what probably won’t change is the top trait breeders are looking for. “Yield is still number one,” said Zischke.

Growers necessarily have to measure the success of any variety by revenue per acre and that equates to tonnage. The veteran seed breeder said there are many other traits that are important—disease resistance, quality, plant vigor and taste, to name a few,—but if a variety doesn’t offer a competitive yield profile, no one is going to grow it.

He did offer that Sakata continues to improve its varieties in all these areas. He also noted that in Florida the company’s tomato breeding program has made major gains in a short amount of time on improving flavor. They are using markers for flavor components developed by Harry Klee, Ph.D. of the University of Florida, and are selecting different combinations of these flavor alleles to optimize flavor and validating with sensory panels. These genetic markers allowed Sakata to accomplish in a handful of years what could have taken much longer through conventional breeding.

Pais de Arruda listed the top three varietal characteristics for tomatoes as yield, quality and flavor. “Yield has to be number one,” he said, indicating that without a yield factor that allows for the making of a profit, nothing else matters.

But he noted that quality is very important and firmness is still something that has to be present in fresh market tomatoes, which is his specialty. Flavor is another important trait that makes his top three for obvious reasons.

While Pais de Arruda did list a top three, he said a successful variety has to have many other good traits including good fruit size and long shelf life. He added that the plant also must have good cover to protect fresh market tomatoes as they grow.