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PENNSYLVANIA TURFGRASS: David R. Huff, Dept of Plant Science, Pennsylvania State University

For the past 27 years, I’ve been working to develop a commercial seed supply of dwarf perennial Poa annua varieties that are tolerant of biotic and abiotic stress for use on golf course putting greens and fairways and I’m proud to announce that the completion of this goal will soon be achieved. This article is an overview of that long 27-year journey and to begin, I need to address one of the very first questions posed to me when I started the Penn State Poa annua breeding project back in 1994 as a brand-new assistant professor. ‘Why would you breed Poa annua, isn’t that the weed we’re all trying to kill?’ was the question. And it’s a great question. That’s because Poa annua is considered a noxious weed in many states and for many decades there’s been research and chemical product development single-mindedly devoted to eradicating Poa annua from planet earth. However, Poa annua is a marvel of evolution and is doggedly reluctant to go extinct. According to Heap (2021; www.weedscience.org), Poa annua has developed herbicide resistance to nine modes of action involving 23 different active chemistries. And so, the battle continues. For example, in 2018, the USDA awarded a $5.6 million grant (http://resistpoa.org) for studying Poa annua’s many herbicide resistance mechanisms and to determine if any cultural practices may lessen the economic impact of Poa annua invasion. So why would anyone spend their entire professional career trying to breed improved varieties of such a beast?

Well, there’s another side to the Poa annua story, which is that it plays an important role in the history and legacy of the game of golf in America and around the world. According to a 2015 land use survey conducted by the USGA & GCSAA (see references), there is more acreage of Poa annua on US golf courses (146,839 ac) than either perennial ryegrass (138,781 ac) or creeping bentgrass (127,608 ac). And, of the nine turfgrass species surveyed, Poa annua ranked third in popularity, behind only bermudagrass and Kentucky bluegrass, and is the only one of these turfgrass species that doesn’t exist as commercially available varieties. Thus, all of this Poa annua acreage exists simply as a collection of localized natural ecotypes (also known as “land races”). On putting greens, the acreage of Poa annua (10,877 ac) is nearly half that (43%) of creeping bentgrass (25,327 ac) and a bit more than bermudagrass (10,055 ac). However, over the 10-year period between 2005-2015, the putting green acreage of Poa annua actually increased (+3.4%) whereas that of creeping bentgrass decreased (-9.6%), and so the relative acreage of Poa annua compared to bentgrass is increasing despite there being no commercial seed supply. Another salient point to make regarding the use and value of Poa annua putting greens is that, according to Golf Digest’s 2015-2016 ranking of the greatest US golf courses (golfdigest.com), seven of the top 10 golf courses utilize Poa annua as their putting green surface. This means that many of the most prestigious golf tournaments are played on Poa annua greens and not on creeping bentgrass. For example, Oakmont Country Club, Oakmont, PA, established in 1903, has reportedly held more combined USGA and PGA championships than any other golf course and has always had Poa annua greens. So, the question I ask is, ‘Why would these elite golf courses utilize a weed as their putting surface when they could easily solid sod all their greens overnight to creeping bentgrass?’ I believe the answer to that question is that Poa annua provides superior quality characteristics including high shoot density, upright growth habit, and persistence under close mowing heights that yields the fast putting speeds demanded by these top courses (Fig. 1). And yet, there’s no commercial enterprise within our industry supplying these courses with seed of improved varieties of Poa annua for renovations and new establishment projects…until now that is.

In 1994, I began the Penn State Poa annua breeding project by collecting, evaluating, crossing, and selecting thousands of family lines of Poa annua for use on greens and fairways. We didn’t spray fungicides because if any lines were susceptible to diseases like dollar spot or anthracnose, then I didn’t want them (Fig. 2). We evaluated for tiller density, genetic color, summer performance and winter survival. We threw away everything that didn’t meet our standards (>99.5%) and kept only the very best (<0.5%). We then tested these lines in places like New York, Connecticut, California, and Australia. In New York and Australia, the evaluations allowed for a side-by-side comparison with the local land races of Poa annua. In both cases, the Penn State varieties outperformed the local land races (Fig. 3). This is an important point to note because I often hear “Well, if my course has had Poa annua greens for 100 years then I must have the very best Poa annua possible.” But that deduction is oversimplified and typically does not hold true. In the adaptive landscape model of the evolutionary process (think of a mountain range), a population’s response to selection pressure is that its fitness always increases (travels up the mountain) and never decreases (never travels down the mountain). As such, the ultimate fitness peak of any particular population (i.e. its elevation) depends on the genetic basis of initial starting material (i.e. the stamina of the hiker) and the random nature of the selection process that was involved (the hiking trial itself). However, as my AGRO 851 students can attest, a population’s fitness peak (i.e. its elevation) is capable of being increased by introducing new genetic variation and restarting the selection process (restarting the hike from the base of the mountain to the “new” top). This is exactly what the plant breeding process is all about and cannot necessarily be duplicated in nature. For example, consider the progress that turfgrass breeders have made in the 70+ years of breeding creeping bentgrass. We started with land races from nature (ex. Seaside, South German Bent), then we crossed land races together to produce varieties that were superior to any one land race (ex. Penncross), then we recombined the genes of creeping bentgrass and imposed increasingly harsher and more stringent selection pressure to develop improved varieties (ex. Penn A’s and G’s) and then, by continuing this process, we have now realized even more improvements (ex. 007XL and Pure Eclipse). Clearly, as exemplified by creeping bentgrass, as well as the breeding of nearly all agricultural commodity crops like wheat, rice, and corn, the efforts of a directed plant breeding process are capable of outperforming land races derived from the random natural selection process of happenstance starting material. The same process holds true for Poa annua. Just imagine the improvements we could make in Poa annua with 70+ years of breeding effort; the very thought boggles my mind.

The problem with Poa annua is not breeding improved varieties capable of outperforming local land races, we’ve proven that’s possible in the first 12 years of the breeding project (Fig. 4). The problem has been to produce commercial quantities of seed of the stress tolerant, dwarf, perennial strains that flourish under greens and fairway mowing heights. Solving that seed production problem has taken the Poa annua breeding project another 12 years of hard, and often frustrating work. However, I’m happy to report that we’ve finally solved the seed production problem and over the past 3 years we’ve been improving our production methods and increasing our production capabilities (Fig. 5). The last step in this overall process will be to increase the acreage of our seed production fields in order to generate the necessary quantities of seed to fill demand. What the ultimate market size will be for seed of elite, stress tolerant Poa annua is anyone’s guess. However, the interest generated from an early announcement at this year’s 2022 Western PA Turf Conference has already exceeded our limited on-campus seed production capabilities. Therefore, we need to go off-site and start the commercial enterprise that will ultimately be capable of producing even larger quantities of seed. To that end, Penn State University has been very supportive through grants and guidance from the Innovation and Entrepreneurship Program, the Research Applications for INnovation (RAIN) Program, and the Office of Technology Management. Of course, none of this breeding project would have been possible without the generous financial support and encouragement by the Pennsylvania Turfgrass Council and the United States Golf Association (USGA). I expect that the commercialization process will take several more years to become a reality and will undoubtedly have its own unique set of challenges and hurdles to overcome. But I believe most of the heavy lifting has been done and, after 27 years, I’m not about to give up now. Ultimately, we plan to produce seed of improved, stress-tolerant varieties of Poa annua for commercial use on golf course putting greens and fairways that will aid golf course superintendents and architects in their own establishment and renovation projects.

References:

Golf Course Environmental Profile. 2017. Land Use Characteristics and Environmental Stewardship Programs on U.S. Golf Courses. USGA & GCSAA. https://www.gcsaa.org/docs/default-source/Environment/phase-2-land-use-survey-full-report.pdf?sfvrsn=c750ea3e_2