Perennial ryegrass (Lolium perenne) is the most extensively used amenity grass species in the UK, forming a key component of grass seed blends and mixtures for winter sports, golf, turf production and landscaping. With well over 100 cultivars listed in the BSPB Turfgrass Seed Booklet, selecting the correct combination of varieties is a tricky task. This analyses the main factors to consider. In addition, recent innovation has seen the successful introduction of amenity annual ryegrass (Lolium multiflorum), for use where cool temperature germination and growth or very fast reinstatement are the over-riding priorities. What are the key considerations when choosing ryegrasses? Specific applications and environmental conditions demand different characteristics and performance capability. Within the species, characteristics such as tolerance to wear, drought, disease, salt, shade, mowing height, cool temperature growth, leaf width, colour and recovery following stress vary considerably. The extensive ryegrass breeding and applied research and development programme at Barenbrug enables us to offer you a distinct range of cultivars in blends and mixtures specifically designed to meet these varied demands. Wear Tolerance and Recovery Wear tolerance is a difficult characteristic to quantify. It is most commonly assessed by analysing visually or by objective means how much ground cover persists after a period of artificial or real wear. Barenbrug undertake wear trials at many of our Research Stations, including our trial site at Cropvale in Worcestershire. Wear trials also take place at Bingley as part of the BSPB Turfgrass Seed Booklet assessments. In terms of individual cultivars, Barorlando and Barcristalla have excelled in recent years. Perennial ryegrass has a tufted growth habit, so normally has to rely on fast shoot recovery following wear or disease pressure to maintain the aesthetics of the turf. Bareuro is an example of a variety that excels in this regard. In reality though, wear tolerance is a more complex trait. Different wear actions impact varying degrees of damage, whether through high footfall on golf courses, tearing actions on sports pitches or crushing impact on racecourses additionally environmental conditions and maintenance programmes also impact on the capability of a cultivar to withstand wear pressure. Wear tolerance must be considered alongside such pressures as disease, mowing height, shade, nutrient input and drought when choosing your blend of ryegrasses. Such constraints significantly influence the capability to tolerate wear. In almost all circumstances, a combination of varieties - a tailored synergistic seed mixture - will outperform any individual cultivar. For further technical advice please call Barenbrug UK Ltd on 01359 272000 email info@baruk.co.uk or visit our website www.barenbrug.co.uk
Do you know your Ryegrasses? RPR Regenerating Perennial Ryegrass Recent advances in breeding have resulted in the introduction of a distinctive new group of cultivars, termed Regenerating Perennial Ryegrasses or simply RPR. RPR is unique because of its creeping growth habit, made possible through the production of elongated tillers or determinate stolons. Determinate stolons are growth shoots emerging from nodes at the base of each plant. They creep horizontally just below the surface, and are capable of developing roots at the internodes, creating entirely new grass plants (see Figure 1 and 2). RPR is a patented concept in USA and cultivars under the RPR description have been accepted taxonomically as an entirely new subspecies of perennial ryegrass. RPR s growth habit results in a new dimension for establishment, wear tolerance, and unparalleled recovery capability. The RPR concept is only available in BAR 7 RPR and Extreme RPR products. In both mixtures Barclay II RPR is combined with traditional ryegrasses to create optimal blends for winter sports and medium/fine summer sports turf, respectively. Since the launch of RPR in 2012, some companies have imported so-called creeping ryegrasses to the UK market. These grasses should not be viewed as viable alternatives to RPR. Most are darkgreen types (see below) from America, typically bred without screening for wear damage, and often not exhibiting DETERMINATE STOLONS morphologically similar structures to RPR s determinate stolons. A dedicated RPR leaflet is available along with further information at www.barenbrug.co.uk/rpr Figure 1: Barclay II s determinate stolons and subsequent formation of new plants Figure 2: RPR sown in rows to demonstrate its spreading growth habit when compared with standard perennial ryegrass PRG RPR
Colour & Growth Perennial ryegrass varieties, despite all being different, can be divided into two broad groups dark green types and bright green types (see Figure 3). The dark green types typically originate from North-America and are bred in areas with very harsh winters or very hot summers. Breeders have to select grasses that can survive these extremes. For instance, in cold winters, dark types persist by shutting down and go through a long period of winter dormancy in growth; they show less growth under low light intensity. They can have aesthetic value as they tend to maintain their colour better in winter months (see Table 1 data; Barlennium), but this benefit is heavily offset by their inability to grow (and recover from wear) during this time. The bright green breeding material has generally originated in Europe, where selections are made more for winter-active growth. In a breeder s trial subject to wear through the winter, those varieties that are still growing and are able to recover during this time will tend to fair best. They are simply better adapted to grow in low light levels, and seem to be more efficient at using available light, particularly during the winter. In recent Barenbrug breeding programmes, new material from France has been particularly successful in UK trials. Barorlando, Barcristalla, Barillion and Bardorado show good winter activity, which may well have been detrimental if bred in a colder winter climate. Barorlando and Barcristalla have an added benefit of a very rich bright green colour for all but the coldest periods of the year (see Table 1 data). These facts clearly point to the predominant use of bright green cultivars in winter sports pitches in the UK, particularly in stadia environments where light levels are low. The use of a minor percentage of a dark type within a mix can be beneficial for certain reasons (e.g. to help underpin a nice year-round mid-green colour) but an over-reliance of dark green material in a blend will have detrimental effects on winter performance under wear. An additional point of caution to make to anyone adopting a high proportion of dark types within their seed mixture is to consider the aesthetic value of a sward with a proportion of Poa annua in it. The ubiquitous annual meadowgrass will visually blend far better with bright green ryegrass varieties than dark cultivars. This may be of minor concern to high-end football pitches that have the luxury of a full annual renovation, but for anyone managing a more permanent grass pitch, golf course or turf crop, this is a very important consideration (see Figure 4).
Figure 3 Figure 3: The BSPB Turfgrass Seed perennial ryegrass lawn trial at STRI. Note the two distinct groups of colour. Figure 4 Figure 4: Poa annua ingression into dark-type perennial ryegrass Table 1 Cultivar Live Ground Cover Visual Merit Mean Score Winter Green Colour Intensity Summer Green Colour Intensity Barorlando 8.1 8.0 8.1 5.6 7.4 Barcristalla 8.1 8.0 8.0 6.1 7.5 Bareuro 7.3 7.3 7.3 5.1 5.7 Barillion 7.1 7.0 7.0 5.4 6.4 Barlennium 6.7 6.5 6.6 7.6 7.7 Bardorado 6.6 6.4 6.5 5.0 5.3 Bargold 6.3 6.6 6.5 5.6 5.7 Table 1: Data from the Turfgrass Seed 2014 guide s Table S1 Barenbrug cultivars in ranking order. Note dark green winter colour of North American-bred Barlennium (dark-green type) and outstanding summer colour of Barorlando and Barcristalla (bright green type, bred in South of France).
Fineness of leaf/tolerance to close mowing When considering ryegrass varieties for use in summer sports, fineness of leaf is a particularly important characteristic. There is a strong correlation between fine leaf width and the ability of a cultivar to tolerate the lower heights of cut associated with summer sports. In addition, in many applications for summer sports, ryegrasses are blended with fine fescues put simply, the finest ryegrasses look far better aesthetically in a mixed sward. Figure 5 shows the remarkable breeding achievements during the last decade which have created an unrivalled portfolio of extremely fine -leafed cultivars for summer sports. Bargold, and more recently Barsignum and Barolympic have all set new standards for the species. If ryegrasses are needed to combine wear tolerance and close mowing, selecting a synergistic blend of varieties like BAR EXTREME is recommended. If combining ryegrasses with fescue for medium/fine turf applications, selecting a variety with the finest leaf possible and mid-green colour is often considered best practice. Figure 5 Figure 5: Fineness of Leaf scores of selected ryegrass cultivars from Table L1 Turfgrass Seed 2014, scored on a scale 1-9, with 9 finest leaf, 1 = broadest.
Disease Tolerance The major turf diseases affecting perennial ryegrasses in the UK are Red Thread, Fusarium Patch and Leaf Spot (Dreschlera spp.) Red Thread has been a major screening selection of breeding programmes for decades, but the importance of improved tolerance to Leaf Spot and Fusarium Patch, particularly for stadium environments, is becoming increasingly vital. During the breeding process new progeny are screened throughout the seasons in order to identify individual cultivars which offer improved tolerance to e.g. Leaf Spot at key times such as end of season pitch renovation in May/June and mid-season in November/December. Blending of such cultivars offers longer tolerance to this specific disease pressure. For Red Thread, Bargold and Barolympic are particularly recommended; Barorlando, Bareuro and Barclay II are highly resistant to Fusarium Patch and for Leaf Spot, Barorlando and Barclay II excel (data from Barenbrug Research and French National Listing, 2013).
Drought and/or Salt Tolerance Perennial ryegrasses are naturally fairly tolerant to both drought and salt stress, but large differences can be seen between cultivars. In some circumstances, e.g. winter sports pitches with minimal irrigation, or areas of golf courses exposed to high salinity or drought pressure, these factors may predominate when selecting appropriate varieties. Barenbrug Research undertakes a thorough cultivar screening process by means of water restitution trials in association with Landlab Studios in Vicenza. Grass plots are studied in controlled conditions in a drought tent, where precise % proportions of evapo-transpiration (ETc) rates are replaced under a stress period (lasting 2-3 months). In perennial ryegrass trials, Romance, ER2703, Barlennium, Bardorado and Barclay II all performed very well. Bardorado features in BAR 9 and BAR 10 RTF; mixtures specifically designed for winter sports pitches exposed to drought conditions. Germination salt tolerance is tested in a laboratory using the parameters set by the International Seed Trade Association (ISTA) using different salt levels equivalent to sea water of 20,000 and 30,000 parts per million (ppm), with 0ppm as a control. Laboratory trials at Barenbrug research demonstrate the huge variation in germination capability of cultivars of perennial ryegrass (see Figure 6). The data represents percentage germination after 21 days at 0ppm (control), 20,000ppm and 30,000ppm. Correlations between plant responses to salt and drought stress are well documented; high salinity causes physiological drought due to osmotic potential. Bardorado and Barlennium can be found in BAR SALT & DROUGHT, blended with specific fine fescues to offer a dedicated mixture for medium fine turf areas under these stress conditions. Bar Salt & Drought available at www.barenbrug,co.uk offers further insight. Figure 6 Figure 6: % Germination of selected ryegrass cultivars subjected to varying concentrations of salt spray after 21 days in controlled conditions.
Diploid Versus Tetraploid Ryegrasses Perennial ryegrasses used for amenity applications are almost exclusively diploids, although a small number of tetraploid ryegrasses are now being artificially created and marketed for amenity use. What differentiates a diploid from a tetraploid ryegrass is the number of chromosomes per cell; diploid plants having two sets of chromosomes while tetraploids have four. This gives tetraploids increased cell size with a higher ratio of soluble carbohydrates to fibre, making them soft and palatable for grazing but potentially detrimental to their wear tolerance. Tetraploids show faster germination and establishment compared to diploids (but not as quick as annual ryegrasses), are typically dark in colour and have good disease tolerance generally. Tetraploid ryegrasses also have increased seed sizes a 20kg bag of tetraploid seeds will contain significantly fewer seed by number. Diploid plants have significantly more tillers than tetraploids, making the shoot density of tetraploids poor in comparison. Poor shoot density and poor wear tolerance combine to make a tetraploid sward more vulnerable to Poa annua ingression. Annual Ryegrass (Lolium italicum) The key benefit of annual ryegrass is the ability to germinate and grow in very cool soil temperatures, some cultivars down as low as 3.5 0 C. The cultivar 4IR-1 found in BAR 50 SOS and SOS100 has been specifically bred to offer turf type characteristics whilst maintaining its cool temperature capabilities, making it ideal for maintaining sward cover through the autumn, winter and early spring. The very fast establishment and growth in comparison with perennial ryegrass also makes it suitable for use in late spring and summer when there is a very limited renovation window or where the pitch is in almost constant year-round use for example, pitch sharing. For further technical information on BAR 50 SOS please refer to the SOS Ultimate Guide at www.barenbrug.co.uk For further technical advice please call Barenbrug UK Ltd on 01359 272000 email info@baruk.co.uk or visit our website www.barenbrug.co.uk