28 I EUROPEAN SEED I EUROPEAN-SEED.COM28 I EUROPEAN SEED I EUROPEAN-SEED.COM INNOVATIONS IN RYEGRASS BREEDING Environmental shifts and turf usage are helping drive innovation in ryegrass. BY MARCEL BRUINS hoever thought that watching grass grow is the most boring activity on the planet cant be more wrong. In this article European Seed sat down with several ryegrass breeders to look at some of the very interesting developments that have happened and are still taking place in ryegrass breeding and we were amazed by the high level of innovation in the sector. TETRAPLOIDISATION IN TURF Although polyploid organisms are very common in nature we can assist nature by making artificial polyploidisation using colchicine a natural product extract from plants of the genus Colchicum. Colchicine inhibits the formation of aster rays which normally pull the duplicated chromosomes to the cell sides allowing a cell wall to develop down the middle. P l a n t b r e e d e r s h a v e m a d e tetraploidisation of grasses for a long time and the first tetraploid forage perennial ryegrass varieties were listed in the 1950s and 1960s. The goal was to improve forage yield and disease tolerance. In the United States and Europe some attempts were made also in turfgrass during the 1980s but without real success. Nevertheless one variety called Juventus created some interest due to its drought tolerance. It was listed in various countries and had some success in France at the beginning of the 1990s. However up against an impressive improvement of traditional diploid varieties e.g. Greenfair Greenway at the end of the 1990s it was difficult to recommend tetraploid material that lacked fineness of leaf compared with these new diploids. TETRAPLOIDS ADD TOUGHNESS TO TURF There are a number of challenges in breeding tetraploid turf varieties of perennial ryegrass which by nature have traits more associated with forage than turf. The challenges are shoot density broader leaves and more frequent mowing. Fortunately there are also some tremendous advantages darker colour better disease tolerance and a general capacity to survive in hostiledry cold or hotconditions which is the main weak point of diploid ryegrasses. Diploids are well adapted to oceanic conditions but suffer in more extreme climates. Through intensive breeding efforts turf quality in tetraploids is now getting much closer to that of the diploids. Slightly broader leaves and lower density are more than compensated for by the other unique qualities of tetraploid varieties making them ideal components in turf mixturesand mixtures play a major role in the turf business. IMPROVED WINTER DISEASE AND DROUGHT TOLERANCE In the early 2000s DLF initiated a new breeding program using chromosome doubling in ryegrass based on very dense diploid material. After some attempts a breakthrough was made with the first listings of the tetraploid varieties Double and Tetragreen. Double showed a significant improvement of winter disease tolerance after testing in Scandinavian turf networks. Trialling in France proved Tetragreen to be one of the most drought-tolerant perennial ryegrasses. These varieties are available in various European countries including Denmark the UK the Netherlands Germany and France. NEXT GEN TETRAPLOIDS Due to an intensive and dedicated breeding program the next generation of tetraploid perennial ryegrass varieties are available. While keeping the beneficial tetraploid traits the variety Fabian has a density very close to diploid varieties. Tetrastar is a perfect complement of diploid varieties for sports pitches due to the best compromise between density and disease tolerance. In addition Tetradark with its dark genetic colour is adapted to Mediterranean regions such as Spain Italy and Turkey and is an excellent match in mixtures with tall fescue. Tetraploid ryegrass provides a very interesting solution for landscapers sports field managers and golf course greenskeepers who care about sustainability as these varieties require less water and pesticides. A NEW ERA BEGINS During the 1990s many plant breeding companies sought to develop DNA markers which were linked to certain traits such as disease resistance. While this task was straightforward in inbreeding species it met with significantly more challenges in outbreeding species such as grasses. The problem was the lack of solid linkages between markers and traits which inherently follows the nature of outcrossing reproduction. Although several disease resistance markers were discovered in scientific experiments mostly they could not be transferred and used in elite breeding material. GENOMIC SELECTION The solution came in the wake of next generation sequencing technologies which were introduced in the mid-2000s. ThisThe tetraploid variety Double showed a significant improvement in winter disease tolerance Fusarium Patch as shown above.