Golf Course Management

SEP 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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09.18 GOLF COURSE MANAGEMENT 73 bermuda grass hybrids and the work that has been done at the University of Georgia. Hybrid bermudagrass biology Usually, better hybrids result from crossing more genetically diverse parents. Whether a hybrid is better than a non-hybrid in a specific plant species depends to a large degree on the genetic makeup of the parents of the hybrid. Consequently, just making crosses is no assur - ance of developing superior hybrids. e pro- duction of thousands of experimental hybrids may result in only a single superior hybrid (3). Because bermudagrass is a sexual species with perfect flowers (male and female organs in the same flower), it can set seed through two mechanisms or a combination of these mechanisms. Bermudagrass plants can be either self-fertile or self-incompatible. In self- fertile plants, pollen from a flower on a plant can fertilize the female organs (stigmas) on the same plant and produce seed. When plants are self-incompatible, pollen from a flower on a plant cannot fertilize the stigmas (pollen will not grow properly on the stigma) on the same plant to produce seed. To set seed, self-incom - patible plants need to be fertilized by pollen from genetically different plants nearby. Many grasses, including bermudagrass, have various degrees of self-fertility or self-incompatibility. Self-incompatibility is controlled by several genetic and environmental mechanisms (2, 3). Crosses can be made within a species, and resulting plants are usually referred to as hy - brids. Crosses between species of a particular genus are interspecific hybrids. e purpose of this manuscript is to clarify the difference be - tween a hybrid (Figure 2) and a triploid inter- specific hybrid (Figure 3) in the bermudagrass genus. Common vs. hybrid bermudagrass Vegetative propagation Common bermudagrass (Cynodon dacty - lon) is predominantly tetraploid (2n = 4x = 36 chromosomes) and produces outcrossed seed because of various levels of self-incompatibil - ity (4). Because of this self-incompatibility, a large portion of the bermudagrass plant pop - ulations around the world consists of natural hybrids. Depending on the genetic makeup of the parents, some of the natural hybrids can be better than other plants in the immediate population. Improved plants are sometimes selected from these populations. Plants with improved and/or desirable plant characteris - tics can be marketed as commercial cultivars. Turf and forage bermudagrass breeding programs usually focus on producing hybrids. University of Georgia programs have pro - duced hybrid cultivars, such as Coastal and Tifton 85 forage bermudagrasses, which were superior hybrid plants selected from thou - sands of experimental hybrids produced by selecting, developing and crossing outstand - ing parents. Examples of vegetatively propa- gated turfgrass hybrid bermudagrass cultivars are Tiflawn (a product of intentional crosses of superior parents), VaMont, Celebration and Tifton 10 (a fertile hexaploid with 54 chromo - somes) bermudagrasses, which were selected from natural populations. eir identity is maintained through vegetative propagation of rhizomes, stolons and/or stems (1). ese hybrid cultivars have various levels of seed production potential from selfing, and from crossing, if pollen is available from different bermudagrass plants in the surrounding area. e seed production by these cultivars can easily produce off-types that can contaminate the purity of the planted cultivar. Although they are hybrids, these cultivars are techni - cally common bermudagrasses with improved characteristics that are maintained by vegeta - tive propagation (4). e released common bermudagrass for - age and turf hybrids have made important contributions to animal nutrition and im - proved landscapes (1). However, it should be remembered that common bermudagrass, especially C. dactylon, can produce deep rhi - zomes that are difficult to control and seed that is easily dispersed. ese two character - istics can make these hybrid cultivars inva- sive in certain situations. Common vs. triploid interspecific hybrids Figure 2. Production of common hybrid bermudagrass. Figure 3. Production of triploid interspecific hybrid bermudagrass. Cynodon dactylon (36 chromosomes & fertile) C. dactylon (36 chromosomes & fertile) Hybrid Bermudagrass (36 chromosomes & fertile) × Cynodon transvaalensis (18 chromosomes & fertile) C. dactylon (36 chromosomes & fertile) Triploid Interspecific Hybrid Bermudagrass (27 chromosomes & sterile) ×

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