Diversity and Vulnerability of Bermuda Turfgrass Species

Abstract

Widespread use of relatively few clonally‐propagated turf bermudagrass ( Cynodon spp. Rich.) cultivars in the USA creates a high risk for extensive damage from new pests. Knowledge of the genetic diversity within Cynodon , and access to that diversity would be important in counteracting pest epidemics. This paper reviews information on the distribution and cytotaxonomic diversity of Cynodon turfgrass species and the status of the current Cynodon collection in the U.S. National Plant Germplasm System (NPGS). Cynodon taxa containing germplasm of importance, or potential importance, as turf are C. arcuatus J. S. Presl. ex C. B. Presl., C. barberi Rang, et Tad., C. dactylon (L.) Pers. var. dactylon , C. dactylon var. polevansii (Stent) Harlan et de Wet, C. incompletus Nees var. incompletus , C. incompletus var. hirsutus (Stent) Harlan et de Wet, C. transvaalensis Burtt‐Davy, and C. × magennisii Hurcombe. Cynodon dactylon var. polevansii, C. incompletus vars. incompletus and hirsutus , C. transvaalensis , and C. × magennisii are endemic to South Africa. Cynodon barberi is endemic to southern India while C. arcuatus is distributed from Malagasy through south Asia to northern Australia. Cynodon dactylon var. dactylon is distributed worldwide between latitudes of 45°N and 45°S. The current Cynodon germplasm collection maintained by the NPGS contains 455 accessions of the indicated species plus 29 accessions classified as C. hybrid or C. species. Cynodon dactylon (L.) Pers. is the best represented taxon having 411 (85%) accessions from 39 geographic areas. The magnitude of genetic variation differs among the Cynodon taxa, being greatest in the cosmopolitan taxon C. dactylon var. dactylon . Taxa endemic to southern Africa are less variable and more susceptible to genetic erosion. To guard against this vulnerability and to exploit the maximum available genetic diversity of the genus for scientific use and breeding improvement will require a more comprehensive and better evaluated collection in the NPGS.