Genetic diversity among forage bermudagrass (Cynodon spp.):: Evidence from chloroplast and nuclear DNA fingerprinting

Genetic analysis of forage bermudagrasses (Cynodon spp.) lags considerably behind other species, including the turf-type bermudagrasses. This research was undertaken to identify and characterize genetic relationships within and between forage bermudagrass ecotypes and varieties. Genetic relationships within 31 forage bermudagrass genotypes were determined by means of 15 amplified fragment length polymorphism (AFLP), 10 chloroplast-specific Simple sequence repeat length polymorphism (CpSSRLP), 10 random amplified polymorphic DNA (RAPD), and 10 directed amplification of minisatelliteregion DNA (DAMD) primers or primer pairs. The unweighted pair group method, using arithmetic averages (UPGMA) and the bootstrap analyses with 2000 replications, were used to calculate the relationships. Overall results indicated that forage bermudagrass genotypes have a narrow genetic base, with genetic similarity (GS) ranging from 0.608 to 0.977. The most genetically similar forage bermudagrass lines were 'Tifton 78 WH' and 'Tifton 78' (GS = 0.977), whereas 'McDonald' and 'Alicia' were the most genetically diverse bermudagrass lines (GS = 0.608). 'Sumrall 007', 'Tanberg', 'Maddox', McDonald, 'Holly Springs', 'Murphy', 'Murphy II', and 'Stallings' were distantly related to known varieties. The GS values of these genotypes were less than 0.85 compared with any other genotypes, indicating that these ecotypes were unique in their genome structure and provided genetic justification for their release as varieties. Close genetic relationships between some ecotypes and varieties were detected as follows: 'Prairie I', 'Prairie II', and 'Prairie HP to 'Grazer'; 'Lott I', 'Lott II', and 'Lancaster' to 'Callie'; and Tifton 78 WH to Tifton 78. Although DNA markers could differentiate these ecotypes, additional molecular, cytological, and phenological evidences are required to further confirm whether they could be considered as new varieties.