Genetic instability of bermudagrass (Cynodon) cultivars 'Tifgreen' and 'Tifdwarf' detected by DAF and ASAP analysis of accessions and off-types

Abstract

DNA amplification fingerprinting (DAF) and arbitrary signatures from amplification profiles (ASAP) were used to evaluate the genetic stability of two important bermudagrass (Cynodon) cultivars, the interspecific cross Tifgreen and its somatic mutant Tifdwarf, and study genetic diversity and origin of derived bermudagrass off-types that exhibit patches of contrasting morphology and performance. Mini-hairpin primers produced complex and reproducible DAF and ASAP profiles with high levels of polymorphic DNA, and established genetic relationships between 11 Tifgreen and 8 Tifdwarf turf plot accessions and 16 off-types. DAF analysis revealed an average 14.1 ± 5.6 (SE) polymorphic bands/primer within cultivar accessions. In contrast, the higher resolving power of ASAP detected 24.5 ± 2.1 polymorphic bands/primer. Similarly, DAF and ASAP produced 13.0 ± 5.5 (SE) and 20 ± 2.8 polymorphic bands/primer within off-types, respectively. Phenetic analysis using cluster (UPGMA) and ordination (PCO) techniques showed that both Tifdwarf and Tifgreen were genetically unstable. The analysis showed that almost all cultivar accessions and one-half of the off-types studied were genetically distinct, but very close to each other. In this case, genetic variation was probably the result of somatic mutations. The other off-types and some Tifgreen accessions represented a genetically distant and diverse bermudagrass group of interspecific hybrid (n=27) origin. Off-types were probably the result of sod contamination. Results complement a previous study that established that the interspecific Tifway bermudagrass was genetically stable whereas derived off-types were contaminants rather than somatic mutants. Tifgreen and Tifdwarf showed genetic instabilities that were readily detected by DNA amplification with mini-hairpin primers. The present study offers a direct molecular alternative capable of evaluating the genetic stability of selected cultivars.