DETECTION OF SOMACLONAL VARIATION IN TISSUE-CULTURE REGENERANTS OF TALL FESCUE

Clones of tall fescue (Festuca arundinacea Schreb.) regenerated from t issue culture are required for examining interactions between the endo phyte, Acremonium coenophialum Morgan-Jones and Gams, and its host. So maclonal variation is common among regenerated plants, and could limit the utility of this technology to study the interactions of tall fesc ue and its endophyte. Various methods are used to detect somaclonal va riation, but there is little agreement as to the relative advantages o f each. Therefore, the objectives of this study were to determine (i) whether somaclonal variation exists among tall fescue plants regenerat ed from somatic embryos, and (ii) whether pollen viability, yield, mor phological traits, or phenological develop ment give consistent estima tes of somaclonal variation. Seven regenerants from non-infected tall fescue genotype PDN2 and a nonregenerated PDN2 control were planted in the field in five replications. Plants were screened for somaclonal v ariation by phenological development, vegetative and flag leaf width/l ength ratios, total biomass, seed yield, and pollen viability over 2 y r. Although regeneration protocols were designed to minimize somaclona l variation, somaclonal variation of quantitative traits was observed. Total biomass and seed yield of regenerants, used together, were most consistent in detecting somaclonal variation. When using tissue cultu re to insert endophytes into tall fescue, we found multiple regenerant s need to be infected with each isolate of endophyte to ascertain whet her differences among response variables are due to endophyte or somac lonal variation.