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In an effort to optimize tissue culture response of tall fescue (Festuca arundinacea) regeneration system, the effects of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 6-Benzylaminopurine(6-BA) on tissue culture responses were investigated using mature seeds in three cultivars,“SHED”,“Plantation”and“Triple A”and immature inflorescence (booting stage), nodes and leaf tips in two clones,“SACD”and“98-19”, which are self-bred dwarf clones of tall fescue, as explants.Taking mature seeds as explants, Murashige and Skoog Stock (MS) + 2,4-D 8 mg/L is the best callus induction medium for whole seeds, with highest callus induction rate 78%; there is significant difference of 2,4-D concentrations in callus induction for two cultivars; the optimal concentra -tions of 2,4-D was from 3 to 11 mg/L, callus introduction rate being from 64 to 78%; significant differences were also observed between the tested cultivars, but no interaction between 2,4-D concentrations and the cultivars; significant difference were not obverted among subculture mediums of 2,4-D concentrations ,but were observed among callus induction mediums of 2,4-D concentrations, 2,4-D 11 mg/L obtained the highest embryogenic callus indu -ction rate (84%) after subculture. the best regeneration medium is MS + 2,4-D 2 mg/L + 6-BA 1.5 mg/L ,with high green plants regeneration induc -tion rate(64%) and highest mean green shoots(3.6). By simply slicing the mature seeds into two halves longitudinally, the time for callus induction reduced half, and the best 2,4-D concentration for half seed is 2.5 mg/L, with callus induction rate 60%,but no significant difference among cultivars . The rooting medium applied“1/2 MS + NAA0.5 mg/L”, getting a high rooting rate of 100%.Taking vegetative organs of dwarf clones of tall fescue as explants, the results showed that the immature inflorescence(booting period) was the best vegetative organ for callus induction, with highest callus introduction rate 79%; but for tips of leaves and nodes, the callus introduction rate were 0%; the optimal concentrations of 2,4-D was from 7 to 9 mg/L in MS, callus induction rate being from 70% to 79%; significant differences were also observed between the tested clones, however, the interaction between 2,4-D concentrations and the clones was not significant; subculture medium of 2,4-D 4 mg/L in MS obtained the highest embryogenic callus induction rate (84%), highest green spot induction rate (63%), and high green plant regener -ation rate (48%) in regeneration medium of“MS + 2,4-D 2 mg/L + 6-BA 1 mg/L); The rooting medium applied“1/2 MS + NAA 0.5 mg/L”, getting a high rooting rate of 100%.When Hygromycin is used as selection marker, The sensibility of embryogenic callus of SHED and SAC to different concentration of Hygro -mycin in MS subculture medium was also researched. The ideal selecting pressure of Hygromycin is 50 mg/L.
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