A regeneration system using cotyledons and cotyledonary node explants of Toona ciliata

We used the cotyledons and cotyledonary nodes of Toona ciliata(Chinese mahogany)as explants to examine callus and adventitious shoot induction when exposed to different ratios of hormones.We also investigated the effects of seedling age,inoculation method,and genotype on the efficient regeneration of T.ciliata.The results showed that different genotypes exhibited significantly different callus induction efficiency.The cotyledons and cotyledonary nodes of 20-day seedlings inoculated onto MS medium with 0.5 mg/L 6-benzylaminopurine(6-BA),0.5 mg/L kinetin(KT)and 0.05 mg/L 1-naphthylacetic acid(NAA)achieved a greater regeneration rate than did other concentrations of cytokinin and auxin.The numbers of shoots per cotyledon and cotyledonary node explant were 7.33 and 6.67.The optimal inoculation method for cotyledons was that the distal end of the explants was placed in contact with the medium.The optimal adventitious shoot differentiation medium for cotyledon explants was MS medium containing 0.3 mg/L 6-BA and 0.2 mg/L NAA,producing a 3.4 cm height of shoot on average.This study established an efficient regeneration system for T.ciliata with cotyledons and cotyledonary nodes as explants.

Strain Cultivation Stage and Infectious Concentration on Soybean Cotyledonary Node via Agrobacterium–mediated Transformation System

In soybean cotyledonary transformation,Agrobacterium infection is influenced by many factors.The cultivation stage of Agrobacterium strain and infectious concentration were studied in this research.Results showed that the highest rate of resistant shoots was obtained when the strain cultivation concentration was OD 600 =0.6,and the infectious concentration was OD 600 =0.5.Seven soybean cultivars in North China were also screened for high susceptibility to Agrobacterium and three genotypes were found to be suitable for transformation.This research has built a good foundation for soybean transformation improvement.

Combination of 6-Benzylaminopurine and Thidiazuron Promotes Highly Efficient Shoot Regeneration from Cotyledonary Node of Mature Peanut (Arachis hypogaea L.) Cultivars

Efficient in vitro plantlet regeneration is an important step to successfully transform genes for the improvement of agronomic traits.A combination of 6-benzylaminopurine(BAP)and thidiazuron(TDZ)plant growth regulators was applied to evaluate shoot regeneration capacity whereasα-naphthalene acetic acid(NAA)combination with 6-benzylaminopurine(BAP),and 2,4-dichlorophenoxyacetic acid(2,4-D)with 6-benzylaminopurine were tested to optimize root induction for two peanut cultivars.The result showed combination(BAP with TDZ)was found to be effective in promoting shoot.The highest shoot regeneration frequency(93%)was obtained on a medium supplemented with 4 mg/L BAP and 0.5 mg/L TDZ while an average regeneration frequency(87%)was achieved in a medium containing combinations of 2 mg/L BAP with 1 mg/L TDZ.The shooting rate increased for both cultivars as the concentrations of BAP increased and TDZ decreased.The highest rooting rate(93%)was obtained on a medium supplemented with 3.5 mg/L NAA with 2.5 mg/L BAP for both cultivars.The rooting rate increased as the concentration of auxin to cytokinin ratio increased.The maximum rooting rate(83%)was obtained on MS medium supplemented with 0.3 mg/L 2,4-D with 0.2 mg/L BAP for the cultivar N3.The result indicated that BAP with NAA was much better than BAP with 2,4-D in rooting rate.Thus,the protocol developed was genotype independent and effective for peanut tissue culture.

Evaluation of Beta-Lactam Antibiotics on the Regeneration of Peanut Plants and Their Inhibitory Effect on Agrobacterium Growth

The effect of beta-lactam antibiotics on shoot induction and plantlet regeneration from cotyledonary nodes was tested using two peanut cultivars.The culture media contained 4 mg/L 6-benzylaminopurine(BAP)as the main growth regulator.Various concentrations(100–600 mg/L)of cefotaxime,carbenicillin,and timentin were applied in the culture media.In all the tested media,there were no significant differences in the shoot induction as compared to the control.However,little phytotoxic effect was observed at higher concentrations of these antibiotics in the shoot elongation media.Under shoot elongation medium,shoots turned brownish and partly died at higher concentrations where shooting rates were not affected by the treatments.In cefotaxime,timentin,and carbenicillin-containing media,levels of antibiotics greater than 400,300,and 200 mg/L,respectively resulted in the brown coloration of plantlets.Moreover,the mean shoot number and shoot weight significantly decreased as their dosage increased.The results indicate that maximum levels of antibiotics have an adverse effect on the growth and development of peanuts.Also,cefotaxime(100–300 mg/L)and timentin(100–300 mg/L)will be sufficient in controlling Agrobacterium growth in the culture media with the least phytotoxic effect on the peanut plants.