Factors promoting sustained divisions of mesophyll protoplasts isolated from dihaploid clones of potato (Solanum tuberosum L.) and a cytological analysis of regenerated plants

A culture protocol has been developed for mesophyll protoplasts isolated from various dihaploid clones of potato. A special effort was made to promote the growth of initially dividing cells to form cell colonies and calli. An increase in plating efficiency in 3 different dihaploid clones and one doubled dihaploid clone was obtained after serial dilution of cultures with a suitable amount and type of medium at different stages of cell colony development. Plating on a refined semi-solid medium after 14 days of culture further improved both the yield and the quality of calli obtained. The refined plating medium also enhanced shoot regeneration ability from 67 to 90% in one of the dihaploid clones (67:9). The refined culture protocol could also be used without causing a decrease in plating efficiency at a low population density adjusted after 3 days of culture. The ploidy level of plants regenerated from dihaploid protoplasts were determined by chromosome counting and DNA analysis by flow cytometry. Most of the plants were aneuploid or tetraploid although, some dihaploid plants were obtained after protoplast culture of 2 dihaploid clones derived from the same cultivar (cv. Stina).Abbreviations BA benzyladenine - 2,4-D dichlorophenoxyacetic acid - GA₃ gibberellic acid - NAA naphthaleneacetic acid     

A medium and simplified procedure for growing single cells from Solanum species

A nutrient medium that allows rapid growth of calli from individual cells of several Solanum species has been developed. The medium is based upon that of Kao and Michayluk (Planta, 126 (1975) 105–110). Modifications that improve plating efficiencies at low density include omission of pyruvate, malate, citrate and fumarate and increasing the phosphate level from 1.25 to 5 mM. The inclusion of 0.1–0.2% bovine serum albumin was essential for growth at low density. At a plating density of 80 protoplasts/ml, plating efficiencies of 1.5—2.0% for Solanum tuberosum L. and S. cardiophyllum Lindl. are often obtained. Single cells of these species were mechanically isolated after 48 h of culture at 800 or 8000 protoplasts/ml and plated singly on fresh medium. The single cells divided and formed rapidly-growing celli with plating efficiencies of 37–75%. Plants have been regenerated from these calli.     

Selection and proliferation of rapid growing cell lines from embryo derived cell cultures of yew tree (Taxus cuspidata Sieb. et Zucc)

Calli were induced from 300,000 embryos isolated from immature to mature stage of seeds collected on late September from 14 elite trees. When the embryos were cultured onto plastic Petri-dish containing 20 mL of modified B5 basal medium supplemented with 3% (w/v) sucrose, 500 mg/L casein hydrolysate, 250 mg/L myo-inositol, 0.5% (w/v) polyvinyl polypyrrolidon (PVPP), 2×MS vitamins, 0.5 mg/L gibberellic acid, and 10 mg/L 2,4-D after 2 weeks of culture, yellowish-white calli were immediately formed on the surfaces of embryos, and subcultured for 4 weeks in same culture medium. Because most of calli maintained for more than 3 months were revealed differences in their colors, surface texture, and growth rate, visual selection was made for first round screening. When the size of visually selected calli larger than 19 mm in their diameter were inoculated, persistent proliferation was observed. Among the plating methods tested for the selection of rapid growing cell lines at single cell and/or small cell aggregate level, 2-layer spread plating revealed as the best for single cell cloning. To enhance cell growth and maintain high rate of viability for long-term culture of yew cells in bioreactor, final cell volume less than 50% in SCV seemed to be the best. Time course study revealed that 30% of inoculum density was suitable for fed batch culture. Among the tested conditional media, the rate of 1∶2 (old medium: fresh medium) was recorded at the best for cell growth.     

Embryo Rescue and Induction of Somatic Embryogenesis as a Method to Overcome Seed Inviability in Zea mays ssp. mays × ; Zea mays ssp. parviglumis Crosses

Zea mays ssp. mays (2n=40) and Z. mays ssp. parviglumis (2n=20) were crossed to obtain hybrid plants by embryo rescue. Hybrid embryos were isolated and cultured on García et al. (1992) basic medium supplemented with 2,4-dichlorophenoxyacetic acid and/or kinetin in different concentrations. Caryopses harvested 23 d after pollination (DAP) were turgid, with 0.3 to 0.5 mm long embryos, while those harvested 30 DAP were shrunken, with 1 to 1.5 mm long embryos. Twenty days after plating, 100 % of the younger embryos gave rise to white, compact embryogenic calli. Subsequently, coleoptiles, leaf-like structures, shoots and roots originated from them and 35 hybrid plants were regenerated from 60 embryos. Embryogenic or organogenic calli frequencies did not differ among hormonal treatments, but they decreased, on average, from 90.5 to 44.3 %, comparing 50 and 120-d-old cultures. The older embryos regenerated plants only by germination, although they gave rise to organogenic callus with low frequencies. Regenerated plants showed a somatic chromosome number of 2n=30, pollen fertility of 40 to 80 % and 15 % viable naked caryopses.     

Protoplast Culture and Plant Regeneration of Winter Wheat (Triticum aestivum L.)

Suspension cultures were established from embryogenic calli derived from cultured anthers of cv. Jinghua No.1 and mature embryos of cv. Youmangbai No. 7, respectively. After being isolated and cultured in WPMI, protoplasts began to form cell walls within 1 day post-isolation, followed by cell division observed between 2–3 days. A division frequency of 22.0% was estimated on the 7th day of culture, and 43.7% on the 14th day. During 10–15 days after the initiation of culture, a large number of cell aggregates emerged, with 0.5–0.8% of plating efficiency. Protoplast-derived calli grew up to lmm or more in diameter when cultured for 4 weeks, and eventually gave rise to green plants through embryogenesis and organogenesis after being transferred to differentiation media. Plant regeneration from protoplasts was already obtained from Jinghua No.l, and protoplast-derived calli from Youmangbai No.7; an experiment on organ differentiation for the latter is under way. A few factors affecting the protoplast cultures were also studied.     

Study on the Hybrid Endosperm Culture of Wheat-Rye In Vitro

The endosperm culture of wheat-rye hybrid was studied in order to explore a new pathway of chromosome engineering. The preliminary results were obtained to show that the endosperm callus formation could be induced from the young endosperm within 7–14 days after crossing on the medium supplemented with 2 ppm 2,4-D, 0.5 ppm kinetin and 3%–8% sucrose. The induction frequency of callus amounts to 35.3%. When the calli were transfered onto an auxin step-down medium containing 0.5 ppm IAA and 1 ppm kinetin, both shoots and roots were formed. 4 endosperm plantlets were obtained. The chromosome number in somatic cells of endosperm plantlets was very unstable. The numbers varied from 6—42, but there is no 49 to be found. The chromosome number with 1—4 times of 7 can be found in higher percentage.     

Plant Eegeneration from Protoplasts of Brassica carinata Braun

Protoplasts of Brassica carinata Braun. (accession No. 84A165) were enzymatically isolated from hypocotyls and cotyledons of 3–5 day-old test-tube seedlings or first true leaves taken from greenhouse grown plants at a three-leaf stage. The protoplasts were suspended in a P-B liquid medium solidified with 0.15%–0.3% low melting agarose which formed a thin layer floating on the surface of the liquid medium. The optimum protoplast density was ranging from 5× l03 to 1 × 104/ml. As for the hypocotyl protoplasts, the first division was observed after 48 h in the culture. The division frequency reached 21% and 34% at day 3 and 6 respectively. The initiation of cell division in the case of cotyledon and mesophyll protoplast culture was late, usually at day 5, and the division frequency was also somewhat lower. One week after culture, the cultures were transferred to fluorescent light condition with an intensity of about 1000 lx. A dilution medium DPDK3 was then added and the dilution procedure was repeated at one week interval thereafter. One month after culture, microcalli with 300–500 μm in size were formed. It was also found that in some cases globular embryoid structure protruded on the callus surface. Totally, a 2%–3% plating efficiency was achieved. Shoot regeneration occurred when cotyledon and mesophyll protoplast-derived calli were transferred onto a modified MS medium supplemented with NAA 0.1, BA 3 mg/l. Individual shoots were rooted on a rooting medium supplemented with 0.2 mg/l of IAA. Intact plants with normal morphology were eventually produced.     

Plantlet Regeneration from Leaf Protoplasts in Seedling of Actinidia eriantha Benth.

Newly extended leaves of in vitro seedling of Actinidia eriantha Benth. were used for protoplast isolation. Protoplasts were cultured in liquid MS medium (devoid of NH4NO3) supplemented with 1.0 mg/L 2, 4-D and 0.4 mol/L glucose. The plating efficiency after 3 weeks of culture was about 19.4 %. Protoplasts-derived cells divided sustainably and developed into calli of 2 mm in size in the original protoplast-culture-medium without adding fresh medium so to decrease the osmotic pressure. These calli regenerated shoots when being transfered to MS medium with 0. 5 mg/L zeatin and 0. 1 mg/L IAA. Regenerated shoots were rooted by immersion in 20 ppm IBA solution before culturing on half-strength MS medium devoid of growth regulators.     

Plant regeneration from protoplasts isolated from suspension cultures of leek (Allium ampeloprasum L.)

A procedure is described for the regeneration of plants from protoplasts of tetraploid leek (Allium ampeloprasum L.), 2n = 4x =32. Regeneration-competent protoplasts could only be obtained from an embryogenic suspension culture that was initiated with friable, embryogenic callus derived from immature embryos. The generally low plating efficiency could be increased by embedding the protoplasts in Ca-alginate, compared to culturing the protoplasts in liquid or agarose-solidified medium. A minimum plating density of 2 × 10⁵ pps/ml was required to obtain microcalli. Upon transfer of the protoplast-derived calli on agarose-solidified BDS medium, morphologically different callus types proliferated. After transfer to regeneration medium, compact or friable calli with an embryogenic appearance produced somatic embryos and plantlets at a frequency of up to 80%. Calli that had been classified as heterogeneous also regenerated shoots, but mainly via organogenesis, at a frequency of 46%. After transfer of shoots to half strength MS medium, healthy, well-rooted plants were obtained, that were successfully transferred to soil. All plants contained the tetraploid DNA level.     

茎用芥菜细胞质雄性不育系子叶原生质体培养和高效植株再生（英文）

利用茎用芥菜细胞质雄性不育系原生质体培养获得了再生植株,并研究了影响原生质体培养的因素.结果表明,子叶是茎用芥菜原生质体培养最佳的外植体,10 d苗龄的子叶原生质体在改良MS培养基上培养3 d后发生第1次细胞分裂,6 d后发生第2次分裂,3周后形成细胞团,5周后形成肉眼可见的小愈伤.培养基中缺少NAA或2,4-D都会降低愈伤组织的再生能力.在含一定浓度的NAA(0.25 mg/L)和2,4-D(0.25 mg/L)培养基上诱导的愈伤组织质地致密且有光泽,芽的分化能力高;在MS+BA l mg/L+NAA 0.2 mg/L的培养基上芽的分化频率高达近29%,再生芽在1/2MS+NAA0.1 mg/L培养基上生根,形成完整植株.     

毛花猕猴桃原生质体再生植株

从毛花猕猴桃（Ａｃｔｉｎｉｄｉａ ｅｒｉａｎｔｈａ Ｂｅｎｔｈ．）试管培养的实生苗新展开叶片分离的原生质体,培养在液体ＭＳ（除去ＮＨ４ＮＯ３）附加２,４－Ｄ １．０ ｍ ｇ／Ｌ和葡萄糖０．４ ｍ ｏｌ／Ｌ的培养基上。培养３周后植板率达到１９．４％ 。在未添加新鲜培养基的情况下,原生质体再生的细胞可持续分裂,并于３个月时长成２ ｍ ｍ 大小的愈伤组织。将该愈伤组织转移到附加玉米素０．５ ｍ ｇ／Ｌ和ＩＡＡ ０．１ ｍ ｇ／Ｌ的固体ＭＳ培养基上,分化出苗。试管苗经诱导生根,长成完整小植株     

水稻原生质体培养再生植株程序化的初步研究

从12个品种水稻成熟种子诱发愈伤组织并继代培养,通过MS培养基中2,4-D浓度的变换,研究了2,4-D对水稻愈伤组织生长的影响。用AA培养基建立适合原生质体培养的胚性细胞悬浮系仅需3个月。由悬浮细胞系游离的原生质体在改良的KPR培养基中进行液体浅层培养,有10个品种获得高植板率的细胞团。变换使用不同的分化培养基,从7个品种得到再生植株。实验重复性达到80%,初步实现了水稻原生质体培养的程序化。     

Plant Regeneration from Protoplasts of Soybean (Glycine max L.)

Protoplasts were isolated enzymatically from immature cotyledons of soybean. The protoplasts divided to form calli in the K8P liquid medium. The calli further grew to 2–3 mm on the solid K8 medium and were transferred onto the MSB medium (MS minerals+B5 organic components+0.5–1.0 mg/l 2,4-D+0.2–0.5 mg/l BA) to obtain compact and nodular calli. Shoot formation was initiated on M1 medium (MSB medium with 0.15 mg/1 NAA, and BA, KT and ZT, 0.5 mg/l of each, 500 mg/1 CH). Differentiation frequency was 13.6–24.2%. Plants have been regenerated from protoplasts of immature cotyledons in 2 cultivars, and normal pods were obtained from them.     

Protoplasts Culture and Plant Regeneration of Soybean (Glycine max L. and G. soja)

Protoplasts were isolated enzymatically from immature cotyledons of soybean. The protoplasts divided to form calli in the K8P liquid medium. The calli further grew to 2–3 mm on the solid K8 medium and were transferred onto the MSB medium (MS minerals+B5 organic components+0.5–1.0 mg/l 2,4-D+0.2–0.5 mg/l BA) to obtain compact and nodular calli. Shoot formation was initiated on M1 medium (MSB medium with 0.15 mg/1 NAA, and BA, KT and ZT, 0.5 mg/l of each, 500 mg/1 CH). Differentiation frequency was 13.6–24.2%. Plants have been regenerated from protoplasts of immature cotyledons in 2 cultivars, and normal pods were obtained from them.     

A novel method for regenerating plants from mesophyll protoplasts of Arabidopsis thaliana line WS

A procedure has been developed for the successful regeneration of plants from mesophyll protoplasts of Arabidopsis thaliana line WS. The protocol is an improved version of that of Damm and Willmitzer (1988). The main changes in original procedure are as follows:

1. A mixture of Cellulase Y-C (0.5%) and Pectolyase Y-23 (0.05%) is used for the isolation of protoplasts. Use of these enzymes reduces the incubation time to 50 min.
2. α-Naphthaleneacetic acid is used as the auxin throughout cultures of protoplasts and calli.
3. Protoplasts and calli are incubated under dim white light (0.8–8 μW/cm²) during culture.

With these modifications, we were able consistently to obtain regenerated shoots from about 70% of calli that had been transferred to shoot-forming medium even though the plating efficiency was rather low (about 0.5–1.5%).     

Regeneration of plants from mesophyll protoplasts of the wild crucifer Eruca sativa Lam.

Protoplasts isolated from mesophyll cells of Eruca sativa Lam., cultured on suitable medium, underwent sustained cell divisions to form calli. The plating efficiency was found to be 0.4%. The protoplast-derived calli subsequently produced plantlets through organogenesis (15.71%) and somatic embryogenesis (11.25%). Regenerated plants exhibited normal appearance. These results indicate potential to introgress desirable traits from this wild crucifer into important oilseed and cole Brassicas by protoplast fusion and hybrid recovery.Abbreviations B5 Gamborg et al., 1968 - K3 Kao and Michayluk, 1974 - MS Murashige and Skoog, 1962 - BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthalene acetic acid - GA₃ Gibberellic acid     

茎用芥菜细胞质雄性不育系子叶原生质体培养和高效植株再生

利用茎用芥菜细胞质雄性不育系原生质体培养获得了再生植株,并研究了影响原生质体培养的因素.结果表明,子叶是茎用芥菜原生质体培养最佳的外植体,10 d苗龄的子叶原生质体在改良MS培养基上培养3 d后发生第1次细胞分裂,6 d后发生第2次分裂,3周后形成细胞团,5周后形成肉眼可见的小愈伤.培养基中缺少NAA或2,4-D都会降低愈伤组织的再生能力.在含一定浓度的NAA(0.25 mg/L)和2,4-D(0.25 mg/L)培养基上诱导的愈伤组织质地致密且有光泽,芽的分化能力高;在MS+BA l mg/L+NAA 0.2 mg/L的培养基上芽的分化频率高达近29%,再生芽在1/2MS+NAA0.1 mg/L培养基上生根,形成完整植株.     

Plants Regenerated from Mesophyll Protoplasts of Cottonwood New Clone

Poplar NL-80106 (Populus deltoides×P, simonii) mesophyll protoplasts were isolated from leaves of 30 days-old sterile shoot, with 4 × 107/g fr. wt of protoplast yield after purification. The protoplasts were cultured in KM8p and MS liquid media containing 2 mg/L 2, 4-D, 0. 5 mg/L NAA and 0.5 mg/L KT. Higher plating density and lower osmatic pressure (0.45 mol/L) were proved to be favourable to division of protoplast-derived cells. The first division initiated 5 days after culture, and the division frequency reached 4.5 % on the 10th day. A number'of cell colonies and microcalli was formed in 12 weeks. Using organic nitrates and glucose in protoplast culture medium was beneficial to increase division frequency and plating efficiency. The calli were allowed to grow to 4--6 mm in height with red colour and compact structure on the gelrite-sohdified NLZ1 proliferation medium in 3 weeks and were transferred onto NLF differentiation medium where the frequency of shoot formation could reach 100%. The 3 cm high shoots were then cut off from the callus and rooted on 1/2 MS medium.     

枸杞原生质体培养及高效成株体系的建立

由枸杞髓部组织诱导出胚性愈伤组织,并由此愈伤组织建立起稳定的细胞悬浮系。从悬浮细胞游离的原生质体在改良KM培养基(1.5 mg/L 6_BA,0.5 mg/L NAA和0.5 mg/L 2,4_D)中进行液体浅层培养,3～4 d后出现第一次分裂,第7 d统计分裂频率为50.3%,15 d左右可形成细胞团,3～4周后形成肉眼可见的愈伤组织,愈伤组织植板率为1.25%。将细胞团转移到液体分化培养基(MS+6_BA 1.5 mg/L+2,4_D 0.2 mg/L) 8～10 d可形成大量胚状体,及时将胚性愈伤组织块转移到固体分化培养基上(MS+6_BA 0.2 mg/L),可形成大量绿芽,分化率54.17%。绿芽在生根培养基（MS+NAA 0.2 mg/L）可形成完整植株,移栽后成活良好。     

籼稻原生质体培养和植株再生

用籼稻IR52、IR8和IR45的幼花序和幼胚愈伤组织在LS培养基建立了稳定的悬浮培养物。悬浮系的建立经历三个阶段:褐变期,长根期,成熟期。建立了适合籼稻原生质体生长的Y8培养基,其植板率显著高于KPR和PCM培养基。悬浮细胞系间差异明显,只有部份系可以提供有分裂能力的原生质体或具看护活性。以上三个品种的原生质体均分裂良好,但只有IR52和IR8分化出苗,其中IR52分化率1.25%,得再生植株50余株,移至田间生长结实正常。