Kuniyuki Walnut Medium Research Articles

Influence of different factors on in vitro multiplication and rooting of three local Juglans regia L. genotypes in Uzbekistan

The Persian walnut (Juglans regia L.) is one of the most lucrative and widely distributed nut crops. It is appreciated as a forestry and ornamental tree in addition to its benefits as a fruit crop. Although Central Asian countries, especially Uzbekistan, are among the origins of the Persian walnut; they are not considered as top industrial producers of walnuts. Uzbekistan possesses a wide range of walnut genetic resources and as a result of conducted research, several promising, fruitful, early-harvesting varieties and forms have been selected. The aim of this study is to optimize microclonal in vitro propagation of selected Uzbekistan local varieties and forms by evaluating concentrations of different plant growth regulators and genotype on multiplication and rooting stages. As mother plants, 2 forms and one variety were selected: the Ideal variety, 'Form PDM23' and 'Form 202YaKT'. ?n the proliferation stage, the growth rate of walnut microshoots on basal medium Driver and Kuniyuki Walnut Medium (DKW) with different concentrations of 6-benzylaminopurine (BAP) and Indole-3-butyric acid (IBA) (0.01 mg/L) was studied. The rooting stage was assessed in half strength macronutrient DKW medium containing different IBA concentrations (0.0, 2.0, 4.0 and 6.0 mg/L). The Ideal variety and 'Form PDM23' performed best in DKW medium supplied with 1.5 mg/L BAP and 0.01 mg/L IBA, whereas 'Form 202YaKT' performed best in DKW medium supplemented with 1.0 mg/L BAP and 0.01 mg/ L IBA for the proliferation stage. For all genotypes, 6.0 mg/L IBA provided the best rooting results.

Efficient plant regeneration through direct shoot organogenesis and two-step rooting in Eucommia ulmoides Oliver.

Eucommia ulmoides Oliver (E. ulmoides Oliver), a multipurpose woody plant, holds great economic significance due to its expansive medicinal, food and industrial applications. The rapid advancement of E. ulmoides in various fields has resulted in the inadequacy of existing breeding methods to meet its growth and annual production demands. Consequently, there is an urgent need for innovative propagation strategies. This study introduces an optimized micropropagation protocol for E. ulmoides, facilitating direct shoot organogenesis from nodal segments with axillary buds. We systematically examined the impact of basal medium composition, plant growth regulators, photosynthetic photon flux density, and sucrose concentration on bud sprouting. Employing cuttings with axillary buds as propagation material, we achieved a shortened cultivation period of merely 4 weeks for bud elongation and proliferation, marking a substantial enhancement in propagation efficiency. Notably, the Driver Kuniyuki Walnut medium, supplemented with 20.0 g L-1 sucrose and 2.0 mg L-1 trans-zeatin, induced shoots sprouting with a 100% success rate and an average length of 5.18 cm per nodal segment, equating to a great bud propagation rate of approximately 500%. Furthermore, a light source with an intensity of 80 μmol m-2 s-1 was shown the most economical choice. To address the primary challenge of inducing roots in regenerated plants, we employed a refined two-step rooting technique. This method yielded the optimal rooting frequency of 93.02%, producing an average of 5.90 adventitious roots per plantlet, each with an average length of 2.77 cm. The micropropagation program developed in this work will be the cornerstone for the preservation of the germplasm of E. ulmoides and its long-term use in medicinal and industrial applications.

A Comparison of Two Media Formulations and Two Vented Culture Vessels for Shoot Multiplication and Rooting of Hemp Shoot Tip Cultures

Micropropagation of hemp (Cannabis sativa) is constrained by problems with hyperhydricity and culture decline of microshoots. These problems can be reduced by increasing agar and nutrients in the media during micropropagation stages 1 and 2, respectfully. Performance of microshoots of ‘Abacus’ and ‘Wife’ hemp cultured in Driver and Kuniyuki Walnut medium (DKW) for 15 weeks (6 weeks of stage 1 + 9 weeks of stage 2), with subculturing every 3 weeks during both stages 1 and 2, or in Murashige and Skoog with vitamins medium (MS) for 6 weeks (stage 1) followed by Lubell-Brand Cannabis medium (LBC) for 9 weeks (stage 2), with subculturing every 3 weeks during both stages 1 and 2, was evaluated. In a separate study, microshoot performance of ‘Abacus’ and ‘Wife’ in MS for 3 weeks (stage 1) followed by LBC for 6 weeks (stage 2), with subculturing every 3 weeks, using boxes (Magenta GA-7) with lids featuring a vent with a diameter of 10 mm and a pore size of 0.2 µM or using microboxes (Sac O2 O95/114 + OD95) with lids featuring a filter (Sac O2 #10) were evaluated. Shoot multiplication rate (SMR) and explant height were greater for ‘Abacus’ in LBC than DKW. For ‘Wife’, SMR at 9 weeks was greater in LBC, as LBC provided more nutrients and water than cultures had received in MS initially during stage 1. Culture medium did not influence ex vitro rooting success, which was 75% for ‘Abacus’ and ≥ 90% for ‘Wife’. Microboxes resulted in greater hyperhydricity of shoots and a lower ex vitro rooting percentage than boxes. For cultivars that are highly prone to developing hyperhydricity, like ‘Abacus’, the microboxes were not adequate to control this condition.

Micropropagation of Raspberries (Rubus idaeus L.) in Liquid Media by Temporary Immersion Bioreactor in Comparison with Gelled Media


 Temporary Immersion Bioreactor (TIB) is a suitable technique for large scale micropropagation of plant species. The aim of this work was to test the capacity of in vitro proliferation of the primocane-fruiting red raspberry cv Maravilla and floricane-fruiting red raspberry cv Willamette on gelled media compared to liquid media. The two varieties were cultured in vitro on two media, Murashige and Skoog 1962 (MS) and Driver and Kuniyuki walnut medium, 1984 (DKW), both supplemented with 0.5 mg/l 6-benzyladenine (BA). In the control cultures on gelled media the media were gelled with 5g/l Plant Agar, whereas for the cultures in liquid media Plantform bioreactors were used. After six weeks of in vitro culture we recorded the proliferation rates and lengths of the axillary shoots obtained in all the experimental treatments. The highest proliferation rate was 16 ± 2.03, obtained in cv. Willamette on gelled MS medium with 0.5 mg/l BA. The longest shoots (3.17 ± 0.32 cm) were obtained at cv. Maravilla on the DKW medium with 0.5 mg / l BA in the bioreactor. Our research highlighted that Rubus idaeus L. Maravilla and Willamette can be TIB propagated, although further research is needed to improve the efficiency of this method.

Cryopreservation and Micropropagation Methods for Conservation of Genetic Resources of Ulmus laevis and Ulmus glabra

Elms are threatened by Dutch elm disease, and conservation methods are needed to protect their genetic diversity. Cryopreservation of dormant buds allows large numbers of genotypes to be conserved with small space requirements and minimal upkeep. Cryopreservation through slow controlled cooling was tested for both elm species native to Finland, Ulmus glabra and Ulmus laevis. Regeneration of the thawed buds by micropropagation was studied on different basal media and using different growth regulators. Multiple surface sterilisation methods were tried out for bud explants. The multiplication of U. glabra was investigated with Driver and Kuniyuki walnut medium with either 0.5 mg/L meta-topolin or 0.5 mg/L 6-benzylaminopurine. Rooting with short indole-6-butyric acid induction in liquid medium and direct transplantation of the shoots to peat ex vitro after induction were tested. For initiation, either Murashige and Skoog or Driver and Kuniyuki walnut medium with 0.02 mg/L gibberellic acid 4 + 7 and 0.5 mg/L 6-benzylaminopurine were found to best promote shoot formation. Surface sterilisation remains the most challenging step. No significant differences were found between the multiplication media in either shoot production or rooting success. Rooting by direct transplanting was achieved in both species, but further development is required before application on a larger scale. With further improvements to sterilisation success especially in U. glabra, the method can be applied to the conservation of genetic resources of both U. laevis and U. glabra, and knowledge of regeneration success can be used to design the cryoconservation plan and optimise the sampling.

Using Driver & Kuniyuki Walnut medium for micropropagation of red raspberry varieties

Using Driver & Kuniyuki Walnut medium for micropropagation of red raspberry varieties

Comparison of systems combining auxins with thidiazuron or kinetin supplemented with polyvinylpirrolidone during embryogenic callus induction in three <i>Theobroma cacao</i> L. genotypes

For two decades, the combination 2,4-dichlorophenoxyacetic acid (2,4-D)/thidiazuron (TDZ) has been the most used to induce somatic embryogenesis in cocoa. The aim of this study was to compare the effect of combination systems, auxin/TDZ and auxin/kinetin (Kin) systems, as well as the addition of polyvinylpirrolidone (PVP) to these combinations on the induction of embryogenic calli in cocoa ( Theobroma cacao L.). To this end, eight induction media combining auxin 2,4-dichlorophenoxyacetic acid (2,4-D) or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) at 4,5 mM with cytokinin thidiazuron (TDZ) (22.8 nM) or kinetin (Kin) (1.125 mM) supplemented or not with PVP (300 mg / L) were evaluated on induction of embryogenic callus with petals or staminodes in three genotypes of cocoa. The basal salts medium was DKW (Driver and Kuniyuki Walnut medium). This study showed that the effect of 2,4-D combinations with Kinetin or TDZ was statistically identical on the induction of embryogenic callus. On the other hand, with 2,4,5-T, the association with Kin was more embryogenic than with TDZ. Furthermore, addition of PVP improved the induction of embryogenic callus in both combination systems. In the presence of PVP, media containing 2,4,5-T exhibited higher levels of embryogenic callus induction than their counterparts containing 2,4-D. This study allows the expansion of the possibilities of induction of embryogenic callus in cocoa. Keywords : somatic embryogenesis, cocoa, petal, growth regulator, staminode, antioxidant.

Use of RSM and CHAID data mining algorithm for predicting mineral nutrition of hazelnut

Defining optimal mineral-salt concentrations for in vitro plant development is challenging, due to the many chemical interactions in growth media and genotype variability among plants. Statistical approaches that are easier to interpret are needed to make optimization processes practical. Response Surface Methodology (RSM) and the Chi-Squared Automatic Interaction Detection (CHAID) data mining algorithm were used to analyze the growth of shoots in a hazelnut tissue-culture medium optimization experiment. Driver and Kuniyuki Walnut medium (DKW) salts (NH4NO3, Ca(NO3)2·4H2O, CaCl2·2H2O, MgSO4·7H2O, KH2PO4 and K2SO4) were varied from 0.5× to 3× DKW concentrations with 42 combinations in a IV-optimal design. Shoot quality, shoot length, multiplication and callus formation were evaluated and analyzed using the two methods. Both analyses indicated that NH4NO3 was a predominant nutrient factor. RSM projected that low NH4NO3 and high KH2PO4 concentrations were significant for quality, shoot length, multiplication and callus formation in some of the hazelnut genotypes. CHAID analysis indicated that NH4NO3 at ≤1.701× DKW and KH2PO4 at >2.012× DKW were the most critical factors for shoot quality. NH4NO3 at ≤0.5× DKW and Ca(NO3)2 at ≤1.725× DKW were essential for good multiplication. RSM results were genotype dependent while CHAID included genotype as a factor in the analysis, allowing development of a common medium rather than several genotype specific media. Overall, CHAID results were more specific and easier to interpret than RSM graphs. The optimal growth medium for Corylus avellana L. cultivars should include: 0.5× NH4NO3, 3× KH2PO4, 1.5× Ca(NO3)2.

A method for micropropagation of Cornus wilsoniana: An important biofuel plant

Cornus wilsoniana Wangerin is cultivated in China as an important biofuel plant due to its high oleic and linoleic acids derived from fruit. Recently, high yield cultivars have been developed, and there is increasing need for vegetative propagation of these new cultivars for commercial production. This study establishes a method for micropropagation of a selected new cultivar Xiang Lin G1 through shoot culture. Shoots were collected from field-grown ‘Xiang Lin G1’. After surface sterilization, shoot explants were cultured on Driver and Kuniyuki Walnut medium (DKW) supplemented with 300mgL−1 polyvinylpyrrolidone (PVP), 0.5mg L−1 zeatin, and 0.1mgL−1 indole-3-butyric acid. Axillary bud break occurred and more than 4 shoots were produced per explant. The axillary shoots could either be used as explants for additional shoot production or be rooted in DKW medium containing 300mgL−1 PVP and 1.0mgL−1 potassium salt of indole butyric acid. Resultant plantlets were transplanted into a substrate and grew vigorously in a shaded greenhouse under a maximum photosynthetic photon flux density of 200μmolm−2 s−1. Since the propagation is based on existing meristems, no somaclonal variants were observed in the micropropagated population. This established method could lead to rapid propagation of the high yield cultivars on a year-round basis and quickly increase their production hectares.

In vitro propagation of Picconia azorica (Tutin) Knobl. (Oleaceae) an Azorean endangered endemic plant species

Picconia azorica (Tutin) Knobl. (Oleaceae) is a woody plant endemic from the Azores. It is considered as a part of a true relict taxon, reflecting its phylogeny, genetics and geography. Given the fragile status of this species, effective management and conservation are necessary for its survival and repopulation, initially for ecological reasons, but ultimately for forestry purposes as a valuable source of timber. Micropropagation is a useful tool for conservation programs, and in vitro culture techniques have, therefore, been developed for P. azorica by testing different combinations of media and growth regulators at each micropropagation stage. Adult plants from the field were successfully established in vitro on Rugini olive medium supplemented with 24.6 µM 2-isopentenyl adenine (2iP), resulting in 91.2 % sprouting of the nodal explants that survived the disinfection stage, although similar results were achieved using 18.2 µM zeatin. At the multiplication stage, the best shoot quality and the best compromise between shoot length and new axillary shoot development were achieved using the modified macronutrients Driver and Kuniyuki walnut medium supplemented with 24.6 µM 2iP and 0.6 µM indole-3 acetic acid. Rooting was most successful with half-strength macronutrients combined with 10 µM indole-3 butyric acid. Using this micropropagation protocol, a wide range of accessions were successfully established in vitro and are now being propagated on a larger scale for ecosystem restoration.

Use of in vitro propagation of ‘Oblačinska’ sour cherry in rootstock breeding

Prunus cerasus L. `Obla?inska? sour cherry germplasm was established in vitrodirectly from in situ plants on different explant collection dates, enabling quick clonal multiplication and introduction to a rootstock breeding program. Rosette initiation of four investigated genotypes was possible from November to April on the medium containing Schenk and Hildebrandt (SH) macroelements, Murashige and Skoog (MS) microelements, and vitamins supplemented with (in mg L?1) 6-benzyladenine (BA), 0.5; indole-3-butyric acid (IBA), 0.01; gibberellic acid (GA3), 0.1; citric acid, 10; and L-ascorbic acid, 10. The lowest percent of contamination was noted in November and December, when dormant buds were used as an explant source, and the highest percentage was found with actively growing shoot tips. The elongation phase of rosettes initiated from dormant buds remained a major obstacle. Survival rates of shoot tips obtained in April were high and subsequent growth more prominent. An increasing index of multiplication from 1.5 to 1.9 was noted on Driver and Kuniyuki walnut medium (DKW) with 0.8 mg L?1 BA and 0.01 mg L?1 IBA in the `OV 32? genotype. Rooting percentages of 71.3% and 81.3% were achieved in `OV 17? and `OV 32? genotypes, respectively, on half-strength MS medium with 1 mg L?1 IBA.

Somatic embryogenesis and plant regeneration from immature cotyledons of European chestnut (Castanea sativa Mill.)

Here, we established a protocol for induction of somatic embryogenesis and plant regeneration from immature cotyledons of open-pollinated seeds of European chestnut (Castanea sativa Mill.) cultivars ‘Osmanoglu’ and ‘Sariaslama’. Basal media, Murashige and Skoog medium (MS), Driver and Kuniyuki Walnut medium (DKW), and Woody Plant Medium (WPM) supplemented with l-glutamine or casein hydrolysate, with or without silver nitrate, agar or gelrite, and various plant growth regulator (PGR) combinations were tested in initial cultures for induction of somatic embryos. The effects of initial cultures on the percentage of somatic embryos and average number of embryos per cotyledon explant, subcultured monthly, were determined at the end of 4 mo. Interactions were observed among the different treatments for ‘Osmanoglu’ cultivar, with the highest rates of somatic embryogenesis (4.7–9.7%) being obtained in MS, DKW, or WPM basal media supplemented with (1) 6-benzyladenine (BA; 1 mg/L) + kinetin (KIN; 2 mg/L) + indole-3-butyric acid (IBA; 0.01 mg/L); (2) BA (1 mg/L) + 1-phenyl-3-(1,2,3-thiadiazol-5-yl; TDZ 0.1 mg/L) + IBA (0.01 mg/L), and (3) KIN (2 mg/L) + TDZ (0.1 mg/L) + IBA (0.01 mg/L) PGR combinations plus l-glutamine or casein hydrolysate, with or without silver nitrate, and with either gelrite or agar. The highest percentages (12.0% and 11.2%) of somatic embryogenesis for ‘Sariaslama’ were obtained in DKW supplemented with PGR combinations of (1) BA (1 mg/L) + KIN (2 mg/L) + IBA (0.01 mg/L), (2) BA (1 mg/L) + TDZ (0.1 mg/L) + IBA (0.01 mg/L), respectively. The average number of somatic embryos ranged between 0 and 0.65 per explant for ‘Osmanoglu’ and between 0 and 0.49 per ‘Sariaslama’ explant. For germination of somatic embryos, root, shoot, and plantlet regeneration, different treatments included desiccation, cold and gibberellic acid (GA3), and BA alone or in combination with auxins (IBA or α-naphthaleneacetic acid, NAA; 0.1 mg/L). The highest rate of somatic embryos regeneration (27.5%) occurred using MS basal media with half-strength microelements containing 0.1 mg/L BA + 0.1 mg/L NAA, after treatments of desiccation, or desiccation plus cold or GA3 (3 mg/L).

High efficiency in vitro organogenesis from mature tissue explants of Citrus macrophylla and C. aurantium

A simple and efficient protocol for obtaining organogenesis from mature nodal explants of Citrus macrophylla (alemow) and Citrus aurantium (sour orange) has been developed by optimizing the concentrations of the plant growth regulators, the incubation conditions, the basal medium and by the choice of explant. In order to optimize the plant growth regulator balance, explants were cultured in the regeneration medium supplemented with several N6-benzyladenine (BA) concentrations or with 2 mg l−1 BA in combination with kinetin (KIN) or 1-naphthaleneacetic acid (NAA). The presence of BA was found to be essential for the development of adventitious buds; the best results were obtained using BA at 3 and 2 mg l−1 for alemow and sour orange, respectively. The combination of BA with KIN or NAA in the culture medium decreased the regeneration frequency, with respect to the use of BA alone. The effect of three different basal media was rootstock-dependent. For C. macrophylla the best results were obtained with Woody Plant Medium or Driver and Kuniyuki Walnut Medium (DKW). However, for C. aurantium, although high percentages of regenerating explants were obtained independently of the basal medium used, the highest number of buds per regenerating explants was obtained with DKW medium. Attempts were made to identify the type of explants which had a higher regeneration ability using particular regions along the mature shoots of C. macrophylla. When nodal segments, where the buds were completely removed, and internode segments were compared, the highest percentage of responsive explants was obtained with nodal segments. The existence of a morphogenetic gradient along the shoot was observed and the organogenic efficiency was highest when explants from the apical zone were used. Incubation in darkness for 3 or 4 wk was essential for regeneration process in both rootstocks.

Efficient propagation and rooting of three citrus rootstocks using different plant growth regulators

The influence of various basal medium and plant growth regulators on the efficient micropropagation of nodal explants from mature trees of alemow, sour orange, and ‘Cleopatra’ mandarin citrus rootstocks was studied. All three citrus rootstock shoot cultures showed a preference for high-salt media, like Murashige and Skoog or Driver and Kuniyuki Walnut medium. Several combinations of N 6-benzyladenine (BA) and adenine (AD), kinetin (KIN) or gibberellic acid (GA) were tested to optimize the shoot proliferation phase. BA/GA combinations improved the proliferation of all the rootstocks studied, especially alemow. The addition of BA and AD to the culture medium improved shoot proliferation in sour orange and ‘Cleopatra’ mandarin in the same way as BA and GA. The addition of different combinations of BA/KIN did not result in further improvement of any of the studied variables. The transfer of in vitro shoots to rooting media, containing different concentrations of indolebutyric acid (IBA) and indoleacetic acid (IAA), resulted in regeneration of complete plantlets. Alemow and ‘Cleopatra’ mandarin shoots rooted well using these plant growth regulators; however, all combinations of IBA and IAA tested resulted in very low rooting percentages in sour orange. To improve rooting in sour orange and ‘Cleopatra’ mandarin, different combinations of naphthaleneacetic acid (NAA) and IBA were tested. All NAA/IBA combinations produced higher rooting percentages than did the IBA/IAA combinations, and in sour orange nearly 100 % of explants developed roots. An efficient and simple protocol for the micropropagation of three citrus rootstocks, alemow, ‘Cleopatra’ mandarin, and sour orange, by culturing nodes from mature plants, has been established.

Micropropagation of dahlia in static liquid medium using slow-release tools of medium ingredients

Growth of dahlia shoots in vitro was ca. 4 times faster in liquid medium than on solidified medium. In liquid standard medium (3% sucrose, macroelements according to Driver–Kuniyuki Walnut medium, microelements according to Murashige–Skoog medium, 0.44 μM benzylaminopurine), the major medium ingredients were consumed for 75–80% during the first 6 weeks. Addition of extra ingredients increased growth, demonstrating that the amount of ingredients added at the start of culture was suboptimal. When the extra ingredients were given at the start of the culture, concentrations became too high and therefore inhibitory. When the ingredients were added during the subculture cycle by means of small aliquots of a concentrated solution or by means of slow-release tools, growth was strongly increased. Osmocote gave satisfactory results as a slow-release tool for inorganics. For organic ingredients (sucrose and benzylaminopurine), a novel slow-release tool was developed.

The influence of plant growth regulators on explant performance, bud break, and shoot growth from large stem segments of Acer saccharinum L

Benzyladenine (BA) and/or gibberellic acid (GA3) were applied in 20% white exterior latex paint separately at 0, 0.3, 1, 3, 10, or 30 mM; and at 1, 10, or 30 mM of each plant growth regulator (PGR) in a 3 × 3 factorial to 40 cm long stem segments of Acer saccharinum L. Softwood shoots were forced from these stem segments at various times of the year in a greenhouse and in a laboratory, these resulting shoots were surface disinfested and used as explants in vitro on Driver and Kuniyuki Walnut medium with 0 or 0.01 μM thidiazuron (TDZ). There was some response to the plant growth regulators applied in paint for shoot production from the stem segments and in vitro. Explants from softwood shoots forced from stems painted with 3 mM BA and cultured on medium with 0.01 μM TDZ produced more shoots than explants taken from softwood shoots forced with other BA concentrations or controls. Callus also grew significantly more on explants from stems treated with 3 mM BA cultured on 0.01 μM TDZ than explants harvested from stems painted with other concentrations of BA excluding 10 mM BA. When stem segments treated with BA plus GA3 were compared as a group to controls, more and longer softwood shoots grew on the stems painted with PGRs when all four runs were pooled (Sept. 2005 through Feb. 2006). Application of PGRs in paint extends the season of production of softwood shoots that may be used as explant materials and their subsequent performance in vitro.

Micropropagation ofLewisia cotyledonusing Axillary Buds from Flower Peduncles

<i>Lewisia cotyledon</i> (S. Wats.) B.L. Robins. (Portulacaceae), a perennial native to the mountainous areas of the western US, was micropropagated using the lower axillary buds from flower peduncles. Successful establishment in tissue culture was genotype dependent. Driver Kuniyuki Walnut medium (DKW) supplemented with 3.5 μM 6-benzylaminopurine (BA) appeared to be a better basal medium for increasing and maintaining <i>in vitro</i> rosettes than either Murashige and Skoog medium (MS) or Woody Plant medium (WPM) supplemented with the same BA concentration, but this response was genotype dependent. Placing rosettes on MS medium supplemented with 9.8 μM indole-3-butyric acid (IBA) for 12 wk resulted in 100% rooting with an average of 16 roots per rosette. Rooted rosettes were successfully transferred to <i>ex vitro</i> culture and were phenotypically normal. Micropropagation of lewisia will enable growers to produce large numbers of plants rapidly for the home landscape.

Micropropagation of Lewisia cotyledon using Axillary Buds from Flower Peduncles

<i>Lewisia cotyledon</i> (S. Wats.) B.L. Robins. (Portulacaceae), a perennial native to the mountainous areas of the western US, was micropropagated using the lower axillary buds from flower peduncles. Successful establishment in tissue culture was genotype dependent. Driver Kuniyuki Walnut medium (DKW) supplemented with 3.5 μM 6-benzylaminopurine (BA) appeared to be a better basal medium for increasing and maintaining <i>in vitro</i> rosettes than either Murashige and Skoog medium (MS) or Woody Plant medium (WPM) supplemented with the same BA concentration, but this response was genotype dependent. Placing rosettes on MS medium supplemented with 9.8 μM indole-3-butyric acid (IBA) for 12 wk resulted in 100% rooting with an average of 16 roots per rosette. Rooted rosettes were successfully transferred to <i>ex vitro</i> culture and were phenotypically normal. Micropropagation of lewisia will enable growers to produce large numbers of plants rapidly for the home landscape.

Shoot regeneration from leaves of Prunus serotina Ehrh. (black cherry) and P. avium L. (wild cherry).

Leaves excised from shoot cultures of Prunus avium cvs. F12/1 and Charger and genotype 1908, and from five genotypes of P. serotina and two hybrids of P. avium×P. sargentii developed shoots on Woody Plant medium (WPM) supplemented with either benzyladenine (BA) or thidiazuron (TDZ). Regeneration in both P. avium 1908 and a genotype of P. serotina was improved using TDZ rather than BA in the medium. Regeneration occurred more frequently in P. serotina if leaves were cultured on medium with WPM rather than modified Driver and Kuniyuki walnut medium. The proportions of leaves that regenerated varied between genotypes of the same species. Regenerated shoots of both P. avium and P. serotina developed into shoot cultures following transfer to the media used to produce the shoot cultures used as explant sources.

Plant Regeneration from Leaf Tissues of Siberian Elm

Plants were regenerated from leaf tissue of greenhouse-grown seedlings of Siberian elm (Ulmus pumila L.). Shoot regeneration was induced on Murashige and Skoog (MS) medium containing 5 to 10 μm of BA. Up to 55% of the leaf explants formed shoots with an average of 2.4 shoots per explant. Addition of 2.5 or 5 μm of IBA failed to enhance regeneration. Thidiazuron at 0.5 or 1.0 μm also induced shoot regeneration, but the shoots failed to elongate as well as shoots regenerated from media containing BA. Incubation in darkness for 7, 14, or 21 d had little effect in promoting shoot regeneration, except that incubation for 21 d increased shoot regeneration on the medium with 5.0 μm BA. Genotypes differed in shoot regeneration potential, with regeneration frequencies ranging from 13% to 55%. Regenerated shoots were micropropagated on Driver and Kuniyuki Walnut medium. Ninety percent of microcuttings rooted directly in potting soil. This regeneration system will be valuable for genetic transformation and cell selection of Siberian elm. Chemical names used: 6-benzylaminopurine (BA); indole-3-butyric acid (IBA); N-phenyl-N′ -1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ).