Callus and cell suspension cultures of Rudgea jasminoides,a tropical woody Rubiaceae

Rudgea jasminoides is a woody Rubiaceae that produces phytoalexins in response to fungal inoculation, the response being dependent of the seasonal conditions. With the aim of studying phytoalexin induction under controlled conditions, callus cultures were established from petiole explants of R. jasminoides on a modified basal MS medium supplemented with picloram alone or in combination with kinetin. The highest frequency of callus formation was observed in solid medium containing 2.22 M kinetin and 2.07 M picloram. Development of fast-growing friable white callus was achieved in the absence of kinetin, in cultures supplemented only with 8.28 M picloram. Cell suspension cultures were established from this friable callus by transferring pieces directly to the same medium without agar. Preliminary experiments revealed that cell suspension cultures of R. jasminoides represent a useful system to analyse induced defensive metabolites produced by this Rubiaceae species.     

Eustenopus villosus (Coleoptera: Curculionidae) Feeding of Herbicide-Resistant Yellow Starthistle (Centaurea solstitialis L.)

A population of yellow starthistle (Centaurea solstitialis L.) near Dayton, Washington developed herbicide resistance in response to repeated applications of picloram and other auxin-type herbicides. Laboratory and field experiments were conducted in 1998 to determine host acceptability and suitability of this herbicide-resistant yellow starthistle population to the biological control weevil Eustenopus villosus (Boheman) (Coleoptera: Curculionidae). In choice and no-choice feeding and oviposition experiments using excised buds, the weevil did not demonstrate a consistent preference for either herbicide-resistant (R) or -susceptible (S) yellow starthistle. When caged on buds of intact plants, the E. villosus feeding rate of 97% did not differ between R and S types. Host plant suitability, measured as larval damage and development to adult weevils, was equivalent in R and S types, with weevils maturing in 46% of the R and in 32% of the S capitula bearing oviposition scars. The number of viable achenes per capitulum was reduced by 87% due to larval feeding, with no difference between R and S types. Observations at the field site where resistance was found revealed oviposition scars on 78% of the late-bud-stage capitula on 23 June 1998 and 73% of the flowering and postflowering capitula on 15 August 1998. Selection for herbicide resistance has not created host incompatibility for E. villosus nor reduced the effectiveness of E. villosus as a biological control agent.     

早花百子莲叶片器官发生和胚胎发生再生体系的建立

以早花百子莲(Agapanthus praecox)叶片为外植体, 建立了器官发生和胚胎发生离体再生体系, 并对移栽驯化基质进行了初步筛选。结果表明, 毒莠定(PIC)对叶片愈伤组织诱导效果良好, 最适培养基为MS+2.0 mg·L ^-1 PIC; 叶片组织分生能力决定愈伤组织诱导效果, 1-2片新叶基部愈伤组织诱导率可达85.71%, 叶片分生区0-0.5 cm愈伤组织诱导率为66.48%, 叶片横切面中部诱导效果优于边缘。不定芽诱导最适培养基为MS+1.5 mg·L ^-1 PIC+0.3 mg·L ^-1 6-BA, 诱导率达80.27%。体细胞胚诱导培养基为MS, 0.05 mg·L ^-1多效唑或1.0 mg·L ^-1 ABA均对体胚诱导具有显著促进作用。1.0 mg·L ^-1 6-BA对幼苗增殖有利, 器官发生和胚胎发生途径幼苗增殖系数分别为2.23和2.93。草炭:珍珠岩:蛭石=1:1:1 (v/v/v)为早花百子莲移栽驯化的最佳基质, 成活率达100%。该研究建立了早花百子莲叶片外植体再生体系, 丰富了百子莲快繁技术体系, 可为其它单子叶植物离体再生体系建立提供参考。     

Picloram induced somatic embryogenesis in Gasteria and Haworthia

Various leaf sections of Gasteria verrucosa Haw. and Haworthia fasciata Haw. were cultured on media to examine the effect of picloram (4-amino 3, 5, 6-trichloropicolinic acid) and 2, 4-D (2, 4-dichlorophenoxy acetic acid) on somatic embryogenesis. Picloram (0.5, 1.0, 2.0, 3.0 mgl^-1) outperformed 2, 4-D (0, 1.0, 2.0, 3.0 mgl^-1) as the auxin source of both earliness of callus and embryo induction and final yield of embryos produced at both kinetin levels examined (0.25, 1.0 mgl^-1). Embryos arose initially as a yellow, compact globular masses from the area just beneath the epidermis in linear pattern parallel with the main axis of the leaf and then developed a heartshaped appearance. Embryo formation was preceded by growth of callus almost crystalline in appearance on the cut surface. Subsequent shoot formation developed from green pigmented loci in crystalline callus derived from embryos. Shoot and root development in Gasteria was induced on a defined medium containing quarter strength MS or B5 salts with no hormonal supplementation.     

Picloram-induced somatic embryogenesis in pejibaye palm (Bactris gasipaes H.B.K.)

Somatic embryogenesis in pejibaye or peach palm (Bactris gasipaes H.B.K.) was induced from callus derived from in vitro cultured shoot tips of young field-grown plants using a modified Murashige and Skoog medium supplemented with 5 mg L^–1 of N⁶-benzyladenine (BA) and 0.06 mg L^–1 of picloram for three months in the dark; this was followed by an additional three months with the same medium and incubation conditions, but using 0.03 mg L^–1 of picloram. The cultures were then transferred to light on a medium without hormones. This led to the formation of morphogenic callus, in which somatic embryos, as well as shoot primordia, and finally complete plantlets were formed. These plantlets continued to grow on transfer to the greenhouse.     

Micropropagation and in vitro flowering of the bamboo Dendrocalamus hamiltonii Munro

Nicotinic acid, pyridoxine, and picloram were stable in a liquid MS culture medium (pH 5.5–5.6) during autoclaving and during cell-free incubation in the dark at 5°C or 25°C for up to 6 weeks. Thiamine loss under the same conditions was 16% at 5°C and 18% at 25°C. Five percent of the sucrose in the liquid medium was hydrolyzed during autoclaving. During cell-free incubation in the light (100 E m^–2 s^–1) at 25°C, pyridoxine was not detected after 6 days, while 78% of the picloram and 56% of the thiamine were degraded after 6 weeks. All of the niacin and pyridoxine, 13% of the picloram and 42% of the thiamine in a liquid MS culture medium were utilized in 4 days by potato (cv. Lemhi Russet) tuber suspension cultures growing in the dark at 25°C.Abbreviations BS Gamborg et al. medium (1968) - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - MS Murashige & Skoog (1962) - NAA naphthaleneacetic acid - PAA phenylacetic acid     

Genotype effects on plant regeneration in callus and suspension cultures of Avena

Regenerative potential of the calli of nineteen genotypes of Avena sativa, Avena nuda, Avena byzantina and one interspecific hybrid were compared over three successive cultures. Highly significant genotype and genotype × subculture interactions were observed. Among the highest plant regenerable genotypes were Corbit (first subculture); GAF/Park and 88Ab3073 (second subculture); and GAF/Park and 87Ab5932 (third subculture). These genotypes regenerated on an average 10 to 17 plants each from a 200 mg callus mass after a 30 to 45 proliferation period. GAF/Park, a progeny of an interspecific cross, regenerated plants at a significantly higher level (11.85 plants/rep), followed by the similarly performing A. sativa (6.23 plants) and A. nuda (5.06 plants) genotypes, which were significantly higher than the A. byzantina genotypes (2.07 plants). Four genotypes were tested for their adaptability to suspension culture and plant regeneration potential by separating their cells and cell clusters into two sizes: larger and smaller than 3 mm. Larger clusters yielded plants for three genotypes GAF/Park, 88Ab3073, and Tibor. The smaller clusters only regenerated plants for GAF/Park and 88Ab3073. From one gram of callus used to initiate suspensions of GAF/Park and 88Ab3073, 119.9 and 18.8 plants, respectively, were regenerated. The plants regenerated for various genotypes from agar-solidified or suspension culture experiments had normal growth and seed set. This study confirms high and sustained regenerative capabilities of GAF/Park, a restricted genotype due to the weedy Avena fatua genetic background and identifies alternative genotypes, especially 88Ab3073 for future tissue culture and transformation studies.     

Influence of Boron on Somatic Embryogenesis in Papaya

Influence of boron on somatic embryogenesis in papaya (Carica papaya L.) cv. Honey Dew was investigated. Immature zygotic embryos were grown in the induction medium containing Murashige and Skoog basal salts, with B₅ vitamins, picloram (1 mg dm⁻³) or 2,4-dichlorophenoxy acetic acid (2 mg dm⁻³) and different concentrations of boric acid (30 to 500 mg dm⁻³). Maximum somatic embryo initiation was observed at 62 mg dm⁻³ boric acid irrespective of the growth regulator used. The cotyledonary stage somatic embryos were germinated on MS basal medium devoid of growth regulators. The regenerated plantlets were hardened under greenhouse conditions and transferred to field. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct somatic embryogenesis from shoot apical meristems of pea, and thidiazuron-induced high conversion rate of somatic embryos

Direct somatic embryogenesis from shoot apical meristems of pea is described. Somatic embryos were induced directly (without callus intervention) from meristematic tissues grown on a medium supplemented with 2.5 μM picloram. Within 4 to 5 weeks, fully morphologically developed somatic embryos were obtained. Somatic embryos originated from apical as well as from basal parts of meristem explants. The initiation and development of somatic embryos was asynchronous, basal somatic embryos developed more quickly than apical ones. Abundant secondary embryogenesis was observed after isolation of primary somatic embryos and culturing them on media for germination. Morphologically normal somatic embryos germinated on medium without growth regulators; the conversion rate was increased by application of 10 μM thidiazuron (TDZ). TDZ was also able to induce shoot bud regeneration on embryos without differentiated a shoot apex, allowing to germinate up to 78 % of all harvested somatic embryos with various morphology. The protocol was successfully tested in 47 out of 48 P. sativum and P. arvense cultivars as well as in two wild peas (P. elatius, P. jomardi). This revised version was published online in July 2006 with corrections to the Cover Date.