Bud Induction Research Articles

Validation of meta-Topolin in organogenesis, improved morpho-physio-chemical responses, and clonal fidelity analysis in Dioscorea pentaphylla L. – an underutilized yam species

The present investigation describes the efficacy of aromatic and synthetic cytokinins, which influence the direct organogenesis, biochemical responses, and ex vitro and in vivo performance of the in vitro propagated plantlets of Dioscorea pentaphylla L., an underrated famine tuber crop. The axillary shoot bud induction was achieved on the Murashige and Skoog's (MS) medium supplemented with 1.0 mg L−1 meta Topolin (mT) (96.9%) and 1.0 mg L−1 Thidiazuron (TDZ) (82.4%). The sprouted shoots were proliferated using 0.5 mg L−1 mT combined with 0.1 mg L−1 indole-3-acetic acid (IAA) with the maximum average number of 43.0 ± 1.29 shoots (7.2 ± 0.55 cm length). The shoots proliferated on mT and IAA combination demonstrated the presence of higher concentrations of carbohydrates and photosynthetic pigment contents in the leaves as compared with TDZ and IAA derived leaves. The healthy micro-shoots were rooted on a half-strength MS medium containing 1.0 mg L−1 indole-3-butyric acid (IBA) with the development of 12.6 ± 0.38 roots (5.9 ± 0.22 cm length). The plantlets were acclimatized in a greenhouse and showed 100% survival under in vivo conditions. The clonal fidelity of the regenerants was evaluated for the first time using Start codon targeted (SCoT) markers. Thirteen primers amplified 62 well-resolved bands and ranged from 1-8 bands. There were no somaclonal variations detected among the regenerants of D. pentaphylla with the mother plant.

In-Vitro Regeneration of Interspecific F1 Hybrid (Eucalyptus citriodora and Eucalyptus torelliana) of Eucalyptus

Tissue culture technique was standardized for in vitro shoot multiplication, using nodal segments of 25- 30 years old trees i.e., promising interspecific F1 hybrid of Eucalyptus (Eucalyptus citriodora and Eucalyptus torelliana). Due to the phenolic exudation explants did not survive and eventually died without regenerating buds. The explants collected from July to September were the best for in vitro studies for icropropagation. The axillary buds were surface sterilized with 0.1% Mercuric chloride solution for 10-15 minutes, followed by 0.1% Bavistin treatment for 1 minute and subsequently washed 3-4 times with sterilized distilled water. These surface sterilized axillary buds were cultured on MS medium supplemented with cytokinin and auxin. MS medium supplemented with 1.5mg/l BAP + 0.1mg/l NAA proved to be the best hormonal combination for induction of axillary bud which resulted in the development of 1-3 axillary shoots. The proliferated shoots were cultured on MS medium with different concentration of BAP (0.1 – 3.0 mg/l) alone or in combination with NAA (0.1-1.5mg/l) and supplemented with sucrose at 3%. The aim of the paper was to obtain maximum rate of in vitro regeneration of FRI-15 by using micropropagation technique.

De Novo Shoot Bud Induction from the Catharanthus roseus Leaf Explants and Agrobacterium tumefaciens-Mediated Technique to Raise Transgenic Plants.

The regeneration of a whole plant from a single cell or organ explant was a valuable task for plant biotechnology. However, important medicinal plants such as Catharanthus roseus have shown recalcitrance to regeneration protocols, thus limiting investigations on MIA metabolism and metabolic engineering in this plant system. In this chapter, successful regeneration protocols were detailed for Catharanthus roseus, either by direct shoot bud induction from leaf explants and Agrobacterium-mediated genetic transformation.

Establishment of Tissue Culture System of Actinidia deliciosa Cultivar “Guichang”

In order to breed virus-free plantlets of the kiwifruit cultivar “Guichang,” which belongs to Actinidia deliciosa, in this study, stem segments with buds were used as explants, the establishment of a tissue culture rapid propagation system was carried out, and then the virus status of tissue culture plantlets was detected via the real-time reverse transcription-polymerase chain reaction (RT-qPCR) method. The tissue culture rapid propagation system proved that the contamination and browning rates could be controlled below 20% and the survival rate could be exceeded by 70% when the single bud stem segment of “Guichang” kiwifruit was sterilized with 70% alcohol for 30–60 s and 15% NaClO for 15 min, respectively. Meanwhile, we screened the hormone concentration to get better results, and the appropriate medium for adventitious bud induction was MS + 6-BA (1.0 mg/L) + IBA (0.2 mg/L); for proliferation, it was MS + 6-BA (1.0 mg/L) + IBA (0.1 mg/L); and for rooting, it was 1/2 MS + IBA (0.3 mg/L), and the efficiency of induction, proliferation, and rooting could reach 74.07%, 79.63%, and 85.18%, respectively. In addition, the RT-qPCR results demonstrated that the infection rate of 9 viruses: apple stem grooving virus (ASGV), cucumber mosaic virus (CMV), Actinidia virus X (AVX), cucumber necrosis virus (CNV), ribgrass mosaic virus (RMV), citrus leaf blotch virus (CLBV), Actinidia virus B (AcVB), Pelargonium zonate spot virus (PZSV), and cherry leaf roll virus (CLRV) in the “Guichang” kiwifruit tissue culture plantlets was 0. This study could lay a foundation for the production of “Guichang” kiwifruit tissue culture seedlings, and the medium formula provided in this study was useful for the industrial rapid propagation of “Guichang” plantlets.

Multiple shoot induction and regeneration of Vanilla borneensis Rolfe - a critically endangered orchid of Assam, India

In the present investigation, a micropropagation protocol has been developed for Vanilla borneensis Rolfe – a critically endangered orchid through multiple shoot regeneration. Through in vitro multiple shoot regeneration from both nodal and shoot tip explants, maximum (100%) shoot induction was observed. The minimum time required for shoot bud induction was observed from the shoot tip (5–7 days) on medium supplemented with BAP (4.44 mM) + KIN (2.32 mM) as compared to the nodal explants. Maximum multiple shoot regeneration was observed from nodal explants on the medium supplemented with BAP (4.44 mM) + TDZ (6.82 mM). However, maximum shoot length was observed on the medium supplemented with BAP (4.44 mM) + 15% CW and the number of nodes (5.27±0.33) per shoot after 90 days. Maximum (80-100%) of root initiation was observed in almost all the concentrations of NAA. The shortest time of root initiation was found on the medium supplemented with NAA (5.37 mM). Further, acclimatization period was found to be 15 days with 70% acclimatization while 60% of survivability was observed in the field condition. This efficient micropropagation method of V. borneensis could be successfully used for mass propagation as well as conservation of the critically endangered wild orchid.

Micropropagation of Rare Scutellaria havanensis Jacq. and Preliminary Studies on Antioxidant Capacity and Anti-Cancer Potential.

We report the development of in vitro propagation protocols through an adventitious shoot induction pathway for a rare and medicinal Scutellaria havanensis. In vitro propagation studies using nodal explants showed MS medium supplemented with 10 µM 6-Benzylaminopurine induced the highest number of adventitious shoots in a time-dependent manner. A ten-day incubation was optimum for shoot bud induction as longer exposures resulted in hyperhydricity of the explants and shoots induced. We also report preliminary evidence of Agrobacterium tumefaciens EHA105-mediated gene transfer transiently expressing the green fluorescent protein in this species. Transformation studies exhibited amenability of various explant tissues, internode being the most receptive. As the plant has medicinal value, research was carried out to evaluate its potential antioxidant capacity and the efficacy of methanolic leaf extracts in curbing the viability of human colorectal cancer cell line HCT116. Comparative total polyphenol and flavonoid content measurement of fresh and air-dried leaf extract revealed that the fresh leaf extracts contain higher total polyphenol and flavonoid content. The HCT 116 cell viability was assessed by colorimetric assay using a 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide, showed a steady growth inhibition after 24 h of incubation. Scanning electron microscopy of leaf surface revealed a high density of glandular and non-glandular trichomes. This research provides a basis for the conservation of this rare plant and future phytochemical screening and clinical research.

Effect of light quality and extended photoperiod on flower bud induction during transplant production of day-neutral strawberry cultivars

Day-neutral (DN) strawberry cultivars are increasingly grown in Canada because they produce flowers and fruits continuously until October. Appropriate artificial lighting conditions during preparation of high-quality transplants is critical. Unfortunately, systematic evaluation of appropriate artificial lighting conditions during transplant production is limited. The objective of this study was to determine how an extended photoperiod supplemented with different light quality affects the vegetative and reproductive growth of a day-neutral cultivar during transplant production. In the first trial, we investigated the photoperiodic nature of the DN cultivar ‘Albion’ under low intensity incandescent light. Transplants were grown under three light combinations with different far-red : blue ratios (1:5, 5:1 and 1:1), supplemented for long day (LD; 24 h), short day (SD; 10 h) photoperiods and during a night interruption (NI) for 2 h. ‘Albion’ cultivar exhibited similar degree of flowering sensitivity regardless of photoperiod duration when incandescent light was used as predominant light source. In case of light emitting diodes (LEDs), dominant blue (1:5) LEDs prompted a significant increase in flower bud induction (FBI), more explicitly under the LD photoperiod. Furthermore, transplants grown under dominant blue light (1:5) supplied during NI produced eight flower buds per plant, the highest among all treatments, and promoted flower development outside the crown. Based on the results, it appears that lower wavelengths advance flowering and higher wavelengths contribute towards the morphological traits especially during transplant production. Results suggest that combination of far-red and blue LEDs at 1:5 ratio could be a potential light source to improve flower bud induction and floral development to subsequently increase fruit production.

Meta-Topolin mediated improved micropropagation, foliar micro-morphological traits, biochemical profiling, and assessment of genetic fidelity in Santalum album L.

An improved in vitro propagation system has been developed for Santalum album L. using meta-Topolin for the first time. Direct organogenesis (100 %) was achieved by induction of axillary buds and a maximum of 8.2 shoots with 4.0 cm length was developed from nodal explants on Murashige and Skoog’s (MS) medium containing 1.0 mg L−1 meta-Topolin (mT). The MS medium supplemented with 0.5 mg L-1 mT and 0.25 mg L−1 α-naphthalene acetic acid (NAA) exhibited maximum shoot proliferation potential (135 shoots with 7.9 cm length per explant) after the 3rd subculture. Further, the combination of mT and NAA resulted in the production of higher levels of free amino acids [33.6 mg g-1 dry weight (DW)], soluble sugar (37.4 mg g-1 DW), and reducing sugar (45.0 mg g-1 DW) in the leaves than the BAP and NAA combinations. The efficiency of mT has also been highlighted in the foliar structural developments. Comparative anatomy of leaves showed the presence of structural variations influenced by the type of cytokinins used. BAP and NAA-derived leaves revealed the presence of under-developed cuticle, unorganized tissue systems, undifferentiated mesophyll tissues, and under-developed mechanical and vascular tissues. Whereas, mT and NAA-derived leaves exhibited comparatively thick cuticle, collenchymatous hypodermis, well-differentiated mesophylls, and increased vascular elements. Roots were induced ex vitro under the greenhouse conditions when the shoot-bases were treated with 500 mg L−1 indole-3-butyric acid (IBA) for 10 min. These plantlets were hardened in soilrite® and cocopeat (1:1) mixture and a 100 % survival rate was achieved in the field. Additionally, the Start codon targeted (SCoT) markers analysis demonstrated that the genetic homogeneity was maintained during in vitro development of plantlets. The application of mT can be an effective growth regulator for in vitro propagation of S. album, as it favoured enhanced and quick production of genetically uniform clones.

Development of high frequency cost-effective micropropagation protocol for Juncus rigidus using liquid culture medium and extraction of cellulose from their in vitro shoots - An important rush

Juncus rigidus is important halophyte with high cellulose content, but no studies has been made on micropropagation of the plant and cellulose extraction from in vitro shoots. To optimize an effective system for shoot multiplication, explants were grown in agar medium, liquid static culture, and bioreactor. Best shoot bud induction was obtained in liquid MS medium supplemented with2.27 μM thidiazuron (TDZ) over 0.46–4.65 μM Kinetin (KN) and 2.22–6.66 μM 6-benzyl aminopurine (BAP). Maximum number of shoot bud (36 ± 1.3) were achieved in static liquid MS medium supplemented with 2.22 μM BAP and 0.57 μM indole acetic acid (IAA). Upon subsequent subcultures >80 shoot buds were achieved in static liquid MS medium supplemented with 1.11 μM BAP, 0.57 μM IAA, and 0.46 μMKN within 30 days of culture. Being halophytic plant NaCl did not have any significant effect on shoot proliferation. Elongated shoots cultured in MS medium supplemented with 0.44 μM BAP, and 0.57 μM IAA developed 97% rooting in filter paper boat culture vessel. Sapling production cost in liquid culture medium was 90% less as compared to solid medium. Cellulose was extracted from the in vitro shoots and 17.64% cellulose achieved from liquid medium cultured shoots. For the first time micro-shoots are tested for in vitro cellulose production. • Maximum shoot bud (36 ± 1.2) induction was achieved in static liquid medium. • More than 80 shoot buds generated in static liquid MS medium supplemented with BAP, IAA, and KN. • 33.4 multiplication rate was recorded in static liquid medium. • 17.64 % cellulose extracted form in vitro shoots of J. rigidus. • In vitro plant based cellulose synthesis is important with future industrial application and bioengineering.

Use of polylactic acid microvessel to obtain microplantlets of Eucalyptus microcorys through indirect organogenesis.

Microplants of Eucalyptus microcorys were produced through indirect organogenesis, and the interaction of plant growth regulators (PGRs) (TDZ-thidiazuron and NAA-α-naphthalene acetic acid), juvenile tissues (cotyledon and hypocotyl) and different types of polylactic acid (PLA) microvessels on plant production were evaluated. Cotyledon-derived callus induction increased by 30-60% in all tested combinations of TDZ and NAA concentrations compared the absence of PGRs. Hypocotyl-derived callus induction was improved in most tested combinations of TDZ and NAA concentrations. Moreover, 100% callus induction from both tissues was achieved with TDZ (1, 2 and 3mg L-1) + NAA (0mg L-1). Bud induction from cotyledon tissues was improved with TDZ (1 and 3mg L-1) + NAA (0mg L-1) and from hypocotyl with TDZ (1 and 2mg L-1) + NAA (0mg L-1). Shoot elongation from cotyledon tissues was not improved from any combination of PGRs, whereas TDZ (1mg L-1) + NAA (0mg L-1), TDZ (1mg L-1) + NAA (4mg L-1), TDZ (2mg L-1) + NAA (4mg L-1) and TDZ (3mg L-1) + NAA (2mg L-1) improved shoot elongation from hypocotyl tissues. Adventitious rooting and acclimatization of microcuttings ranged from 40 to 70% in three of the tested microvessels. The acclimatized microcuttings had low genetic variability. Successful production of E. microcorys microplants was achieved in this study using hypocotyl tissue and cultivated a culture medium supplemented with TDZ and NAA, using PLA-based microvessels.

Transplant pre-chilling induces earlier flowering and fruiting for forcing-cultured June-bearing strawberries

Advancing the flowering and fruiting to extend the shelf life possesses a great commercial value for industrial strawberry production. This study was conducted to investigate the effects of chilling and photoperiod on flower induction and fruit productivity in three June-bearing strawberries. The experiment was carried out in an industrial refrigeration warehouse and a greenhouse. One month-old cutting-propagated transplants were moved to and grown in rooms with an chilling air temperature of either 8 or 15°C for 4 or 6 weeks starting on July 15. White LEDs with a 150 μmol•m−2•s−1 PPFD were lit in these cold rooms for 11 hours (a short day) or 15 hours (a long day) to provide the necessary light for plant growth. The plants were transplanted to hydroponic systems in a greenhouse after being chilled. The results showed that chilling transplants at either 8 or 15°C for either 4 or 6 weeks significantly promoted flower bud induction in all three cultivars, while the photoperiod supplied in cold rooms did not affect the flowering. Moreover, the time of initiation of the secondary inflorescence was not significantly affected by chilling, except in ‘Kuemsil’. Fruits of ‘Seolhyang’ were ready to be harvested at the end of September, while those of ‘Kuemsil’ and ‘Maehyang’ were ready for harvest at the beginning of October, which corresponded to 52, 55, and 57 days earlier than that of their respective control, not chilled plants. The fruit yield decreased after chilling because the high temperature during fruiting in autumn resulted in a great number of small and decayed fruits. However, the soluble solids content and acidity of the fruits harvested on chilling-treated plants did not show any differences with those of the control, indicating that the flavor was marketable. In a conclusion, 4 weeks of chilling at 15°C during the summer can be used for early flowering and fruiting in June-bearing strawberries. Further work should be focused on mitigating the problem of producing small and decayed fruits.

Variation in non-target traits in genetically modified hybrid aspens does not exceed natural variation

Genetically modified hybrid aspens (Populus tremula L. x P. tremuloides Michx.), selected for increased growth under controlled conditions, have been grown in highly replicated field trials to evaluate how the target trait (growth) translated to natural conditions. Moreover, the variation was compared among genotypes of ecologically important non-target traits: number of shoots, bud set, pathogen infection, amount of insect herbivory, composition of the insect herbivore community and flower bud induction. This variation was compared with the variation in a population of randomly selected natural accessions of P. tremula grown in common garden trials, to estimate how the “unintended variation” present in transgenic trees, which in the future may be commercialized, compares with natural variation. The natural variation in the traits was found to be typically significantly greater. The data suggest that when authorities evaluate the potential risks associated with a field experiment or commercial introduction of transgenic trees, risk evaluation should focus on target traits and that unintentional variation in non-target traits is of less concern.

Basal stem cluster bud induction and efficient regeneration for the Tibetan endemic medicinal plant Swertia conaensis

The artificial rapid propagation system for Swertia conaensis T. N. Ho et S. W. Liu was explored to screen the appropriate plant regeneration method and to provide an efficient propagation mode, useful for artificial breeding technology or for further research and development of the Tibetan endemic medicinal plant. In this study, the most suitable explant and hormone were chosen according to single factor test. Next, the effects of different hormone combinations on basal stem cluster bud induction, callus induction, adventitious bud occurrence and plant regeneration were investigated by using complete combination and orthogonal experiment. The obtained results showed that the explants suitable for in vitro of S. conaensis were stem tips with leaves, which were regenerated through the method of basal stem cluster bud occurrence in the MS medium with 2.0 mg∙L-1 6-BA, 0.5 mg∙L-1 NAA, but the proliferation coefficient was low, only 3.16 after 40 days of culture. Subsequently, the proliferation coefficient failed to improve, irrespective of change of the concentration ratio of 6-BA and NAA. Therefore, in the orthogonal experiment of adding ZT, the MS medium with 1.0 mg∙L-1 ZT, 0.5 mg∙L-1 NAA and 2.5 mg∙L-1 6-BA induced a large number of callus green and compact, with 86.30% callus occurrence rate. After 40 days of culture, the rate of adventitious bud occurrence was 96.55% and the proliferation coefficient was high (10.37). The rooting rate was 100% in the 1/2MS medium with 0.5 mg∙L-1 NAA. The survival rate of regenerated plants was more than 95%. Indirect organogenesis was more efficient than direct organogenesis in in vitro culture of S. conaensis. In this study, the efficient and stable regeneration system of S. conaensis was achieved through the method of explant to callus to adventitious buds, which provided an effective way to an endangered species.

Review on the ecophysiology of important Andean fruits: Passiflora L.

The development of Andean fruit crops is viewed as an important and healthy contribution to global food consumption but ecophysiological studies on these fruit trees are scarce. 96% of approximately 520 Passiflora L. species are distributed in the Americas, especially in Colombia and Brazil. Many of these species originated on the edges of humid forests in tropical valleys. The four species: yellow passion fruit (Passiflora edulis f. flavicarpa Degener), sweet granadilla (Passiflora ligularis Juss.), purple passion fruit (Passiflora edulis f. edulis Sims) and banana passion fruit (Passiflora tripartita var. mollissima (Kunth) Holm-Niels & P.M. Jørg) are widely cultivated in Colombia, and their ecophysiological findings are described in this review. The demands, in terms of temperature (°C) and altitude (masl) are, for yellow passion fruits: 15-28 °C and 0-1,300 masl; sweet granadillas: 15-23 °C and 1,800-2,600 masl; purple passion fruits: 15-22/12-14 °C (day/night) and 1,600-2,300 masl; and banana passion fruit: 13-16 °C and 1.800-3.200 masl; all of them have high requirements for solar radiation, a minimum of 7 h of sunshine per day, to encourage flowering and fruit quality. Cloudy days decrease growth, flower bud induction and flower opening. Temperature and photosynthetic active radiation are the climatic factors that have the greatest effect on plant development. Relative humidity between 60 and 80% supports effective pollination and fecundation. Passiflora L. crops do not support long periods of waterlogging, with a maximum of 4 days for yellow passion fruit. Climatic events such as prolonged rain, intense droughts, strong winds and hail are harmful for these plants.

Exogenous application of 6-benzyladenine and spermine improves shoot bud induction of shoot apex of Terminalia bellerica Roxb.

Shoot regeneration was optimized from shoot apex explants of mature tree species Terminalia bellerica using 6-benzyl adenine (BA) and spermine (Spm). The maximum shoot bud regeneration response (100%) was observed on BA supplemented Murashige and Skoog (MS) medium. However, MS medium with 2.22 μM BA and 9.90 μM Spm induced an average of 21 micro shoots per shoot apex and averaged 2.4 cm shoot length after 4 weeks of culture. Of four combinations tested, 2.22 μM BA + 1.50 μM gibberellic acid (GA3) was found to be most responsive for shoot bud proliferation, followed by intermediate response on BA (4.44 μM), BA (2.22 μM) and further lower on combination of 2.22 μM BA, 1.50 μM GA3 and 9.90 μM Spm. Micro shoots production reached to 100%, with maximum number of 32 micro shoot buds per explant cultured on MS medium with 2.22 μM BA and 1.50 μM GA3 after an interval of 8 weeks. Between auxin combinations as indole-3-acetic acid (IAA)/indole-3-butyric acid (IBA), IAA/naphthalene acetic acid (NAA) or IBA/NAA, the root induction was highest (94%) on the latter medium added with 2.46 μM IBA and 2.69 μM NAA producing 11.8 healthy roots per shoot with an averaged root length of 1.8 cm within 15–30 days of culture. Successful acclimatization of plantlets in the garden soil resulted to 90% healthy plants with no differences observed in the morphological characteristics of the growing shoots.

Direct Shoot Bud Proliferation Protocol from Stevia rebaudiana Leaf Culture for Healthy Biomass Production

AN EFFICIENT and simple regeneration protocol using leaf explants was described on MS medium in the presence of various plant growth regulators. After four weeks of culture, the highest induction of adventitious shoot buds from leaf culture (90%) was achieved on MS medium with 1.0mg/L BA. The largest number of shoot buds (3.02) per leaf explant with no callus formation was achieved on MS medium with 2.0mg/L BA. The best combination for the induction of numerous shoot buds was found to be TDZ + BA + IBA (0.5, 1.0, and 0.5mg/L, respectively), which presented 10.4 shoots per explant with 3.15cm in length. For in vitro root formation stage, Healthy shoots were collected and cultivated on a half-strength MS with various concentrations of NAA and IAA alone or in combination with 2,4-D or IBA. Furthermore, the highest roots (8.17) per shoot with root formation (100 %) was observed using a half-strength MS medium in the presence of 2.0mg/L IAA. Therefore, healthy in vitro rooted plantlets were acclimatized successfully after four weeks in the greenhouse.

An efficient regeneration pathway through adventitious organogenesis for the endangered Argania spinosa (L.) Skeels

An efficient in vitro propagation system through adventitious organogenesis is reported for argan (Argania spinosa (L.) Skeels). Seed germination of two argan genotypes, ‘Mejji’ and ‘R’zwa’, was evaluated under different treatments. Afterwards, the effects of different factors on adventitious shoot bud induction, shoot multiplication, elongation and rooting were evaluated. The findings of this study showed that soaking argan seeds in GA3 during 12 h speeds germination increases the germination percentage. Besides, the use of a sucrose-free medium, without ammonium and with a low nitrate concentration significantly increased the germination percentage. To induce organogenesis, different seedling-derived explants were used. However, epicotyl segments were the only explants capable of regenerating adventitious shoot buds. Highest organogenesis percentage (79.17%) was observed in genotype ‘Mejji’ on Murashige and Skoog (MS) medium containing 2 mg L−1 6-benzylaminopurine (BAP) under dark conditions. Adventitious shoot bud multiplication was performed on MS medium supplemented with different combinations of BAP and GA3. The highest number of adventitious shoot buds per explant (4.0) was observed on MS medium containing 1 mg L−1 BAP and 2 mg L−1 GA3. Regarding in vitro root induction, it was found that combining indole-3-butyric acid (IBA) and putrescine is necessary for rhizogenesis. The highest rooting percentage (56.66% in genotype ‘R’zwa’) was observed on MS medium supplemented with 1.5 mg L−1 IBA and 160 mg L−1 putrescine, with an average number of 2.74 roots per shoot and an average root length of 1.93 cm. The regenerated plantlets were successfully acclimatized and showed normal growth and development.

Toward Systematic Understanding of Flower Bud Induction in Apple: A Multi-Omics Approach.

The induction of flower buds in apple (Malus × domestica Borkh.) is tightly connected to biennial bearing, which is characterized by alternating years with high (ON) and low or no (OFF) crop loads. In order to study this irregular cropping behavior, spur buds from ON- and OFF-trees of the biennial-bearing cultivar ‘Fuji’ and the regular bearing cultivar ‘Gala’ were collected. First, the time of flower bud initiation was precisely determined for both cultivars by histological analysis. Moreover, for a systematic understanding of flower bud induction in apple, the physiological and molecular mechanisms within the bud tissue were evaluated over four weeks prior to flower bud initiation by employing a multi-omics approach, including RNA sequencing, proteomic and metabolic profiling. Gene and protein enrichment analysis detected physiological pathways promoting and inhibiting early flower bud development. Metabolic profiles from the cropping treatments revealed a greater abundance of thiamine, chlorogenic acid, and an adenine derivative in spur buds from OFF-trees, whereas tryptophan was more abundant in the buds collected from ON-trees. Cultivar comparison indicated that chlorogenic acid was more abundant in ‘Gala’ than in ‘Fuji’ spur buds, whereas the opposite effect was found for tryptophan. Genes controlling tryptophan biosynthesis were not affected by ON- and OFF-treatments, but genes assigned to the metabolism of tryptophan into indoleacetate were differentially expressed between cultivars and treatments. The multi-omics approach permitted analyzing complex plant metabolic processes involved in early flower bud development and more specifically presumably in flower bud induction by tracing some pathways from gene to product level.

Effect of branch bending time on induction of shoot and flower bud, productivity and quality of guava var. Sardar (L-49)

Effect of branch bending time on induction of shoot and flower bud, productivity and quality of guava var. Sardar (L-49)

English

Purple passion fruit (Passiflora edulis Sims) has gained attention in Southern China, and its planting area has increased during the last several years. Through tissue culturing, virus-free plants are produced as maternal parents for seedling production. However, there are some difficulties that affect passion fruit tissue culture efficiency, including high contamination rates in explant disinfection, low shoot proliferation, yellow or albino leaves, slow growth, and time-consuming processes. In this work, the aforementioned problems were investigated, and disinfection was optimized. Results revealed that the repeat disinfection method (0.1% HgCl2 for 15 min + 0.1% HgCl2 for 12 min) with a 2-d interval was the most suitable disinfection treatment for young stem segments of purple passion fruit. The addition of silver thiosulfate (STS) improved proliferation efficiency. Moreover, additional 1X iron salt was added to the bud induction and rooting medium. The regenerated shoots had a better seedling state with healthier green leaves, roots were more easily induced and better developed and the chlorophyll contents were higher. Thus, more efficient tissue culturing of purple passion fruit was achieved. © 2021 Friends Science Publishers