Indole-3-butyric Acid Treatment Research Articles

Structural and ultrastructural variations in in vitro and ex vitro rooting of microcuttings from two micropropagated Leucospermum (Proteaceae)

Abstract In vitro rooting of two Leucospermum cultivars (L. cordifolium ‘Flame Spike’ and L. ‘Tango’) microcuttings was studied with different indole-3-butyric acid (IBA) treatments: A) including in a solid medium (0, 0.2, 1 and 2 mg L−1), B) by dipping the base of the shoots in 500–2500 mg L−1 for 5 s and C) including in a liquid medium (12.5 and 25 mg L−1) for 24–96 h (induction step). After the treatments B and C, shoots were transferred to an auxin-free root elongation medium containing 20 g L−1 sucrose and solidified with 7 g L−1 agar. The long-term presence of IBA in the culture-medium inhibited root development. The culture of shoots in a liquid medium with higher IBA concentrations and the application of IBA pulses at the base of the microcuttings proved to be suitable treatments to induce rhizogenesis. Culturing microcuttings in a growth-regulator free solid medium after IBA treatments (B and C) triggered root initiation and differentiation. The results show that the microcuttings cultured in a liquid medium with IBA had the highest percentages of rooting. The sequence of anatomical changes during rooting was similar in vitro and ex vitro, the origin of the adventitious root in the vascular cambium. In vitro roots with an organized tissue system emerged from the microcutting stems 6 days after the root induction treatments. The acclimatized plantlets showed a suitable root system. Roots were formed ex vitro from the stem vascular cambium and connections were established between the stem vascular bundles and the roots, allowing root elongation. Some modifications were also observed in the basal rooting zone of stems in L. ‘Tango’.

Stem cuttings and substrates in Dovyalis asexual propagation

The objective of this study was to evaluate the asexual propagation of Dovyalis, through the use of substrates and cuttings. Three experiments were conducted in Marechal Cândido Rondon, Paraná State, Brazil, and the first experiment consisted of three removal positions of the cuttings (apical, middle and basal) x 4 Indole butyric acid (IBA) concentrations (0 mg L-1, 1000 mg L-1, 2000 mg L-1 and 3000 mg L-1); the second experiment evaluated the number of leaves in the cuttings (2, 4 and 6) x 3 cutting sizes (10, 15 and 20 cm); and the third experiment evaluated four substrates for rooting. The experiment was carried out in a randomized blocks design, with the first in a 3x4 and the second in a 3x3 factorial, respectively, containing 4 repetitions of 15 cuttings. The third experiment consisted of 5 repetitions of 15 cuttings. After the IBA treatment, the cuttings were taken to rooting in sandy beds during 70 days. The agronomical variables were evaluated. Basal and middle cuttings resulted in root systems with better development. The use of 1666 mg L-1 of IBA favors the Dovyalis cuttings rooting. Cuttings with 15 and 20 cm with four leaves favors the Dovyalis vegetative propagation. Dovyalis cuttings develop better on substrates containing latosol and vermiculite.

Arabidopsis thaliana GH3.15 acyl acid amido synthetase has a highly specific substrate preference for the auxin precursor indole-3-butyric acid

Various phytohormones control plant growth and development and mediate biotic and abiotic stress responses. Gretchen Hagen 3 (GH3) acyl acid amido synthetases are plant enzymes that typically conjugate amino acids to indole-3-acetic acid (IAA) or jasmonic acid (JA) to inactivate or activate these phytohormones, respectively; however, the physiological and biological roles of many of these enzymes remain unclear. Using a biochemical approach, we found that the Arabidopsis thaliana GH3.15 (AtGH3.15) preferentially uses indole-3-butyric acid (IBA) and glutamine as substrates. The X-ray crystal structure of the AtGH3.15·AMP complex, modeling of IBA in the active site, and biochemical analysis of site-directed mutants provide insight on active site features that lead to AtGH3.15's preference for IBA. Assay-based in planta analysis of AtGH3.15-overexpressing lines indicated that their root elongation and lateral root density were resistant to IBA treatment but not to treatment with either IAA or JA. These findings suggest that AtGH3.15 may play a role in auxin homeostasis by modulating the levels of IBA for peroxisomal conversion to IAA. Analysis of AtGH3.15 promoter-driven yellow fluorescent protein reporter lines revealed that AtGH3.15 is expressed at significant levels in seedlings, roots, and parts of the siliques. We conclude that AtGH3.15 is unique in the GH3 protein family for its role in modifying IBA in auxin homeostasis and that it is the first GH3 protein shown to primarily modify a plant growth regulator other than IAA and JA.

ITRAQ-Based Proteomic Analysis Reveals Potential Regulation Networks of IBA-Induced Adventitious Root Formation in Apple.

Adventitious root (AR) formation, which is controlled by endogenous and environmental factors, is indispensable for vegetative asexual propagation. However, comprehensive proteomic data on AR formation are still lacking. The aim of this work was to study indole-3-butyric acid (IBA)-induced AR formation in the dwarf apple rootstock ‘T337’. In this study, the effect of IBA on AR formation was analysed. Subsequent to treatment with IBA, both the rooting rate and root length of ‘T337’ increased significantly. An assessment of hormone levels in basal stem cuttings suggested that auxin, abscisic acid, and brassinolide were higher in basal stem cuttings that received the exogenous IBA application; while zeatin riboside, gibberellins, and jasmonic acid were lower than non-treated basal stem cuttings. To explore the underlying molecular mechanism, an isobaric tags for relative and absolute quantification (iTRAQ)-based proteomic technique was employed to identify the expression profiles of proteins at a key period of adventitious root induction (three days after IBA treatment). In total, 3355 differentially expressed proteins (DEPs) were identified. Many DEPs were closely related to carbohydrate metabolism and energy production, protein homeostasis, reactive oxygen and nitric oxide signaling, and cell wall remodeling biological processes; as well as the phytohormone signaling, which was the most critical process in response to IBA treatment. Further, RT-qPCR analysis was used to evaluate the expression level of nine genes that are involved in phytohormone signaling and their transcriptional levels were mostly in accordance with the protein patterns. Finally, a putative work model was proposed. Our study establishes a foundation for further research and sheds light on IBA-mediated AR formation in apple as well as other fruit rootstock cuttings.

EFFECT OF SOME NATURAL EXTRACTS, INDOLBUTIRIC ACID AND NAPHTHALENE ACETIC ACID ON ROOTING OF PICUAL OLIVE CUTTINGS

This study was carried out during 2014 and 2015 seasons in a private plastic green house at Belbies District, Sharkia Governorate, Egypt in an attempt to replace the traditional olive cutting rooting synthetic growth regulators by some auxin releasing natural extracts. Cuttings of Picual olive cv. were prepared on November of each season (about 15 cm long and7-9 mm in diameter), cutting were dipped in concentrations of indole-3-Butyric acid (IBA) at 4000 ppm and naphthalene acetic acid (NAA) at 500 ppm solution for 5 seconds or soaked in the natural extracts for half hour. The results revealed that the maximum rooting percentage (81.44 and 85.60%), number of roots/cutting (14.84 and 14.90 root/cutting), shoot number/ transplant (2.74 and 2.17 shoot/plant), leaf number/plant (6.49 and 6.61 leaf/plant) and bud sprouting percentage (48.46 and 48.14 %) respectively were recorded for cuttings dipped in IBA at 4000 ppm in comparison with those dipped in moringa extracts, which gained the lowest values of the considered parameters during the two seasons. The highest cutting survival percentages were recorded for IBA and NAA treatments, garlic at 10 or 20%, liquorice at10 g and algae at 2.5 or 5 cm in both seasons without significant differences between them. Total carbohydrates percentages in the roots and shoots were gradually increased with the advance in planting months, and reached the highest values after seven months, but total soluble phenols in the roots were decreased after six months then increased in the seventh month in both seasons. The algae, garlic and liquorice treatments were considered the best natural extracts compared to yeast and in turn can be used as an alternative of growth regulators for rooting Picual olive cuttings.

Rooting of cuttings of the wild Indian almond tree (Sterculia foetida) enhanced by the application of indole-3-butyric acid (IBA) under leafy and non-leafy conditions

Abstracts Vegetative propagation is one of the important conservation means of wild, native, and threatened tree species. The experiment finds out the opportunities of rooting of leafy and non-leafy branch cuttings of Sterculia foetida with different concentration of IBA in a non-mist propagator. Five treatments were used for this experiment. The treatments were T0 (control), T1 (0.2% IBA), T2 (0.4% IBA), T3 (0.6% IBA) and T4 (0.8% IBA). The experiment revealed the importance using IBA treatments rather than the types of cuttings used. The experiment showed that the highest rooting percent was observed in 0.8%IBA concentration and lowest rooting percent was observed in control in both leafy and non-leafy condition. Rooting success varied among the IBA treatments from 33.1% to 86.2% in leafy and 34.5 to 82.6% in non-leafy cuttings. The two way analysis of variance (ANOVA) showed no significant difference (p > 0.05) among type of cuttings (leafless / leafy) but it showed significant difference (p 0.05) but there were significant differences (p 0.05). The overall survival of rooted cutting was higher in 0.8% IBA concentration (66.6 in leafy and 69.3% in non-leafy cuttings) and lower in control. The two way ANOVA also showed significant differences on survival of rooted cutting among the treatments but no significant difference between leafy and non-leafy cuttings. Tukey post-hoc test showed the comparisons of different mean values of treatments of rooting success, sprouting success of rooted cuttings and overall survival. NMDS ordination plot showed rooting and sprouting success parameters and how the parameters of leafy and non-leafy cutting shifted from each other. On the basis of this study, 0.8% IBA may be applied for rooting of cuttings of Sterculia foetida.

The effect that indolebutyric acid (IBA) and position of cane segment have on the rooting of cuttings from grapevine rootstocks and from Cabernet franc ( Vitis vinifera L.) under conditions of a hydroponic culture system

Abstract The present study aimed at determining the effect of indolebutyric acid (IBA) and of the part of cane from which the cuttings were taken on the rooting ability of three rootstocks and of a grapevine variety using a hydroponic system employing water as the culture medium. Under hydroponic conditions, three different auxin treatments (control water, 120 and 250 ppm IBA) were applied on the three rootstocks, namely 1103 Paulsen, SO4, Dog Ridge and cv Cabernet franc ( Vitis vinifera L.). The treatments were applied annually for a period of two (2) years and, more specifically, in 2014 and 2015, using a completely randomized design. The cuttings were collected from the Experimental Vineyard, Laboratory of Viticulture, Agricultural University of Athens. The study continued by evaluating the effect of that three factors, rootstock/variety, cane part donating the cuttings, and IBA concentration had on the following: percentage of callogenesis, percentage of rhizogenesis, average diameter of roots, average number of roots per cutting, total surface of roots, and total length of roots. The results of the experiment revealed that treatment with 250 ppm IBA and cuttings coming from the middle part of the cane yielded the highest rhizogenesis percentages. At the same time, the highest callogenesis percentage was observed in the basal cuttings of rootstock 1103 P that underwent the same treatment. Following the 120 ppm IBA treatment, the basal cuttings of rootstock Dog Ridge presented the highest average number of roots. Under the 250 ppm IBA treatment, the basal, middle and middle cuttings of the Dog Ridge rootstock respectively presented the highest average diameter, surface, and length of roots. The experiment led to the conclusion that, under hydroponic conditions and when treated in low IBA concentrations, the grapevine variety and the rootstocks under study can give rooting results which are quite satisfactory. Based on those results, a hydroponic system employing water as its culture medium may prove practical and economical when it comes to vine propagation.

Nitric oxide in combination with indole-3-butyric acid improves root growth in ‘Ferdor Julior’ hardwood cuttings (Prunus insistitia (L.) × Prunus domestica (L.))

ABSTRACTThe production of plants for high density fruit orchards requires a highly efficient clonal propagation method. ‘Ferdor Julior’ rootstock is well adapted to different soil conditions, but its natural rooting potential is very limited. Propagation treatments, such as bottom heat and indole-3-butyric acid (IBA) applications have previously been used to improve rooting. The aim of this work is to evaluate the effects of either IBA, or sodium nitroprusside (SNP; a nitric oxide (NO) donor), or a combination of both on the rooting of hardwood cuttings of ‘Ferdor Julior’. As metabolism markers, ascorbic acid (AA) and glutathione (GSH) were measured in adventitious roots. ‘Ferdor Julior’ hardwood cuttings were treated as follows: untreated, 0.3 mM IBA, 1 mM SNP, 1 mM SNP previously exposed to light (as a negative control), and 1 mM SNP + 0.3 mM IBA. After 4 months, the combined use of SNP and IBA had increased root growth and lateral rooting, but resulted in less shoot growth, whilst AA and GSH concentrations were also reduced. IBA and SNP individual treatments showed intermediate results, compared to untreated cuttings. According to the results obtained, there may be an additive effect of auxin and NO signaling pathways. In conclusion, this new and promising technique for ‘Ferdor Julior’ propagation could improve lateral root development and promote early lateral root growth.

Production of Three Eastern U.S. Native Shrubs: Effects of Auxin Concentration on Rooting and Shade Level on Container Plant Growth

American fly honeysuckle (Lonicera canadensis), hobblebush (Viburnum lantanoides), and sweetbells (Eubotrys racemosa) are eastern U.S. native shrubs with ornamental value, which might become successful nursery crops if they propagate readily from stem cuttings and grow uniformly in containers. We evaluated rooting success for hobblebush and sweetbells using stem cuttings treated with indole-3-butyric acid (IBA) in talc at concentrations of 0, 1000, 3000, or 8000 ppm. For hobblebush, IBA at 1000, 3000, or 8000 ppm will yield 70% rooting success. For sweetbells, IBA treatment did not enhance rooting, and 88% rooting success can be achieved with untreated cuttings. Stem cuttings of american fly honeysuckle root at 49% (previously published). We also evaluated all three native shrubs grown in nursery trade #1 containers under shade levels of 0%, 40%, or 70%. American fly honeysuckle grown under 40% or 70% shade were larger, had a greener hue angle, and higher chlorophyll fluorescence (Fv/Fm) than plants grown in full sun. Throughout the study period, Fv/Fm values for full-sun american fly honeysuckle were 0.6 or below, indicating plants were stressed. Hobblebush in 40% and 70% shade were wider, had more leaves, and enhanced foliage color compared with full-sun plants. Hobblebush in 70% had the highest Fv/Fm values at 0.78 or higher across the study period. For sweetbells, plant width increased as shade level increased. Even though sweetbells in 70% shade were wider and larger, they lacked density and had a less appealing habit than 40% shade and full-sun plants. Of the three study species, sweetbells might be the easiest plant for growers to incorporate into production because it propagates readily from stem cuttings and can be grown in full sun to 40% shade. Hobblebush and american fly honeysuckle may present more challenges for growers because hobblebush requires considerable shade to grow and american fly honeysuckle is more difficult to propagate.

Evaluation of different doses of indole-3-butyric acid (IBA) on the rooting, survival and vegetative growth performance of hardwood cuttings of Flordaguard peach (Prunus persica L. Batch)

The present study was conducted on the evaluation of different doses of indole-3-butyric acid (IBA) on the rooting, survival and vegetative growth performance of hardwood cuttings of Flordaguard peach (Prunus persica L. Batch) during the years 2012-13 and 2013-14 at Punjab Agricultural University, Regional Research Station, Gurdaspur. The hardwood cuttings of 10 years old Flordaguard peach plant having 15-20cm in length and 0.8-1.2cm in diameter with 6-7 buds were prepared in the first fortnight of January .The basal portion of the cuttings was dipped in different doses of IBA viz. 1000ppm, 2000ppm, 3000ppm, 4000pppm, 5000ppm and control (without IBA treatment) for 1-2 minutes and planted in an open field conditions by following the recommended cultural practices for nursery raising. It was noticed that hardwood cuttings of Flordaguard peach treated with 3000ppm of IBA for 1- 2 minutes significantly took the minimum number of days to sprouting (7.05), rooting (6.0) with highest sprouting percentage (98.45%), survival percentage (90.55%), plant height(195.45cm), plant girth(10.50cm), number of branches(13.50) ,number of leaves (260.4), leaf length (19.55cm), leaf breadth (4.12cm), leaf weight (2.0gm), per-cent rooting (94.45%), number of roots (75.83), root length (38.0cm), root girth (0.98 cm) and root weight (13.50gm).Therefore, the application of 3000 ppm IBA was found to be best in terms of rooting, survival and vegeta-tive growth of hardwood cuttings of Flordaguard peach (Prunus persicaL. Batch). The beneficial effect of present work develop protocol which can be reliably used to develop the rootstock plant of Flordaguard which is resistant to nematodes through cutting which become ready for budding/grafting in the field in one year instead of two years as raised through seed

Differential responses to isoprenoid, N 6-substituted aromatic cytokinins and indole-3-butyric acid in direct plant regeneration of Eriocephalus africanus

Eriocephalus africanus is a medicinal and aromatic plant species that is part of South Africa’s remarkable diversity. As a result of illegal and over-harvesting, most plant communities have become unsustainable and as such, effective and efficient conservation strategies have to be implemented. In the present study, an isoprenoid cytokinin (CK): isopentenyladenine (iP) and four aromatic CKs namely benzyladenine (BA), meta-topolin (mT), meta-topolin riboside (mTR) and 6-(3-hydroxybenzylamino)-9-(tetrahydropyran-2-yl)purine (mTTHP) at 1, 5 or 10 µM were evaluated for in vitro plant regeneration in E. africanus. Different concentrations of indole-3-butyric acid (IBA) were also evaluated for shoot and root organogenesis. The highest number of shoots was produced by mT (1 and 5 µM) treatment, longest shoots were stimulated by iP (1 µM) and the highest fresh mass was obtained in BA (5 and 10 µM), mT (5 and 10 µM) and mTTHP (5 µM)-treated plants. During acclimatization, all the in vitro plants obtained from the lowest concentration of CKs survived and 1 µM iP regenerants recorded a 100% survival rate. For the rooting experiment, more vigorous adventitious roots were observed in the 1 µM IBA treatment. All IBA treatments had 100% survival rate after 6 weeks of acclimatization. Overall, the concentration and type of plant growth regulators had a remarkable influence on the growth and development of in vitro-derived E. africanus.

INFLUENCE OF INDOLE-3-BUTYRIC ACID (IBA) IN PLANT RENAISSANCE OF RAUVOLFIA SERPENTINA (L). BENTH. EX KURZ.

Rauvolfia serpentina (L). Benth. ex Kurz. (Apocynaceae) commonly known as Sarpagandha, is an important medicinal plant. It is rapidly disappearing and is now listed as an endangered species. The seeds are non-viable and regeneration with seeds also does not allow true-to-type multiplication. Therefore, the study influence of indole-3-butyric acid (IBA) in plant renaissance of Rauvolfia serpentina was undertaken to examined the role of (IBA) for their stimulatory effects on Rauvolfia serpentina. The germplasm was collected from different sites of Uttarakhand and Uttar Pradesh, Twenty cuttings were planted in four replications. Four IBA treatments viz. 4000 ppm, 5000 ppm, 6000 ppm and 7000 ppm and control were applied. Data on rooting and plant percent were recorded after twelve weeks of planting. In this study Rauvolfia serpentina, 7000 ppm IBA generally showed better rooting and plant percent than other IBA concentrations. Rooting percentage among all germplasm collections and all IBA concentrations, except control, ranged from 50.0 to 62.5 per cent while plant percent varied from 45.0 to 56.3 per cent. The performance of 4000 ppm was significantly lower than 7000 ppm. Thus, irrespective of source of germplasm, this species could be reliably propagated with 7000 ppm IBA.

Vegetative propagation of Tali (Palaquium polyanthum Engl.) for commercial harvest and landscape conservation

The experiment was conducted to find out suitable vegetative propagation techniques for Tali (Palaquium polyanthum Engl.), a native threatened tree species of Bangladesh. One year old stock plants growing in hedgerows were topped leaving 50–60cm stump above the ground. The effects of different concentrations of IBA (Indole-3 Butyric Acid) hormones on the rooting ability of Tali were investigated in a non-mist propagator. IBA application significantly enhanced the rooting percentage of the species. The species showed (67±4.04)% rooting response with 0.4% IBA treatment after 87 days. There were significant differences among IBA treatments and control at 95% significant level. Maximum number of roots (5±1) was found in 0.8% IBA treated cuttings while the highest root length (3.05±0.27)cm was observed in 1.2% IBA treated cuttings. However, the highest survival percentage (100%) was observed in 0.4% IBA treated cuttings. The results suggest that rooting of juvenile leafy stem cuttings with IBA application may be an effective mean of rooting and suitable vegetative propagation technique for the species.

Induction, Identification, and Characterization of Tetraploids in Japanese Privet (Ligustrum japonicum)

A number of privet species (Ligustrum spp.) that are important to the nursery and landscape industry have escaped cultivation and become invasive or weedy in the United States and other countries. Induced tetraploids in these species may produce new selections or cultivars with reduced or eliminated invasive potential. Applying drops of semisolid agar containing 0.1% to 0.3% colchicine and 0.2% dimethyl sulfoxide (DMSO) to newly emerged seedlings of japanese privet (Ligustrum japonicum Thunb.) resulted in 15.6% to 22.6% tetraploid induction. The nuclear DNA content of tetraploids was 5.31 pg/2C, 101.9% higher than that of diploids. Compared with diploid plants, tetraploids were more compact, with an average of 31.0% shorter plant height and 33.1% smaller canopy width. Tetraploids had 29.2% thicker internodes, and their leaves were 39.5% larger and 33.8% thicker, resulting in 42.1% to 24.1% greater fresh or dry leaf weights (per leaf) in tetraploids compared with diploids. Without indole-3-butyric acid (IBA) treatment, cuttings from tetraploids showed 28% lower rooting than diploids. IBA treatments improved the rooting of tetraploid cuttings, resulting in 65% rooting success. These results indicate that tetraploids can be readily induced in japanese privet and induced tetraploids show significant changes in plant growth and size, shoot growth, leaf morphology, and rooting of cuttings. The modified tetraploid induction method and the induced tetraploids are expected to be useful for producing new selections or cultivars with reduced invasive potential in japanese and other privets.

In vitro clonal propagation and evaluation of genetic fidelity using RAPD and ISSR marker in micropropagated plants of Cassia alata L.: a potential medicinal plant

Present study reports successful in vitro clonal propagation of a potential medicinal plant, Cassia alata using mature nodal explants. Murashige and Skoog (MS) medium supplemented with different concentrations (0.5, 2.5, 5.0, 7.5, 10.0 and 12.5 μM) of 6-benzyladenine (BA), kinetin and 2-isopentenyl adenine (2-iP) singly as well as in combination with different auxins, α-naphthalene acetic acid (NAA), Indole-3-butyric acid (IBA) or Indole-3-acetic acid (IAA) (0.1, 0.5 and 1.0 μM) were used. MS medium enriched with 7.5 μM BA and 0.5 μM NAA yielded the highest regeneration frequency (92 %) with maximum multiple shoots (12.3 ± 0.6) and shoot length (4.7 ± 0.1 cm) after 12 weeks of culture. Shoots were rooted best on full MS containing 0.5 μM IBA. Ex vitro rooting of in vitro derived microshoots was also achieved in 150 μM IBA treatment for 20 min followed by transfer to thermocol cups containing sterile Soilrite™. About 85 % plantlets survived acclimatization procedure to the field. The genetic fidelity of in vitro regenerated plants was analyzed using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers. Of the 20 RAPD primers, 18 primers produced clear, reproducible and scorable bands while out of 13 ISSR primers screened, only ten generated well-defined and scorable bands in all the tested plants. A total of 69 and 71 bands were scored with an average of 3.8 and 7.1 bands per primer for RAPD and ISSR primers respectively. All banding profiles from micropropagated plants were monomorphic and similar to of the mother plant, thus confirming the true-to-type nature of the in vitro-raised clones.

Auxin-mediated expression of a GH3 gene in relation to ontogenic state in Chestnut

The CsGH3 - 1 gene was isolated from chestnut microshoots. Expression analysis during induction of adventitious roots indicates an alteration in shoot auxin homeostasis during maturation that negatively affects adventitious rooting. A new auxin inducible gene isolated from chestnut microshoots was found to encode a protein belonging to group II of the Gretchen Hagen 3 (GH3) family. The gene was, therefore, named CsGH3-1. Predicted protein sequence analysis revealed the presence of conserved domains involved in the conjugation of amino acids to indole-3-acetic acid (IAA). Modelling of the protein and molecular docking of IAA, indole-3-butyric-acid (IBA), 1-naphthaleneacetic acid (NAA), and benzothiazole-2-oxyacetic acid (BTOA) into the active site of CsGH3-1 indicated a high and similar binding affinity for the four substrates. Expression analysis by qPCR indicated that CsGH3-1 is regulated by wounding, darkness, and auxin in chestnut microshoots, in an ontogenetic-dependent manner. Under IBA treatment, upregulation of CsGH3-1 was higher in mature than in juvenile shoots and was negatively correlated with the ability of microshoots to form roots. High levels of auxin-induced expression of CsGH3-1 were detected in mature shoots 24 h after the IBA treatment, whereas transcript levels decreased in rooting-competent shoots with cell-type-specific expression. CsGH3-1 transcripts were specifically localized in cells involved in the initiation of adventitious roots only in rooting-competent shoots at the time when cells switch their fate to root initial cells. Thus, these data show a correlation between the specific localization of transcripts and rooting competence, and they also suggest a role for CsGH3-1 in regulating auxin homeostasis during the onset of adventitious root formation.

Collection season and auxin treatment in the propagation by cuttings of mandarin hybrids

ABSTRACT Propagation by cuttings is an alternative for obtaining citrus rootstocks. The exogenous application of indolebutyric acid (IBA), cutting collection season and genotypes used may affect the rooting and vegetative growth of citrus rootstocks cuttings. Two experiments were conducted to study the influence of these factors. In the first one, semi-hardwood cuttings from the 'Sunki' mandarin hybrids H49 and H77 were collected in the fall and late spring of 2013 and treated with IBA (0 mg L-1, 1,500 mg L-1 and 3,000 mg L-1). For each collection season, a 2 x 3 (two genotypes x three IBA concentrations) factorial scheme was adopted, in a randomized blocks design. In the second experiment, the development of cuttings that rooted in the late spring was evaluated until grafting. In this case, a completely randomized experimental design was adopted, with the hybrids H49 and H77. The IBA treatments positively influenced rooting and number of roots only in the fall collection, peaking at 23.3 % of rooted cuttings. In the late spring collection, rooting was close to 100 %, with the IBA treatment being unnecessary. Around 50 % of cuttings from the 'Sunki' mandarin hybrids were ready for grafting at 14 months after cutting.

Cloning of Ceylon olive (Elaeocarpus serratus L.) using conventional methods

ABSTRACTCeylon olive (Elaeocarpus serratus L.; family Elaeocarpaceae) is an under-utilised edible fruit tree that is sparsely distributed in the southern peninsula of the Indian sub-continent. Fresh and ripened fruit are edible and are used to prepare value-added products such as squash, jams and pickles. Methods to produce clonal E. serratus plants using softwood cuttings, air-layers, and grafts were investigated. Softwood cuttings were collected during the wet summer season (June–August) and showed 96.7% rooting success following 2.5 mM indole-3-butyric acid (IBA) treatment for 3 h. Hardwood cuttings collected during the wet summer season and subjected to IBA treatment failed to root. The duration of the auxin treatment significantly influenced the rooting percentage of softwood cuttings. Seasonal variations in the rooting response of softwood cuttings was also noted. The wet summer (June–August) was the best season for rooting softwood cuttings. Air-layers of hardwood branches, prepared during the wet summer season by pre-treating with 7.5 mM IBA resulted in 87.1% rooting. The spliced grafting technique could be applied also to elite Ceylon olive clones, with 70% and 50% survival rates of softwood and hardwood grafts, respectively. Ceylon olive could therefore be cloned by adopting these methods. Propagation based on softwood cuttings would facilitate moderate-scale cloning of this valuable, elite germplasm.

Conversion of Indole-3-Butyric Acid to Indole-3-Acetic Acid in Shoot Tissue of Hazelnut (Corylus) and Elm (Ulmus)

Indole-3-butyric acid (IBA) is an endogenous compound that appears to regulate both lateral and adventitious root formation in many plant species and is also the auxin most available commercially for application to promote rooting. IBA is converted to indole-3-acetic acid (IAA) by β-oxidation in the peroxisomes. This process has been observed in a number of plant species and has been shown to be critical for normal root development in response to treatment with IBA. In this study, we investigated this process in hybrid hazelnut (Corylus americana × C. avellana), American elm (Ulmus americana), and Cathedral hybrid elm (U. pumila × U. davidiana var. japonica ‘Cathedral’), in which adventitious rooting is a major bottleneck for vegetative propagation, and the efficacy of IBA treatment is highly variable across different cultivars and at different collection times. Using differentially stable isotope-labeled IBA and IAA tracer and internal standard, respectively, and using gas chromatography coupled with selected reaction monitoring mass spectrometry, IBA-derived IAA was measured in shoot tissue treated with stable isotope-labeled IBA. In elm, higher levels of IBA-to-IAA conversion were generally observed in cultivars which formed adventitious roots most easily in softwood stem cutting trials. IBA-to-IAA conversion was observed in hazelnut genotypes with different rooting abilities and suggested a complex relationship exists between IBA conversion and root organogenesis. In both hazelnut and elm, endogenous free IAA levels were not significantly different across the genotypes examined. High rates of root formation is a key trait for establishment of large-scale production systems. Screening for optimal rates of IBA-to-IAA conversion may facilitate selection against genotypes which respond poorly to exogenous IBA and are thus difficult to propagate using hormone treatment.

Transcriptomic analysis reveals the gene expression profile that specifically responds to IBA during adventitious rooting in mung bean seedlings.

BackgroundAuxin plays a critical role in inducing adventitious rooting in many plants. Indole-3-butyric acid (IBA) is the most widely employed auxin for adventitious rooting. However, the molecular mechanisms by which auxin regulate the process of adventitious rooting are less well known.ResultsThe RNA-Seq data analysis indicated that IBA treatment greatly increased the amount of clean reads and the amount of expressed unigenes by 24.29 % and 27.42 % and by 4.3 % and 5.04 % at two time points, respectively, and significantly increased the numbers of unigenes numbered with RPKM = 10-100 and RPKM = 500-1000 by 13.04 % and 3.12 % and by 24.66 % and 108.2 % at two time points, respectively. Gene Ontology (GO) enrichment analysis indicated that the enrichment of down-regulated GOs was 2.87-fold higher than that of up-regulated GOs at stage 1, suggesting that IBA significantly down-regulated gene expression at 6 h. The GO functional category indicated that IBA significantly up- or down-regulated processes associated with auxin signaling, ribosome assembly and protein synthesis, photosynthesis, oxidoreductase activity and extracellular region, secondary cell wall biogenesis, and the cell wall during the development process. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment indicated that ribosome biogenesis, plant hormone signal transduction, pentose and glucuronate interconversions, photosynthesis, phenylpropanoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, ribosome, cutin, flavonoid biosynthesis, and phenylalanine metabolism were the pathways most highly regulated by IBA. A total of 6369 differentially expressed (2-fold change > 2) unigenes (DEGs) with 3693 (58 %) that were up-regulated and 2676 (42 %) down-regulated, 5433 unigenes with 2208 (40.6 %) that were up-regulated and 3225 (59.4 %) down-regulated, and 7664 unigenes with 3187 (41.6 %) that were up-regulated and 4477 (58.4 %) down-regulated were detected at stage 1, stage 2, and between stage 1 and stage 2, respectively, suggesting that IBA treatment increased the number of DEGs. A total of 143 DEGs specifically involved in plant hormone signaling and 345 transcription factor (TF) genes were also regulated by IBA. qRT-PCR validation of the 36 genes with known functions indicated a strong correlation with the RNA-Seq data.ConclusionsThe changes in GO functional categories, KEGG pathways, and global DEG profiling during adventitious rooting induced by IBA were analyzed. These results provide valuable information about the molecular traits of IBA regulation of adventitious rooting.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2372-4) contains supplementary material, which is available to authorized users.