Presence Of Growth Regulators Research Articles

Comprehensive Phytohormone Profiling of Kohlrabi during In Vitro Growth and Regeneration: The Interplay with Cytokinin and Sucrose

The establishment of an efficient protocol for in vitro growth and regeneration of kohlrabi (Brassica oleracea var. gongylodes) allowed us to closely examine the phytohormone profiles of kohlrabi seedlings at four growth stages (T1–T4), additionally including the effects of cytokinins (CKs)—trans-zeatin (transZ) and thidiazuron (TDZ)—and high sucrose concentrations (6% and 9%). Resulting phytohormone profiles showed complex time-course patterns. At the T2 stage of control kohlrabi plantlets (with two emerged true leaves), levels of endogenous CK free bases and gibberellin GA20 increased, while increases in jasmonic acid (JA), JA-isoleucine (JA-Ile), indole-3-acetic acid (IAA) and indole-3-acetamide (IAM) peaked later, at T3. At the same time, the content of most of the analyzed IAA metabolites decreased. Supplementing growth media with CK induced de novo formation of shoots, while both CK and sucrose treatments caused important changes in most of the phytohormone groups at each developmental stage, compared to control. Principal component analysis (PCA) showed that sucrose treatment, especially at 9%, had a stronger effect on the content of endogenous hormones than CK treatments. Correlation analysis showed that the dynamic balance between the levels of certain bioactive phytohormone forms and some of their metabolites could be lost or reversed at particular growth stages and under certain CK or sucrose treatments, with correlation values changing between strongly positive and strongly negative. Our results indicate that the kohlrabi phytohormonome is a highly dynamic system that changes greatly along the developmental time scale and also during de novo shoot formation, depending on exogenous factors such as the presence of growth regulators and different sucrose concentrations in the growth media, and that it interacts intensively with these factors to facilitate certain responses.

Impact of cultural conditions on germination of olive (Olea europaea L.) somatic embryos and plantlets development from the Algerian cultivar Chemlal

The in vitro propagation techniques are currently a commercial alternative for the production of plants with good quality in several plant species, including the olive tree (Olea europaea L.). Somatic embryogenesis is the process practically used for the application of several biotechnological tools of improvement and in vitro plant regeneration via the germination of somatic embryos. Our work aims to evaluate the effect of the chemical and hormonal composition of the culture medium on the germination of olive somatic embryos (cv. Chemlal) as well as the micropropagation of the obtained plantlets before their acclimatization to natural conditions. The results indicated that the production of olive plants by somatic embryogenesis depends strongly on the genotype of the somatic embryos (cell line) and more on the culture conditions, particularly the presence of growth regulators. Indeed, a solid OM medium supplemented with hormones (BA and IBA) permitted an advanced root emergence and germination allowing the production of well-developed plants with several leaves. In addition, an OM medium supplemented with Zeatin and IBA allowed better reactivity of micro-cuttings producing well-developed shoots with several emitted roots which facilitates their further acclimatization to natural conditions.

Effects of different hormonal treatments on growth parameters and secondary metabolite production in organ culture of Hyssopus officinalis L.

Hyssopus officinalis L. is a medicinal plant containing valuable phytochemicals and is used extensively in the pharmaceutical industry. As this plant naturally contains low levels of these metabolites, plant cell and tissue culture technologies are used to produce them in large volumes. The present study aimed first to evaluate the effects of different types of cytokinins, including benzyl adenine (BA), kinetin (KIN), and thidiazuron (TDZ), at 1 ppm concentration in the culture medium on growth parameters and production of secondary metabolites and photosynthetic pigments in organ culture of H. officinalis; in the second step, the study investigated the effect of different concentrations (0, 0.2, 1, 1.5, and 2 ppm) of the most effective type of cytokinin. The results showed that TDZ was the optimal type of growth regulator compared to BA and KIN as it showed a positive influence on the studied traits; furthermore, its highest concentration of 2 ppm in culture medium was determined to be the best one that enabled the highest production of secondary metabolites and photosynthetic pigments. We conclude that the presence of growth regulators can strongly influence the growth and development of plants in tissue culture conditions.

English

Dendrobium primulinum Lindl. (D. Primulinum L.) is one of the important epiphytic orchid species for horticultural and commercial use. It is listed as a rare and critically endangered species of orchid. The present study is intended to conserve the orchid species through the micropropagation technique. The in vitro seed germination and seedling growth was carried out by taking a mature pod of D. Primulinum L. in Murashige and Skoog (MS) media, and the MS media supplemented with a varied concentration (0.5, 1.0, 1.5 and 2 mg/L) of 6-benzylaminopurine (BAP), and a fixed concentration (0.5 mg/L) of α-naphthalene acetic acid (NAA). Sequential phases of seed germination, protocorm formation, and seedling development in the presence of growth regulators were determined in the study. The significance of hormonal effects was determined by using One-Way Analysis of Variance (ANOVA, p≤0.05). The seed germination started after two weeks of culture in the media supplemented with BAP. The maximum seedling growth was obtained in the media supplemented with 1.5 mg/L of BAP. Although the hormone-free basal medium revealed an ideal condition for seed germination and spherules formation, the presence of an appropriate concentration of growth regulators such as 0.5 mg/L NAA or a combined 0.5 mg/L BAP + 0.5 mg/L NAA expressed a synergistic effect to enhance the protocorm formation and seedling development. Key words: In vitro, Dendrobium primulinum, 6-benzylaminopurine (BAP), α-Naphthalene acetic acid (NAA).

IN VITRO MULTIPLICATION OF CASSAVA VARIETIES

The implantation of a model of sustainable development for agriculture can happen with the contribution of the mandiocultura. But for this, culture needs to be strengthened. In vitro propagation is an instrument for this purpose. Micropropagation can provide growers with large quantities of vigorous and healthy cassava seedlings in a short time. The objective of this study was to evaluate the in vitro establishment of four varieties of cassava cultivated in the municipality of Colorado do Oeste, State of Rondônia, popularly known as Arara, Caturra, Cacau Vermelha and Roxinha. For that, an experiment was carried out in the Laboratory of In Vitro Cultivation at the Pole of Technological Innovation of the University of Cruz Alta (UNICRUZ), with a completely randomized design in a 4 x 2 factorial scheme, with 6 replications. The treatments consisted of explants grown in Murashige and Skoog (MS) medium without the presence of growth regulator and MS medium supplemented with of 6-benzylaminopurine (BAP). The results indicate that the average contamination percentage of the explants was 47.19%, differing among the varieties. The best growth response in culture media, in the multiple comparison of means (Scott-Knott's test, 5%), was obtained with MS medium without BAP addition, with significant difference between varieties. Under the conditions of this experiment, it was evidenced that micropropagation is a viable tool for obtaining varieties of interest, with desired phytosanitary qualities, with varietal and large scale authenticity.

MICROPROPAGATION STUDIES AND ANTIOXIDANT ANALYSIS OF THE ENDANGERED PLANTS OF BULGARIAN YELLOW GENTIAN (Gentiana lutea L.)

In order to develop an efficient micropropagation system, it is essential to establish the appropriate concentration of growth regulators for seed germination, shoot formation and rooting. Nodal segments from in vitro obtained seedlings of Gentiana lutea L. were cultured in vitro in Murashige and Skoog’s medium supplemented with BAP, Thidiazuron and Zeatin (0.5, 1.0 and 2.0 mg L−1). A maximum number of shoots with the highest height was recorded at 2.0 mg L−1 BAP. For further optimization of the process, we used nutrient media containing BAP and Zeatin with a combination of low concentration of Indoleacetic acid. MS medium containing 2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA resulted in maximum numbers of shoots 94.3) with shoot height 2.5 cm. The multiple plants were successfully ex vitro acclimatized with 65% survival. The presence of growth regulators (2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA) in the nutrient media resulted in an effective antioxidant activity in G. Lutea determined by the low molecular antioxidant metabolites such as phenols and flavonoids and activities of antioxidant enzymes – catalase, ascorbate peroxidase, guaiacol peroxidase, and superoxide dismutase. The described protocol allows the establishment of numerous micropropaged plants of rare and endangered G. lutea.

Temporary Immersion Bioreactors: Establishment of Cassava

Cassava (Manihot esculenta Crantz-Euphorbiaceae) is one of the most important crops for world agriculture. It is the main source of many family’s calorie intake and contributes toward food security. Its cultivation is necessitated sterile vegetative propagules with essential physiological and genetic quality, which can be obtained by plant tissue culture techniques. However, the maintenance of in vitro propagation processes requires automation, making large-scale production feasible. This work aimed at developing protocols for the establishment of cassava cultivation in Temporary Immersion Bioreactors (TIBs). Two nutrient media (MS medium reduced to half-strength of the salt concentration and the same formulation plus 4,43µM of 6-Benzylaminopurine [BAP]) and different culture cycles were evaluated in Bioreactors (15 minutes of immersion and 4 hours of stationary phase [15M4H]; 15 minutes of immersion and 8 hours of stationary phase [15M8H]). The establishment of culture in bioreactors was promising. Based on our results, the use of MS medium without growth regulators was more effective for shoot formation; there were differences in the 15M4H cycle when growth regulators were used. However, the 15M8H cycle had better performance in both treatments: with or without growth regulators. The use of culture medium without BAP led to better rooting; calli formation increased when BAP was used. The present research investigation indicated the use of MS medium reduced to half- strength the salt concentration without the presence of growth regulator and the use of the culture cycle constituted by 15 minutes immersion and 8-hour intervals in stationary phase was effective for Cassava cultivation in TIBs.

Effect of Icariin on Engineered 3D-Printed Porous Scaffolds for Cartilage Repair.

In recent times, cartilage defects have been the most common athletic injuries, often leading to dreadful consequences such as osteoarthritis, pain, joint deformities, and other symptoms. It is also evident that damage to articular cartilage is often difficult to recover or self-heal because of poor vascular, nervous, and lymphatic supplies. Moreover, cartilage cells have poor regeneration ability and high maturity. Inspired by these facts and the rapid advances in the field of tissue engineering (TE), we fabricated highly porous three-dimensional (3D) scaffold architectures based on cell-responsive polymeric inks, i.e., sodium alginate and gelatin (SA-Gel, 1:3 ratio), by a novel 3D printing method. Moreover, the effect of various processing parameters was systematically investigated. The printed scaffolds of polymer composites gels with excellent transparency, moderate viscosity, and excellent fluid properties showed good surface morphology, better thermal stability and swelling effect, and unique interconnected porous architectures at the optimized operating parameters. In vitro cell proliferation experiments of these cytocompatible scaffolds showed the excellent adhesion rate and growth behavior of chondrocytes. In addition, the porous architectures facilitated the efficient distribution of cells with only a few remaining on the surface, which was confirmed by confocal laser scanning microscopic (CLSM) observations. Icariin (ICA) addition at a concentration of 10 μg/mL further significantly enhanced the proliferation of chondrocytes. We envision that these cell-responsive polymeric inks in the presence of growth regulators like ICA may have potential in engineering complex tissue constructs toward diverse applications in TE.

Induction of in vitro androgenesis in anther and isolated microspore culture of different spelt wheat (Triticum spelta L.) genotypes

This is the first report on isolated microspore culture—derived spelt wheat. The efficiency of anther- and isolated microspore was compared using four genotypes (‘Franckenkorn’, ‘GK Feher’, ‘Mv Martongold’, ‘Oberkulmer Rotkorn’). In anther culture, genotype dependency was observed, and cold pre-treatment enhanced the efficiency of the method. In isolated microspore culture, the ovary co-culture supported the development of embryo-like structures. The presence of growth regulators (0.5 mg/l 2,4-D and 0.5 mg/l kinetin) were not essential for the induction of androgenesis, but these increased the production of embryo-like structures, green and albino plantlets. The low plant regeneration rate and high number of albinos hinder the practical application of isolated microspore culture while anther culture was efficient for in vitro green plantlets production in spelt wheat. The mean of green plantlets production was 41.45/100 anthers (from 20.93 to 83.07 depending on genotype). The phenomenon of albinism was mitigated in anther culture (3.48 albinos/100 anthers). Altogether, 1720 anther culture—derived green plantlets were produced from the four genotypes.

Graft compatibility-incompatibility in fruit crops: Mechanism and determination techniques

Commercial fruit trees are usually formed by the combination of a rootstock and a scion to broaden the adaptability of scion cultivars to soil and climatic conditions, facilitate agricultural management, and/or increase productivity. In general, closely related cultivars and species tend to be compatible, but taxonomically distant plants often manifest incompatibility. The physiological, metabolic and molecular mechanisms that cause incompatibility remain unclear and several hypotheses have been proposed to explain it, mostly based on herbaceous species. We sum up different reasons that may have an influence on graft success: inherent system of cellular incompatibility, formation of plasmodesmata, vascular tissue connections, and the presence of growth regulators and peroxidases. Understanding the spatial organization of the graft interface is important to the evaluation of new rootstock genotypes and to the development of new grafting technologies. An early and accurate prediction of graft incompatibility has great importance because incompatible combinations could be avoided while compatible ones could be selected. The complexity of incompatibility and the mechanism behind the reactions have been investigated in several ways. More research is needed to fully understand the mechanism of graft incompatibility, particularly in woody plants. This knowledge is essential to develop molecular markers useful in rootstock breeding programmes.

Plantlets from encapsulated shoot buds of Catalpa ovata G. Don

Shoot buds isolated from in vitro shoot cultures of <em>Catalpa ovata</em> G. Don were encapsulated using 3% sodium alginate with sucrose (3%) and 50 mM calcium chloride. The morphogenic response of encapsulated buds was affected by such factors, like composition of the media and the presence of growth regulators. The highest frequency of plantlet germination from encapsulated buds (70% within 4 weeks) was obtained on Woody Plant medium (WP) (Lloyd and McCown 1980) containing indole-3-butyric acid (IBA) (1 mg/l). The process was substantially inhibited by cold-storage (4<sup>o</sup>C) of encapsulated buds. In this case, the frequency response ranged from 3% to 22% dependent on storage period (28 or 42 days) and the presence of the paraffin coat covering the alginate capsules. The plantlets developed from both unstored and stored encapsulated buds of <em>C. ovata</em> were transplanted to soil and grew in pots to phenotypically normal plants.

Extract on germination and growth of influence of Allium sativum Solanum melongena L. seeds in vitro

The study was Conducted for stimulation of seeds germination of eggplant (Solanum melongena L.) and measure vegetative growth in vitro under the influence of garlic (Allium sativum) alcoholic extract and the plant growth regulators, 0.5 mg/L Naphthalene acetic (NAA) and 1.0 mg/L Benzyl adenine (BA) and the MS and B5 media. The results showed that the presence of garlic plant extract in the media have a positive effect on the germination of seeds of eggplant, which gave the highest germination 10 seed in concentration 4 mg/L in the all of MS media and B5 media full force without growth regulators, but the presence of growth regulators with the extract gave the same result under study containing extract contained (0,2)mg/L. For the length of branches showed extract 4mg/L significant effect for of the rest of the transaction experience, which gave the highest along the branches in the MS media full force and MS half strength macro and micro elements, (7.66,7.60)cm, respectively, followed by concentration of extract 2mg /L in media used in the experiment and without growth regulators.

Production of podophyllotoxin from roots and plantlets of Hyptis suaveolens cultivated in vitro.

Background:Hyptis suaveolens was an important source of food and medicines in pre-hispanic Mιxico and is actually used popularly to treat respiratory and skin diseases, fever, pain, and cramps, between other ailments. In 2008 the presence of podophyllotoxin (PTOX) was reported in this plant.Objective:To establish in vitro cultures of H. suaveolens able to produce PTOX.Materials and Methods:Explants of H. suaveolens were cultivated in Murashige and Skoog (MS) medium supplemented with different concentrations of the phytohormones 6-benzylaminopurine (6-BAP), 2,4-dichlorophenoxyacetic acid (2,4-D), 1-naphthaleneacetic acid (NAA) and kinetin (Kin), in order to induce the production of podophyllotoxin. Root cultures without hormones were also established and the quantification of PTOX was performed by HPLC analysis.Results:The presence of growth regulators during in vitro cultivation of H. suaveolens, provoked morphological variations in explants, and induced the accumulation of different levels of PTOX. Roots grown without phytohormones accumulated PTOX at 0.013% dry weight (DW), while in three of the callus cultures cell lines growing together with roots, PTOX accumulated at concentrations of 0.003, 0.005 and 0.006% DW when NAA was combined with either Kin or BAP. In wild plant material PTOX was present in trace amounts in the aerial parts, while in the roots it was found at 0.005% DW.Conclusion:This study demonstrated that although it is possible to obtain PTOX in a variety of in vitro cultures of H. suaveolens, in vitro roots grown without the addition of growth regulators were better producers of PTOX.

In vitro seed germination and seedling propagation in Campanula spp

The present research investigated in vitro seed germination and seedling multiplication methods to preserve and introduce new naturalized valuable Campanula species to the floriculture markets. Populations of Campanula barbata L., Campanula latifolia L., Campanula rapunculoides L., Campanula spicata L., and Campanula trachelium L. from various sites in northern Italy were considered in this study. Seeds were sown on half-strength Murashige and Skoog (MS) basal medium with 1-naphthaleneacetic acid (NAA), 6-benzyladenine (BAP) and kinetin, added or withheld, after which final germination percentage (FGP), mean germination time and time of 50% germination (T 50) indices were measured. C. rapunculoides showed the highest FGP after 2 weeks in both the presence (53%) and absence (56%) of plant growth regulators. Among the other species, no statistical differences were detected in the presence of growth regulators, except for C. barbata, in which FGP was nearly 0%. In the absence of phytohormones, seed germination in C. spicata was statistically higher (34%), compared to C. barbata (0%), and both C. latifolia and C. trachelium (about 19%). After 4 months, the seedlings were transferred to full-strength MS basal medium with or without NAA and BAP. In all Campanula species tested, the best shoot-forming and rooting response was observed on substrates that contained plant growth regulators.

Indicadores de estresse salino em abacaxizeiro cultivado na ausência e presença de fitorreguladores

O objetivo do presente estudo foi avaliar o efeito de diferentes concentrações de NaCl nas fases de multiplicação e enraizamento in vitro do abacaxizeiro cultivar MD Gold. Brotos de abacaxizeiro foram inoculados em meio MS, na ausência e presença dos fitorreguladores ácido naftalenoacético (ANA) e 6-benzilaminopurina (BAP) e também de diferentes concentrações de NaCl (Controle - 0; 50; 100 e 150 mM). Mensalmente, os brotos foram subcultivados e foram analisados altura média, número de folhas vivas e mortas, taxas de brotação e enraizamento. Durante a multiplicação e na ausência de ANA e BAP, o NaCl provocou significativa redução no crescimento e desenvolvimento de brotos de abacaxizeiro, expresso pela altura e pelo número de folhas, nas doses mais elevadas, contrariamente, na presença dos fitorreguladores. Durante os 60 dias iniciais, ocorreu aumento na produção de folhas. Contudo, aos 90 dias, observou-se decréscimo na média de folhas vivas nos brotos tratados com sal. O cultivo in vitro de abacaxizeiro em presença de sal é mais eficiente na presença de ANA e BAP, garantindo a manutenção do crescimento, aumentando o número de folhas, produzindo novas gemas e acelerando o processo de enraizamento.

Micropropagation of Alibertia edulis Rich

The aim of this work was to develop a micropropagation protocol for Alibertia edulis, a medicinal Brazilian Cerrado plant. A. edulis seeds were sterilized and germinated in water-agar. Fifteen millimeter long explants from the seedlings cultivated for 50 days were used for the multiplication in three consecutive subcultures. The cytokinin benzyladenine (BA) alone or combined with indole-3-butyric acid (IBA) was added to ¼ MS medium. The treatments containing combinations of the BA + IBA induced more shoot proliferation than the BA alone, with the optimum concentration of 0.5 mg.L-1 for both growth regulators. A. edulis shoots elongated easily and the presence of growth regulators did have a positive effect on the shoot elongation. Consecutive subcultures also had a positive effect on both sprouting and shoot elongation. Activated charcoal was essential for rooting, and all rooted plants were able to acclimatize.

The use of in vitro culture to improve the propagation of Rhododendron ponticum subsp. baeticum (Boiss. & Reuter)

AbstractRhododendron ponticum subsp. baeticum is endemic in the southern region of the Iberian Peninsula. The relict populations of this species are vulnerable, due mainly to difficult conditions for the establishment of seedlings, resulting in a virtual lack of sexual recruitment. In order to preserve the surviving populations, in vitro culture methods have been applied for both the sexual and the agamic propagation of the species. The in vitro germination of seeds was high when conducted with Anderson’s medium without plant growth regulators. The self-rooted seedlings obtained were easily transplanted to outside conditions. The presence of growth regulators in the medium interfered with the development of the seedlings, causing heavy callus formation. The in vitro growth of explants took place readily in Anderson’s medium plus 0.072 mg L−1 of BA and 0.036 mg L−1 of NAA although the explants did not form roots. Rooting was achieved by the basal dipping of the explants in hydroalcoholic solutions of 500 mg L−1 IAA during the outside transplanting process. Therefore, the combination of in vitro grown explants together with ex vitro rooting, results in a good method for the agamic propagation of Rhododendron ponticum subsp. baeticum.

Somatic embryo, adventitious root and shoot regeneration in in vitro grown quince leaves as influenced by treatments of different length with growth regulators

The purpose of this work was to acquire more information on the capacity of in vitro grown quince ( Cydonia oblonga Mill.) leaves to simultaneously regenerate somatic embryos, adventitious roots and shoots, and to evaluate the variations induced on regeneration response by treatments of different length with growth regulators. After 2 days of liquid treatment with 2,4-dichlorophenoxyacetic acid, the leaves were cultured for 0, 3, 6, 9, 12, 15, 18 and 21 days on gelled growth medium containing the basal components of Murashige and Skoog and kinetin (Kin) 4.5 μM + naphthaleneacetic acid (NAA) 0.5 μM. At the end of each treatment period, the leaves were cultured on a transfer medium in the absence or in the presence of a growth regulator combination represented by N 6-benzylaminopurine (BA) 2.66 μM + gibberellic acid 0.58 μM + indole-3-butyric acid 0.3 μM. The culture period for all the treatments was fixed to 52 days. Simultaneous regeneration response of somatic embryos, adventitious roots and shoots differed according to the length of the kinetin + naphthaleneacetic acid treatment and to the absence or the presence of growth regulators in the transfer medium. In the absence of growth regulators, only somatic embryos and roots were regenerated; the number of somatic embryos increased from the 0 day to the 6–9th day of treatment with kinetin + naphthaleneacetic acid, while root regeneration showed the opposite trend. After the 9th day, the production of somatic embryos decreased up to the 15th day and then stabilized, while roots showed only very small reduction up to the end of the experiment. In the presence of growth regulators in the transfer medium, adventitious shoots were regenerated together with somatic embryos and roots. The highest number of shoots was observed when the leaves were directly transferred from 2,4-dichlorophenoxyacetic acid treatments to growth regulator medium. Increasing the length of kinetin + naphthaleneacetic acid treatment, shoot regeneration decreased and by the 12th day no more shoots were produced. Somatic embryo regeneration peaked on the 6th day of culture with kinetin + naphthaleneacetic acid and showed the same trend as in the absence of growth regulators in the transfer medium, while root formation tended to increase with prolonging the kinetin + naphthaleneacetic acid treatment.

Long-term effects of growth regulators on growth and turnover of symplastic and apoplastic sugars in the suspension subculture of kidney bean

Suspension cells of kidney bean were grown for 42 d in MS medium supplemented with growth regulators (2.0 mgL-1 2,4-D and 0.5 mgL-1 kinetin) or without At the stationary growth phase (42 d), the sugars were fractionated into the symplastic (ethanol and starch) and apoplastic [low-molecular pectin (lm-pectin), high-molecular pectin (hm-pectin), hemicellulose, and cellulose] sugars. The neutral sugars (NS) of hm-pectin and hemicellulose fractions were analyzed by GLC. The growth of the suspension cells in the liquid MS media, in terms of settled cell volume (SCV), remained similar, to the end of the experiment, irrespective of the presence or absence of growth regulators, indicating the nonnecessity of the exogenous growth regulators for the subculture. Total sugar (TS) of the ethanol fraction and NS of the Im-pectin of the suspension cells grown in the medium with growth regulators were higher than in the medium without growth regulators. However, starch content in the starch fraction and uronic acid (UA) content of the Im-pectin fraction did not exhibit any differences. From these results, it was suggested that the growth regulators modulated the structure of the cell wall polysaccharide. Analysis of the NS composition of the hm-pectin fractions revealed that the Rha, Arb, and Gal contents in the presence of growth regulators were higher than in the absence, while the Xyl, Man, and Glc contents in the presence of growth regulators were higher than in the absence, indicating the turnovers of rhamnogalacturonan and/or arabinogalactan. On the other hand, analysis of NS composition of hemicellulose fractions revealed that the Ara and Glc contents in the presence of growth regulators was higher than in the absence, whereas Xyl and Glc contents were nearly consistent, indicating the turnovers of arabinaogalactan I or II. The cellulose contents remained similar, irrespective of the presence (19.1%) or absence (18.7%) of growth regulators.

In vitro biocontrol activity of Trichoderma harzianum on Alternaria alternata in the presence of growth regulators

The in vitro biocontrol ability of Trichoderma harzianum on the phytopathogen Alternaria alternata improved in the presence of the growth regulators gibberellic acid (GA 3 ), or indolacetic acid (IAA) or benzylaminopurine (BAP) or foliar nutrient at concentrations similar or higher than those used at the field level. These plant hormones decreased the secretion of endopolygalacturonase (endo-PG) of A. alternata by approximately 20%, did not modify endochitinase (endo-CH) secretion of T. harzianum and did not alter germination of conidia or mycelia growth of any of these fungi. The presence of T. harzianum decreased endo-PGase secretion of A. alternata by about 50%. This inhibitory effect was independent of the presence of growth regulators. The level of secreted endo-PG of T. harzianum was not modified by the presence of A. alternata , but the presence of this phytopathogen in cultures of T. harzianum , increased both the growth of the biocontroller and its secretion of endo-CH.