Initiation Of Primordia Research Articles

Roles of Phytohormones and Their Signaling Pathways in Leaf Development and Stress Responses.

Phytohormones participate in various processes over the course of a plant's lifecycle. In addition to the five classical phytohormones (auxins, cytokinins, gibberellins, abscisic acid, and ethylene), phytohormones such as brassinosteroids, jasmonic acid, salicylic acid, strigolactones, and peptides also play important roles in plant growth and stress responses. Given the highly interconnected nature of phytohormones during plant development and stress responses, it is challenging to study the biological function of a single phytohormone in isolation. In the current Review, we describe the combined functions and signaling cascades (especially the shared points and pathways) of various phytohormones in leaf development, in particular, during leaf primordium initiation and the establishment of leaf polarity and leaf morphology as well as leaf development under various stress conditions. We propose a model incorporating the roles of multiple phytohormones in leaf development and stress responses to illustrate the underlying combinatorial signaling pathways. This model provides a reference for breeding stress-resistant crops.

A single-cell analysis of the Arabidopsis vegetative shoot apex.

The shoot apical meristem allows for reiterative formation of new aerial structures throughout the life cycle of a plant. We use single-cell RNA sequencing to define the cellular taxonomy of the Arabidopsis vegetative shoot apex at the transcriptome level. We find that the shoot apex is composed of highly heterogeneous cells, which can be partitioned into 7 broad populations with 23 transcriptionally distinct cell clusters. We delineate cell-cycle continuums and developmental trajectories of epidermal cells, vascular tissue, and leaf mesophyll cells and infer transcription factors and gene expression signatures associated with cell fate decisions. Integrative analysis of shoot and root apical cell populations further reveals common and distinct features of epidermal and vascular tissues. Our results, thus, offer a valuable resource for investigating the basic principles underlying cell division and differentiation in plants at single-cell resolution.

Development of improved strain in species of Pleurotus by gamma irradiation.

The oyster mushroom (Pleurotus spp.) is the second important edible mushroom in the world, with 19 per cent contribution to total mushroom production (Sharma et al., Mushroom Res 26(2):111-120, 2017). The cultivated mushrooms face the problems like loss of genetic diversity and strain degeneration (Wang et al., Curr Microbiol 65(4):424-431, 2012). Thus to enhance the productivity within short duration, three species of Pleurotus namely Pleurotus djamor, Pleurotus florida and Pleurotus ostreatus were gamma irradiated at 20 and 25Gy at 9.779kGy/h and performance of mutants followed by three generation of selection in paddy straw substrate were observed. Biological efficiency (BE) of P. djamor mutants irradiated at 20Gy was increased by 9.25 per cent. The number of days taken for primordial initiation was also reduced by 1 day compared to P. djamor. P. florida irradiated at 25Gy recorded increase in sporocarp size over P. florida. The biological efficiency of P. ostreatus irradiated at 25Gy was improved by 12.89 per cent and there was earliness in primordial initiation by 3 days compared to P. ostreatus. The polymorphism per cent was analysed by Random Amplified Polymorphic DNA (RAPD) and revealed that P. djamor, P. florida and P. ostreatus had 16.70%, 25% and 22% polymorphism with their respective improved strains.

Shoot Apical Meristem Growth in Saguaro (Carnegiea gigantea, Cactaceae) Is Episodic and Radially Asymmetrical Rather Than Uniform

Premise of research. As a shoot of Carnegiea gigantea (saguaro, columnar cactus) grows longer, its shoot apical meristem (SAM) occasionally adds new ribs, presumably because the SAM is increasing in size, giving it a larger basal circumference (the leaf primordium initiation zone). A new rib, which is a phyllotactic orthostichy, can be initiated when the SAM basal circumference has increased by the width of a leaf primordium. Rib initiation sites are markers that indicate when and where an SAM has enlarged. If SAMs grow uniformly, steadily, and symmetrically, the initiation sites of new ribs should occur at uniform intervals upward along the shoot and should also be symmetrical around the shoot’s circumference.Methodology. In the field, 18 mature plants were examined, and the height and circumferential position of the start point of every new rib were mapped.Pivotal results. Two to five new ribs would be initiated in rapid succession longitudinally, followed by a considerable period of shoot growth during which no new ribs would be initiated. Circumferentially, new ribs tended to be located laterally close to a previous new rib rather than being located symmetrically or randomly.Conclusions. SAMs of C. gigantea grow episodically and asymmetrically.

Effect of media concentration and growth hormones on shoot regeneration and in vitro rooting of sugarcane varieties (Saccharum spp. )

The protocol for plantlet induction and regeneration through in vitro culture was standardized for the sugarcane variety Co 06022 with Co 86032. Genotype specific media combinations for establishment and rooting efficiency was identified and standardized. Multiple shoot regeneration was observed at different frequencies, using different concentration and growth regulator combination. In vitro propagation of Saccharum offers opportunities for increasing plant material for cultivation. Apical meristems were cultured on modified MS medium containing different concentrations of auxins. In Co 06022, the most effective concentration was combination of ½ MS medium supplemented with IBA (2.0 mg/l) which induced an average of 3.00±0.14 number of shoots per microshoot with 10.77±0.42 cm shoot length. Among the auxins used, NAA showed better response than IBA for profuse rooting in Co 06022. The number of roots formed was maximum (14.80±0.09) in MS with NAA (2mg/l) which had taken 10 days for root initiation with the root length of 6.45±0.07 cm. However, in Co 86032, the best performance was observed on ½ MS medium supplemented with IBA (2.0 mg/l) with more number of shoots (2.00 ± 0.19) and average shoot length of 12.30± 0.44 cm. Best rooting was observed in ½ MS medium supplemented with NAA (2.0 mg/l) and maximum number of roots were 11.60±0.12 which has taken 8 days for initiation of root primordia with average root length of 1.16±0.12 cm. Thus, it can be deduced that this protocol can be used successfully for in vitro rooting and acclimatization of these genotypes.

The TARANI/ UBIQUITIN PROTEASE 14 protein is required for lateral root development in Arabidopsis

ABSTRACT In our article published in Plant Physiology, we had reported tarani (tni) mutant in Arabidopsis, in which poly-ubiquitin hydrolysis is adversely affected, shows pleiotropic phenotypic defects including fewer lateral roots due to the stabilization of several AUX/IAAs and reduced auxin response. TNI encodes UBIQUITIN-SPECIFIC PROTEASE14 that maintains normal auxin response through ubiquitin recycling. Fewer lateral roots observed in tni could be due to defects in their primordia initiation or subsequent elongation post-initiation. Here we have tested this by marking the lateral root primordia with pCycB1;1::CycB1;1(DB):GUS reporter and counting the number of lateral root at various stages development of as a marker of lateral root primordium. The results suggest that TNI/UBP14 is required for LRP development, and a reduction in TNI activity causes a delay in LRP initiation and consequently shorter lateral roots in the tni seedlings. ABBREVIATIONS: LRP, lateral root primordium; XPP, xylem pole pericycle; LRFC, lateral root founder cells

Asynchrony of ovule primordia initiation in Arabidopsis

ABSTRACTPlant ovule initiation determines the maximum of ovule number and has a great impact on the seed number per fruit. The detailed processes of ovule initiation have not been accurately described, although two connected processes, gynoecium and ovule development, have been investigated. Here, we report that ovules initiate asynchronously. The first group of ovule primordia grows out, the placenta elongates, the boundaries of existing ovules enlarge and a new group of primordia initiates from the boundaries. The expression pattern of different marker genes during ovule development illustrates that this asynchronicity continues throughout whole ovule development. PIN-FORMED1 polar distribution and auxin response maxima correlate with ovule primordia asynchronous initiation. We have established computational modeling to show how auxin dynamics influence ovule primordia initiation. Brassinosteroid signaling positively regulates ovule number by promoting placentae size and ovule primordia initiation through strengthening auxin response. Transcriptomic analysis demonstrates numerous known regulators of ovule development and hormone signaling, and many new genes are identified that are involved in ovule development. Taken together, our results illustrate that the ovule primordia initiate asynchronously and the hormone signals are involved in the asynchrony.

Ray flower initiation in the Helianthus radula inflorescence is influenced by a functional allele of the HrCYC2c gene.

The radiate pseudanthium, with actinomorphic disk flowers surrounded by showy marginal zygomorphic ray flowers, is the most common inflorescence in the Helianthus genus. In Helianthus radula, ray flower primordia are normally absent at the dorsal domain of the inner phyllaries (discoid heads) while the occurrence of radiate inflorescences is uncommon. In Helianthus spp., flower symmetry and inflorescence architecture are mainly controlled by CYCLOIDEA (CYC)-like genes but the putative role of these genes in the development of discoid inflorescences has not been investigate. Three CYC genes of H. radula with a role in ray flower identity (HrCYC2c, HrCYC2d, and HrCYC2e) were isolated. The phylogenetic analysis placed these genes within the CYC2 subclade. We identified two different alleles for the HrCYC2c gene. A mutant allele, designed HrCYC2c-m, shows a thymine to adenine transversion, which generates a TGA stop codon after a translation of 14 amino acids. We established homozygous dominant (HrCYC2c/HrCYC2c) and recessive (HrCYC2c-m/HrCYC2c-m) plants for this nonsense mutation. Inflorescences of both HrCYC2c/HrCYC2c and HrCYC2c/HrCYC2c-m plants initiated ray flowers, despite at low frequency. By contrast, plants homozygous for the mutant allele (HrCYC2c-m/HrCYC2c-m) failed at all to develop ray flowers. The results support, for the first time, a role of the HrCYC2c gene on the initiation of ray flower primordia. However, also in the two dominant phenotypes, discoid heads are the prevalent architecture suggesting that this gene is required but not sufficient to initiate ray flowers in pseudanthia. Other unknown major genes are most likely required in the shift from discoid to radiate inflorescence.

CLAVATA Signaling Ensures Reproductive Development in Plants across Thermal Environments

The ability to thrive in diverse environments requires that species maintain development and reproduction despite dynamic conditions. Many developmental processes are stabilized through robust signaling pathways that cooperatively ensure proper development.1 During reproduction, plants like Arabidopsis thaliana continuously generate flowers on growing indeterminate inflorescences.2 Flower primordia initiation and outgrowth depends on the hormone auxin and is robust across diverse environments.3-6 Here, we show that reproductive development under different thermal conditions requires the integration of multiple pathways regulating auxin-dependent flower production. In colder/ambient temperatures, the receptor complex CLAVATA2/CORYNE (CLV2/CRN) is necessary for continuous flower outgrowth during inflorescence development. CLV2/CRN signaling is independent of CLAVATA1 (CLV1)-related receptor signaling but involves the CLAVATA3 INSENSITIVE RECEPTOR KINASE (CIK) family co-receptors, with higher order cik mutant combinations phenocopying clv2/crn flower outgrowth defects. Developing crn inflorescences display reduced auxin signaling, and restoration of auxin biosynthesis is sufficient to restore flower outgrowth in colder and ambient temperatures. In contrast, at higher temperatures, both clv2/crn signaling and heat-induced auxin biosynthesis via YUCCA family genes are synergistically required to maintain flower development. Our work reveals a novel mechanism integrating peptide hormone and auxin signaling in the regulation of flower development across diverse thermal environments.

Early Low-Fluence Red Light or Darkness Modulates the Shoot Regeneration Capacity of Excised Arabidopsis Roots.

In plants, light is an important environmental signal that induces meristem development and interacts with endogenous signals, including hormones. We found that treatment with 24 h of low-fluence red light (24 h R) or 24 h of darkness (24 h D) following root excision greatly increased the frequency of shoot generation, while continuous low-fluence red light in callus and shoot induction stages blocked the explants’ ability to generate shoots. Shoot generation ability was closely associated with WUS expression and distribution pattern. 1-N-naphthylphtalamic acid (NPA) disrupted the dynamic distribution of the WUS signal induced by early 24 h R treatment, and NPA plus 24 R treatment increased the average shoot number compared with early 24 h R alone. Transcriptome analysis revealed that differentially expressed genes involved in meristem development and hormone signal pathways were significantly enriched during 24 R or 24 D induced shoot regeneration, where early 24 h R or 24 h D treatment upregulated expression of WOX5, LBD16, LBD18 and PLT3 to promote callus initiation and formation of root primordia, and also activated WUS, STM, CUC1 and CUC2 expression, leading to initiation of the shoot apical meristem (SAM). This finding demonstrates that early exposure of explants to transient low-fluence red light or darkness modulates the expression of marker genes related with callus development and shoot regeneration, and dynamic distribution of WUS, leading to an increased ability to generate shoots.

Dynamic cytokinin signaling and function of auxin in cytokinin responsive domains during rice crown root development

We reveal the onset and dynamic tissue-specific cytokinin signaling domains and functional importance of auxin in the auxin-cytokinin interaction domains in shaping root architecture in the economically important rice plant. Plant hormones such as auxin and cytokinin are central regulators of root organogenesis. Typical in the grass species, the root system in rice is primarily composed of post-embryonic adventitious/crown roots (ARs/CRs). Antagonistic auxin-cytokinin activities mutually balance each other to ensure proper root development. Cytokinin has been shown to inhibit crown root initiation in rice; albeit, the responsive domains remain elusive during the initiation and outgrowth of crown root primordia (CRP). Here, we show the cytokinin response domains during various stages of CRP development. RNA-RNA in situ hybridization and protein immunohistochemistry studies of the reporter gene expressed under the cytokinin responsive synthetic promoter revealed detailed spatio-temporal cytokinin signaling domains in the developing CRP. Furthermore, rice lines genetically depleted for endogenous auxin in the cytokinin responsive domains provided insight into the functional importance of auxin signaling during crown root development. Thus, our study demonstrates the onset and dynamic tissue-specific cytokinin response and functional significance of auxin-cytokinin interaction during root architecture formation in rice, a model grass species.

Effects of composition, age and sterilization techniques of mother culture on the growth and yield of Volvariella volvacea (Bull.) Singer

The research work was carried out to investigate the efficacy of different mother culture media viz., rice straw (T-1), rice straw and rice bran (T-2), rice husk (T-3), rice grain (T-4), maize grain (T-5), and rice straw and wheat bran (T-6) and the impact of age of mother culture and substrate sterilization techniques viz., sun dried for 8 hrs covering with transparent polythene (A-1), black polythene (A-2), blue polythene (A-3) sheet, autoclave for two hrs at 121°C (A-4), and hot water for one hr (A-5) for the commercial cultivation of Volvariella volvacea (Bull.) Singer. The maximum mycelium run rate and minimum days required for completing the mother culture were recorded in T-4. The lowest days required for primordial initiation (DRFPI) was 6 in T-1 and T-2, whereas highest DRFPI was recorded in T-3. The maximum (13.33) days required for first harvest (DRFFH) and lowest (109) number of effective fruiting bodies (NEFB) were recorded in T-3. The minimum (10.67 days) DRFFH was found in T-2 and maximum (239.30) NEFB was recorded in T-1. The lowest length and diameter (LFB and DFB) were recorded in T-5 (3.03 cm) and T-1 (1.66 cm), while highest LFB and DFB were observed in T-3 (3.20 and 2.39 cm). Maximum biological yield and efficiency were observed in rice straw and wheat bran materials. The highest NEFB, DFB, biological yield and efficiency were recorded in 30 days old of mother culture. The results revealed that combined rice straw and wheat bran were the excellent mother culture medium and 30 days old was the best age for the commercial production of paddy straw mushroom. Considering the experimental results on the sterilization techniques it may be suggested that hot water sterilization of rice straw substrate was the best sterilization technique for the commercial production and yield improvement of V. volvacea.

MERISTEM ACTIVITYLESS (MAL) is involved in root development through maintenance of meristem size in rice.

Rice MERISTEM ACTIVITYLESS (MAL), a RING-H2 finger domain (RFD)-containing gene, regulates meristem cell viability after the initiation of root primordia mediated by cytokinin signaling. Genes in the RING-H2 finger domain (RFD) family play various roles during plant development and in biotic/abiotic stress responses. Rice gene MERISTEM ACTIVITYLESS (MAL), being contained in the RING-H2 finger domain (RFD), is characterized by a transmembrane domain at the N-terminal and a C3H2C3 zinc finger domain at the C-terminal. To elucidate the physiological and molecular functions of MAL, we generated MAL knockdown transgenic plants by RNA interference. MAL RNA-interfered (MRi) transgenic plants exhibited a phenotype with shorter crown root length and lower crown root number, accompanied by a lower cell division rate. The low division rate was observed in the root meristem exactly where MAL was expressed. Furthermore, transcriptome data revealed that cell wall macromolecule metabolism-related genes and redox-related genes were enriched in MAL RNAi lines. Most of these differentially expressed genes (DEGs) were induced by exogenous cytokinin. Hence, we conclude that MAL, as a novel regulatory factor, plays a major role in maintaining cell viability in the meristem after the initiation of root primordial formation, mediated by cytokinin signaling and reactive oxygen species (ROS).

Factors involved in the success of Castanea henryi stem cuttings in different cutting mediums and cutting selection periods

Chinquapin (Castanea henryi) is a dual-purpose tree species in China valued for as a source of timber and starch. We investigated the effect of four cutting mediums (pure vermiculite; peat:river sand at 3:1 v/v; peat:krasnozem at 1:1 v/v; and pure krasnozem) and three stem cutting periods (March, May, and July) on rooting performance of C. henryi cuttings. Different cutting periods and cutting mediums greatly influenced the rooting rate of C. henryi, ranging from 3.35 to 77.31%. Principal component analysis indicated that the best combination of cutting period and cutting medium was semi-hardwood cuttings (May cuttings) + krasnozem. Histological evidence indicated that adventitious root initials were present by week 5–6, and that the site of root primordia initiation was observed in the vascular cambium. Stem anatomical structures observed at different periods indicated that a xylem/radius ratio of 29.90–37.42% and a fractured phloem fiber ring are indicative of rooting success. The relational model between rooting index and medium properties indicated that nutrient content and porosity significantly influenced callus production. However, pH strongly affected C. henryi root formation, with the Pearson correlation coefficients for May and July cuttings of − 0.856 and − 0.947, respectively. Our protocol is helpful to achieve mass clone propagation of improved C. henryi genotypes, thus overcoming a common hurdle in chinquapin breeding programs.

Optimization of Culture Conditions for Mycelial Growth and Basidiocarp Production of Cyclocybe cylindracea (Maire)

Agrocybe cylindracea is an exotic and unknown species of mushroom among Filipinos. In our intention to develop production technology for this mushroom, the influences of culture media, pH and physical factors such as aeration, illumination and temperature for optimum mycelial growth and fruiting body production were investigated in the present work. Among media evaluated, potato sucrose gulaman, rice bran decoction gulaman and malt extract agar recorded the highest mycelial growth rate (9.00 mm/day), shortest incubation period (10.00 days) with very thick mycelial density. Potato sucrose gulaman (most common culture medium) at pH 6 incubated in either sealed or unsealed, lighted or dark, and in room temperature (28-33°C) or air-conditioned temperature (23-25 ºC) registered the highest mean mycelial growth rate. Corn grit was the best grain spawning material. The substrate formulation of 7:3 rice straw- sawdust ratio recorded the shortest incubation period and primordial initiation, and the highest total yield of 106.94 g. Therefore, A. cylindracea is an addition to the list of exotic edible mushrooms with great potential for cultivation in the Philippines.

Floret development and spike fertility in wheat: Differences between cultivars of contrasting yield potential and their sensitivity to photoperiod and soil N

Abstract In a previous paper (Field Crops Res. 203, 114–127), we showed that the difference in yield potential between a contemporary and a traditional cultivar was due to differences in fruiting efficiency, likely derived from differences in spike fertility (fertile florets per spike) while having similar spike dry weights at anthesis. In this study, we determined the mechanistic bases of these genotypic differences in spike fertility analysing the initiation of all floret primordia per spike (up to 8), the maximum number of florets initiated per spikelet, and the associated floret developmental rates and their fate to become fertile florets under contrasting photoperiod (natural vs extended) and nitrogen availability (50 or 200 kg N ha−1) during the stem elongation phase. Under potential growing conditions (natural photoperiod, high nitrogen availability), the contemporary cultivar owed its higher spike fertility to the improved rate of floret development, which mainly determined an improved level of floret primordia survival to produce fertile florets. The sensitivity of the floret developmental patterns to faster development due to exposure to an extended photoperiod and, to a larger extent, a reduction in N availability was similar for both cultivars, providing a basis for the consistent differences in spike fertility across a range of environments. The response again determined a main effect through increasing floret mortality reducing therefore the level of fertile florets per spikelet in these conditions.

Genome-Wide Association Analysis Identifies Candidate Genes Regulating Seed Number Per Silique in Arabidopsis thaliana.

Seed weight and number ultimately determine seed yield. Arabidopsis seed number comprised of silique number and seed number per silique (SNS). Comparing seed development and weight, determinants of seed number remain largely uncharacterized. In this study, taking advantage of 107 available Arabidopsis accessions, genome-wide association analysis (GWAS) was employed to identify the candidate genes regulating SNS. GWAS-based genotype and phenotype association analysis identified 38 most significant SNPs marker sites that were mapped to specific chromosomal positions and allowed us to screen for dozens of candidate genes. One of them (PIN3) was selected for functional validation based on gene expression analysis. It is a positive regulator of Arabidopsis SNS. Although silique length of PIN3 loss of function mutant was not significantly changed, its SNS and seed density (SD) were significantly reduced as compared with the wild type. Notably, PIN3 overexpression lines driven by a placenta-specific promoter STK exhibited significantly shorter siliques, slightly reduced SNS, but significant increased SD compared with wild type, suggesting that PIN3 positively regulates SD through inducing ovule primordia initiation regardless of the placenta size. Ovule initiation determines the maximal possibility of SNS, and new genes and mechanism regulating SNS through modulating ovule initiation is worth further investigated.

Prediction of phenological stages of six maize (Zea mays L.) hybrids based on required growing degree days

An experiment was under taken at the Agricultural College farm, Bapatla during two consecutive years of rabi 2016-17 and 2017-18. The experiment was laid out in randomized block design with six treatments in four replications. Maize hybrids 900M Gold, DKC 9142, DKC 9120, DKC 9081, DKC 9042 and Pinnacle showed significant differences in plant height, stem girth, number of leaves and initiation of reproductive organs. All maize hybrids grew to its maximum height in 77 to 84 calendar days after sowing with a thermal requirement of 1131 to 1221 °cd. Maize hybrids attained maximum stem girth (2.63 to 2.84) in 70 calendar days with thermal requirement of 1033 0Cd. Significantly higher stem girth was found in pinnacle and DKC 9142 followed by 900M Gold and DKC 9120 in both the seasons of crop growth. The maximum number of leaves was attained at 70 DAS with cumulative heat units of about 1028 0Cd. During rabi 2016 to 17, DKC 9142 took less number of days (28.50) for tassel primordial initiation followed by pinnacle (29.0), DKC 9042 (29.25) and DKC 9120 (29.50) and 900MGold took more (30.00) followed by DKC 9081(29.75). During rabi 2017 to 18, it was less in DKC 9142 (28.38) followed by DKC 9042 (29.00) and more in 900M Gold (29.38), Pinnacle (29.38) and DKC 9081 (29.25). During tassel primordial initiation, the heat units accumulated was 467.0 0Cd for DKC 9081 and 900M Gold during rabi 2016 to 17, while in rabi 2017 to 18 it was 488.7 °Cd for DKC 9042, 503.3 0Cd for pinnacle and 900M Gold, 503.8 0Cd for DKC 9120 and 517.6 °Cd for DKC 9081.

Transcriptomic profiling and discovery of key genes involved in adventitious root formation from green cuttings of highbush blueberry (Vaccinium corymbosum L.)

BackgroundPropagation of cuttings is frequently used in various plant species, including blueberry, which shows special root characteristics that may hinder adventitious root (AR) formation. AR formation is influenced by various factors, and auxin is considered to play a central role; however, little is known of the related regulatory mechanisms. In this study, a comparative transcriptome analysis of green cuttings treated with or without indole-butyric acid (IBA) was performed via RNA_seq to identify candidate genes associated with IBA-induced AR formation.ResultsRooting phenotypes, especially the rooting rate, were significantly promoted by exogenous auxin in the IBA application. Blueberry AR formation was an auxin-induced process, during which adventitious root primordium initiation (rpi) began at 14 days after cutting (DAC), root primordium (rp) was developed at 21 DAC, mature AR was observed at 28 DAC and finally outgrowth from the stem occurred at 35 DAC. Higher IAA levels and lower ABA and zeatin contents might facilitate AR formation and development. A time series transcriptome analysis identified 14,970 differentially expressed genes (DEGs) during AR formation, of which there were 7467 upregulated and 7503 downregulated genes. Of these, approximately 35 candidate DEGs involved in the auxin-induced pathway and AR formation were further identified, including 10 auxin respective genes (ARFs and SAURs), 13 transcription factors (LOB domain-containing protein (LBDs)), 6 auxin transporters (AUX22, LAX3/5 and PIN-like 6 (PIL6s)) and 6 rooting-associated genes (root meristem growth factor 9 (RGF9), lateral root primordium 1 (LRP1s), and dormancy-associated protein homologue 3 (DRMH3)). All these identified DEGs were highly upregulated in certain stages during AR formation, indicating their potential roles in blueberry AR formation.ConclusionsThe transcriptome profiling results indicated candidate genes or major regulatory factors that influence adventitious root formation in blueberry and provided a comprehensive understanding of the rooting mechanism underlying the auxin-induced AR formation from blueberry green cuttings.

Development of improved strain in Pleurotus spp. by gamma irradiation

The oyster mushroom ( Pleurotus spp.) is the second important edible mushroom in the world, with 19 per cent contribution to total mushroom production (Sharma et al., 2017). The cultivated mushrooms face the problems like loss of genetic diversity and strain degeneration (Wang et al ., 2012). Thus to enhance the productivity and other quality traits, three species of Pleurotus viz., Pleurotus djamor , Pleurotus florida and Pleurotus ostreatus were gamma irradiated at 20 and 25 Gy at 9.779 kGy h -1 . Biological efficiency (BE) of P. djamor was increased by 9.25 per cent when the mycelia were irradiated at 20 Gy. The number of days taken for primordial initiation was also reduced by one day compared to P. djamor . Though P. florida irradiated at 25 Gy recorded increase in sporocarp size, there was no significant difference in the BE over P. florida . The BE of P. ostreatus irradiated at 25 Gy was improved by 12.89 per cent and there was earliness in primordial initiation by three days compared to P. ostreatus . The polymorphism per cent was analysed by Random Amplified Polymorphic DNA (RAPD) and revealed that P. djamor , P. florida and P. ostreatus had 16.70%, 25% and 22% polymorphism with their respective improved strains.