Crown Buds Research Articles

Impact of Infection Timing and Autumnal Fungicide Applications on Perennation of Pseudoperonospora humuli and Severity of Hop Downy Mildew.

Pseudoperonospora humuli, causal agent of hop downy mildew, is known to survive winter as systemic mycelium in the crown and developing buds of hop (Humulus lupulus). Field studies were conducted over three growing seasons to quantify the association of infection timing to overwintering of P. humuli and development of downy mildew. Cohorts of potted plants were inoculated sequentially from early summer to autumn, overwintered, and then evaluated for symptoms of systemic downy mildew in emerging shoots. Shoots with systemic P. humuli developed after inoculation at any time in the previous year, with the most severe disease typically resulting from inoculation in August. Independent of the timing of inoculation, diseased shoots emerged coincident with the emergence of healthy shoots, beginning as early as late February and continuing through late May to early June. Surface crown buds on inoculated plants exhibited internal necrosis associated with P. humuli at rates ranging from 0.3 to 1.2%, whereas P. humuli was detected by PCR on 7.8 to 17.0% of asymptomatic buds depending on the timing of inoculation and year. Four experiments were conducted to quantify the impact of foliar fungicides applied in autumn on downy mildew the following spring. There was a small reduction of disease in only one study. Together, these studies indicate that infection by P. humuli that leads to overwintering can occur over a broad period of time, but delaying infection until autumn tends to reduce disease levels in the following year. However, in established plantings, postharvest application of foliar fungicides appeared to have little impact on severity of downy mildew in the ensuring year.

Alfalfa MsATG13 Confers Cold Stress Tolerance to Plants by Promoting Autophagy.

Autophagy is a conserved cellular process that functions in the maintenance of physiological and metabolic balance. It has previously been demonstrated to improve plant tolerance to abiotic stress. Numerous autophagy-related genes (ATGs) that regulate abiotic stress have been identified, but there have been few functional studies showing how ATGs confer cold stress tolerance. The cold transcriptome data of the crown buds that experienced overwintering of the alfalfa (Medicago sativa L.) showed that MsATG13 is upregulated in response to cold stress. In the present study, we found that MsATG13 transgenic tobacco enhanced cold tolerance compared to wild-type (WT) plants. Transmission electron microscopy demonstrated that transgenic tobacco overexpressing MsATG13 formed more autophagosomes than WT plants in response to cold stress conditions. The transgenic tobacco increased autophagy levels due to upregulation of other ATGs that were necessary for autophagosome production under cold stress conditions. MsATG13 transgenic tobacco also increased the proline contents and antioxidant enzyme activities, enhancing the antioxidant defense capabilities under cold stress conditions. Furthermore, MsATG13 overexpression decreased levels of superoxide anion radicals and hydrogen peroxide under cold stress conditions. These findings demonstrate the role of MsATG13 in enhancing plant cold tolerance through modulation of autophagy and antioxidant levels.

Morphogenetic variations of Pinus sylvestris L. seedlings depending on altitude

Scotch pine is a primary species that spreads from sea level to very high altitudes in Turkey and has a very wide distribution area in the world. For this reason, it is important to investigate the variations of the species depending on the altitude. The research aims to determine the morphogenetic variations of the seedling characters in populations representing the vertical distribution area of Scotch pine and to reveal the within and among population variations in the vertical distribution areas. In the study, seedlings (three, four and five-year-old) grown from the seeds collected from five populations in the altitudinal zones up to 2,250 m from sea level in the natural distribution area of Scotch pine in Trabzon region were used. The seedling’s height, root collar diameter, the number of side branches and crown buds and sturdiness quotient were determined. As a result of the study, it was determined that there were statistically significant differences (p

Establecimiento in vitro de Fragariax ananassa var. Aroma a partir de yemas de corona

The objective of the research was to determine a protocol for disinfection and in vitro establishment of explants from strawberry crown buds Fragaria x ananassa Var. Aroma, from the Minor Town Center Mallampampa, Huancabamba and the La Florida sector, Chontabamba district, Oxapampa, Pasco, Peru, through a randomized complete block design. Three disinfection methods were used T1 (adapted from Coba, 2009), T2 (adapted from Sánchez-Cuevas and Salaverría, 2004)and T3 (adapted from Mamani, 2005) and in the establishment were the treatments, t1 (MS+ BAP 0.5 mg l -1+ NAA 0.5 mg l-1), t2 (MS+BAP 0.5 mg l-1+ NAA 0.3 mg l-1+ GA3 0.2 mg l-1), t3 (MS+BAP 0.5 mg l-1+ IAA 0.6 mg l-1), t4 (MS+BAP 0.5 mg l-1+ IAA 0.5 mg l-1+ GA3 0.3 mg l-1) and t5 (MS without regulators). At 36 days after inoculation (dai),the best disinfection treatment was T3, because it presented less contamination by bacteria and less phenolization and without significant differences in fungi and explant survival. The best establishment medium was t3, for present a lower degree of phenolization, greater survival, sprouting and number of shoots and leaves.

Occurrence of Crown Bud and Growth of Cut Flower by Cutting Period and Short-day Treatment Time in Standard Cut Chrysanthemum ‘Baekma’

Occurrence of Crown Bud and Growth of Cut Flower by Cutting Period and Short-day Treatment Time in Standard Cut Chrysanthemum ‘Baekma’

PENGARUH PEMBERIAN PUPUK KOTORAN KAMBING DAN ATONIK TERHADAP PERTUMBUHAN SETEK DAUN MAHKOTA NENAS (Ananas comusus L. Merr) KUALU PADA MEDIA GAMBUT

The Kualu pineapple propagation technique uses crown bud cuttings which is made as a pineapple plant propagation material for peat media that is added with goat manure and several concentrations of Atonic. The aim is to obtain an effective source of cutting material for the procurement of Kualu pineapple seedlings cultivated on peat soil. This research used a Completely Randomized Design (CRD) factorial with two factors. First factor was the dose of goat manure at levels 0, 10, 20, and 30 g/polybag dan second factor was various atonic concentrations at levels 0, 2, 4, and 6 ml/L. The data were statistically analyzed and further tested for honest real difference (BNJ) at the 5% level. The results obtained from the interaction of the two treatment factors were significantly different to the time of shoot emergence and the percentage of shoot life. There was no significant difference in seedling height and number of leaves, as well as the main effect of each treatment. Crown shoot cuttings planted on peat media added 20 g/polybag of goat manure and 4ml/l Atonic obtained a better source of cutting material to be used as a source of seeds than others. The success of obtaining seeds from crown leaf cuttings sources through this research has answered that crown leaf cuttings have potential and great opportunity to be developed.

Comparative transcriptome analysis of a fan-shaped inflorescence in pineapple using RNA-seq

Pineapple plant usually has a capitulum. However, a fan-shaped inflorescence was exceptionally evolved in pineapple, having multiple crown buds. In order to reveal the molecular mechanisms of the formation of the fan-shaped inflorescence, fruit traits and the transcriptional differences between the fan-shaped inflorescence and the wild-shaped inflorescence pineapples were analyzed in three tissues, i.e., the flower stem apex, the base of the inflorescence, and the inflorescence axis. The weight (i.e., individual yield) of fan-shaped fruit is 4.5 times that of wild-shaped fruit；and non-significant difference in soluble solids, soluble sugar, titratable acid, and Vitamin C was found. Between the fan-shaped inflorescence and wild-shaped inflorescence, a total of 5370 differentially expressed genes were identified across the three tissues. Of these genes, there were 489 overlapping differentially expressed genes in all three tissue comparisons. Between the two pineapples, functional analysis indicated that 444 transcription factors and 206 inflorescence development-related genes were differentially expressed in at least one tissue comparison, while 45 transcription factors and 21 inflorescence development-related genes were overlapped across three tissues. Among the 489 overlapping differentially expressed genes in the three tissue comparisons, excluding the inflorescence development-related genes and transcription factors, 80 of them revealed a higher percentage of involvement in the biological processes relating to response to auxin, and reproductive processes. RNA-seq value and real-time quantitative PCR analysis exhibited the similar gene expression patterns in the three tissues. Our result provided novel cues for understanding the molecular mechanisms of the formation of the fan-shaped inflorescence in pineapple, making a valuable resource for the study of plant breeding and the speciation of pineapple.

Application of Cytokinin and Mycorrhiza to Increase Production and Quality of Pineapple Seedlings from Crown Leaf Bud Cuttings

The pineapple vegetative propagation method using crown leaf bud cuttings has potential to produce seedlings of greater uniformity and in larger quantities than other methods. This study, aimed to explore the potential eff ects of concentration and frequency of Benzylaminopurine (BAP) application for increasing the production and quality of pineapple seedlings from crown leaf bud cutting propagation. The experiment used a randomized complete block design (RCBD) with two factors. The fi rst factor was the concentration of BAP (0, 200, 400, 600, 800 ppm) and the second factor was the frequency of BAP application (1, 2, 3 times). Furthermore, this study investigated the eff ects of applying mycorrhizae to accelerate seedling growth and improve seedling quality during production from crown leaf bud cutting propagation. The experiment used a RCBD with one factor (dose of mycorrhiza: 0, 50, 100, 150, 200 spores). The results indicated that the eff ects of concentration and frequency of BAP application and their interaction increased seed production as determined by sprout cuttings at 5 weeks after planting by applying 600 ppm 2 times. Generally, with increasing concentration and frequency of BAP application, leaf chlorophyll content was reduced. However, the application mycorrhiza positively infl uenced the production of seedlings from pineapple crown bud cuttings and improved seedling quality as measured by root dry weight, chlorophyll content, root infection, and phosphatase enzyme activity.

Concentration and Timing of Exogenous Foliar Spray of Benzyladenine and Ethephon Influence Crown Bud Formation in Three Hosta Taxa

Concentration and Timing of Exogenous Foliar Spray of Benzyladenine and Ethephon Influence Crown Bud Formation in Three Hosta Taxa

Germplasm diversification – a kiwi perspective on tools and strategies

The international ornamentals industry is benefiting from perennial plants developed in New Zealand (NZ) such as begonia Bonfire™, limonium Sinzii™, and the gentian Showtime™ series. The 'Bonfire' series of begonia, with its distinctively new flower shape, was released in the year 2000. While flower and foliage colour were important; architectural form, vigour and floral productivity were key selection criteria. Understanding the underlying physiology of plant architecture (physiologically informed breeding) was key in the introduction of subsequent new cultivars to the series. These screening criteria allowed us to evaluate annually ten times more begonia seedlings per season. Planting of limonium Sinzii continues to expand exponentially: in 2018/19 plantings almost doubled compared with those of the previous year. The limonium Sinzii range resulted from successful hybridisation between Limonium sinuatum and L. perezii. Embryo culture, chromosome doubling, and backcrossing were some of the in vitro and in vivo tools and strategies applied to achieve the current range. The sterile gentian 'Little Pinkie' was another plant developed using wide crosses and embryo rescue. As with other gentians in the Showtime series, a physiologically informed breeding strategy was used. In the case of 'Little Pinkie', an understanding of how crown buds arise was used to generate at least double the number of shoots on propagules. This has underpinned the success of this crop for us, and our industry partners. The preceding examples illustrate how, for each crop species, our breeding programmes have diversified germplasm, through exploiting a diverse skill base within the team. Our conclusion is that our most successful examples of breeding programmes have been those in which plant breeders, plant physiologists, in vitro specialists, horticulturalists, and marketers are all actively engaged.

Can Nicosulfuron plus Metsulfuron Effectively Control or Suppress King Ranch Bluestem?

Core Ideas Nicosulfuron plus metsulfuron combinations failed to effectively control KR bluestem even when used in consecutive years. Lack of control in permanent plots was due to the high populations and also the crown bud bank, which were not entirely killed by herbicide treatments. Glyphosate provided effective control at the end of each growing season and provided 55 to 60% control the following spring. The use of herbicides alone is probably not an effective method for control or suppression for KR bluestem. Research was conducted in south-central Texas to evaluate nicosulfuron plus metsulfuron combinations or glyphosate for King Ranch (KR) bluestem (Bothriochloa ischemum var. Songarica) control. In one study, at one location, where KR bluestem was interspersed in a Tifton 85 bermudagrass [Cynodon dactylon (L.) Pers. × C. nlemfuënsis Vanderyst] pasture, control up to 9 weeks after an early fall application was 98% for nicosulfuron plus metsulfuron combinations and 99% for glyphosate. At another location, with a solid stand of KR bluestem, control was 60% or less for nicosulfuron plus metsulfuron combinations. When evaluated the following spring, control at either location was no better than 25% for nicosulfuron plus metsulfuron combinations and 60% for glyphosate. In another 2-year study with permanent plots having a solid stand of KR bluestem, control was ineffective for nicosulfuron plus metsulfuron combinations applied in either late spring, mid-summer, or early fall. When evaluated in mid- to late December, the best control was provided with sequential applications, either in late spring plus mid-summer or mid-summer plus early fall while in another year, the mid-summer plus early fall sequential applications were best. However, none of these sequential applications had greater than 45% control. Applying nicosulfuron plus metsulfuron combinations reduced KR bluestem herbage yields up to 10% as compared with the untreated check.

Plantlets Regeneration from Crown Bud Slicing of Pineapple (Ananas comosus)

Pineapple propagation by lateral shoots, suckers or crowns is often confronted with limited number of regenerated seedlings and high diversity in flowering and fruit formation. In order to solve this problem, this study offer an alternative method by using tissue culture techniques. This study aimed to determine the effect of growth regulators on plantlet regeneration from bud slicing of pineapple cv. Tangkit. Four levels of 2.4-D (0.0, 0.001, 0.01 and 0.1 ppm) in combination with BA (0.0, 0.1, 1.0 and 10.0 ppm) were tested on solid MS medium. Cultures were incubated in total darkness for a week followed by transfer to 16-hour photoperiod. Results showed that explants treated with 2,4-D and/or BA succeeded in regenerating adventitious shoots. Average leaf number did not differ significantly among treatments (P = 0.60). Highest leaf number (2.99 ± 0.23) was obtained on medium with 0.01 ppm 2,4-D without BA, followed by 0.1 ppm 2,4-D without BA (2.85 ± 0.33). Meanwhile, roots were only formed on medium with 0.1 ppm 2.4-D without BA (4.2 ± 0.37 per shoot). Thus, complete plantlets were regenerated only on medium supplemented with 0.1 ppm 2,4-D without BA. The growth of plantlets was relatively uniform, and plantlet acclimatization succeeded 100% on Jiffy pots. The finding of optimum concentration of 2.4-D and BA in this study is important to develop standard protocol for in vitro propagation of pineapple cv. Tangkit. Thus, the benefit of producing seeds in large quantities and relatively uniform in growth is made possible through tissue culture technique.

Evaluation of the micropropagation potential of curauá pineapple hybrids for fiber production

ABSTRACT Plant fiber is a renewable and biodegradable material that can be used effectively to reinforce various composites. Pineapple hybrids selected for their fiber quality are in the phase of agronomic validation in Brazil by the Embrapa Cassava and Fruits research unit. The selection of a hybrid for large-scale fiber production depends on obtaining a large number of seedlings. This study evaluated the morphogenetic response and propagation potential of eight hybrids of Ananas comosus var. erectifolius, for the purpose of producing high-quality seedlings on a large scale. Stem and crown buds were reduced and placed in MS nutritive medium supplemented with BAP at 0.5 mg L-1, NAA at 0.01 mg L-1 and Phytagel® at 2.5 g L-1. After 45 days, the number of oxidized, contaminated and surviving buds was determined. Swollen buds and plantlets were transferred to a multiplication medium containing MS sucrose, salts and vitamins. The propagation potential was evaluated based on the geometric growth rate among sub-cultures. The FIB-NEG hybrid presented the best results for the establishment phase (40.28%). The best propagative potential was obtained from crown buds with the highest values for FIB-EST (3.93), FIB-MIN (3.91) and FIB-BOY (3.91) hybrids.

Risk Factors for Bud Perennation of Podosphaera macularis on Hop.

The hop powdery mildew fungus Podosphaera macularis persists from season to season in the Pacific Northwestern United States through infection of crown buds because only one of the mating types needed to produce the ascigerous stage is presently found in this region. Bud infection and successful overwintering of the fungus leads to the emergence of heavily infected shoots in early spring (termed flag shoots). Historical data of flag shoot occurrence and incidence in Oregon and Washington State during 2000 to 2017 were analyzed to identify their association with the incidence of powdery mildew, growers' use of fungicides, autumn and winter temperature, and other production factors. During this period, flag shoots were found on 0.05% of plants evaluated in Oregon and 0.57% in Washington. In Oregon, the incidence of powdery mildew on leaves was most severe and the number of fungicide applications made by growers greatest in yards where flag shoots were found in spring. Similarly, the incidence of plants with powdery mildew in Washington was significantly associated with the number of flag shoots present in early spring, although the number of fungicide applications made was independent of flag shoot occurrence. The occurrence of flag shoots was associated with prior occurrence of flag shoots in a yard, the incidence of foliar powdery mildew in the previous year, grower pruning method, and, in Washington, winter temperature. A census of hop yards in the eastern extent of the Oregon production region during 2014 to 2017 found flag shoots in 27 of 489 yards evaluated. In yards without flag shoots, 338 yards (73.2%) were chemically pruning or not pruned, whereas the remaining 124 (26.8%) were mechanically pruned. Of the 27 yards with flag shoots, 22 were either chemically pruned or not pruned and 4 were mechanically pruned in mid-April, well after the initial emergence of flag shoots. The prevalence of yards with flag shoots also was related to thoroughness of pruning in spring (8.1% of yards with incomplete pruning versus 1.9% of yards with thorough pruning). A Bayesian logistic regression model was fit to the data from the intensively assessed yards in Oregon, with binary risk factors for occurrence of a flag shoot in the previous year, occurrence of foliar mildew in the previous year, and thoroughness of pruning in spring. The model indicated that the median and 95% highest posterior density interval of the probability of flag shoot occurrence was 0.0008 (0.0000 to 0.0053) when a yard had no risk factors but risk increased to 0.0065 (0.0000 to 0.0283) to 0.43 (0.175 to 0.709) when one to all three of the risk factors were present. The entirety of this research indicates that P. macularis appears to persist in a subset of chronically affected hop yards, particularly yards where spring pruning is conducted poorly. Targeted management of the disease in a subset of fields most at risk for producing flag shoots could potentially influence powdery mildew development regionwide.

Optimization of Soluble Dietary Fiber Extraction Process from the Crown Bud of Pineapple by Using Response Surface

Optimization of Soluble Dietary Fiber Extraction Process from the Crown Bud of Pineapple by Using Response Surface

Susceptibility of Hop Crown Buds to Powdery Mildew and its Relation to Perennation of Podosphaera macularis.

In the Pacific Northwestern United States, the hop powdery mildew fungus, Podosphaera macularis, survives overwintering periods in association with living host tissue because the ascigerious stage of the pathogen is not known to occur in this region. Field experiments were conducted over a 5-year period to describe the overwintering process associated with crown bud infection and persistence of P. macularis. Surface crown buds increased in abundance and size beginning in early July and continuing until mid-September. Buds of varying sizes remained susceptible to powdery mildew until late September to early October in each of 3 years of experiments, with susceptibility decreasing substantially thereafter. Potted plants were inoculated sequentially during early summer to autumn, then evaluated in the following year for development of shoots colonized by the powdery mildew fungus (termed flag shoots) due to bud perennation. Emergence of flag shoots was asynchronous and associated with shoot emergence and elongation. Flag shoots emerged over a protracted period from late February to early June, year dependent. In all 4 years of experiments, some infected buds broke and produced flag shoots after chemical desiccation of shoots in spring, a common horticultural practice in hop production conducted to set training timing and eliminate initial inoculum. Flag shoots were most numerous when plants were inoculated with P. macularis in early summer and, consequently, when powdery mildew was present throughout the entire period of crown bud development. The number of flag shoots produced was reduced from 6.8- to 46.6-fold when comparing the latest versus earliest inoculation dates. However, all inoculation timings yielded flag shoots at some level, suggesting that bud infection that occurs over an extended period of time in the previous season may allow the fungus to perennate. In studies in two commercial hop yards in Washington State, fungicide applications made after harvest reduced the level of powdery mildew on leaves in the current year but did not significantly reduce flag shoots in the following year. Given that bud infection occurred over a 10-week period, flag shoots developed even when plants were exposed to inoculum in October and some flag shoots survived chemical pruning practices, management efforts seem best directed to both preventative measures to reduce the likelihood of bud infection and remedial practices to physically eliminate infected crown buds in the ensuing year.

Foliar Glyphosate Treatment Alters Transcript and Hormone Profiles in Crown Buds of Leafy Spurge and Induces Dwarfed and Bushy Phenotypes throughout its Perennial Lifecycle.

Leafy spurge ( L.) is an invasive weed of North America and its perennial nature attributed to underground adventitious buds (UABs) that undergo seasonal cycles of para-, endo-, and ecodormancy. Recommended rates of glyphosate (∼1 kg ha) destroy aboveground shoots but plants still regenerate vegetatively; therefore, it is considered glyphosate-tolerant. However, foliar application of glyphosate at higher rates (2.2-6.7 kg ha) causes sublethal effects that induce UABs to produce stunted, bushy phenotypes. We investigated the effects of glyphosate treatment (±2.24 kg ha) on vegetative growth, phytohormone, and transcript profiles in UABs under controlled environments during one simulated seasonal cycle. Because shoots derived from UABs of foliar glyphosate-treated plants produced stunted, bushy phenotypes, we could not directly determine if these UABs transitioned through seasonally induced endo- and ecodormancy. However, transcript abundance for leafy spurge dormancy marker genes and principal component analyses suggested that UABs of foliar glyphosate-treated plants transitioned through endo- and ecodormancy. Glyphosate treatment increased shikimate abundance in UABs 7 d after treatment; however, the abundance of shikimate gradually decreased as UABs transitioned through endo- and ecodormancy. The dissipation of shikimate over time suggests that glyphosate's target site was no longer affected, but these changes did not reverse the altered phenotypes observed from UABs of foliar glyphosate-treated leafy spurge. Transcript profiles further indicated that foliar glyphosate treatment significantly affected phytohormone biosynthesis and signaling, particularly auxin transport; gibberellic acid, abscisic acid and jasmonic acid biosynthesis; ethylene responses; and detoxification and cell cycle processes in UABs. These results correlated well with the available phytohormone profiles and altered phenotypes.

Comparison of phytohormone levels and transcript profiles during seasonal dormancy transitions in underground adventitious buds of leafy spurge.

Leafy spurge (Euphorbia esula L.) is an herbaceous perennial weed that maintains its perennial growth habit through generation of underground adventitious buds (UABs) on the crown and lateral roots. These UABs undergo seasonal phases of dormancy under natural conditions, namely para-, endo-, and ecodormancy in summer, fall, and winter, respectively. These dormancy phases can also be induced in growth chambers by manipulating photoperiod and temperature. In this study, UABs induced into the three phases of dormancy under controlled conditions were used to compare changes in phytohormone and transcriptome profiles. Results indicated that relatively high levels of ABA, the ABA metabolite PA, and IAA were found in paradormant buds. When UABs transitioned from para- to endodormancy, ABA and PA levels decreased, whereas IAA levels were maintained. Additionally, transcript profiles associated with regulation of soluble sugars and ethylene activities were also increased during para- to endodormancy transition, which may play some role in maintaining endodormancy status. When crown buds transitioned from endo- to ecodormancy, the ABA metabolites PA and DPA decreased significantly along with the down-regulation of ABA biosynthesis genes, ABA2 and NCED3. IAA levels were also significantly lower in ecodormant buds than that of endodormant buds. We hypothesize that extended cold treatment may trigger physiological stress in endodormant buds, and that these stress-associated signals induced the endo- to ecodormancy transition and growth competence. The up-regulation of NAD/NADH phosphorylation and dephosphorylation pathway, and MAF3-like and GRFs genes, may be considered as markers of growth competency.

Occurrence and Characterization of a 16SrII‐D Subgroup Phytoplasma Associated with Parsley Witches’ Broom Disease in Iran

AbstractDuring 2010–2013 surveys for the presence of phytoplasma diseases in Yazd province (Iran), a parsley witches’ broom (PrWB) disease was observed. Characteristic symptoms were excessive development of short spindly shoots from crown buds, little leaf, yellowing, witches’ broom, stunting, flower virescence and phyllody. The disease causative agent was dodder transmitted from symptomatic parsley to periwinkle and from periwinkle to periwinkle by grafting inducing phytoplasma‐type symptoms. Expected length DNA fragments of nearly 1800 and 1250 bp were, respectively, amplified from naturally infected parsley and experimentally inoculated periwinkle plants in direct polymerase chain reaction (PCR) using phytoplasma primer pair P1/P7 or nested PCR using the same primer pair followed by R16F2n/R16R2 primers. Restriction fragment length polymorphism and phylogenetic analyses of 16S rRNA gene sequences showed that the phytoplasma associated with PrWB disease in Yazd province belong to 16SrII‐D phytoplasma subgroup. This is the first report of association of a 16SrII‐related phytoplasma with PrWB disease in Iran.

Ontogeny of Crown Bud Clusters and Dormancy-breaking Treatments Influence Productivity and Spread of Harvest Maturity of Gentian ‘Showtime Diva’

Cut flower productivity and quality of gentian is associated with growth and development of crown buds. Experiments were carried out with the gentian cultivar Showtime Diva to identify the response to treatments that break dormancy [cold temperature (chilling), gibberellic acid (GA3)] applied at different stages of development of crown buds (plants with nonemerged crown buds, shoots recently emerged, or shoots emerged and elongated). The comparative growth potential of crown buds within the cluster was also investigated. At the stages of development examined, the application of GA3 (100 ppm) increased emergence of crown buds as shoots, leading to development of more flowering shoots. A similar response was observed with exposure to cold, but only on plants with nonemerged crown buds. Shoot emergence increased in response to increased duration of cold from 0 to 42 days (5 °C). Both chilling and GA3 could potentially be used to reduce the duration to, and spread of, harvest maturity if applied before shoot emergence. The hierarchical relationship of buds in crown bud clusters led to differential responses to application of GA3. Buds ontogenetically positioned at the proximal end of the bud cluster took a similar duration to reach shoot emergence or harvest maturity. For buds located at the distal end there was a positive correlation between ontogenetic bud position and the duration to reach shoot maturity. Shoot length and number of nodes at harvest maturity showed slight negative correlations with the position of the bud in the bud cluster. The results provide an explanation for possible sources of the variation in quality and quantity of floral shoots, and spread in time to harvest maturity within a single plant, and with development stage.