Academic literature on the topic 'Enamel pearl'
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Journal articles on the topic "Enamel pearl"
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Risnes, S. "Ectopic Tooth Enamel. An SEM Study of the Structure of Enamel in Enamel Pearls." Advances in Dental Research 3, no. 2 (1989): 258–64. http://dx.doi.org/10.1177/08959374890030022701.
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Eighteen human molars with enamel pearls ranging in diameter from 0.8 to 2.7 mm were sectioned, acid-etched, and processed for SEM observation. In addition to pearl enamel, the specimens contained crown enamel for comparison. All pearls were of the composite type. The enamel layer reached maximal thicknesses of between 0.3 and 0.7 mm opposite the tip of the dentinal cone. The enamel structure was normal, but more variable and irregular than crown enamel. The prism course was often irregular throughout the whole thickness of enamel. Distinct Hunter-Schreger bands were absent. Prisms and interprism were occasionally difficult to identify as separate entities. The packing of crystals seemed to be less tight in pearl enamel. The scarcity of Retzius lines was attributed to the method of preparation. Prism cross-striations with a periodicity ranging between 1.3 and 4.5 μm were frequently encountered. A superficial prism-free zone with a regular 1.7-2.5-μm striation was present in localized regions of many pearls. The formation time of a medium-sized pearl was calculated to be about 11.5 months. A variety of cross-cut prism configurations was observed. Occasional hypoplastic lesions and hypomineralized areas were encountered. In conclusion, pearl enamel possesses most of the structural attributes of crown enamel, but in general its organization seems to be less orderly. Enamel pearls represent developmental disturbances in position and timing more than in structure.
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Rathva, Vandana. "Ectopic enamel pearl." Clinics and Practice 2, no. 2 (2012): 46. http://dx.doi.org/10.4081/cp.2012.e46.
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Enamel pearls are one of a number of different enamel structures that can be found on the roots of deciduous and permanent teeth. They have a distinct predilection for the furcation areas of molar, particularly the maxillary third and second molars. However, they have been found less commonly on the apical portions of the root. This report describes an unusual case of enamel pearl on apical third of mandibular molar teeth. Enamel pearl was confirmed as predisposing factor for the cause of localized periodontitis; it is very important to recognize their radiographic aspect to ensure proper treatment of involved teeth.
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Vanishree, H. S., and Anand S. Tegginamani. "Enamel Pearl." JOURNAL OF MULTIDISCIPLINARY DENTAL RESEARCH 5, no. 2 (2019): 67–69. http://dx.doi.org/10.38138/jmdr/v5i2.3.
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Moharir, Anuja Nitin, Malya Akkottillam, Sachin Bhagat, Vaishali Pagare, Anuja Hakkepatil, and Hiroj Bagde. "Enamel Pearls: A Culprit of Localised Periodontitis." Journal of Pharmacy and Bioallied Sciences 17, Suppl 2 (2025): S2007—S2009. https://doi.org/10.4103/jpbs.jpbs_566_25.
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ABSTRACT A small piece of enamel forms the basic structure of enamel pearls that appear in maxillary molars. Periodontal destruction at its most advanced stage leads to the formation of enamel pearls. A 45-year-old female patient sought treatment at the Department of Periodontics located at DY Patil Dental School Lohegaon due to pain in the lower right back teeth region of her jaw. The patient did not have any noteworthy health problems from her past. Tooth no. #2 displayed caries and #30 presented grade I mobility together with grade III furcation involvement and deep periodontal pocket during the intraoral exam. The patient underwent root canal treatment before receiving #30 flap surgery. Enamel pearls were noticed through the debridement process in the middle and apical segments of the root. Periodontal destruction could have progressed significantly as a result of the enamel pearl discovery reported in this case.
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Zenóbio, Elton Gonçalves, Thaís Ribeiral Vieira, Roberta Paula Colen Bustamante, Hayder Egg Gomes, Jamil Awad Shibli, and Rodrigo Villamarin Soares. "Enamel Pearls Implications on Periodontal Disease." Case Reports in Dentistry 2015 (2015): 1–3. http://dx.doi.org/10.1155/2015/236462.
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Dental anatomy is quite complex and diverse factors must be taken into account in its analysis. Teeth with anatomical variations present an increase in the rate of severity periodontal tissue destruction and therefore a higher risk of developing periodontal disease. In this context, this paper reviews the literature regarding enamel pearls and their implications in the development of severe localized periodontal disease as well as in the prognosis of periodontal therapy. Radiographic examination of a patient complaining of pain in the right side of the mandible revealed the presence of a radiopaque structure around the cervical region of lower right first premolar. Periodontal examination revealed extensive bone loss since probing depths ranged from 7.0 mm to 9.0 mm and additionally intense bleeding and suppuration. Surgical exploration detected the presence of an enamel pearl, which was removed. Assessment of the remaining supporting tissues led to the extraction of tooth 44. Local factors such as enamel pearls can lead to inadequate removal of the subgingival biofilm, thus favoring the establishment and progression of periodontal diseases.
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Viswanathan, Shanthi, Vezhavendhan Nagaraj, Sanguida Adimoulame, Sathish Kumar, and Gaurav Khemaria. "Dens Evaginatus in Proximal Surface of Mandibular Premolar: A Rare Presentation." Case Reports in Dentistry 2012 (2012): 1–3. http://dx.doi.org/10.1155/2012/603583.
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Dens evaginatus is a developmental anomaly that is characterized by occurrence of an extra cusp-like structure projecting from the crown portion of the tooth. Unusual extension of enamel has been found in posterior teeth as enamel pearl or as cervical enamel extensions from the cementoenamel junction or at the furcation areas. We hitherto report a case of extra enamel formation from the proximal surface of the crown in a mandibular premolar, a finding that has previously not been reported.
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Thakur, Aditi. "Enamel Pearl: A Factor Predisposing Localized Periodontitis-A Case Report." CODS Journal of Dentistry 4, no. 1 (2012): 47–48. http://dx.doi.org/10.5005/cods-4-1-47.
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Roa, Ignacio. "Imágenes en odontología clínica. Perlas del esmalte." Mouth 2, no. 1 (2017): e26072017es. https://doi.org/10.5281/zenodo.834926.
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Una mujer de 19 años de edad asiste a la consulta odontológica con indicación de exodoncia del diente 1.8. Luego del acto quirúrgico se examinó el diente y se observó la presencia de dos perlas del esmalte a nivel radicular. Las perlas de esmalte son una anomalía del desarrollo dental, que se presentan como glóbulos ectópicos de esmalte en la superficie radicular. La prevalencia media de perlas de esmalte es 2,69%; teniendo predilección por los molares y rara vez se asocian con premolares, caninos o incisivos. La teoría sugiere que se desarrollan debido a presencia de remanentes de la vaina epitelial radicular (de Hertwig). Adquieren real relevancia debido a su asociación como factor retentivo de placa subgingival y a enfermedad periodontal localizada.
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EZİRGANLI, Şeref, Alper KUŞTARCI, and Uğur GÜRER. "An Enamel Pearl on Maxillar Wisdom Tooth: A Rare Case Report." Turkiye Klinikleri Journal of Dental Sciences 21, no. 2 (2015): 163–65. http://dx.doi.org/10.5336/dentalsci.2011-24536.
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Archita, Datta, Kaur Lamba Arundeep, Faraz Farrukh, Tandon Shruti, I. Anuppriyanka, and Dhingra Sachin. "Developmental Anomalies- Catalyst of Periodontal Diseases: A Report of 2 Cases." A Journal of Clinical Dentistry HealTalk 14, no. 06 (2022): 27–29. https://doi.org/10.4880/zenodo.7839807.
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Abstract Periodontal disease is multifactorial; therefore, determining the exact etiology of the same is critical when planning the treatment. Developmental disturbances of the teeth may manifest by variation in number, position, size, shape, eruption, or structure. It can be in generalized or localized form. Concrescence and enamel pearl are developmental anomalies that can cause periodontal pockets to persist by acting as a nidus for plaque accumulation and interfering with patient oral hygiene. This necessitates a proper diagnosis of such anomalies, which, although rare, necessitate suitable management to aid in periodontal therapy and maintenance.
Books on the topic "Enamel pearl"
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Suto, Carlton. Church Growth: Precious Pearls Enable Churches to Create Sustainable Church Growth. Independently Published, 2022.
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Hughes-Hassell, Sandra, Pauletta Brown Bracy, and Casey H. Rawson, eds. Libraries, Literacy, and African American Youth. ABC-CLIO, LLC, 2016. http://dx.doi.org/10.5040/9798400678943.
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This important book is a call to action for the library community to address the literacy and life outcome gaps impacting African American youth. It provides strategies that enable school and public librarians to transform their services, programs, and collections to be more responsive to the literacy strengths, experiences, and needs of African American youth. According to National Assessment of Educational Progress (NEAP), only 18 percent of African American fourth graders and 17 percent of African American eighth graders performed at or above proficiency in reading in 2013. This book draws on research from various academic fields to explore the issues surrounding African American literacy and to aid in developing culturally responsive school and library programs with the goal of helping to close the achievement gap and improve the quality of life for African American youth. The book merges the work of its three authors along with the findings of other researchers and practitioners, highlighting exemplary programs, such as the award-winning Pearl Bailey Library Program, the Maker Jawn initiative at the Free Library of Philadelphia, and the Blue Ribbon Mentor Advocate writing institute in the Chapel Hill-Carrboro City Schools, among others. Readers will understand how these culturally responsive programs put theory and research-based best practices into local action and see how to adapt them to meet the needs of their communities.
Book chapters on the topic "Enamel pearl"
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Aldred, Michael, Netasha Steyn, and Anna Talacko. "Enamel Pearls." In Encyclopedia of Soil Science. Springer Netherlands, 2016. http://dx.doi.org/10.1007/978-3-319-28085-1_695.
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Wilson, Rhonda, Barbora de Courten, and Karen Livesay. "Non-Binary Approaches to Enable a Flexible Work-Life Rhythm." In Leadership Pearls in Healthcare. Springer Nature Singapore, 2025. https://doi.org/10.1007/978-981-96-4233-5_39.
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"Enamel Pearls." In Diagnostic Imaging: Oral and Maxillofacial. Elsevier, 2017. http://dx.doi.org/10.1016/b978-0-323-47782-6.50046-6.
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Olubode Ogunsalu, Christopher. "The Radiology of Developmental Dental Defects Demystified: An e-Based Learning System." In Clinical Concepts and Practical Management Techniques in Dentistry. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101435.
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The purpose of this perspective-type chapter is to provide the readership with in-depth knowledge in the area of developmental abnormalities with special emphasis on radiology together with its clinical implications. The intention of this chapter is not only to be descriptive of the radiology of the developmental dental defects, but to provide the readership with the various possible differential diagnoses and how to arrive at a definitive diagnosis and being mindful of the fact that some of these radiological presentations can be pathognomonic while others are variable in presentation. The ultimate goal of this chapter is to provide the pre-requisite knowledge to the clinicians to enable them to arrive at a definitive diagnosis based on radiology and radiographic presentation without the need of any other investigation if possible. It is as such important that in this chapter the readership will be elevated to a level of realistic, yet clinician with the reasoning and interpretation of a radiologists in the area of developmental dental defects (DDD) since by understanding the basis of utilizing radiography to arrive at the definitive diagnosis of these developmental defects amidst of the various differential diagnoses, they would have gained full knowledge and control of the pertinent use of terminologies in this specific and unique area of dentistry. Conventional radiography such as periapical radiographs, bitewings and dental panoramic tomography will be utilized largely in this chapter, without the need for computerized tomography or CBCT. Certain conditions such as concrescence (not fusion and germination) and enamel pearl may be very difficult to identify or distinguish using conventional radiography and the role of advanced imaging technique will be mentioned. It is as such the intention of this unique book chapter to display in an Atlas work note format, the radiology of the developmental dental defects, with the intention to bring in the knowledge required to the undergraduate students of dentistry and postgraduate dentists and inclusive of the practicing clinicians in the field of dentistry.
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Gumzej, Roman, and Wolfgang A. Halang. "The Language Specification PEARL for Co-Designing Embedded Systems." In Computational Models, Software Engineering, and Advanced Technologies in Air Transportation. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-800-0.ch015.
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The Specification PEARL language and methodology for hardware/software co-design of embedded control systems is presented. The Specification PEARL language has its origins in standard Multiprocessor PEARL, and was enhanced as foreseen by the standard to model layered and asymmetrical multiprocessor system architectures. Its constructs were extended by additional parameters for model verification and validation by schedulability analysis. Graphical symbols were introduced for Specification PEARL constructs to enable graphical modeling while maintaining their semantic background. Originally, Specification PEARL was intended as a superlayer for normal PEARL programs, implementing the Multiprocessor PEARL specification. Later on, however, it evolved to a methodology to specify and codesign applications for other target programming languages, such as C and C++, based on the superior programming model of PEARL. To supplement structural modeling by a behavioural model, Timed State Transition Diagrams were defined to model program tasks. A system model is verified for coherence by model checking as well as for temporal feasibility with co-simulation. The resulting information is used to correct and fine-tune a current model. To enhance availability and safety as well as to support maintainability, dynamic re-configuration planning is included in the software-to-hardware mapping specifications. Since UML has become the de facto standard also for designing embedded control systems, a UML profile for the methodology was defined using UML’s extension mechanisms.
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Lottering, Nicolene, Iris Lim, and Suzanne Gough. "Re-Imagining Health and Medicine Education." In Supporting Self-Regulated Learning and Student Success in Online Courses. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-6500-4.ch009.
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Gamification is an active-learning approach commonly used in education to promote learner engagement. This chapter provides an overview of how gamified approaches can be applied to enable university students comprising of Generation Z and Y learners, to access authentic learning resources to self-regulate their learning in preparation for assessment. Methods and flexible strategies that can be incorporated into undergraduate and postgraduate education programs worldwide are provided. Three case studies illustrate the use of technology-enhanced weekly quizzes to optimise student engagement, knowledge retention, and academic performance. Key educational theories and practices that underpinned the case studies include social constructivism, disuse theory, and complexity theory alongside the use of scaffolding, chunking, flipped classroom, deliberate practice, and periodic revisitation. The chapter concludes with 12 pearls of wisdom to optimize leaner engagement using a gamified approach to enhance the students' ability to self-regulate their learning and achieve their learning goals.
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Roger, Philippe. "Barthes’s Frenchness." In Interdisciplinary Barthes. British Academy, 2020. http://dx.doi.org/10.5871/bacad/9780197266670.003.0002.
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Barthes doesn’t think in terms of identity, even less national identity, yet amongst his contemporaries (the ‘French theorists’) his writing seems the most ‘French’. He admits this somewhat paradoxically by devoting sarcastic analyses to ‘Frenchness’ whilst testifying, in the more intimate pages of Roland Barthes par Roland Barthes, to a profound attachment to the ‘land’ of his childhood, the ‘light of the South-West’, ways of being and speaking, or of preferring pears to exotic fruit. This book sparked the revisionist reading of Barthes’s intellectual itinerary that would gather momentum after his death: behind the structuralist and fellow-traveller of the avant-garde lurked a conservative writer, a crypto-Gidian explorer of the self. In fact, a benefit of the 1975 commission was to enable Barthes’s return to anthropology. Michelet par lui-même (1954) and Mythologies (1957) had allowed Barthes to explore national identity in historical and anthropological terms, and a custom-made ‘ethnology of France’ (‘Notre France, in the manner of Michelet’) was a persistent project. Although formulated with calculated lightness, the question of Frenchness runs throughout this ‘Barthes by himself’; far from signalling a farewell to politics and ideology, it provided the right frame for a socio-anthropological exploration of France and Barthes’s ‘French’ identity.
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Bakovic Darija, Palada Ivan, and Dujic Zeljko. "Apnea Diving." In Biomedical and Health Research. IOS Press, 2010. https://doi.org/10.3233/978-1-60750-497-9-431.
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Men and women have been diving for thousands of years to gather a variety of products, including food, sponges, and pearls, to conduct salvage and military operations, and to explore. In 1911, one of the first freediving competitions was held when a Greek fisherman, Yorgos Haggi Statti, was offered a few dollars to dive and to rescue the anchor of an Italian ship which had become stuck in the Aegean Sea. The Italian ship was set free and Yorgos became known as the “father of freediving”. After World War II, breath hold diving became an international sport where athletes test the human limits of time, depth and distance. Exposure to excessive depths, though, can be very dangerous and cause a collapse of the lungs, cardiac arrest, blackouts, decompression sickness and, at worst, death. Whatever the reason for breath hold diving, its success depends on how a diver tolerates the physiological stress related to the depth and duration of dive. The human body has several adaptations under diving conditions, which stem from the mammalian diving reflex. These adaptations enable the human body to endure depth and lack of oxygen far beyond what would be possible without the reflex. Human diving response involves bradycardia, vasoconstriction of selected vascular beds with increase in blood pressure, changes in cardiac output and spleen contraction. Variety of studies frequently discussed parts of diving response. However, the concept of spleen contraction has recently been described as a property of diving response. The spleen serves as a dynamic blood cell reservoir which can be released into systemic circulation during exercise, diving or intermittent hypoxia. Since contraction of the spleen increases hemoglobin and hematocrit circulating in blood, than the O2transport will also be enhanced. In humans, the rapidity of spleen contraction indicates that the initial stimulation is likely neural in origin, but contraction may be sustained throughout the dive by circulating catecholamines released from the adrenal gland. Leucocytes and platelets accumulate in the human spleen to a much greater extent than erythrocytes, accounting for approximately 40% of both body populations. The destiny of these two populations during apnea induced spleen contraction is also the aim of our chapter.
Conference papers on the topic "Enamel pearl"
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McIntosh, Tyler L., Erick Verleye, Jennifer K. Balch, et al. "Cyberinfrastructure deployments on public research clouds enable accessible Environmental Data Science education." In PEARC '23: Practice and Experience in Advanced Research Computing. ACM, 2023. http://dx.doi.org/10.1145/3569951.3597606.
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Heng, Olivia. "Towards a Facility Efficiency Tracking Application: Improving Metric Granularity to Enable Research on Optimal Work Situations through Software Development." In PEARC '24: Practice and Experience in Advanced Research Computing. ACM, 2024. http://dx.doi.org/10.1145/3626203.3670571.
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Hutchins, Robert C., and Shankar Hemmady. "How to write Awk and Perl scripts to enable your EDA tools to work together." In the 33rd annual conference. ACM Press, 1996. http://dx.doi.org/10.1145/240518.240597.
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SKAČKAUSKIENĖ, Ilona, and Jurga VESTERTĖ. "SERVICE MODULARISATION COMPATIBILITY TO ORGANISATIONAL OBJECTIVES." In International Scientific Conference „Contemporary Issues in Business, Management and Economics Engineering". Vilnius Gediminas Technical University, 2021. http://dx.doi.org/10.3846/cibmee.2021.583.
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Purpose – the article aims to explore how service modularisation objectives are compatible with organisa- tional objectives. Research methodology – the paper is a part of continuous research. It takes a conceptual approach and integrates rele- vant literature to develop a framework on the potential avenues to create a decision-support tool that assists in service modularity planning. The research proceeds with evidence from the peer-reviewed literature. The relevant literature was identified through “pearl growing” and citation chasing techniques using the assembled body of topic literature from authors’ previous research and employing the related keywords for filtering. Findings – the previous literature is silent on establishing objectives for service modularisation with the consideration of what a provider will achieve by engaging in this. The paper addresses this gap and discovers how antecedents of service modularisation transform into organisational objectives. Research limitations – although bibliographic research methods are limited, they enable the analysis and identification of structure within the research. Such analysis has implications by suggesting future directions in investigating how modularity approach can be used in the service context and how it can be applied in practice more actively. Practical implications – the findings provide potentially vital information to service organisation managers and allow better understand how service modularisation would benefit performance results in gaining service competitiveness. Originality/Value – the study contributes to the discourse on service modularity planning and provides a basis for comprehension of service modularisation merit when pursuing competitiveness.
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Khamidi, Mohd Faris, and Jiin Baek. "A study on the perception of walkability in tourist attraction places in Qatar using text mining techniques." In Post-Oil City Planning for Urban Green Deals Virtual Congress. ISOCARP, 2020. http://dx.doi.org/10.47472/mlrr3543.
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Walking is an important part of the tourist experience and comfort travel. There is increasing attention to encourage tourists to walk as a mode of sustainable transportation. Emergence of new and diverse forms of data has expand the field of research via text mining analysis. This is an alternative for common research methodology as a good analysis tool to reflect pedestrians’ opinions in spatial design and urban planning. In this regard, the novelty of this paper is to investigate the relationship between walkability and successful tourism in Doha, Qatar by utilizing text mining analysis on a readily available datasets, i.e. the customer generated contents from TripAdvisor. The collected data for tourist attractive places in Doha, Qatar shows higher frequency (connection) of words that reflect the characteristics of each research location and its respective relationship with public transportation (Doha Metro) to support the walkable environment. The findings have determined some users-friendly walking environment especially for research locations like The Pearl, Souq Waqif and Museum of Islamic Arts. On the other hand, it is indicated that the rate of Metro use is still low compared to the city’s population and this will take some time for Doha Metro to be used as main mode of transportation among the tourists. The outcome of this study will enable to propose some guidelines to enhance the walking environment for tourists within the challenging weather condition like hot and arid climate of Qatar
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Clemen, Carsten, Murthy Ravikanti, Nicholas La Bianca, Ruud Eggels, Benno Wurm, and Kenneth Young. "Considerations for Hydrogen Fueled Aerospace Gas Turbine Combustion Sub-System Design." In ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/gt2024-122593.
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Abstract As part of its commitment to the decarbonization of the aviation sector and the UN Race to Zero global campaign, Rolls-Royce is actively developing hydrogen combustion gas turbine engine technology capable of powering a range of aircraft from 2035 onwards. These innovative technologies are undergoing integration and validation through a demonstrator project, which involves the modification of a Pearl15 engine for ground testing with gaseous and liquid hydrogen. The design of an aerospace combustor needs to satisfy conventional requirements such as cost, weight, aero-thermal performance, and lifespan. However, the introduction of hydrogen as the primary fuel introduces additional challenges, including potential novel failure modes, operability considerations and pollutant emissions. The NOx emissions resulting from hydrogen combustion are currently the subject of extensive research and are considered, to be one of the key considerations which will ultimately influence the design of the optimum hydrogen combustion sub-system for aerospace applications. This paper describes the development of the first prototype combustion technology at Rolls-Royce. Innovative fuel injection concepts were investigated to enable operation with 100% hydrogen on the Pearl 15 combustor architecture which is to serve as the test vehicle for ground demonstration in the Clean Aviation Project “CAVENDISH”. The paper details the process which began with prototype development and validation on a single sector atmospheric test rig to map the design space and understand sensitivities. This allowed the selection of four leading configurations based on NOx emissions, flame stability (measured using optical methods), ignition and weak extinction performance. The four configurations were then tested in a single sector, intermediate pressure rig testing at engine-representative low power conditions. This testing aimed at identifying challenges related to flame stability and combustor temperature distribution, thereby mitigating risks associated with engine combustor testing. Finally, tests were undertaken in a full annular, high pressure combustion rig at engine-representative maximum takeoff conditions. Aerothermal performance, as measured by NOx emissions, weak extinction and exit temperature traverse, demonstrated promising comparisons to kerosene-based fuel. These results demonstrate that a retrofittable combustion solution is credible and realistic for a minimum viable hydrogen gas turbine product.
Reports on the topic "Enamel pearl"
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Flaishman, Moshe, Herb Aldwinckle, Shulamit Manulis, and Mickael Malnoy. Efficient screening of antibacterial genes by juvenile phase free technology for developing resistance to fire blight in pear and apple trees. United States Department of Agriculture, 2008. http://dx.doi.org/10.32747/2008.7613881.bard.
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Objectives: The original objectives of this project were to: Produce juvenile-free pear and apple plants and examine their sensitivity to E. amylovora; Design novel vectors, for antibacterial proteins and promoters expression, combined with the antisense TFL1 gene, and transformation of Spadona pear in Israel and Galaxy apple in USA. The original objectives were revised from the development of novel vectors with antibacterial proteins combined with the TFL-1 due to the inefficiency of alternative markes initially evaluated in pear, phoshomannose-isomerase and 2-deoxyglucose-6-phosphate phosphatase and the lack of development of double selection system. The objectives of project were revised to focus primarily on the development additional juvenile free systems by the use of another pear variety and manipulation of the FT gene under the control of several promoters. Based on the results creation of fire blight resistance pear variety was developed by the use of the juvenile free transgenic plant. Background: Young tree seedlings are unable to initiate reproductive organs and require a long period of shoot maturation, known as juvenile phase. In pear, juvenile period can last 5-7 years and it causes a major delay in breeding programs. We isolated the TFL1 gene from Spadona pear (PcTFL1-1) and produced transgenic ‘Spadona’ trees silencing the PcTFL1 gene using a RNAi approach. Transgenic tissue culture ‘Spadona’ pear flowered in vitro. As expected, the expression of the endogenous PcTFL1 was suppressed in the transgenic line that showed precocious flowering. Transgenic plants were successfully rooted in the greenhouse and most of the plants flowered after only 4-8 months, whereas the non-transformed control plants have flowered only after 5-6 years of development. Major achievements: Prior to flower induction, transgenic TFL1-RNAi ‘Spadona’ plants developed a few branches and leaves. Flower production in the small trees suppressed the development of the vegetative branches, thus resulting in compact flowering trees. Flowering was initiated in terminal buds, as described for the Arabidopsis tfl1 mutant. Propagation of the transgenic TFL1-RNAi ‘Spadona’ was performed by bud grafting on 'Betulifolia' rootstock and resulted in compact flowering trees. The transgenic flowering grafted plants were grown in the greenhouse under a long photoperiod for one year, and flowered continuously. Pollination of the transgenic flowers with ‘Costia‘ pear pollen generated fruits of regular shape with fertile F1 seeds. The F1 transgenic seedling grown in the greenhouse formed shoots and produced terminal flowers only five months after germination. In addition, grafted F1 transgenic buds flower and fruit continuously, generating hybrid fruits with regular shape, color and taste. Several pear varieties were pollinated with the transgenic TFL1-RNAi ‘Spadona’ pollen including `Herald Harw` that was reported to have resistance to fire blight diseases. The F-1 hybrid seedlings currently grow in our greenhouse. We conclude that the juvenile-free transgenic ‘Spadona’ pear enables the development of a fast breeding method in pear that will enable us to generate a resistance pear to fire blight. Implications: The research supported by this grant has demonstrated the use of transgenic juvenile free technology in pear. The use of the juvenile free technology for enhancement of conventional breeding in fruit tree will serve to enhance fast breeding systems in pear and another fruit trees.
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Lindow, Steven E., Shulamit Manulis, Dan Zutra, and Dan Gaash. Evaluation of Strategies and Implementation of Biological Control of Fire Blight. United States Department of Agriculture, 1993. http://dx.doi.org/10.32747/1993.7568106.bard.
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The main objective of this study was to develop data that would facilitate a consistently effective method of biological control of fire blight disease to be developed and to enable its implementation for disease control by ensuring its compatibility with variations in the biological, environmental, and chemical conditions present in pear orchards. As considerable information on the pathogen and biological control of fire blight was already gathered from studies in California and elsewhere, an emphasis was placed on investigating the genetics and ecology of Erwinia amylovora, the causal agent of fire blight in Israel. Studies of plasmid profile, virulence on several host, serological characteristics, as well as DNA fingerprints with selected primers all revealed E. amylovora strains in Israel to be homogeneous. Strains did vary in their resistance to streptomycin, with those from more northern locations being resistant while those in the southern costal plain were all sensitive to streptomycin. Resistance appeared to be conferred by chromosomal mutations as in streptomycin-resistant strains in California. The biological control agent Pseudomonas fluorescens strain A506 colonized flowers of both the Costia and Spodona pear cultivars in Israel as well as Bartlett pear in California. Flowers that were open at the time of spray inoculation of trees subsequently harbored from 105 to 107 cells of strain A506 per flower, while those that opened subsequent to spraying developed population sizes of about 105 cells/flower within 5 days. The incidence of fire blight infections were reduced about 3-fold in several trials in which moderate amounts of disease occurred in the plot areas; this degree of biological control is similar to that observed in California and elsewhere. On two occasions warm and moist weather that favored disease led to epidemics in which nearly all flowers became infected and which was so severe that neither P. fluorescens strain A506 nor chemical bactericides reduced disease incidence. A novel method for identifying antagonistic microorganisms for biological control of fire blight and other diseases was developed. A bacterial ice nucleation gene was introduced into E. amylovora to confer an Ice+ phenotype and the population sizes of this modified pathogen on flowers that had been pre-treated with potential control agents was estimated by measuring the freezing temperature of colonized flowers. Antagonistic strains that prevented the growth of E. amylovora in flowers were readily detected as those in which flowers froze at a low temperature. The method is both rapid and unbiased and several bacterial strains with substantial biological control potential have been identified using this method.