Littérature scientifique sur le sujet « Ulmus minor »

Diethyl ether-petroleum ether extracts were prepared from 49 samples of bark from four elm species (Ulmus glabra Hudson, Ulmus laevis Pall, Ulmus minor Miller, and Ulmus pumila L.) and hybrids from crosses between three of these species. Chemical analyses were performed by gas chromatography – mass spectrometry. Ten triterpenes and three sterols were identified. These compounds are discussed in terms of chemotaxonomy of the genus and identification of hybrids, and in relation to the differential attractivity for elm bark beetle feeding. Separation of the four pure species was successfully achieved by the use of the multivariate discriminant analysis. Ulmus minor × U. pumila hybrids were clearly segregated from their parental species, while U. minor × U. glabra trees were misclassified as U. minor by a multivariate discriminant analysis. Three compounds are described for the first time in the family Ulmaceae and two more in the genus Ulmus. Some of the triterpenes and sterols isolated only in U. glabra and U. laevis may be responsible for the deterrence of bark beetles to feed on these least preferred species.

Tetraneura (Tetraneurella) nigriabdominalis (Sasaki, 1899) is a holocyclic and heteroecious species widely distributed throughout the world. Its primary hosts are various elm species, on which it forms galls. The results of this study complement those of previous research on the development of T. nigriabdominalis on primary hosts. Our research was conducted on two elm species, Ulmus minor and Ulmus glabra, at three locations and for three successive seasons between 2017 and 2019. Fundatrices hatched between 27 April and 12 May. The first galls were observed 6–8 days after the hatching date of the fundatrices. On average, there were 1–7.5 galls on one leaf. The highest abundances of T. nigriabdominalis galls were found in the medial and basal parts of the leaf blades. The fundatrices matured within 12–21 days after hatching and produced nymphs within 2–3 weeks. The fecundity of the fundatrices was influenced by the temperature in April, the size of the laminae, and the size of the galls. The females developing on U. glabra were more fecund (2–58 nymphs), whereas those developing on U. minor produced 1–29 nymphs. The winged migrants of the second generation appeared between late May and late June, when the first cracks on the galls were also observed. The entire development of two aphid generations on the primary host was temperature-dependent and lasted from four to almost six weeks. Our results show that U. glabra and U. minor are suitable hosts for T. nigriabdominalis. The development of aphids proceeded similarly on both tree species. Temperature, especially in April, significantly influenced the duration of individual developmental phases and the fecundity of fundatrices.

Spontaneous hybrids between the native elms (genus Ulmus L.) have been observed in the forests of Europe. Gene conservation raises questions regarding the genetic background for the complex morphology and taxonomy of elms. Our objective was to dissect morphological and genetic variation in the natural swamps of Ulmus species groups in Lithuanian forests with the aid of leaf morphology and microsatellite (SSR) markers. We sampled leaves from 189 elms at 26 locations to grasp the phenotypic diversity in variable natural habitats in Lithuanian forests. We assigned the elms into six taxonomic and genetics groups based on 31 leaf morphology parameters and tested the genetic differentiation between these six groups at six nuclear SSR loci by using Bayesian and genetic distance-based clustering. The genetic and leaf morphometric analyses of putative elm hybrid swamps indicated a low genetic exchange between U. laevis Pall. and the other Ulmus groups. The genetic and morphometric data supported the differentiation of U. glabra Huds. and U. glabra (female) × U. minor Mill. (male) spontaneous hybrids. In addition, the results of the genetic analysis also confirmed the high level of genome sharing among U. minor and U. minor subsp. minor Richens., where leaf morphology failed to differentiate genetically discrete groups. For gene conservation, we would suggest considering separate gene conservation units selected based on leaf and stem morphology for U. laevis, U. glabra, U. glabra × minor, and the U. minor species complex.

The “Ukrderzhlisproekt” Ukrainian State Forest Management Planning Association Database by 2017 was analysed for Donetsk, Kharkiv and Sumy Regional Forest and Hunting Management Administrations (RFHMA) to recognize the distribution of forest-covered area, area with Ulmus sp. as a main forest-forming species, and area of subcompartments with Ulmus sp. in the stand composition by forest site condition (FSC) types. Forests of Donetsk, Kharkiv and Sumy RFHMA are located in 16, 17 and 16 FSC types, with Ulmus sp. in 14, 13 and 11 FSC types, and with Ulmus sp. as the main forest-forming species in 11, 9 and 8 FSC types, respectively. U. minor is the most common; U. glabra is the least common. U. pumila dominates in Donetsk RFHMA and is absent in Sumy RFHMA. U. laevis is most common in Kharkiv RFHMA. U. minor prefers fresh and dry fertile FSC. U. laevis in Donetsk RFHMA prefers dry and fresh fertile FSC types, in Kharkiv RFHMA fresh fertile FSC types, in Sumy RFHMA fresh relatively poor, relatively fertile and fertile FSC types. U. pumila In Donetsk RFHMA prefers dry relatively fertile FSC, in Kharkiv RFHMA fresh fertile FSC, in Sumy RFHMA fresh relatively poor FSC, fresh relatively fertile FSC and moist fresh relatively fertile FSC. U. glabra prevails in moist relatively fertile FSC types, and in Kharkiv RFHMA also widely spread in fresh fertile FSC types.

Doutoramento em Biologia
O ulmeiro que predomina em Portugal (Ulmus minor Mill.), é uma árvore de extrema importância como ornamental e como fornecedora de madeira de excelente qualidade. Infelizmente, desde o início do século passado, a grafiose dos ulmeiros ou DED (“Dutch Elm Disease”) está a provocar uma devastadora mortandade tendo o número de ulmeiros diminuído drasticamente por todo o Hemisfério Norte. Esta catástrofe desencadeou uma intensa pesquisa que incidiu na obtenção de híbridos tolerantes à doença e no controlo desta. Os resultados obtidos não recompensaram o investimento realizado. A conservação e a melhoria dos ulmeiros continua assim a ser uma prioridade dada a perda de variabilidade genética que surge como consequência do seu desaparecimento. A cultura in vitro é uma área que permite a concretização destes objectivos, uma vez que possibilita a multiplicação e conservação de genótipos importantes mas também a sua melhoria através, por exemplo, da fusão de protoplastos. Actualmente, defende-se ainda que o estabelecimento de um sistema eficiente de regeneração de plantas é indispensável na recuperação de clones/indivíduos conservados pelo frio, dado que a preservação de colecções de ulmeiros em campo é muito dispendiosa. Protocolos de introdução in vitro foram já desenvolvidos para algumas espécies de Ulmus. No entanto, o ulmeiro exibe uma grande variedade de respostas no que respeita ao seu cultivo in vitro pelo que, para um determinado genótipo, é frequente ser necessário desenvolver um particular sistema de cultura. Por todas estas razões, o estudo sobre a cultura in vitro do ulmeiro existente em Portugal era importante e inadiável. A cultura in vitro de U. minor foi iniciada com o estabelecimento de um protocolo de proliferação de rebentos, a partir de várias árvores, utilizando um meio com a constituição base de DKW. Após uma fase de enraizamento in vitro ou em solo, as plantas aclimatizadas foram transferidas para o campo. Foram também obtidas plantas por produção adventícia de rebentos em calo e folhas. Na presença de 1 mg/l de BAP foram obtidos rebentos via organogénese indirecta em calo e, nas folhas, foram obtidos rebentos por via directa e indirecta. Numa segunda fase, foram isolados protoplastos a partir de folhas e de calo, usando uma série de combinações de enzimas hidrolíticas. Os protoplastos de folha in vitro foram cultivados usando vários métodos, tendo o método de cultura em gotas de agarose promovido a formação de colónias e de microcalos. Pela primeira vez, o meio KM foi usado com sucesso no cultivo de protoplastos de folha de ulmeiro. Finalmente, foram ensaiados protocolos para o estabelecimento de culturas embriogénicas. Sendo a embriogénese somática uma das vias mais lucrativas de regeneração de plantas, esta enquadra-se na estratégia actual adoptada para o ulmeiro como uma inegável mais valia. Uma vez que este tipo de cultura ainda não tinha sido estabelecido a partir de material adulto do género Ulmus, o seu estudo era fundamental e foi abordado com especial interesse e detalhe. O protocolo que se mostrou mais eficiente foi aquele que envolveu o uso de folhas jovens in vitro que foram colocadas em meio MS com 2,4-D e cinetina, no escuro, durante oito semanas. Nestas condições obteve-se um calo embriogénico a partir do qual se formaram as estruturas embriogénicas. Os protocolos de cultura in vitro do ulmeiro, estabelecidos nesta tese, fornecem assim uma imprescindível base de trabalho em futuros programas de conservação e melhoramento da população Portuguesa de ulmeiros.
The elm tree that predominates in Portugal (Ulmus minor Miill.) is important both as ornamental and as a timber supplier of excellent quality. Unfortunately, DED (Dutch Elm Disease) has been the cause of a catastrophic drop in the number of elms in all the Northern Hemisphere, since the beginning of the 20th century. This catastrophe has lead an intense research about, in one way, the control of the disease and in another way in the production of tolerant hybrids. Despite this intense research, the results do not reward the performed investment. The goals of elm preservation and improvement remains regarding the genetic losses due to elm disappearance. In vitro culture is an area that allows the concretization of these goals since it permits the multiplication and preservation of important genotypes and also their improvement by, for example, protoplast fusion. Actually, the establishment of an efficient system of plant regeneration is also defended as indispensable in the recuperation of clones/genotypes criopreserved, since the maintenance of elm collections in the field is very expensive. Micropropagation protocols had already been developed for some species of Ulmus. However, there is a great genotypic variety concerning elm’s in vitro culture and often, for one determined genotype, it is necessary to develop a particular system of culture. For these reasons, the study of in vitro culture of the elm from Portugal was very important and undelayable. Ulmus minor in vitro culture was initiated by the establishment of a protocol for proliferation of shoots, from various trees, using a medium with the basal constitution of DKW. After a rooting stage in vitro or in soil, the acclimatized plants were transferred to the field. Plants were also produced by adventitious regeneration of shoots in callus and leaves. In the presence of 1 mg/l of BAP shoots were produced through indirect organogenesis in callus and, in leaves, shoots were produced via direct and indirect organogenesis. In a second phase, protoplasts were isolated from leaves and callus using a series of hydrolytic enzymes combinations. In vitro leaf protoplasts were cultivated following some methods of culture, and the method of culture in agarose droplets promoted the production of colonies and microcalli. For the first time, KM medium was used with success in the culture of elm leaf protoplasts. Finally, protocols for the establishment of embryogenic cultures had been experimented. Since somatic embryogenesis is one of the most advantageous ways of plant regeneration, it fits in the current elm’s strategy as an undeniable value. Until now, this type of culture had not been developed from adult material of any species of the Ulmus genus. Because of this, its study was indispensable and was boarded with special interest and detail. The protocol that showed most efficient involved the use of young in vitro leaves that were placed in MS medium with 2,4-D and kinetin, in the dark, during eight weeks. In these conditions, an embryogenic callus was formed and from this callus embryogenic structures were produced. The elm in vitro culture protocols, established in this thesis, provides an essential work base in future preservation and improvement programs of Portugal elm population.

La tesi introduce criticamente, riassume e discute gli studi svolti dall'Autrice sulla variazione osservata nella suscettibilità alla grafiosi dell'olmo negli olmi europei e il ritmo di crescita delle specie ospite inclusa la fenologia del germogliamento e il controllo della dormienza invernale - The thesis introduces, summarizes and discusses the studies carried out by the Author on the relationship between susceptibility to Dutch elm disease and growth rhythm of host plants in European elm species including leaf phenology and control of winter bud dormancy