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Chromosomes in species of Myrciinae. A Gomidesia sp. (2n = 22); B Marlierea clausseniana (2n = 22); C Marlierea warmingiana (2n = 22); D Marlierea tomentosa (2n = 22); E Myrcia bella (n = 11); F Myrcia formosiana (2n = 22); G Myrcia sp. 4 (2n = 22); H Myrcia sp. 1 (2n = 22); J Myrcia sp. 2 (2n = 44). Scalebars: 5 µm.
Source publication
In this paper we describe the chromosome numbers of several species of Myrtaceae (subtribe Myrciinae) from south-eastern Brazil, in order to help determine the circumscription and limits of this group. The chromosomal counts of 20 species were obtained, 17 of which are new. The number 2n = 22 occurs in almost all of species and genera analysed exce...
Contexts in source publication
Context 1
... numbers of 20 species of Myrciinae are presented (Table 3, Fig. 1). In Gomidesia, three of the four species analysed were diploid with 2n = 22, one species, G. gaudichaudiana, was polyploid, with 2n = 44 (Table 3). In Marlierea, three species were diploid, i. e. 2n = 22 (Table 2, Fig. 1B, C, D). In Myrceugenia, both M. ovata and M. myrcioides had 2n = 22 (Table ...
Context 2
... numbers of 20 species of Myrciinae are presented (Table 3, Fig. 1). In Gomidesia, three of the four species analysed were diploid with 2n = 22, one species, G. gaudichaudiana, was polyploid, with 2n = 44 (Table 3). In Marlierea, three species were diploid, i. e. 2n = 22 (Table 2, Fig. 1B, C, D). In Myrceugenia, both M. ovata and M. myrcioides had 2n = 22 (Table ...
Context 3
... Myrcia nine species were diploid with 2n = 22 and two were polyploid with 2n = 44 (Table 3, Fig. 1J). In only two species, M. bella and M. fallax, was it possible to confirm both the gametic (n = 11) and somatic (2n = 22) chromosome numbers ( Table ...
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Citations
... In family Myrtaceae, the diploid chromosome number 2n=2x=22 is the most common, although variations of ploidy level occur, with some triploid (2n=3x=33) and tetraploid (2n=4x= 44) records. Karyotype details in this group are scarce because the chromosomes are small ( 2 µm) (Costa and Forni-Martins 2007). In the previous study 26 species were studied and reported 2n=22, 33, 44, 55, and 66 (Table 1). ...
Syzygium laetum (Myrtaceae) is an endemic species of Western Ghats. The karyomorphology is reported for the first time with mitotic chromosome number 2n=22. The karyotype formula is 2n=22=18m+4sm. The karyotype is a 2A type of the Stebbins category.
... Forni-Martins & Martins (2000) reported the first chromosome counts for two species of Myrcia, both 2n = 22. Fourteen species of Myrcia have now been sampled, and the chromosome number of 2n = 22 has been recorded in 13 of them (Costa & Forni-Martins, 2007;Costa & al., 2008;Amorim, 2012). ...
... Additionally, for certain studies fertility is a sine qua non condition. For example, flower buds are a prerequisite for determination of gametic chromosome number, n (Costa & Forni-Martins, 2007a), and fruits are needed for determination of somatic chromosome number, 2n, from tissue prepared 2 Using herbarium data to find fertile plants from the root tips of germinating seeds (Costa & Forni-Martins, 2007a, 2007b; these chromosome counts are essential information on which to base the choice of parents for plant-breeding experiments (Bretagnolle & Thompson, 1995). Flower buds and flowers are obviously necessary for floral ontology studies (Gomes et al., 2008), and seeds have been collected for propagation since ancient times, and in recent decades, for conservation in seed banks (Wishnie et al., 2007). ...
The Phenological Predictability Index (PPI) is an algorithm incorporated into Brahms, one of the most widely used herbarium database management systems. PPI uses herbarium specimen data to calculate the probability of the occurrence of various phenological events in the field. Our hypothesis was that use of PPI to quantify the likelihood that a given species will be found in flower bud, flower or fruit in a particular area in a specific period makes field expeditions more successful in terms of finding fertile plants. PPI was applied to herbarium data for various angiosperm species locally abundant in Central Brazil to determine the month in which they were most likely to be found, in each of five areas of the Distrito Federal, with flower buds, flowers or fruits (i.e. the ‘maximum probability month’ for each of these phenophases). Plants of the selected species growing along randomised transects were tagged and their phenology was monitored over 12 months (method 1), and two one-day field excursions to each area were undertaken, by botanists with no prior knowledge of whether the species had previously been recorded at these sites, to record their phenological state (method 2). The results showed that field excursions in the PPI-determined maximum probability month for flower buds, flowers or fruits would be expected to result in a > 90% likelihood of finding individual plants of a given species in each of these phenophases. PPI may fail to predict phenophase for species with supra-annual reproductive events or with high event contingency. For bimodal species, the PPI-determined maximum probability month is that in which a specific phenophase is likely to be most intense. In planning an all-purpose collecting trip to an area with seasonal plant fertility, PPI scores are useful when selecting the best month for travel.
... Another feature shared by the members of this clade is the small size of the chromosomes. Costa & Forni-Martins (2007) have found very small chromosomes (< 2.0 µm) in Myrtaceae, and we can see in Fig. 1 that Vochysiaceae also present small chromosomes (ca. 1.0 µm). ...
With five neotropical genera and ca. 220 species, Vochysieae is the largest tribe of Vochysiaceae, comprising more than 90 % of its species. Preliminary phylogenetic analyses with matK sequence data indicated that Vochysieae may be paraphyletic, separated into the clades QRC (Qualea, Ruizterania and Callisthene) and VS (Vochysia, Salvertia). Whether the genera and the infrageneric taxa are artificial is still controversial. In this study, we analyzed the distribution of chromosome numbers in mitotic or meiotic cells among 20 species belonging to the genera Callisthene, Qualea, Salvertia, and Vochysia, that are native and common in Central and Southeast Brazilian forests or savannas. Species of Callisthene and Qualea possessed 2n = 22, while species of Salvertia and Vochysia had 2n = 24 (or n = 12). Th ese chromosome numbers corroborate the recognition of two groups, and also suggest that chromosome evolution based on numerical variation is conservative in these lineages.
... The chromosome number observed to the accessions 15, 16 and 17 of P. cattleaynum and P. guineense (accession 7) indicates that they are cytotypes. Costa and Forni-Martins (2006a) The values obtained for the DNA amount diverge from the number presented by Costa et al. (2008), who observed for P. guajava (red guava), P. guajava (white guava), P. cattleyanum (red fruit), P. cattleyanum (yellow fruit), values of 2C = 0.55 with 2n = 22, 2C = 0.50 with 2n = 22, 2C = 2.91 with 2n = 66, and 2C = 1.05 with 2n = 44, respectively. ...
... For P. cattleaynum Costa and Forni-Martins (2006a) and Costa et al. (2008) found 2n = 44 in chromosome counts, confirming the results obtained by studies in the access 6 of this species. For the rootstocks of araça tree, P. cattleaynum In addition to the polyploidy series, chromosome counts performed on the accession of purple guava tree (P. ...
The objective of this study was to determine the chromosome number and DNA amount of accessions of
Psidium sp. (arac¸a tree, used as rootstocks) and accessions of P. guajava (guava tree) resistant/susceptible to M. enterolobii, which holds some morphophysiological affinity and which could enable their use as rootstocks compatible with commercial varieties of guava. Metaphase chromosomes
were obtained by the squash technique and stained with 2 % Giemsa. The determination ofDNAamount was done by flow cytometry using Mary buffer. The intraspecific variation in DNA amount (2C) was of the order of 9x, with 2n = 22 observed in only one species of P. guajava. The other species presented variations in the ploidy level in relation to the basic chromosome number x = 11, including the occurrence of polyploidy, cytotypes and disploidy. In some species, the interspecific variation of 2C showed a direct relationship with
the ploidy level. Our data confirm that variations in the number of chromosome and in ploidy level are important events to Psidium and can support the understanding of the incompatibility of the graft on rootstocks of guava and arac¸a trees resistant to the nematode M. enterolobii.
... Table 3 summarizes combinations of morphological characters that define each clade. It is hoped that future studies will refine this arrangement, possibly adding data from other disciplines (Dias-Leme et al. 1995;Porter et al. 2000;Costa and Forni-Martins 2007). The following section assesses the implications of this study for previously accepted taxa now included in Myrcia s.l. ...
Phylogenetic relationships of Myrcia s.l., the most species-rich tree genus in the Brazilian cerrado and Atlantic forests, are reconstructed by analysis, with parsimony and Bayesian inference, of four plastid regions (psbA-trnH intergenic spacer, trnL intron, trnL-F intergenic spacer, and matK exon) and the external and internal transcribed spacer regions of nuclear ribosomal DNA. The resulting phylogenetic hypothesis is evaluated in conjunction with key morphological characters and abiotic factors suggested to have influenced the group’s current distribution. Some lineages identified by previous classifications are supported; others with morphological and/or ecological correspondence are recognized for the first time. Sequence divergence levels provide good resolution of relationships within but not between the main clades of Myrcia s.l. The previously recognized genera Calyptranthes and Gomidesia are shown to be monophyletic, whereas Marlierea is shown not to be; all are nested within paraphyletic Myrcia. A new subgeneric classification is required. An interpretation of the origins of Myrcia s.l. and potential causes of speciation in the group is made on the basis of recently published data and accepted geological events.
Myrtaceae are one of the largest families of flowering plants and are widely distributed in the Neotropics, where they are mainly represented by the tribe Myrteae. Myrteae are the most species-rich tribe of Myrtaceae and include groups with significant ecological and economic importance. Myrteae are considered to be a model group for biodiversity studies in the Neotropics, and so understanding the history of their diversification in this area is extremely important. The last decade has witnessed an increase in macro- and microevolutionary studies of the group, and summarizing this knowledge is now crucial to plan future steps in research on Myrteae. Here we provide the first overview of evolution and diversification studies on Myrteae, highlighting recent advances in understanding their evolutionary history. We discuss biogeography, phylogeny, phylogeography, population genetics, genomics and cytology in light of current knowledge. Finally, we provide perspectives and open hypotheses to be tested in future studies to fill gaps in the evolutionary knowledge of specific groups/taxa in Myrteae.
Background and Aims
Psidium is the 4th largest genus of Myrtaceae in the Neotropics. Psidium guajava is widely cultivated in the tropics for its edible fruit. It is commercially under threat due to the disease guava decline. P. cattleyanum is one of the 100 most invasive organisms in the world. Knowledge of the phylogenetic relationships within Psidium is poor. We aim to provide a review of the biology, morphology and ecology of Psidium, a phylogenetic tree, an infra-generic classification and a list of species.
Methods
Morphological and geographic data were obtained by studying Psidium in herbaria and in the field between 1988 and 2020. Forty-six herbaria were visited personally. A database of c. 6,000 specimens was constructed, and the literature was reviewed. Thirty species (c. 1/3 of the species in the genus) were sampled for molecular phylogenetic inference. Two chloroplast (psbA-trnH and ndhF) and two nuclear (ETS and ITS) regions were targeted. Phylogenetic trees were constructed using Maximum Likelihood (ML; RaxML) and Bayesian Inference (BI; MrBayes).
Key Results
Psidium is a monophyletic genus with four major clades recognized as sections. Section Psidium (ten species), to which P. guajava belongs, is sister to the rest of the genus; it is widespread across the Neotropics. Section Obversifolia (six species; restricted to the Brazilian Atlantic Forest), which includes P. cattleyanum, is sister to the innermost clade composed of sister sections Apertiflora (31 species; widespread but most diverse in the Brazilian Atlantic Forest) + Mitranthes (26 species; widespread in dry forests and probably diverse in the Caribbean). Characters associated to diversification within Psidium are discussed.
Conclusions
Research on prefoliation, colleters, leaf anatomy, leaf physiology, staminal development, placentation, and germination associated to the anatomy of the opercular plug is desirable. Studies are biased towards sections Psidium and Obversifolia, with other sections poorly known.
A goiaba é das mais importantes frutas do Brasil e do mundo, tanto pelo consumo ao natural quanto pela grande demanda da indústria de doces. A fruta possui bom teor de vitaminas A e do complexo B, sendo excepcionalmente rica em vitamina C (ácido ascórbico), chegando a superar o conteúdo desta vitamina nos sucos cítricos. Nos últimos poucos anos a incidência do nematoide Meloidogyne enterolobii Yang & Eisenback, 1983 (= M. mayaguensis Rammah & Hirschmann, 1988)1 (Nematoda: Tylenchida: Meloidogynidae) criou nova e exasperante situação de problema fitossanitário para o cultivo da goiabeira. Hoje, em todo o País, a área infestada pelo nematoide é estimada em 5.000 hectares, distribuída por 16 estados, e o impacto econômico sobre a produção devido ao declínio vegetativo causado por essa espécie de nematoide foi calculado, no ano de 2008, em cerca de 66 milhões de dólares (Pereira et al. 2009).
O uso de cultivares resistentes é o meio mais eficaz e econômico para o controle da ferrugem, mas na literatura foram encontrados raríssimos trabalhos de seleção para essa característica, apesar das indicações de sua importância. Entretanto, para o enfrentamento do M. enterolobii, na cultura da goiabeira, o uso de porta-enxertos resistentes parece ser o caminho mais viável, neste contexto entrando outras espécies de Psidium como genótipos potenciais de resistência a este nematoide.
Embora a goiabeira seja o centro de atenção como frutífera no gênero Psidium, outras espécies cogenéricas nativas ou endêmicas do Brasil, como os denominados araçás, têm potencial para exploração, quer para aproveitamento alimentar (consumo in natura ou transformado industrialmente), quer para outros usos (inclusive através da industria farmacêutica), já que popularmente estas plantas têm tido seus frutos utilizados como alimento e considerável uso medicinal (Franzon et al. 2009). Além do mais, devido à proximidade genética, essas espécies podem ser úteis como porta-enxerto da goiabeira como meio de controlar suas pragas e doenças. Assim, em face do perigo de acentuação de erosão genética (perda de diversidade) causada pela deterioração dos biomas brasileiros e outras áreas onde ocorrem nativamente essas espécies, devido à pressão antrópica, é necessário contínuo empenho de esforços para conservar o germoplasma dessas espécies, criando e mantendo coleções de trabalho e bancos de germoplasma.
