Relationship between pollen morphology and chromosome numbers in Brazilian species of Lippia L. (Verbenaceae).

The pollen morphology and exine structure of 17 species of Lippia L. were investigated in this work using light and scanning electron microscopy. Among the species studied, 14 showed tricolporate pollen grains, two had tri- and tetracolporate pollen grains and a single species exhibited, only tetracolporate pollen. The amb ranged from triangular to square, and the shape varied from oblate-spheroidal to prolate-spheroidal. Three different types of exine ornamentation were observed: psilate, scabrate and perforate. In addition to morphological data, we found positive association between the chromosome numbers and size of pollen grains, and also between the length and width of the colpi. The results indicate that the characteristics of pollen grains in Lippia may be used as an additional taxonomic character of the genus.

Karyotype analysis, DNA content and molecular screening in Lippia alba (Verbenaceae).

Cytogenetic analyses, of pollen viability, nuclear DNA content and RAPD markers were employed to study three chemotypes of Lippia alba (Mill.) (Verbenaceae) in order to understand the genetic variation among them. Different ploidy levels and mixoploid individuals were observed. This work comprises the first report of different chromosome numbers (cytotypes) in L. alba. The chromosome numbers of La2-carvone and La3-linalool chemotypes suggested that they are polyploids. Flow cytometric analysis showed an increase of nuclear DNA content that was not directly proportional to ploidy level variation. A cluster analysis based on RAPD markers revealed that La3-linalool shares genetic markers with La1-citral and La2-carvone. The analysis showed that the majority of genetic variation of La3-linalool could be a consequence of ixoploidy. ur data indicates that sexual reproduction aong those three chemotypes is unlikely and suggests the beginning of reproductive isolation. The results demonstrated that chromosome analysis, nuclear DNA content estimation and RAPD markers constitute excellent tools for detecting genetic variation among L. alba chemotypes.

Karyotype analysis, DNA content and molecular screening in Lippia alba (Verbenaceae)

Cytogenetic analyses, of pollen viability, nuclear DNA content and RAPD markers were employed to study three chemotypes of Lippia alba (Mill.) (Verbenaceae) in order to understand the genetic variation among them. Different ploidy levels and mixoploid individuals were observed. This work comprises the first report of different chromosome numbers (cytotypes) in L. alba. The chromosome numbers of La2-carvone and La3-linalool chemotypes suggested that they are polyploids. Flow cytometric analysis showed an increase of nuclear DNA content that was not directly proportional to ploidy level variation. A cluster analysis based on RAPD markers revealed that La3-linalool shares genetic markers with La1-citral and La2-carvone. The analysis showed that the majority of genetic variation of La3-linalool could be a consequence of ixoploidy. ur data indicates that sexual reproduction aong those three chemotypes is unlikely and suggests the beginning of reproductive isolation. The results demonstrated that chromosome analysis, nuclear DNA content estimation and RAPD markers constitute excellent tools for detecting genetic variation among L. alba chemotypes.

Análises citogenéticas, de viabilidade do pólen, do conteúdo de DNA nuclear e marcadores RAPD foram empregadas no estudo de três quimiotipos de Lippia alba (Mill.) (Verbenaceae) visando contribuir para o entendimento da variação genética entre os mesmos. Diferentes níveis de ploidia e indivíduos mixoploides foram observados. Este trabalho compreende o primeiro relato de diferentes números cromossômicos (citótipos) em L. alba. Os números cromossômicos dos quimiotipos La2-carvona e La3-linalol sugere que eles seja poliploides. A análise da citometria de fluxo mostrou um aumento do conteúdo de DNA nuclear que não foi diretamente proporcional à variação no nível de ploidia. A análise de agrupamento baseada nos marcadores RAPD demonstrou que La3-linalol compartilha marcadores genéticos com La1-citral e La2-carvona. A análise mostrou que a maior parte da variação genética de La3-linalol pode ser consequência da mixoploidia. Nossos dados indicam que a reprodução sexual entre os três quimiotipos parece improvável, sugerindo o início de isolamento reprodutivo. Os resultados demonstraram que a análise cromossômica, a quantificação do DNA nuclear estimado e os marcadores RAPD constituem excelentes ferramentas para detecção de variação genética entre quimiotipos de L. alba.

Conidial anastomosis tubes in Colletotrichum.

We describe the occurrence of special kinds of hyphae that create anastomoses directly between conidia. They can be found both in the laboratory and on infected plants. They first appear within asexual fruiting bodies approximately 15 days after conidiation has begun leading to the appearance of chains of connected conidia. Coincident with this we demonstrate in Colletotrichum lindemuthianum nuclear dynamics, including fragmentation, with cytoplasmic flow and passage of nuclei and organelles between conidia through the anastomosis tubes. We propose that conidial anastomosis tubes play an important role in the life cycle of these fungi.

Conidial anastomosis fusion between Colletotrichum species.

Colletotrichum lindemuthianum is a pathogen of the common bean plant (Phaseolus vulgaris) causing anthracnose. Large numbers of isolates can rapidly arise with different genetic and chromosomal compositions but their origin is unknown since sexual fruit bodies have only been found in the laboratory. We have recently described the occurrence of special kinds of hyphae that create anastomoses directly between conidia. In this work we show that conidial anastomoses can occur between two different Colletotrichum species. The implications of this observation on the generation of genetic diversity in these species are discussed.

Template preparation for rapid PCR in Colletotrichum lindemuthianum

Isolation of DNA for PCR is time-consuming and involves many reagents. The aim of this work was to optimise a rapid and easy PCR methodology without previous DNA isolation. Different strains of the phytopathogenic fungus Colletotrichum lindemuthianum were used. Protoplasts were generated using lytic enzymes under high incubation temperatures using different methodologies to obtain the template. A rapid (10 minute) methodology was successful for smaller amplicons (<750 bp).