-The purpose of this study was to evaluate the meiotic behavior and determine the meiotic index and

ABSTRACT. Coconuts (Cocos nucifera L.) are tropical palm trees that are classified into Tall and Dwarf types based on height, and both types are diploid (2n = 2x = 32 chromosomes). The reproduction mode is autogamous for Dwarf types and allogamous for Tall types. One hypothesis for the origin of the Dwarf coconut suggests that it is a Tall variant that resulted from either mutation or inbreeding, and differences in genome size between the two types would support this hypothesis. In this study, we estimated the genome sizes of 14 coconut accessions (eight Tall and six Dwarf types) using flow cytometry. Nuclei were extracted from leaf discs and stained with propidium iodide, and Pisum sativum (2C = 9.07 pg DNA) was used as an internal standard. Histograms with good resolution and low coefficients of variation (2.5 to 3.2%) were obtained. The 2C DNA content ranged from 5.72 to 5.48 pg for Tall accessions and from 5.58 to 5.52 pg for Dwarf accessions. The mean genome sizes for Tall and Dwarf specimens were 5.59 and 5.55 pg, respectively. Among all accessions, Rennel Island Tall had the highest mean DNA content (5.72 pg), whereas West African Tall had the lowest (5.48 pg). The mean coconut genome size (2C = 5.57 pg, corresponding to 2723.73 Mbp/haploid set) was classified as small. Only small differences in genome size existed among the coconut accessions, suggesting that the Dwarf type did not evolve from the Tall type.

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SummaryThe objective of this study was to evaluate the genetic relationship between five Vasconcellea species (V. cauliflora, V. goudotiana, V. quercifolia, V. monoica, and V. cundinamarcensis) and Carica papaya based on their chromosome features. To do that, five metaphase plates showing well spread and condensed chromosomes were used for the chromosome measurements: the absolute chromosome length (CL) and the lengths of the long (LA) and short (SA) arms. Further, we estimated the ratio between the arms (r), the centromeric index (CI), and the total length of haploid set (TLH). The Total Form index (TF%), the Rec, and the SYi were estimated for symmetry/ asymmetry of the karyotype. Most species show karyotype formulae of nine pairs of metacentric chromosomes (9m) except for V. goudotiana, which has five pairs of metacentric chromosomes and four pairs of sub-metacentric chromosomes (5m+4sm). V. goudotiana had the longest total length of haploid set, whereas V. quercifolia showed the shortest one. Based on the estimates of symmetry/ asymmetry indexes, four species have symmetric karyotype; moreover, V. goudotiana has asymmetric karyotype because it showed the lowest values of Syi and TF% index. The similarity matrix of five parameters for the six species was employed and based on the dendogram four clusters were formed; the first included C. papaya and V. cundinamarcensis, the second cluster was formed by V. monoica and V. cauliflora, the third by V. quercifolia and fourth by V. goudotiana. So, based on chromosome features V. cundinamarcensis, V. cauliflora, and V. monoica are closer to papaya than V. goudotiana.Key words Chromosome, Karyotype, Vasconcellea spp., Carica.The genus Vasconcellea (Caricaceae) was considered for a long time a section within the genus Carica L. (Badillo 1971). However, Badillo (2000, 2001 separated the monospecific section Carica from the section Vasconcellea, based on morphological and genetic evidence (Aradhya et al. 1999) rehabilitating the Vasconcellea section on generic level; since then the genus is formed by 25 species, and the Carica by only one, the cultivated form. Most of the Vasconcellea species has Ecuador as the center of origin or diversification, but V. microcarpa and V. cundinamarcensis are found in the Andes while V. cauliflora is found in Mexico (Badillo 1971). The Vasconcellea species are found at wild or at semi-domesticated conditions and five of them have been placed on

SummaryThe aim of this study was to analyze the meiotic behavior and to estimate the meiotic index and the pollen grain viability of three papaya genotypes, male (Cariflora) and hermaphrodite (Golden and UENF/CALIMAN01). In considering of the fact that the genotypes have different flower sizes, initially, meiotic stages were defined in relation to bud size, and, after that, meiosis was observed in the three genotypes. To observe meiosis, flower buds of different sizes were collected and the length of each bud was measured using graph paper. Once the measurements had been taken, two slides were prepared for each flower bud by squashing the anthers in 1% acetic carmine solution. Slides were observed under an optical microscope and for each bud, size was determined as indicating one of three stages, depending on meiotic phase: pre-meiotic, meiotic stage, or post-meiotic stage. In this way, meiosis was observed for the three genotypes, with particular attention given to possible irregularities in cell division in relation to prophase I. It was observed that there is a relation between flower bud size and meiosis. In general, meiosis was normal, but all genotypes showed some meiotic irregularity, with laggard chromosome being the most common. The Cariflora (male) genotype had a higher frequency of irregularities compared to the hermaphrodite genotypes. The meiotic indices estimated for the Golden, UENF/CALIMAN01, and Cariflora genotypes were 92.6%, 91% and 76.9%, respectively; however, the pollen grain viability, on average, was higher than 90%. In conclusion, the meiotic behavior of male and hermaphrodite genotypes was similar, and all three genotypes had some degree of meiotic abnormality. Papaya (Carica papaya L.) is a diploid species with nine pairs of chromosomes (Damasceno Jr. et al. 2010). It is trioecious with female, male, and hermaphrodite plants, and is considered to be sexually polymorphic. The cultivars are ginoandromonoicas, consisting of female and hermaphrodite plants. Key wordsThe most accepted theory for sex determination in papaya plants is that the sex of plants is determined by a gene with three allelic forms (M 1 , M 2 , m); so, the genotype of the female plants is mm, that of the male is M 1 m and that of the hermaphrodite is M 2 m (Hofmeyr 1938, Storey 1938. However, Liu et al. (2004) formulated another theory that the sex of the plants is due to the presence of an incipient sex chromosome pair differentiated by a small male-specific region of the Y chromosome (MSY). According to Ming et al. (2007) there are two Y chromosomes in papaya, a controlling male designated as Y and the other, controlling the sex hermaphrodite, designated as Y h . The female plant is homogametic with XX chromosome constitution, the male is XY, and the hermaphrodite is XY h .

The objective of this study was to characterize the Brazilian green Dwarf coconut (Cocos nucifera L.) by meiotic analysis and by conventional and differential karyotyping (CMA/DAPI and telomeric FISH). Sixteen pairs of bivalent were observed in the meiosis, indicating that the species is diploid and has 2n=2x=32 chromosomes. Some abnormalities were observed, such as asynchronous division and anaphase with converging fibers. The estimated recombination rate for this species was 17.04, equivalent to an average of 1.06 chiasmata per bivalent. The meiotic index was 79% and the pollen viability was 89.5%, both values considered satisfactory. The conventional karyotyping validated the observed number of chromosomes in the meiosis, i.e., 2n=32 chromosomes. The length of chromosomes ranged from 5.57 µm to 2.13 µm. The karyotype was considered asymmetric, with 11 metacentric and five submetacentric chromosomes pairs. The CMA/DAPI banding revealed terminal blocks in two chromosome pairs (one metacentric and one submetacentric), which was coincident with the nucleolus organizing region (NOR), and allowed the satellite characterization, which had 1.36 µm (chromosome 4) and 0.85 µm (chromosome 7). The telomeric FISH revealed signs only in the terminal region in all chromosomes, suggesting that this species has undergone no structural rearrangement of chromosomes during its evolution and that the telomeres of the coconut chromosomes are Arabidopsis type (TTTAGGG).