Luiz Alberto Rocha Batista

Seleção de descritores na caracterização de germoplasma de Paspalum sp. por meio de componentes principais

Foram avaliados 15 descritores reprodutivos, 22 vegetativos e 21 agronomicos, em que os agronomicos compreenderam sete descritores para a avaliacao anual, sete descritores para a avaliacao de inverno e sete descritores para a avaliacao de verao, com o objetivo de selecionar os melhores descritores botânico-agronomicos para caracterizar acessos das especies Paspalum guenoarum e Paspalum plicatulum. Utilizou-se a analise de componentes principais para descartar os descritores considerados redundantes ou nao-discriminantes. Este metodo permitiu reducao de 53, 68 e 43% dos descritores reprodutivos, vegetativos e agronomicos, respectivamente, do conjunto inicialmente considerado. Foi possivel selecionar, por intermedio desta tecnica, oito descritores, considerados mais importantes na descricao da variabilidade presente na colecao de acessos do germoplasma estudado.

Chromosome numbers and meiotic behavior of some Paspalum accessions

Chromosome number and meiotic behavior were evaluated in 36 Brazilian accessions of the grass Paspalum (which had never previously been analyzed) to determinate which accessions might be useful in interspecific hybridizations. The analysis showed that one accession of Paspalum coryphaeum was diploid (2n = 2x = 20) and one accession of Paspalum conspersum hexaploid (2n = 6x = 60), the remaining 34 accessions being tetraploid (2n = 4x = 40). The pairing configuration was typical for the ploidy level i.e. in the diploid, chromosomes paired as 10 bivalents, in tetraploids as bi-, tri- and quadrivalents, and in hexaploid as 30 bivalents. A low frequency of meiotic abnormalities (less than 10%) was observed in the diploid, hexaploid and some tetraploid accessions, although the majority of tetraploid accessions showed a high frequency of meiotic irregularities. The use of accessions with a low frequency of meiotic abnormalities in breeding programs is discussed.

Chromosome elimination in Paspalum subciliatum (Notata group)

Abstract This paper reports the occurrence of chromosome elimination during microsporogenesis in a Brazilian accession of Paspalum subciliatum. The accession was tetraploid (2n=4x=40) and meiosis was normal until diakinesis, with 20 regularly distributed bivalents. Starting at metaphase I, meiosis was very peculiar. In this phase, while ten bivalents were clustered in the equatorial plate, the other ten were still dispersed in the cytoplasm. In anaphase I the chromosomes showed different abilities to migrate to the poles. While one genome reached the poles in telophase I, the laggard was in metaphase or anaphase and was engulfed by extra nuclei. In the second division, behavior was the same. Our results show clear asynchrony in cell cycle, especially in some meiotic phases. Unfortunately we cannot explain the causes of the phenomenon, but this event shows once more that chromosome elimination serves as an incompatibility barrier preventing divergent genomes from coexisting in the same cellular system. The chromosome elimination affected pollen fertility but did not impair seed viability.

Failure of cytokinesis and 2n gamete formation in Brazilian accessions of Paspalum

Cytological analysis on 112 Brazilian accessions of Paspalum showed that 52 were affected by failure of first or second cytokinesis during microsporogenesis. When the failure of cytokinesis occurred only in the first division and in the second division the cytokinesis was normal, a dyad of microspores was formed. In most of them the two cells remained binucleate, but in some a restitutional nucleus was observed. When the first division was normal and the failure of cytokinesis occurred only in the second division, dyads and triads were observed. A restitutional nucleus in one or both cells of the dyad, or in the binucleate cell of the triad was also observed. The percentage of dyads and triads varied among accessions, reaching 15.75 of the sporads in some. The absence of cytokinesis indicates the possibility that the widespread occurrence of polyploidy in the genus Paspalum originates from 2n pollen grains.

Chromosome number in germplasm accessions of Paspalum (Plicatula group) from different regions in Brazil

We determined the chromosome number of 52 accessions of Paspalum from the germplasm collection of the Centro de Pesquisa de Pecuária do Sudeste (CPPSE/EMBRAPA) originating from different regions in Brazil. All accessions belonged to the Plicatula group, 13 of them being P. plicatulum, three P. guenoarum, two P. yaguaronense, two P. compressifolium, one P. atratum, and 31 still unidentified Paspalum sp. Except for a P. yaguaronense accession that presented 2n=60, all the remaining ones presented 2n=40 chromosomes. This is the first report of the chromosome number of P. atratum. Considering that the basic number for most species in the genus Paspalum is ×=10, the accessions analyzed are tetraploids (2n=4×=40) and hexaploids (2n=6×=60).

An original meiotic mutation in Paspalum regnellii

Abstract Cytogenetic studies carried out over a period of 2 consecutive years on a native Brazilian accession of Paspalum regnellii (2n=40) revealed a meiotic mutation that has not been previously reported for any other species. Among 13 inflorescences investigated during the first collection year, three presented anomalous meiotic behavior starting from metaphase I. At the beginning of this phase, the chromosomes occupied the entire equatorial plate in a membrane-to-membrane arrangement, and the spindle fibers, which were clearly visible, did not converge towards the poles. Degeneration of spindle fibers occurred at the end of metaphase I. Chromosome segregation did not occur and the bivalents were left scattered at random in the cytoplasm. Remnants of chromosome fibers could be seen close to the centromere during this stage. The bivalents gave origin to micronuclei in telophase I, with extremely wide variations in number and size among cells. With the absence of spindle formation during meiosis II, metaphase and anaphase II were not observed. Second cytokinesis occurred in prophase II cells after the occurrence of first cytokinesis. The final product of meiosis was completely abnormal, with a predominance of polyads with microspores of different sizes that resulted in abortive pollen grains. In the affected inflorescences, all microsporocytes presented this anomaly, which caused total sterility.

Biomassa e composição química de genótipos melhorados de espécies medicinais cultivadas em quatro municípios paulistas

The objective of this work was to evaluate the production and chemical constituents of selected genotypes of Artemisia annua, Cordia verbenaceae, Phyllanthus amarus and Mikania laevigata cultivated in Altinopolis, Campinas, Jales and Sao Carlos. Biomass variations, and qualitative and quantitative differences in plants chemical composition are observed among the locations, with higher values of interesting substances being detected in Jales.

Caracterização preliminar e seleção de germoplasma do gênero Paspalum para produção de forragem

ABSTRACT - With the objective to increase the germoplasm availability for forage production, 215 accessions of the genus Paspalum collected in different regions and introduced at the Embrapa Southeast - Cattle Research Center, located at the central region of the Sao Paulo state. These accessions were evaluated and selected based on their yields in the first year, of dry matter from the vegetative development throughout the year and during the period of high and low rain preciptation. The accesses were evaluated in three experiments using a randomized blocks desing with two replicates. Dry matter production was obtained and analyzed from four cuts during the year (DMYEAR), which were representative of the development during the spring/summer (DMRAINY) and autumn/winter (DMDRY) seasons. The individual analyses, per experiment, showed variability among the accessions for the evaluated characteristics. The analyses as a set for the experiments was analyzed by the methodology of total analyses of the experiments in a randomized blocks desing with a common treatments (controls - Brachiaria decumbens and Andropogon gayanus cv. Baeti). Due to the significant variance interaction among common treatments by experiments, the selection was done for each experiment by choosing the accesses that presented yields at least equivalent to the worst control. Fifty-eight accessions were selected (27%), which demonstrated the possibility of obtaining cultivars with dry matter yields equal or better than the controls.ABSTRACT – With the objective to increase the germoplasm availability for forage production, 215 accessions of the genus Paspalum collected in different regions and introduced at the Embrapa Southeast – Cattle Research Center, located at the central region of the Sao Paulo state. These accessions were evaluated and selected based on their yields in the first year, of dry matter from the vegetative development throughout the year and during the period of high and low rain preciptation. The accesses were [...]

Chromosome number and microsporogenesis in Paspalum maritimum (caespitosa group; gramineae)

Despite of economic importance of the genus Paspalum, little or no cytologic information is available for many species. This is the first report about chromosome number and meiotic behavior for P. maritimum. The three accessions collected in Amapa State (North Region of Brazil) were tetraploid (2n=4x=40) with the chromosomes associating predominantly as bivalents. The low frequency of multivalents suggested that they were segmental allotetraploids. All accessions showed a low rate of meiotic irregularities, and as a consequence the pollen fertility was high. The results suggested that these accessions presented potential for use in a hybridization program.

Caracterização de Linhagens Puras Selecionadas de Guandu (Cajanus cajan (L.) Millsp) (1)

The purpose of this work was to characterize morphologically seventeen previously selected pigeon-pea lines that went, after selection, through processes of self pollination, selection and multiplication, to obtain pure lines. It also had the objectives of checking the efficiency of the descriptors and describing its vegetative cycle. It was possible to perform the description and to conclude that the seventeen lines have distinct characteristics and can easily be identified by these traits. The used descriptors could properly perform this task and it was concluded that they can be simplified. The seeds of the commercial lines used in this work had mechanical mixture.