Some species of Brachiaria, generally tetraploid apomictic varieties, have become important forage grasses in the tropics. Breeding of Brachiaria depends on compatibility with the available apomitic tretraploid cultivars. This paper describes a procedure for chromosome duplication of two Bracharia brizantha diploid sexual accessions, using colchicine treatment of basal segments of in-vitro-grown plants. Explants were cultured on a medium containing 1 mg/l naphthaleneacetic acid, 3 mg/l kinetin and 0.01% colchicine for 48 h and transferred to the same medium without colchicine until shoot regeneration occurred. Regenerated plants were screened by flow cytometry, and chromosome number duplication was confirmed by cytological analysis of root tips.

Chromosome numbers were determined in 29 accessions of wild and semidomesticated Capsicum species from the EMBRAPA Hortaliças (Brazil) germplasm collection. 2 n = 24 was found in C. baccatum var. praetermissum , C. chinense , C. flexuosum and C. parvifolium , while C. buforum , C. campylopodium , C. cornutum , C. schottianum , C. villosum var. villosum and five other native south-eastern Brazilian species not yet taxonomically named all had 2 n = 26 chromosomes. These are the first chromosome number determinations for C. cornutum , C. schottianum , C. villosum var. villosum and the five other Brazilian taxa. Our data confirm published data for C. baccatum var. praetermissum , C. campylopodium , C. chinense , C. flexuosum and C. parvifolium , but not for C. buforum . The prevalence of 2 n = 26 chromosomes among Brazilian species, along with the morphological and ecological characteristics presented by the wild and semidomesticated species occurring in Brazil, form a pattern different from that found in Andean wild and semidomesticated species. This supports the hypothesis that there are two different evolutionary lines in the genus and that the native south-eastern Brazilian species belong to the ancestral Capsicum gene pool.

Chromosome numbers are reported for 127 germplasm accessions of Paspalum notatum maintained by EMBRAPA (Empresa Brasileira de Pesquisa Agropecuária) in two research centers in Brazil. Most accessions were collected in their natural habitats in Southern Brazil. Tetraploidy (2n = 40 chromosomes) was predominant (91% of the accessions studied), confirming previous reports for the species. Eleven accessions with 2n = 20 chromosomes, although collected in the wild, are possibly derived from 'Pensacola' bahiagrass, commonly cultivated in the area since its introduction from the United States in the 60's, for the establishment of permanent pastures.
Números cromossômicos são relatados para 127 acessos de Paspalum notatum mantidos pela EMBRAPA (Empresa Brasileira de Pesquisa Agropecuária) em coleções de germoplasma em dois centros de pesquisa, no Brasil. A maioria dos acessos foi coletada em seus habitats naturais no Sul do Brasil. O nível tetraplóide (2n = 40) é predominante entre os acessos estudados (91%), confirmando ser esta a situação mais normal para a espécie. Onze acessos com 2n = 20 cromossomos, embora coletados na natureza, provavelmente descendem de populações exóticas da grama Pensacola, comumente cultivadas desde sua introdução no Sul do Brasil, vindas dos Estados Unidos, para cultivo de pastagens permanentes, na década de 60

Summary Meiotic behavior was analysed in 30 accessions of 12 wild (Capsicum flexuosum, C. parvifolium, C. buforum, C. campylopodium, C. cornutum, C. pereirae, C. friburgense, C. schottianum, C. villosum var. villosum, and 3 new species) and 2 semi-domesticated (C. baccatum L. var praetermissum and C. chinense) Brazilian Capsicum species. This is the first report on meiosis for most of these taxa. Except for C. baccatum L. var praetermissum, C. chinense, C. flexuosum and C. parvifolium, with 2nϭ24 chromosomes, all other taxa had 2nϭ26 chromosomes, a number previously considered as not common in the genus. Meiotic pairing was generally regular (12 or 13 bivalents) for most of the species analyzed. However, different irregularities such as univalents, multivalents, bridges, chromosome stickiness, unoriented chromosomes, monads, dyads and polyads, among others, were found at both meiosis I and meiosis II, leading to unbalanced final meiotic products but generally not a high pollen sterility. It was not possible to establish with certainty if these irregularities were due to genetic (meiotic mutations) or environmental (such as pests and diseases) causes.

RESUMO -(Contagens cromossômicas em espécies brasileiras dePaspa/um L. (Gramineae».A partir de coletas de germoplasma de espécies de Paspa/um, realizadas nas cinco regiões do Brasil, e subseqüentes análises citológicas em mitose ou meiose, reportam-se os números de cromossomos de 107 acessos, distribuídos por 33 espécies, representativas de 13 dos grupos taxonômicos informais em que o gênero é tradicionalmente subdividido. No grupo Plicatula, sob intensa revisão taxonômica, 27 acessos são citados ainda sem identificação específica. A região sul é muito bem representada, com 65 acessos, seguida pela região centro-oeste, com 33. Os números cromossômicos de P. ji/(fo/ium (2n = 20), P. hartwegiallum (2n = 60), P. rhodopedum (2n = 40) e P. wetlsteillii (2n = 40 e 60) são relatados pela primeira vez. Também são novas as contagens de 2n = 50 para P. p/ellum e para uma forma de P. di/a/atum com anteras amarelas. Encontrou-se um novo acesso diplóide (2n = 20) de P. p/ica/u/um e mais um acesso de P. malldiocallum com 2n = 50, que discrepa do nível hexaplóide, mais freqüente na espécie. Outras contagens confirmam os números já conhecidos, estendendo sua representatividade geográfica.Palavras-chave -Paspa/um, Brasil, gramíneas, número somático, nível de ploidia ABSTRACT -(Chromosome counts in Brazilian species of Paspa/um L. (Gramineae)). Germplasm accessions obtained in collecting missions covering ali the five regions of Brazil were submitted to cytological analysis, either in mitosis or meiosis. Chromosome numbers are reported from 107 accessions of 33 species, representative of 13 ofthe informal taxonomic groups, in which the genus is traditionally divided. In the Plicatula group, under intensive taxonomic investigation, 27 accessions are mentioned without any specific identification. The Southem region is very well represented, with 65 accessions, followed by the West Central region, with 33. The chromosome numbers of P.ji/(fo/ium (2n = 20), P. hartwegiallum (2n = 60), P. rhodopedum (2n = 40) and P. wells/eil1ii(2n = 40 and 60) are reported for the first time. Also new are the reports of 2n = 50 for P. p/ellum and for a yellow-anthered form of P. di/ala/um. The new findings include an additional diploid accession of P. p/icatulum (2n = 20) and a second accession of P. malldiocanum with 2n = 50, a number in disagreement with the most frequent hexaploid levei in this species. Additional data confirm previous counts, thus extending their geographic amplitude.

Difficulties in obtaining new breeding lines of Brachiaria (Trin.) Griseb., an important forage grass in Brazil, are mostly related to differences in ploidy among the accessions, and to apomixis, an asexual mode of reproduction. Usually, sexual accessions are diploid while apomicts are polyploid. Induced tetraploids of Brachiaria brizantha (A. Rich.) Stapf have been successfully obtained and this paper presents the results of a study of their reproductive modes and fertility. Despite frequent meiotic aberrations during microspore development, the induced tetraploids produced viable pollen and produced progeny after controlled self-pollination. Similarly to the original diploid sexual progenitor, embryo sacs of the Polygonum type with confirmed meiotic origin were present in the induced tetraploids suggesting chromosome doubling did not alter the reproductive mode. The embryo sac of the Polygonum type was also observed in progenies obtained after self and open pollination. Nevertheless, embryo sacs of the Polygonum and the Panicum types within the same ovule were observed in some progenies obtained after open pollination, probably having resulted from hybridization with tetraploid, apomictic plants. Indeed, the compatibility of the progeny with tetraploid, apomictic B. brizantha was confirmed by the formation of mature caryopses after controlled pollination. Evidence is presented that the induced tetraploids and their progeny are sexual plants and that they are compatible with natural tetraploid B. brizantha. The induced tetraploids will be useful for analyses of apomictic inheritance as well as in the development of sexual tetraploid lines in Brachiaria breeding programs.

Fourteen germplasm accessions of Paspalum compressifolium native from southern Brazil were cytologically and embryologically analysed . The study revealed that one accession was diploid (2n = 20), twelve were tetraploid (2n = 40) and one was hexaploid (2n = 60) . This is the first report of diploid and hexaploid cytotypes for this species . Studies on microsporogenesis, megasporogenesis, and embryo sac development indicated that the diploid cytotype had regular meiotic behavior and reproduces sexually . Tetraploid cytotype usually had an important proportion of chromosomes that associated as quadrivalents during meiosis and reproduced by mean of aposporous apomixis . The hexaploid cytotype showed irregular meiotic behavior with about one third of the chromosomes associated as multivalents and reproduced by aposporous apomixis . Thus, P. compressifolium could be an agamic complex. Breeding in this complex is possible due to the presence of diploid sexuals which can be treated by colchicine and pollinated by apomicts .

Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argentina, Paraguay and Bolivia. The chromosome numbers 2n=12, 20, 24, 30, 40, 50, 60, 80