Flowering is essential in any breeding programme, particularly in genetic introgression programmes in which flowering synchronism is required. In this work, 16 sugarcane genotypes were evaluated using three different flowering-inductive photoperiod treatments (30 s, 45 s, and 1 min of a daily photoperiod decrease from 12 h 55 of light). Each genotype was planted in 43 L pots (equal proportion of soil, sand, and substrate) with three tillers per pot. Plants with 4 to 6 internodes were placed in a photoperiod facility with three controlled chambers, each chamber containing all 16 genotypes (one treatment per chamber). The temperature range (21˚C to 32˚C) and humidity were the same for all of the treatments. The flower induction started in September 2010 and ended in April 2011. The plant elongation and flag leaf and inflorescence emergence were recorded and the pollen viability was evaluated by using the iodine staining method. The photoperiod facility provided suitable conditions for flowering, as the plants in the three treatments successfully flowered. The genotypes in the three treatments behaved differently in relation to the date of panicle emergence, with the treatment of 45 s showing better results. The results here presented contribute to synchronise flowering for desired sugarcane crosses, particularly those from introgression programmes between commercial cultivars and species from the Saccharum complex.
In order to identify new sources of resistance for future introgression crosses, wild sugarcane germplasm was screened for resistance to Sugarcane mosaic virus (SCMV) under high inoculum pressure. Evaluation of symptoms by a grade scale associated with serological diagnostic by plate-trapped antigen-enzyme-linked immunosorbent assay (PTA-ELISA) with a specific antiserum were performed in 43 accessions, encompassing Saccharum officinarum, S. barberi, S. spontaneum and S. robustum species and hybrids. Differential patterns of resistance and susceptibility were observed among the Saccharum species, with S. officinarum followed by S. robustum accessions showing higher susceptibility, whereas S. barberi and S. spontaneum had the most resistant accessions. The results indicate that accessions IS76
RESUMO -(Caracterização citogenética em Anadenanthera colubrina (Vell.) Brenan (Mimosoideae) e Guazuma ulmifolia Lam. (Sterculiaceae)). Análises cariotípicas são importantes ferramentas de auxílio aos estudos de relações taxonômicas dentro dos grupos vegetais. Espécies arbóreas nativas encontradas no cerrado brasileiro têm sido pouco analisadas do ponto de vista citogenético e citotaxonômico. Com o objetivo de determinar o número cromossômico diplóide, a biometria e a morfologia cromossômica de Anadenanthera colubrina (angico-branco) e Guazuma ulmifolia (mutambo), sementes dessas espécies foram coletadas no município de Três Lagoas, Mato Grosso do Sul, Brasil. A utilização de 8-hidroxiquinoleína 0,003M a 36°C, durante três horas possibilitou a separação cromossômica. Coloração Giemsa 2% por três minutos permitiu o estudo cariológico. A classifi cação cromossômica foi baseada no índice centromérico. Anadenanthera colubrina possui 2n = 26 cromossomos com comprimento cromossômico médio de 1,349 μm ± 0,017 e formulação cariotípica 8SM + 14M + 2T + 2AC. Guazuma ulmifolia apresenta 2n = 16 cromossomos com comprimento médio de 1,225 μm ± 0,023 e formulação cariotípica 4SM + 10M + 2T. Esses resultados podem subsidiar estudos de taxonomia, de manipulação cromossômica, bem como auxiliar na produção de progênies híbridas em programas de melhoramento. Palavras-chave: cariótipo, índice centromérico, número cromossômico, mitose ABSTRACT -(Cytogenetic characterization in Anadenanthera colubrina (Vell.) Brenan (Mimosoideae) and Guazuma ulmifolia Lam. (Sterculiaceae)). Karyotype analyses are important aid tools for taxonomic relationship studies. Native arboreal species found in the Brazilian "cerrado" have been poorly analyzed cytogenetically and cytotaxonomically. To determine diploid chromosome number, biometry and chromosome morphology of Anadenanthera colubrina ("angico-branco") and Guazuma ulmifolia ("mutambo"), seeds of these species were collected in Três Lagoas municipality, Mato Grosso do Sul, Brazil. The use of 8-hydroxiquinoleine 0.003M at 36°C, for three hours caused chromosome separation. Giemsa coloration 2% for three minutes allowed the karyological study. Chromosome classifi cation was based on the centromeric index. Anadenanthera colubrina has 2n = 26 chromosomes with chromosome medium length of 1.349 μm ± 0.017 and karyotype formulation 8SM + 14M + 2T + 2AC. Guazuma ulmifolia has 2n = 16 chromosomes with medium length of 1.225 μm ± 0.023 and karyotype formulation 4SM + 10M + 2T. These results can subsidize taxonomic and chromosomic manipulation studies, as well as the production of hybrid progenies in improvement programs.
-The hypothesis assumed was the existence of biotypes within populations, which has been the cause of difficulties in itchgrass control by farmers. For that, the genetic variability of three populations of Rottboellia cochinchinensis in sugarcane fields in the state of São Paulo was investigated by using the Amplified Fragment Length Polymorphism (AFLP) technique. Six primers were used to obtain molecular characterization data. AFLP gels were analyzed based on marker presence (1) and absence (0). Using NTSYs (Numerical Taxonomy and Multivariate Analysis System) software, the genetic similarity was calculated by the Jaccard coefficient and, from that, a dendrogram was built through the UPGMA (Unweighted Pair Group Method Arithmetic averages) method, besides determining the isopolymorphic marks. The average genetic similarities seen in the region was 0.742 for Igarapava, 0.793 for Mococa and 0.808 for Piracicaba. Between regions it was 0.730 (Igarapava vs Mococa), 0.735 (Mococa vs Piracicaba) and 0.694 (Igarapava vs Piracicaba). In line with the dendrogram, it is possible to detect the formation of two groups, one with 8 plants from Igarapava and Mococa and the other with 21 plants from Igarapava, Mococa and Piracicaba, as well as the presence of 1 discriminant individual from Piracicaba. It can be concluded that the genetic similarity among itchgrass populations from the state of São Paulo was high (72%), which denotes that the difficulties in chemical management are not only due to different biotypes but also due to other characteristics linked to tolerance of the species to herbicides. However, biotype existence cannot be discarded because of the polymorphic marks generating 22% average genetic variability.Keywords: Saccharum spp., itchgrass, chemical management, AFLP. (0) RESUMO -Considerando a hipótese de que a dificuldade de controle observada pelos produtores com a espécie do gênero Rottboellia pode ser pela existência de biótipos nas populações, objetivouse estudar a variabilidade genética entre três populações de R. cochinchinensis em regiões de cana-de-açúcar do Estado de São Paulo, utilizando-se da técnica Amplified Fragment Lenght Polimorfism (AFLP). Para a caracterização molecular, seis iniciadores foram utilizados para obtenção dos dados. Os géis de AFLP foram analisados com base na presença (1) e na ausência
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