The genetic relationships among 81 maize accessions consisting 79 landraces and two improved varieties, maintained by farmers in southern Brazil were investigated using Random Amplified Polymorphic DNA (RAPD). Thirty-two highly informative primers amplified 255 markers of which 184 (72.2%) were polymorphics. Based on the RAPD markers, a dendrogram was constructed using the UPGMA method. The range of genetic similarity was from 0.78 to 0.91. The molecular data grouped the accessions into two main clusters, which were correlated according to kernel colors. Small clusters were seen associated to characteristics, such as kernel morphology. The analysis of the molecular data revealed that maize management adopted by small-scale farmers has contributed to the maintenance of genetic variability and since field isolation is a regular practice, variety identities have been preserved. These results will be useful to establish and maintain a germplasm collection of landrace maize and may guide us in designing strategies that maximize the utility of maize genetic resources.

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Sugarcane is cultivated in tropical and subtropical regions where cold stress is not very common, but lower yields and reduced industrial quality of the plants are observed when it occurs. In our efforts to enhance cold tolerance in sugarcane, the gene encoding the enzyme isopentenyltransferase (ipt) under control of the cold inducible gene promoter AtCOR15a was transferred via biolistic transformation into sugarcane (Saccharum spp.) cv. RB855536. Semiquantitative RT-PCR using GAPDH encoding glyceraldehyde-3-phosphate dehydrogenase as the normalizer gene showed the increased expression of the ipt gene under cold stress. The detached leaves of genetically modified plants subjected to low temperatures showed visible reduction of leaf senescence in comparison to non-transgenic control plants. Induced overexpression of ipt gene also enhanced cold tolerance of non-acclimated whole plants. After being subjected to freezing temperature, leaf total chlorophyll contents of transgenic plants were up to 31 % higher than in wild type plants. Also, lower malondialdehyde content and electrolyte leakage indicated less damage induced by cold in transgenic plants. Thus, the expression of ipt driven by the stress inducible COR15a promoter did not affect plant growth while providing a greater tolerance to cold stress.

O objetivo deste estudo foi avaliar 11 linhagens e três cultivares de feijão-vagem de crescimento determinado, quanto a divergência genética e o potencial agronômico nas condições de Londrina e Cambé, Paraná, Brasil. O experimento foi em blocos ao acaso, com três repetições, e parcelas constituídas por quatro fileiras com 4,0m de comprimento e 0,5m entre fileiras. Oito caracteres foram avaliados e submetidos às análises de variância individual, conjunta e multivariada. Houve diferenças significativas entre os genótipos para as características consideradas. A interação genótipo x locais não foi significativa para produção e diâmetro de vagem, revelando um desempenho consistente destas características e dos genótipos nestes locais. A divergência genética observada entre os genótipos de feijão-vagem foi quantificada pelos três primeiros componentes principais e três primeiras variáveis canônicas que explicaram 90,2% e 88,7% da variação total disponível, respectivamente. As características morfológicas de vagens e produção de sementes foram agrupadas nos dois primeiros componentes e as características relacionadas à produção de vagens foram agrupadas no terceiro componente, para a análise de componentes principais. Os dendrogramas, baseados nas distâncias euclidianas a partir dos escores dos três principais componentes principais e variáveis canônicas, separaram os genótipos em cinco e sete grupos respectivamente. As cultivares ficaram representadas em diferentes agrupamentos. As linhagens mais promissoras, HAB 402, HAB 415 e HAB 417, pertencem ao mesmo grupo e são dissimilares em relação às cultivares testadas.