Accelerated in vitro propagation of elite oil palm genotypes (Elaeis guineensis Jacq.) by substituting cytokinin with putrescine

Clonal multiplication of oil palm enables the formation of commercial plantations with higher yield, which is possible through somatic embryogenesis. However, due to different modifications made in the existing protocols to avoid the appearance of the “mantled flower”, the success of this technique has been limited. Thus, this study aimed to apply a cloning protocol, using somatic embryogenesis, to 32 elite oil palm genotypes from a commercial plantation on which cytokinin was substituted with putrescine. All tested genotypes responded positively to callus induction. Moreover, the percentages of responses were differentiated: 65.62% of these genotypes produced embryogenic lines, and 40.62% out of that percentage presented lines with moderate or high multiplication capacity, which is the main factor that enabled the obtaining of clones to form a commercial clonal plantation. The somatic embryogenesis was efficient, making this protocol applicable at a commercial scale, since it allows the obtaining of clones up to 360 days. However, future evaluations on these clones are needed to investigate the appearance of the “mantled flower”.Keywords: Cloning, polyamines, tissue culture, commercial plantatio

Markers prospection for early selection of dieback tolerance in Eucalyptus

A seca de ponteiros do eucalipto é um distúrbio fisiológico caracterizado pelo aparecimento de lesões no ápice dos ramos, comprometendo o crescimento da planta e podendo causar a morte prematura das árvores. O déficit hídrico é relatado como um potencial causador do distúrbio em regiões mais secas por afetar o metabolismo da planta como um todo. Contudo, dados empíricos sugerem que genótipos que apresentam maior tolerância à seca de ponteiros também têm apresentado tolerância ao déficit hídrico. Dessa forma, a identificação de genótipos tolerantes à falta de água pode ser usada como estratégia de seleção de genótipos tolerantes à seca de ponteiros. Diante disso, genótipos com distintos graus de tolerância à seca de ponteiros foram submetidos a tratamentos de déficit hídrico a fim de identificar características que possam ser utilizadas em programas de melhoramento para seleção precoce de genótipos de eucalipto tolerantes a este distúrbio. Para isso foram avaliadas características morfológicas, fisiológicas, nutricionais e metabólicas. Não foram observadas diferenças significativas entre as variáveis fisiológicas avaliadas, entretanto o genótipo tolerante apresentou maior área foliar e diâmetro do caule e níveis mais elevados de Ca em relação ao genótipo suscetível. Com relação às variáveis metabólicas avaliadas, os níveis de serina, asparagina, metionina, ornitina, ácido sinápico, fenilalanina e ácido fumárico permitiram distinguir o genótipo tolerante do suscetível. As variáveis que discriminaram o genótipo tolerante do suscetível estão associadas às diferentes taxas de crescimento, ao investimento em formação de parede celular e lignificação, à ciclagem de nitrogênio através do ciclo da ureia e à produção de compostos fenólicos, características que estão relacionadas à tolerância ao estresse hídrico.The eucalyptus dieback is a physiological disorder characterized by the appearance of lesions on the apex of the branches, compromising the plant growth and can cause premature death of the trees. The water deficit is reported as a possible cause for this disorder in drier regions because it affects plant metabolism as a whole. However, empirical data suggest that genotypes that have increased tolerance to tolerance to dieback also shown tolerance to drought. Accordingly, the identification of genotypes tolerant water deficit can be used as a selection strategy to obtain dieback tolerant genotypes. Thus, genotypes with distinct tolerance to eucalyptus dieback were submitted to water deficit treatments in order to identify characteristics that can be used in breeding programs to early selection of eucalyptus tolerant genotypes. In order to accomplish this we evaluated morphological, physiological, nutritional and metabolic characteristics. The physiological characteristics did not differed significantly, however, the tolerant genotype exhibited higher leaf area and stem diameter and more elevated levels of Ca in relation susceptible genotype. Regarding the metabolic variables evaluated, the levels of serine, asparagine, methionine, ornithine, sinapic acid, phenylalanine and fumaric acid allowed to distinguish the tolerant from susceptible genotype. The variables that discriminate the tolerant genotype from the susceptible one are associated with different rates of growth, investment on cell wall formation and lignification, the cycling of nitrogen through the cycle of urea and on production of phenolic compounds, characteristics that are related to tolerance to water stress.Conselho Nacional de Desenvolvimento Científico e Tecnológic