No abstract

-The objective of this work was to develop a genetic transformation system for tropical maize genotypes via particle bombardment of immature zygotic embryos. Particle bombardment was carried out using a genetic construct with bar and uidA genes under control of CaMV35S promoter. The best conditions to transform maize tropical inbred lines L3 and L1345 were obtained when immature embryos were cultivated, prior to the bombardment, in higher osmolarity during 4 hours and bombarded at an acceleration helium gas pressure of 1,100 psi, two shots per plate, and a microcarrier flying distance of 6.6 cm. Transformation frequencies obtained using these conditions ranged from 0.9 to 2.31%. Integration of foreign genes into the genome of maize plants was confirmed by Southern blot analysis as well as bar and uidA gene expressions. The maize genetic transformation protocol developed in this work will possibly improve the efficiency to produce new transgenic tropical maize lines expressing desirable agronomic characteristics.

No abstract

-The objective of this work was to evaluate the pathogenicity of 24 Beauveria isolates to Spodoptera frugiperda larvae, and characterize them molecularly through rDNA-ITS sequencing and RAPD markers. Sequencing of rDNA-ITS fragments of 570 bp allowed the identification of isolates as B. bassiana or B. brongniarti by sequence comparison to GenBank. Sixty seven polymorphic RAPD fragments were capable to differentiate 20 among 24 Beauveria isolates, grouping them according to the derived host insect and to pathogenicity against maize fall armyworm larvae. Three RAPD markers were highly associated to the pathogenicity against S. frugiperda, explaining up to 67% of the phenotypic variation. Besides identification and molecular characterization of Beauveria isolates, ITS sequence and RAPD markers proved to be very useful in selecting the isolates potentially effective against S. frugiperda larvae and in monitoring field release of these microorganisms in biocontrol programs.Index terms: Spodoptera frugiperda, entomopathogenic fungi, RAPD, rDNA-ITS. Caracterização molecular e virulência de isolados de Beauveria spp. contra a lagarta-do-cartuchoResumo -O objetivo deste trabalho foi avaliar a patogenicidade de 24 isolados de Beauveria contra larvas de Spodoptera frugiperda e caracterizá-los molecularmente, por meio do seqüenciamento da região ITS do rDNA e de marcadores RAPD. O seqüenciamento de fragmentos de 570 pares de bases, da região ITS do rDNA, possibilitou a identificação dos isolados como B. bassiana e B. brongniarti, pela comparação com seqüências depositadas no GenBank. Sessenta e sete fragmentos polimórficos de RAPD foram capazes de diferenciar 20 entre 24 isolados de Beauveria, e agrupá-los de acordo com o inseto hospedeiro e com a patogenicidade contra a lagarta-do-cartucho do milho. Os marcadores RAPD foram altamente associados à patogenicidade contra S. frugiperda e explicaram até 67% da variação fenotípica. Além da identificação e caracterização molecular de isolados de Beauveria, o seqüenciamento da região ITS, aliado aos marcadores RAPD, é útil na seleção de isolados potencialmente eficazes contra larvas de S. frugiperda e no monitoramento de liberações desses microrganismos em programas de biocontrole.Termos para indexação: Spodoptera frugiperda, fungo entomopatogênico, RAPD, rDNA-ITS.

Foram estudados os efeitos da concentração de sais, doses de sacarose e freqüência de renovação do meio de cultura para o desenvolvimento de eixos embrionários de cupuaçu (Theobroma grandiflorum Schum.). Testaram-se 2 concentrações de sais MS (100 e 50%), 2 níveis de sacarose (1,5 e 3%) e 3 freqüências de renovação dos meios (sem renovação, renovação aos 30 e aos 60 dias), com os meios acrescidos de ANA (0,5 mg/L) e BAP (0,3 mg/L.), semi-solidificados com ágar 0,7% e pH 5,7. Observou-se que a utilização do meio MS na concentração de sais completa, com a adição de 3% de sacarose e renovações do meio em intervalos de 30 dias, apresentou melhor desenvolvimento dos eixos embrionários.

Phosphorus (P) stress responsive genes have been identified and characterized, including the highaffinity phosphate transporter AtPHT1;4 from Arabidopsis thaliana. This gene encodes a membrane protein that is primarily expressed in roots under phosphorus deficiency. A 2.3-kb promoter region from AtPHT1;4 has been fused with the β-glucuronidase (GUS) encoding gene and introduced into maize via biolistic bombardment to evaluate its spatiotemporal activity in a heterologous system. AtPHT1;4::GUS expression is detected preferentially in transgenic maize roots under P deficiency. Further analysis of transgenic plants has also revealed that GUS activity is higher in roots than in leaves by about sixfold. These results demonstrate the ability of AtPHT1;4 promoter to direct expression of the reporter gene in a monocot root system under P stress. This property of AtPHT1;4 promoter makes it useful to engineer maize plants to modify the soil's rhizosphere and increase efficiency of P acquisition under P stress conditions.

No abstract

No abstract