Plant regeneration protocols for sugarcane GT54-9(C9) cultivar were developed for direct organogenesis and indirect somatic embryogenesis, using young leaf segments as explants by studying the influence of different concentrations and types of cytokinin and auxin hormones. For the callus formation from young leaves, a medium containing 4mg/l 2,4-D was found very effective. For embryo formation, MS medium supplemented with 1mg/l Kin and 0.5 mg/l 2,4-D was used. While in the case of direct organogenesis protocol, the medium containing 1mg/l BAP and 2mg/l NAA was the best for direct shoot formation. Data showed that the best shoot regeneration and elongation medium for direct organogenesis and indirect somatic embryogenesis was obtained on medium with 2 mg/l Kin and 0.1 mg/l BAP. Root induction was best performed on 2mg/l NAA and complete plantlets were hardened in the greenhouse before transferring to the field for further evaluation. For transformation, young leaf segments of sugarcane from the cultivar GT54-9(C9) were inoculated and co-cultivated with Agrobacterium tumefaciens strain LB4404 harboring the binary vector pISV2678 with the bar and the gus-intron genes. The obtained putative transgenic plantlets were able to grow under bialaphose containing medium. Stable integration of the bar gene into the plant genomes was tested by PCR and Southern blot hybridization. Histochemical assay and leaf painting analysis were carried out to study the expression of the gus and bar genes in transgenic plants, respectively. The results indicated that the direct organogenesis produced a higher yield of regenerated plants (22% more) within shorter time (4 weeks less). Therefore, this method is recommended for sugarcane regeneration and for further use in genetic transformation via A. tumefaciens with desired genes.

The sugarcane (Saccharum X officinarum) is one of the most important crops used to produce sugar and raw material for biofuel in the world. One of the main causes for sucrose content and yield losses is the attack by insect. In this investigation, cry1Ac gene was introduced into sugarcane variety GT54-9 (C9) using the Agrobacterium tumefaciens transformation method for transgenic sugarcane production presenting insect-resistance. The A. tumefaciens strain GV1303 including pARTcry1Ac vector was used for the production of transformed sugarcane. The Bacillus thuringiensis cry gene were successfully used to produce transgenic plants used for the improvement of both agronomic efficiency and product quality by acquiring insect resistance. PCR and Southern hybridization techniques were used to confirm the cry1Ac gene incorporation into sugarcane genome. Transformation percentage was 22.2% using PCR analysis with specific primers for cry1Ac and npt-II (Neomycin phosphotransferase) genes. The expression of cry1Ac gene was determined using reverse transcriptase polymerase chain reaction (RT-PCR), QuickStix test, and insect bioassays. Bioassays for transformed sugarcane plants showed high level of toxicity to Sesamia cretica giving 100% mortality of the larvae. Sugarcane insect resistance was improved significantly by using cry1Ac gene transformation.

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A dose-effect relationship has been established for high-energy neutrons (maximum energy 600 MeV) within a dose range of 0.2 to 80 cGy and for low-energy neutrons produced by a 252 Cf source (mean energy 2.35 MeV) for doses between 0.2 and 5 cGy. The number of micronuclei produced by neutron radiations was found to increase linearly with dose. The Relative Biological Effectiveness (RBE) values calculated using 6 °Co radiation as a reference were, in the high-dose ·region, 4.7 ± 0.4 and 11.8 ± 1.3 for the high-and low-energy neutrons, respectively. At doses below 1 cGy constant values of 25.4 ± 4.4 and 63.7 ± 12 were reached for the respective neutron energies. (Submitted to Int. J. Radiat. Biol.) *) Present address: Rad. Environ. Lab., Brookhaven National Laboratory, Upton, NY, USA.-iii-RESUME Nous avons etabli des courbes d'effet de dose pour des neutrons de haute energie (energie max.: 600 MeV) pour des doses comprises entre 0,2 et 80 cGy, et pour des neutrons de basse energie, provenant d'une source de 252 Cf (energie moyenne: 2,35 MeV), pour des doses entre 0,2 et 5 cGy. Le nombre de micronoyaux augmente lineairement avec la dose. Aux hautes energies, les valeurs de l'efficacite bio-logique relative (EBR) calculee en utilisant les rayons y du 60 co comme radiations de reference etaient de 4,7 ± 0,4 et 11,8 ± 1,3 respectivement pour les neutrons de haute et de basse energie. A des doses inferieures a 1 cGy, nous avons trouve, pour les deux energies, des valeurs constantes de l'EBR: 25,4 ± 4,4 et 63,7 ± 12. ABRISS Eine Dosis-Effekt-Beziehung wurde aufgestellt fur hochenergetische Neutronen (max. Energie 600 MeV) bei Bestrahlungsdosen von 0,2 bis 80 cGy und.fur Neutronen niederer Energien (mittlere Energie 2,35 MeV), die aus einer 252 Cf Quelle produziert wurden, mit Bestrahlungsdosen zwischen 0,2 und 5 cGy. Es zeigte sich, dass die Zahl der durch die Neutronenbestrahlung produzierten Mikrokerne linear mit der Dosis ansteigt. Die Werte fur Relative Biologische Wirksamkeit (RBW) wurden unter Bezugnahme auf Resultate mit 60 co Gammastrahlen berechnet und betrugen bei hohen Bestrahlungsdosen 4,7 ± 0,4 fur hochenergetische Neutronen und 11,8 ± 1,3 fur Neu-tronen niederer Energien. Bei Bestrahlungsdosen unter 1 cGy ergaben sich fur beiden Neutronenenergien konstante Werte von 25,4 ± 4,4 bzw. 63,7 ± 12.