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.
Highlights
The enormous progress achieved by molecular and cellular biology in recent years has generated a new understanding for many basic genetic concepts and biochemical mechanisms, allowing the emergence of improved strategies for breeding and cultivar development
Among the new generated technologies, plant transformation is an important tool for the genetic manipulation and improvement of crop species (Carneiro et al, 2000)
Seeds used in these experiments were from the L1345 and L3 tropical maize inbred lines, with high capacities for plant regeneration (Carvalho et al, 1997) and favorable agronomic characteristics
Summary
The enormous progress achieved by molecular and cellular biology in recent years has generated a new understanding for many basic genetic concepts and biochemical mechanisms, allowing the emergence of improved strategies for breeding and cultivar development. Among the new generated technologies, plant transformation is an important tool for the genetic manipulation and improvement of crop species (Carneiro et al, 2000). Most studies on maize transformation have utilized genotypes adapted to temperate zones (Frame et al, 2000). The application of this technology in the tropics was delayed due to additional steps of backcrossing tropical lines with transgenic temperate lines. To accelerate the process it is essential to develop technologies for the
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