Abstract
Despite production of fertile transgenic plants through transformation mediated by Agrobacterium tumefaciens, transformation efficiency is still low. Apart from plant genotype, Agrobacterium strains, plasmid vectors, virulence (vir) gene inducing compounds, medium composition and tissue specific factors, some other factors are becoming important for improving transformation efficiency of plant species. Sucrose treatment of explant increased T-DNA delivery in rice while desiccation improved the T-DNA delivery and stable transformation of sugarcane, maize, wheat and soybean. Silver nitrate suppresses the Agrobacterium growth and facilitates plant cell recovery that resulted in increased efficiency of transformation in wheat. Inclusion of thiol compounds, L-cysteine, dithiothreitol and sodium thiosulphate in co-cultivation medium increased transformation efficiency as high as 16.4% in soyabean. A temperature of 22 0C was found to be optimal for T-DNA delivery in tobacco. The optimal temperature for both T-DNA delivery and stable transformation was 23-25 0C for wheat and 23 0C for maize. Surfactants Silwet 77, pluronic acid F68, Tween 20 enhanced T-DNA delivery in wheat. Evidence that Agrobacterium density, co-culture medium, antibiotic and selectable marker influence T-DNA delivery and integration and stable transformation of plants were also presented.
Key words: Agrobacterium, stable transformation, T-DNA delivery, T-DNA integration, transformation
efficiency.
