Morphological alterations and root nodule formation in Agrobacterium rhizogenes-mediated transgenic hairy roots of peanut (Arachis hypogaea L.)

Abstract

Transformed hairy roots were induced at the excised site of the epicotyl of dry mature seed of a Spanish type peanut (Arachis hypogaea) cv. Java 13 2 weeks after inoculation with a wild type strain of Agrobacterium rhizogenes, MAFF-02-10266. Composite plants consisting of transformed roots with non-transformed shoots were cultured using pouches. Forty days after inoculation, the composite plant showed a root system with abundant root mass, more lateral branching and high fractal dimension compared to the control. No differences were observed in production of rosette-type root hairs or the cross sectional structure between transformed and non-transformed roots. The inoculation of Bradyrhizobium sp. A2R1 strain to the composite plants led to the induction of transformed root nodules. These transformed root nodules showed production of leghaemoglobin in the bacterial zone and nitrogenase activity as assayed by C2H2 reduction, and exhibited enlargement of the nodule cortex region and de novo root formation from the nodule cortex.