Due to the fact that various plants can exhibit differential susceptibility to a given Agrobacterium strain, several different strains for generating peanut hairy root lines were tested. Of the two A. rhizogenes strains tested (R1000 and ATCC 15834), the agropine type strain, ATCC 15834, was successful in providing the most consistent hairy root responses. A. tumefaciens EHA105 containing the pRYG plasmid harboring therol genes ( Komarnytsky et al., 2004) was successful in the initiation of hairy roots; however, these roots did not provide sustained proliferation in liquid cultures. Based on these observations, the ATCC 15834 strain was used in all successive experiments. Improvement in overall infection events and recovery of sustainable hairy root tissues were obtained with the use of younger explants (15-day old seedlings). Isolated cotyledonary node tissue was more reliable for hairy root production than stem, petiole or hypocotyl explants and consistently responded with larger more prolific roots at the inoculation site ( Table 1). Isolation of independent hairy root lines on B5 medium containing cefotaxime was performed to eliminate excess Agrobacteria associated with the tissues. Hairy root lines were tested for vigor and those lines failing to sustain vigorous growth were discarded.