Heterografting cryopreserved meristems to wake up latent plant bacteria

Abstract

Melia volkensii is a drought resistant and fast growing tree originating from the East-African savannah that is currently overexploited. Plant tissue culture tools are explored to meet the large demand of plantlets for their mahogany type timber production but also to preserve the rapidly declining gene pool. Meristems of M. volkensii that were contaminated with endogenous bacteria were cryopreserved and thawed. Radish seeds were sown on Murashige and Skoog basal medium and the roots of the young seedlings were cut in pieces and placed vertically on the same medium. Fresh and cryopreserved M. volkensii meristems were grafted on the isolated roots or directly placed on semi-solid medium. The meristems survived, but as expected, there was no vascular connection with the radish roots. Interestingly, the combination cryopreservation + heterografting stimulated endogenous bacteria to grow out. This indicates the failure of cryotherapy to eradicate bacteria. On the contrary, this combination seems a be a useful technique to detect endogenous latent bacteria.