Plant roots exude a variety of sugars, organic acids, etc. that attract and feed fungi and bacteria.  Many of these microbes are know to protect the roots from attacks from other fungi and bacteria.  Those that grow along the growing root are generally designated as 'rhizosphere competent'.  However, in potato there are both roots and rhizomes.  There are several pathogens that attach the rhizome and the potato tuber.  So, the question is whether or not the rhizomes or tuber exude chemicals that would support microbiological growth in the same way the root does?  If so, this might allow for the discovery and application of microorganisms to the root zone of potato that would protect the rhizome and tuber from infection.