Movement of a factor in tobacco infected with Peronospora tabacina Adam which systemically protects against blue mold

Stem inoculation of Burley tobacco with sporangia of the blue mold pathogen, Peronospora tabacina, elicited high systemic resistance in the foliage against disease caused by subsequent inoculation with the pathogen. Girdling the stem above the site of inoculation prior to 9 days after stem inoculation prevented the elicitation of resistance, whereas girdling below the site did not. Increased growth (height, number of leaves, reduced time to flowering) was observed in ungirdled, stem-inoculated plants, plants stem-inoculated and girdled above the site of inoculation at day 6 or later and in plants stem-inoculated and girdled below the site of stem inoculation. The factor responsible for resistance did not precent penetration by the fungus, and it may or may not be the factor responsible for enhanced growth. The resistance factor was graft transmissible between rootstock and scion. Induced scions (10 cm in length), when grafted onto control rootstocks, developed into fully grown plants that remained systemically protected against blue mold.