Growth of Fig Varieties Resistant to Ceratocystis Canker following Infection with Ceratocystis fimbriata

Ceratocystis canker is caused by Ceratocystis fimbriata and is a serious soil disease affecting fig cultures. ‘Masui Dauphine’ is a major fig variety in Japan and is susceptible to this disease. In the present study, the effect of C. fimbriata infection was tested on the growth of 4 fig varieties, ‘Celeste’, ‘Boldido Negra’, ‘Ischia Black’, and ‘Negronne’. Specifically, the potential of these varieties as a disease-resistant rootstock for ‘Masui Dauphine’ was assessed. Fig cuttings of ‘Celeste’ were grown in 350 mL root boxes with sterilized coarse sand. Inoculation with C. fimbriata immediately inhibited root elongation, reduced the root respiration rate from 2 months after inoculation, and caused lesions in the rootlets. The trees of the 4 varieties tested were grown in 3.5-L pots for 5 months. C. fimbriata inoculation caused slight lesions on the underground part of all 4 varieties. Inoculation did not kill any trees and did not reduce root respiration, except with an unreasonable amount of inoculum. No significant reduction in the weights of leaves, shoots or roots was observed except for ‘Celeste’. ‘Masui Dauphine’ trees on the rootstocks of the 4 varieties tested were grown in 22-L containers for 2 years. C. fimbriata inoculation tended to inhibit scion and root growth, and killed a few trees from the 2nd year, except ‘Negronne’. ‘Masui Dauphine’ trees grafted on the rootstocks of the 4 varieties tested, in addition to 2 susceptible varieties, and ownrooted trees, were grown in the field with ceratocystis canker infection. Trees of the 4 varieties tested showed lower mortality and most survived for 5 years. No year-by-year reduction in scion growth was observed for any rootstock variety. Our results demonstrate that the varieties tested are not truly resistant, but are horizontally resistant to ceratocystis canker. We expect these rootstocks to maintain the scion ‘Masui Dauphine’ despite some continuing damage by disease. Of the varieties tested, ‘Negronne’ is the most resistant.