イチジクとイヌビワとの種間交雑体BC₁が有するイチジク株枯病に対する抵抗性の評価：土壌経由の感染に関する既存抵抗性品種との比較

抄録

Ceratocystis ficicola is the causal agent of Ceratocystis canker in Japanese fig orchards. Ceratocystis canker is a soil-borne plant disease that causes wilting and mortality in fig orchards. Some rootstocks, such as “Celeste”, have been used to control the disease. However, these rootstocks are not perfect. Ficus erecta is highly resistant to Ceratocystis canker and might be suitable for use as a resistant rootstock. Unfortunately, the grafting compatibility between F. carica and F. erecta is extremely low. We successfully produced BC₁ lines, interspecific hybrids between F. carica and F. erecta as new rootstock candidates, and compared them with “Celeste” in relation to resistance to Ceratocystis canker infection via soil. Fig varieties, “Houraishi” and “Masui Dauphine”, were grafted on three BC₁ lines and the “Celeste” rootstock. Own-rooted cuttings of “Houraishi” and “Masui Dauphine” were also tested. All cuttings were planted in an orchard infected with C. ficicola. The roots, rootstock, and scions were sampled for C. ficicola and external symptoms were recorded. Infection and mortality occurred on 86.1% and 87% of the own-rooted “Houraishi” and “Masui Dauphine” cuttings, respectively. The infection rate on “Celeste” rootstock was 41.7%, but mortality was not observed; C. ficicola infection was restricted within the roots of “Celeste”. However, the disease was not detected in cuttings with BC₁ rootstock. These results indicate that BC₁ is more resistant to infection of C. ficicola via soil than existing resistant varieties like “Celeste”. Further investigation is required to select a suitable BC₁ line as a rootstock to control Ceratocystis canker and to achieve stable fig production.