Symptomless reaction of Sechium edule (Jacq.) Sw. to Verticillium dahliae Kleb.

Chayote (Sechium edule, fam. Cucurbitaceae) is not reported as a host of Verticillium dahliae. In an olive orchard intercropped with horticultural crops and infested by Verticillium dahliae, chayote did not show Verticillium wilt symptoms over three years (2015-2017). Hence, we hypothesized that chayote is not a V. dahliae host. Using a V. dahliae isolate obtained from a wilted eggplant located in that field, we carried out a pathogenicity test on two chayote varieties, one with spiny fruits and another with non-spiny fruits (10 plants each). Eggplant, tomato and 'Carosello' ecotype (Cucumis melo), all susceptible to the disease, were included as positive controls. After four months in the greenhouse, chayote plants did not show Verticillium wilt symptoms, which occurred in the control plants since 4-6 weeks after planting. From chayote roots, isolation on PDA did not yield colonies of V. dahliae, but PCR assays from some plants were positive. This indicated very limited colonization of roots by V. dahliae, which is known to occur even in resistant or symptomless responses. In conclusion, we demonstrate the symptomless response of chayote to V. dahliae, while assessment of the non-host response needs further pathogenicity test with V. dahliae isolates from diverse plant species.