Cilantro, or coriander (Coriandrum sativum), is a leafy vegetable in the Apiaceae and is grown commercially in California primarily for use as a fresh herb. During 2002 and 2003 in coastal California (Santa Barbara County), commercial cilantro fields showed symptoms of a wilt disease. Affected plants grew poorly and were stunted. Lower foliage turned yellow with reddish tinges, and plants wilted during warmer times of the day. The main stem, crown, and taproot exhibited vascular discoloration that was reddish to light brown. As disease progressed, plants eventually died. For both years, the disease distribution was limited to isolated small patches (each patch measuring less than 1 m2 in area). A fungus was consistently isolated from symptomatic vascular tissue in crowns and taproots. On the basis of colony and conidial morphology, the isolates were identified as Fusarium oxysporum (2). No other fungi or bacteria were recovered from these plants. To test pathogenicity, suspensions containing 1 × 106 conidia/ml were prepared for five isolates. The roots of 30-day-old cilantro plants of four cultivars (30 plants each of Festival, Leisure, Santo, and LSO 14) were clipped and then soaked in the suspensions for 20 min. The roots of 30 plants of each cultivar were soaked in water as a control. Plants were repotted into new redwood bark + peat moss rooting medium and maintained in a greenhouse setting at 24 to 26°C. After 1 month, 95% or more of the inoculated plants showed yellowing and vascular discoloration symptoms similar to those seen in the field. F. oxysporum was reisolated from all inoculated plants. The four cilantro cultivars did not show differences in disease severity. Control plants showed no symptoms, and the fungus was not recovered from these plants. The experiment was repeated and the results were the same. Experiments also were conducted to determine if cilantro isolates could cause disease in celery (Apium graveolens var. dulce). Celery transplants and cilantro seedlings were prepared and inoculated as described above. However, after 2 months, celery plants did not show any disease symptoms, while the cilantro developed wilt symptoms and eventually died. A Fusarium wilt disease has been reported on coriander in Argentina and India where the pathogen was named F. oxysporum f. sp. coriandrii (1,3). To our knowledge, this is the first report of Fusarium wilt of cilantro in California.
References: (1) M. Madia et al. Fitopatologia 34:155, 1999. (2) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (3) U. S. Srivastava. Indian Phytopathol. 22:406, 1969.
