STUDIES ON FUSARIUM WILT OF JOJOBA (SIMONDSIA CHINENSIS)-A NEW DISEASE IN CHINA Ⅱ. Biological Characteristics of the Pathogens and Occurrence of the Disease

The pathogens causing a wilt disease of Jojoba(Simmondsia chinensis(Link) Schneider)are Fusarium oxysporum,F.solani,F.equiseti and F.moniliforme. The temperature range for their mycelial growth and sporulation was 10~35℃;with 25~30℃ as the best for mycelial growth and 30~35℃ as the best for sporulation.The optimum temperature for conidial germination differed among these Fusarium species.Mycelia could grow and the conidia could germinate between pH4~9,but the optimum pH range was 6~8.High relative humidity was required for conidial germination and the maximum germination was obtained in water drops.Among the 5 carbon and 5 ni-trogen compounds tested,starch served as the best carbon source,and peptone and asparagine as nitrogen sources were favorable for the mycelial growth of all the four Fusarium species while cellulose and urea were found to be poor sources. Field observation showed that symptoms were particularly prominent in the dry sea-son.The occurrence of the wilt disease of Jojoba was closely related to the soil texture and water content.Based on the above results,it was suggested that the efficient way of con-trolling this disease should integrate the cultivated,ecological and phytopathological measures.