VIEW ARTICLE

Ecology and Epidemiology

Virulence of Fusarium Species Causing Fig Endosepsis in Cultivated and Wild Caprifigs. K. V. Subbarao, Department of Plant Pathology, University of California, Davis, U.S. Agricultural Research Station, 1636 E. Alisal Street, Salinas 93905; T. J. Michailides, Department of Plant Pathology, University of California, Davis, Kearney Agricultural Center, 9240 S. Riverbend Avenue, Parlier 93648. Phytopathology 83:527-533. Accepted for publication 19 January 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-527.

Fusarium spp. associated with endosepsis of figs were characterized for growth rate, sporulation, temperature optima, and virulence. F. moniliforme and F. solani were the dominant causal agents of fig endosepsis. A total of 62 Fusarium isolates were collected from cultivated and wild caprifigs with endosepsis symptoms from most fig-production areas of California. One isolate was F. dimerum, seven were F. solani, and 54 were F. moniliforme. In vitro growth rates of isolates within species differed significantly. Sporulation was determined after colony diameters were recorded by flooding the colonies with 10 ml of sterile deionized water and determining the number of spores using a hemacytometer. Sporulation correlated significantly (r = 0.43; P = 0.0001; and n = 236) with growth rate. The majority of F. moniliforme and F. solani isolates had a temperature optimum of 25 C; the F. dimerum isolate had an optimum temperature of 30 C for linear growth. The solitary F. dimerum isolate was moderately virulent; F. solani isolates were either virulent or highly virulent; and among F. moniliforme isolates, ~11% were avirulent, 67% were weakly to moderately virulent, and 22% were virulent to highly virulent. The teleomorph of most F. moniliforme isolates was Gibberella fujikuroi mating population A, and only a few were population F. F. moniliforme isolates from wild caprifigs were significantly more virulent than those from cultivated caprifigs, but no such differentiation was found with F. solani. Infusion of F. moniliforme from wild caprifigs into cultivated figs may cause significant, long-term problems for the fig industry in California.