VIEW ARTICLE

Ecology and Epidemiology

Effects of Temperature on Isolates of Fusarium moniliforme Causing Fig Endosepsis and Aspergillus niger Causing Smut. K. V. Subbarao, Department of Plant Pathology, University of California, Davis, c/o 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 Ave., Parlier 93648. Phytopathology 85:662-668. Accepted for publication 20 March 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-662.

Isolates of Fusarium moniliforme causing endosepsis, two obtained from cultivated fig and three from wild fig pollinator trees, and an isolate of Aspergillus niger causing smut on figs were evaluated for fruit colonization and lesion expansion at five constant temperatures. Surface-disinfested fruit halves from fig pollinator trees were inoculated individually with isolates of F. moniliforme and A. niger on the uncut surfaces and incubated at 15, 20, 25, 30, and 35°C under high humidity (>97%). Lesion sizes of smut and endosepsis were recorded after 3 and 5 days of incubation, respectively. To determine rates of lesion expansion, lesion sizes of endosepsis and smut were recorded at 48- and 24-h intervals after inoculation, respectively. Optimal temperature for F. moniliforme colonization was 30°C. Isolates from cultivated caprifigs failed to colonize at 35°C. Higher temperatures resulted in shorter latent periods for both F. moniliforme (40 to 60 h at 30°C) and A. niger (44 h at 35°C). Fusarium moniliforme isolates from the wild caprifigs had a significantly shorter latent period at 30°C (40 h) than isolates from cultivated caprifigs (60 h). Lesion sizes caused by isolates at different temperatures differed significantly (P = 0.0001). At each temperature, isolates from wild caprifigs caused significantly larger lesions and sporulated more than isolates from cultivated caprifigs. Optimal temperature for A. niger colonization was 35°C. At temperatures of <25°C, lesions areas caused by F. moniliforme isolates were significantly larger; at 30 and 35°C, lesion areas caused by A. niger were significantly larger. At 30 and 35°C, the rates of lesion expansion for A. niger were twice as great as rates for any isolate of F. moniliforme. Because temperatures of <30°C are not conducive to A. niger development, smut is rare on caprifigs and is common on Calimyrna figs.