EFFECTS OF TEMPERATURE ON ISOLATES OF FUSARIUM-MONILIFORME CAUSING FIG ENDOSEPSIS AND ASPERGILLUS-NIGER CAUSING SMUT

Isolates of Fusarium moniliforme causing endosepsis, two obtained from cultivated fig and three from wild fig pollinator trees, and an isola te of Aspergillus niger causing smut on figs were evaluated for fruit colonization and lesion expansion at five constant temperatures. Surfa ce-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 degrees C under high humidity (>97%). Lesion sizes of smut and endosepsis were recorded af ter 3 and 5 days of incubation, respectively. To determine rates of le sion expansion, lesion sizes of endosepsis and smut were recorded at 4 8- and 24-h intervals after inoculation, respectively. Optimal tempera ture for F. moniliforme colonization was 30 degrees C. Isolates from c ultivated caprifigs failed to colonize at 35 degrees C. Higher tempera tures resulted in shorter latent periods for both F. moniliforme (40 t o 60 h at 30 degrees C) and A. niger (44 h at 35 degrees C). Fusarium moniliforme isolates from the wild caprifigs had a significantly short er latent period at 30 degrees C (40 h) than isolates from cultivated caprifigs (60 h). Lesion sizes caused by isolates at different tempera tures differed significantly (P = 0.0001). At each temperature, isolat es from wild caprifigs caused significantly larger lesions and sporula ted more than isolates from cultivated caprifigs. Optimal temperature for A. niger colonization was 35 degrees C, At temperatures of <25 deg rees C, lesions areas caused by F. moniliforme isolates were significa ntly larger; at 30 and 35 degrees C, lesion areas caused by A. niger w ere significantly larger. At 30 and 35 degrees 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 degrees C are not conduci ve to A. niger development, smut is rare on caprifigs and is common on Calimyma figs.