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Development of Phenological Scales for Figs and Their Relative Susceptibilities to Endosepsis and Smut. Krishna V. Subbarao, Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, 1636 E. Alisal Street, Salinas, CA 93905. Themis J. Michailides, Department of Plant Pathology, University of California, Davis, Kearney Agricultural Center, 9240 S. Riverbend Avenue, Parlier 93648. Plant Dis. 80:1015-1021. Accepted for publication 13 May 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1015.

The relative susceptibilities of figs to infection by Fusarium moniliforme, which causes endosepsis, and Aspergillus niger, which causes smut, were evaluated on figs sampled at weekly intervals. Both caprifigs and Calimyrna figs were resistant to endosepsis infection up to 7 weeks prior to maturity, whereas smut could occur at any time on injured Calimyrna figs. Several morphological and physiological factors affecting the two pathogens during the development of figs were studied, and phenological scales for caprifigs and Calimyrna figs were developed. The effects of fig latex and different carbon sources on germination of conidia, germ tube elongation, and linear growth of the two pathogens were evaluated. Fig latex significantly inhibited all three variables on F. moniliforme but had no effect on A. niger. Of the carbon sources tested, lactose, mannose, maltose, and starch supported more growth of F. moniliforme than other carbon sources, although not more than on water agar (P ? 0.05). Growth of A. niger on fructose-, mannose-, and maltose-amended agar was greater than on the other sugars tested. Of the two principal sugars (glucose and fructose) in figs, A. niger grew better on fructose than on glucose, whereas F. moniliforme grew equally well on both sugars. The linear growth of both pathogens also was evaluated on media amended with 9, 18, 36, 54, and 72% glucose or fructose. Radial growth of A. niger increased with increasing fructose concentrations of up to 36%, whereas growth of F. moniliforme increased only up to 18% fructose. In contrast, radial growth of F. moniliforme decreased at glucose concentrations of greater than 9%, whereas A. niger growth was reduced at greater than 18% glucose concentration. The relationships between the radial growth of the two pathogens and increasing glucose or fructose concentrations were quadratic (P = 0.0001), although the slopes for fructose were not as steep as for glucose. Other factors, such as the timing of ostiole opening, determined when smut infection occurred.

Keyword(s): caprification, Ficus carica, internal rot, pink rot