A Parasitic Storage Rot of Sugar Beets Caused by Aspergillus fumigatus. J. M. Halloin, USDA-ARS, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. D. L. Roberts, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 75:751. Accepted for publication 28 February 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0751B.
Aspergillus fumigatus Fresen was associated with a rot oocurring
on nearly one-half of a group of sugar beet (Beta vulgaris L.) roots
stored longer than 1 wk at 35 C. Koch's postulates were satisfied
with the fungus and live beets at 35 C. Disease progressed rapidly,
with as little as 1 wk between first appearance of the fungus on the surface and complete rotting of a 4-kg root. A. fumigatus (frequently
mistaken for Penicillium sp. because of similar gross appearance) is
a common saprophyte in beet storage but is not known to be a
pathogen. Because sugar beets with resistance to Rhizoctonia solani
Kuhn show resistance to some parasitic storage rots (1), roots of a
commercial Rhizoctonia-susceptible hybrid and two breeding lines
resistant to R. solani were inoculated with A. fumigatus and incubated
at 30, 35, or 40 C for up to 16 days. The commercial hybrid was
highly susceptible to A. fumigatus at 40 C. intermediate at 35 C,
and resistant at 30 C. The breeding lines were susceptible to A.
fumigatus at 40 C, slightly susceptible (infrequent, sIow-developing
rot) at 35 C, and resistant at 30 C. The slime-producing bacterium
Leuconostoc mesenterioides (Tsenkovskii) van Tieghem often was
found in association with A. lumigatus but appeared to occur as a
secondary invader. Parasitic rot caused by A. fumigatus it a potential
problem in hot spots (>30 C) within stored beets.