PNABD246.pdf

Both a virulent and an avirulent isolate of Rhizoctonia solani were able to
produce in vitro a substance phytotoxic to mungbean seedlings. The substance is
dialyzable and he-- stable. Infection with Rhizoctonia solani consistently
increased respira- 'a of mungbean plant tissues at least two fold. Infection
also increased host cell membrane permeability. A substance responsible for
increased membrane permeability was isolated from droplets which collected on
lesion surfaces. The substance was heat-labile and non dialyzable and appeared
to be a pectolytic enzyme of the endo-PG type. [EMS]
*0482 Lai, M.T. ; Weinhold, A.R. ; Hancock, ,J.G. 1966. Cell permeability
increases in mung bean during infection by Rhizoctonia solani [Abst.j.
PHYTOPATHOLOGY, v.56:886. [EnJ (REP.MB-1071)
MEETING: Annual Meeting of the American Phytopathological Society, 58th --
Denver, CO, USA, Aug 20-24, 1966
Increases in cell membrane permeability were detectable (30-80% greater
rate of electrolyte leakage) in mungbean (Vigna radiata) hypocotyls 12-18 h
after inoculation with Rhizoctonia solani. Initial symptoms developed after
20-24 h. After 24-48 h, droplets collected on lesion surfaces; this liquid
contained a heat-labile, nondialyzable substance that induced increases in
permeability when infiltrated into healthy hypocotyl tissues; i.e., the rate of
electrolyte and amino acid leakage was twice as high as that of the controls,
and cell deplasmolysis time was 36% less than the control. Fractionation by gel
filtration yielded a component that separated from the bulk of the protein and
was active in altering permeability. The lesion liquid contained two pectolytic
enzymes (endo-polygalacturonase [PGJ type) with different mobilities on
Sephadex G-200 columns. The permeability-altering factor coincided exactly with
one of the PG fractions. The fraction containing the second endo-PG, commercial
PG, and culture filtrates containing PG had a slight effect on the rate of
electrolyte and amino acid leakage. These results indicate that increased cell
membrane permeability is an initial host response to infection by R. solani and
that a permeability-altering factor (perhaps an enzyme) is associated with
infected tissues. [AS]
*0483 Kraft, J.M. ; Erwin, D.C. 1967. Stimulation of Pythium aphanidermatum
by exudates from Rung bean seeds. PHYTOPATHOLOGY, v.57:866-868. [En] [En
Abstj (REP.MB-0908)
Germinating mungbean seeds exuded greater quantities of sugars and amino
acids when incubated at 12 and 42 C than at intermediate temperatures. Exudates
from seeds germinated at 12 and 42 C stimulated slightly more mycelial growth
in a zoospore suspension of Pythium aphanidermatum than did exudates from seeds
incubated at intermediate temperatures. When zoospores were supplemented with
exudates, virulence of the fungus to mungbean seedlings was increased. [AS]
*0484 Wu, L.C. 1967. Physiology of parastism. 2. Biochemical changes in the
mung bean seedling infected with Rhizoctonia solani Kuehn. BOTANICAL BULLETIN
OF ACADEMIA SINICA, v.8:271-283. [EnJ [En Ch AbstJ (REP.MB-0480)
Infection of mung bean by Rhizoctonia solani caused an increase in both
reducing sugar and amino acid fractions during the early stages of disease
development. Three days after inoculation, reducing sugar content in inoculated
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