PNABD246.pdf

plants was more than twice over that in healthy plants, whereas free amino acid
rose to the level 1.4 times over that in the control plants followed by an
appearance of characteristic symptoms on hypocotyls and roots one day later.
Changes in reducing sugars and free amino acids during the early period of
disease development may be very meaningful. The infection by the fungus reduced
the nucleic acid and protein contents in diseased plants. Different dilutions
of culture filtrate revealed different effect on the treated plants in their
chemical changes. It seemed likuly that the culture filtrates contained more
than one biologically active substances. And the plants grown on water agar
impregnated with 5% culture filtrate showed similar trend of reducing sugar,
nucleic acid, and protein patterns to those mungbean seedlings infected with
Rhizoctonia solani per se. Thus, the establishement of infection was thought to
be determined by a complex of metabolites secreted by the fungus during the
critical period of pathogenesis. LASJ
*0485 Kraft, J.M. ; Erwin, D.C. 1968. Effects of inoculum substrate and
density on the virulence of Pythium aphanidermatum to mung bean seedlings.
PHYTOPATHOLOGY, v.58(10):1427-1428. [En] (REP.MB-0163)
The results of in vitro study showed that a favorable source of nitrogen
was necessary for infection of mungbean seedlings by Pythium aphanidermatum at
low inoculum densities. [THH]
*0486 Lai, M.T. ; Weinhold, A.R. ; Hancock, J.G. 1968. Permeability changes
in Phaseolus aureus associated with infection by Rhizoctonia solani.
FHYTOPATHOLOGY, v.58:240-245. [Enj [En Abstj (A:PS)
increases in cell membrane permeability were detectable (100% greater rate
of electrolyte leakage) in mungbean (Vigna radiata) hypocotyls 14-18 h after
inoculation with Rhizoctonia solani. Initial symptoms did not develop until
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 tiss'.s, i.e., the rate of
electrolyte and amino acid leakage was twice as high as che controls, and cell
deplasmolysis time was 33% less than the -ontrol. Fractionation by gel
filtration yielded a component that separated from the bulk of the protein and
was active in altering cell membrane permeability. The lesion liquid contained
two pectolytic enzymes (endopolygalacturonase type) with different mobilities
on Sephadex G-200 columns. The permeability-altering factor coincided exactly
with one of the endopolygalacturonase fractions. The fraction containing the
second endopolygalacturonase and commercial polygalacturonase had no effect on
rate of electrolyte and amino acid leakage. These results suggest 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]
*0487 Ragunathan, V. 1968. Damping-off of green gram, cauliflower, daincha,
ragi and clusterbean. INDIAN PHYTOPATHOLOGY, v.21(4):456-457. [En] (A:PS)
Pythium indicum, causal agent of damping-off of mungbean, causes light
brown water soaked lesions near the hypocotyl region, spreading towards roots
which become yellowish to dark brown and are constricted at the ground level.
Immediate collapse of the seedlings is noticed. [AS]
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