PNABD246.pdf

The parasite-host association Vigna radiata - Rhizoctonia solani was used
to study the effect of various organic amendments on infestation of soil
samples by R. solani. Incorporating straw into the soil markedly increased
infestation, which was further increased by adding N green manure, especially
when using a susceptible species such as mungbean as green manure. [EMS]
*0479 Wu, L.C. 1965. Physiology of parasitism. 1. Growth, pathogenicity,
and toxin production of Rhizoctonia solani Kuehn. BOTANICAL BULLETIN OF
ACADEMIA SINICA, v.6:144-152. [Enl [En Ch Abst] (REP.MB-G483)
In the present studies, the growth, pathogenicity, and toxin productioc of
an isolate of R. solani were found to be directly correlated when the cultures
of this fungus were incubated at different temperatures. Plant extracts
obtained from infected seedlings provided further evidence of the important
role of Rhizoctonia-toxin in the disease incidence. A possible reversal of
Rhizoctonia-toxin by gibberellic acid was illustrated. [ASJ
*0480 Kraft, J.M. 1966. Effects of nutrients and inoculum density on the
virulence of Pythium aphanidermatum and Pythium ultinum to mungbean seedlings.
Ann Arbor, MI : Univ. Microfilms International. 67 leaves [En] [En Abstj
(Thesis - Ph.D. (Plant Pathology)) (TH-087)
P. aphanidermatum and P. ultimum grew best in a liquid, synthetic medium at
pH 5.8-5.9. Excellent pH control was obtained with O.05M KH2P04 - K2HPO4
buffer. Optimum growth of P. aphanidermatum occurred only when casein
hydrolysate was used as a source of nitrogen. In contrast, P. ultimum utilized
a wide range of inorganic and amino acid sources of nitrogen. When casein
hydrolysate was included in the basal medium on which both fungi were grown, P.
aphanidermatum and P. ultimum caused a higher incidence of disease than when
casein hydrolysate was omitted. When 8 mm agar and mycelium discs were used to
inoculate seeds or seedlings of mungbean, the incidence of disease was high
with either adequate or subadequate nutrients in the inoculum. When 4 mm agar
and mycelium discs were used, a much lower incidence of disease occurred when
nutrients in the inoculum were subadequate than when they were adequate for
growth. When sources of nitrogen which P. aphanidermatum or P. ultimum failed
to utilize for growth were used in the media on which the inoculum was grown,
much less infection resulted than when casein hydrolysate was used. At 12 C, P.
ultimum caused a high incidence of disease of mungbean seedlings but P.
aphanidermatum could not infect mungbean seedlings at 12 C. In contrast to P.
ultimum, P. aphanidermatum caused a high incidence of disease at 39 C with an
adequate or subadequate source of nutrients. Germinating mungbean seeds exuded
larger quantities of sugars and amino acids at an extremely low (12 C) and high
(42 C) temperature than at intermediate temperatures. The exudates obtained
from seeds germinated at 12 and 42 C also stimulated a greater growth response
of P. aphanidermatum and increased disease incidence caused by this fungus
especially when the inoculum contained a low number of zoospores. [AS/THH]
*0481 Lai, M.T. 1966. Respiration and permeability changes in Phaseolus
aureus Roxb. associated with infection by Rhizoctonia solani Kuhn. Ann Arbor,
MI : Univ. Microfilms International. 85 leaves [Enj [En Abst] (Thesis - Ph.D.
(Plant Pathology)) (TH-086)
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