Imposition of Nutrient Stress on Soilborne Fungal Pathogens

다국어 초록 (Multilingual Abstract)

Propagules of soiborne pytopathogenic fungi are subjected to numerous abiotic (soil moisture, temperature, pH, oxygen, radiation, chemicals etc.) and biotic (predation, hyperparasitism, antibiosis etc.). In soil fungal propagules must survive with numerous other microorganisms and compete for available energy (carbon) substrate. The competition for energy substrate influences the ability of fungal inoculum to persist in soil. It is found that enhanced exudation of carbon compounds from fungal propagules may also result from exposure to competitive stress imposed by soil microorganisms. The imposition of mycostasis by nutrient deprivation appears to be related to increased endogenous exudation losses. The loss of 14C-exudation from the fungai inoculum was found to be directly related with germination suppression. This phenamenon was experimentally evaluated imposing the propagules under diffusive stress, in soil and in the presence of specific microorganisms.
Greater rate of 14C-exudation was found in soil and in the presence of specific microorganisms than from the propagules exposed to artificial diffusive stress. Loss of endogenous carbon from the fungal propagules has also been directly realated to elevation of nutrient requirements for the germination, progressive loss of viability, formation of persisten structures and decreased aggressiveness. The consequences of imposed stress on propagules have potential significance in the management of soilborne fungal diseases. The cellular mechanism by which biotic or abiotic stress suppresses germination is not known. Possibly, depletion of nutrients from the fungal propagules occurs by enzyme-hydrolysis $quot;sensor$quot; system which depends upon degree of imposed competitive nutrient stress.