HYPOBIOTIC PHENOMENA IN FUNGI AND 

 THEIR SIGNIFICANCE IN PLANT PATHOLOGY 



I. WAHL, 



Department oj Plant Pathology, Faculty of Agriculture, Hebrew 'Jniversity, 



Rehovot (Israel) 



The aim of this paper is to discuss some significant aspects 

 of hypobiotic phenomena in fungi mainly from the plant 

 pathologist's point of view. In order to define the scope of this 

 discussion it seems to be necessary to clarify some basic concepts. 

 It is suggested to use the term hypobiosis for resting stages in the 

 life cycle of the fungus which exhibit two different biological 

 phenomena. Hypobiosis can be expressed as latent existence of 

 the organism, imposed by adverse environmental factors and 

 lack of proper nutrients. The organisms can be easily reactivated 

 by applying favorable conditions answering the requirements of 

 the fungus. In this case hypobiosis constitutes an important facet 

 of the protective potential of the species. In contrast to this 

 concept of latent existence, Gottlieb^ and Garrett- deal primarily 

 with obligate dormancy, involving only the innate state of the 

 cell. A spore is dormant when it does not germinate under the 

 same nutritive and environmiental influences which later allow 

 production of germ tubes^. In many instances, the present state 

 of knowledge does not permit distinction between these two 

 processes. For this reason it is preferred to deal with the resting 

 phases of the fungus life cycle as one general problem. 



Determining and understanding the resting period of the 

 fungus, its duration, dependence on genetic factors and environ- 

 mental conditions are of paramount importance in the control 

 of plant disease by agronomic procedures such as crop rotation, 

 time of planting, plowing, etc. Resting states, such as spores, 

 sclerotia, resting hyphae, and rhizomorphs are important in 

 enabling the pathogen to survive from one growing season to 

 another. The organisms may remain in a hypobiotic stage when 

 a congenial host is absent: the ideal resting state functions as 



References p. J 16 



