ABSTRACT
The means of survival are the first action in infection chain or disease cycle. The initial infection that occurs from the sources of pathogen survival (Infected host as a reservoir of inoculum, saprophytic survival outside the host or dormant spores and other structures in or on the host or outside the host) in the crop is primary infection and the propagules that cause this infection are called primary inoculum. Soil is the major substrate for the survival of pathogens in its active or inactive stages over a period of time. The dormant structure of fungi includes resting propagules like sclerotia, rhizomorph, chlamydospores; sexual spores like oospores, zygospores and fruiting body like acervuli, pycnidia, ascoma etc. Many soil and foliar pathogens survives in infected plant debris in soil as saprophytes for long time. Tobacco ringspot is associated with the nematode Xiphinema americana. The fungi, Polymyxa graminis and Spongospora subterranea carry the viruses internally and transmit them through the resting spore.
