Biology, Structure, Functions and Possible Origin of Viroids

The great interest viroids have attracted ever since their discovery is reflected in numerous review articles (Diener 1972 a, b, 1974, Semancik 1976, Diener and Hadidi 1977, Diener et al. 1977, Diener 1979a, Dickson 1979, Sanger 1979 a, b, Semancik 1979, Sanger 1980 a, b, Gross and Riesner 1980, Kleinschmidt et al. 1981). Thus, one might get the impression that the viroid field is now in some way overreviewed especially after an entire book on viroids has appeared (Diener 1979 b). However, the rapid progress in viroid research still justifies up-dated treatments which are, nevertheless, obsolete in many parts at the time of their appearance. The same will apply for this contribution which surveys the data on the biology, structure, funetion and possible origin of viroids as available early in 1982.