[On the nature of the pathogen of pale-green dwarfism in cereals]

The paper presents more precise data concerning optimal temperature demands to growth of white-yellow dwarfness of cereals (WYDC) identified before as Acholeplasma laidlawii var. granulum, its relation to sterols and genome properties was determined using pulse-electrophoresis. It was established that the agent strains 84 and 118, characterized by phytopathogenicity, grew most intensively at 32 degrees C; they behaved as mesoplasmas but, as it had been found, they were capable to synthesis of carotenoids and displayed close serologic affinity for A. laidlawii PG8. That is, the above strains are typical acholeplasmas capable to live in leafhoppers which carry a disease and in cereals plants and cause a disease with typical symptoms of "yellows" in the latter. Molecular weight of the strain 84 genome was 2200 t.p.n. (GC = 33 mol %); in strains 118 it was 2310 t.p.n. (GC = 34.2 mol %). Allowing for the fact that molecular weight of genome of A. laidlavii var. granulum is almost by 1/3 (1600 + 710 t.p.n.) more than that of A. laidlawii PG8 genome, the authors think that the agent of WYDC is the evolution precursor (or one of precursors) which initiated the Acholeplasma and Phytoplasma genera as a results of splitting of their genomes.