Object - resistance of corn to the root and stalk rots biotypes on various ontogenetic stages under conditions. The aim - is to study immunological peculiarities of corn to the root and stalk rots biotypes on various ontogenetic stages under conditions, to improve genetic methods of the resistance evaluation. Methods - phytopathological, mycology, statistical. Novelty - 1) dissemination and harmfulness of corn to the root and stalk rots are received as a result of studying in the Northern of Ukrainian steppe; 2) complex of the pathogenic fungus are taken from the infected plants (Fusarium moniliforme Sheld., F. sporotrichiella Bilai, F. oxysporum Schl., Sclerotium bataticola Taub.); 3) absence of the maize biotypes resistance is revealed at a different stages of ontogeny and to agents of the root and stalk rots in drought conditions; 4) source of the resistance are revealed in two subgroup of steppe, which have a peculiar feature against from the root and stalk rots at all stages development (line -Dk 427); 5) some corn genotypes are resistance to diseases and lodging: line Ik 203-3, P 502, P 346, Gk 26, Dk 427; 6) to give evaluation to the maize resistance to the root and stalk rots in dry conditions, it is necessary to carry out selection separately from germs and adult plants; 7) scale of the evaluation are formed as a result (of the phenotypic resistance) of the samples of corn species resistance to the root and stalk rots; according to this some groups are divided into: high resistance 0,0 <bi<0,9 (R), medium resistance 0,91<bi<1,3 (MR, MS), acquisitive - 1,31<bi<1,9 (S); 8) evaluate the resistance of defend biotype on a border of ecological conditions and carry out with a help of Coefficient of Potential Resistance Realization (CPSR), index bi?0,9. Results of the study. It is obvious that lesion of corn to the root and stalk rots in the Northern steppe ran can be of 9.7-54.1%, Southern - 27.6, but on adult plants are of- 19.5-20.0% and 8.9%. Fives samples of corn species with resistance againstfungus diseases and lodging as revealed as a result of the evaluation of the 5 lines. In extreme weather conditions the line Dk 427 are revealed in two subgroup of steppe and other hazardous diseases (moulds seeds, earl spades rot, blister leaf smut). It can be included into hybridization as the source of resistance in creating new lines and gibrids. Gield loses of corn can exceed up to 54.7 in lines, to 51.9% in gibrids aue to the development of root and stalk rots, and sometimes it leads to barrenness. Lesion of germs are lead to it's weakness and even death (5%) by diseases agents. Final stage of the ontogeny is accompanied by the lodging of infected plants (at 19.5%). The results of the study can be used in selection of new lines and gibrids and in agricultural production in inventing immunological method of corn protection from diseases. Branch - agriculture.
