Corn (Zea mays) rusts (Puccinia sorgi, P. polysora, Physopella zeae). III. Race of commom rust (P. sorghi ) and differential corn lines

Abstract

Methods of P. sorghi urediospore inoculation in corn seedlings and monospore or monosore isolation methods are outlined. Individual protection of pots and isolated room protection was used. Twelve samples from four states of the Brazilian Center-South yielded 55 monosore isolates. From these, were separated thirteen physiologic races by means of the US-differential series. The author failed to reproduce the series in local photoperiodic conditions, but crosses with sixteen Instituto de Pesquisas e Experimentação Agropecuárias do Centro-Sul-lines yielded ninety hybrid ears. During the inoculation test, US-differential one B-38 never permitted any pustule formation, but GG-208-R was susteptible to nearly all 13 races. Thus the author concluded the biotypes tested by him might have a different genetic constitution of those tested in North America. By finding out active susceptibility in eleven local com lines the inicial basis for a local additional differential series was established. Reading of reaction types was much easier than on US-differential series (Figs. 3 to 7).