Effect of fusarium seed infection on the chilling tolerance of maize (Zea mays L.) at emergence

The chilling tolerance of six generically different maize inbred lines with different degrees of chilling tolerance and that of four hybrids produced from four of these lines using line 156 as the male parent was studied after seed infection with Fusarium species: Fusarium culmorum (W. G. Smith) Sacc., Fusarium poae (Peck) Wollenweber, Fusarium graminearum Schwabe, Fusarium oxysporum Schlecht, or with a mixture of these species, followed by cold incubation at 13.5 degreesC for three different periods. As the result of infection with the Fusarium species there was a reduction in the emergence percentage and a prolongation of the emergence time. Of the Fusarium species, infection with Fusarium culmorum (W. G. Smith) Sacc. and Fusarium graminearum Schwabe caused the greatest reduction in the chilling tolerance of the genotypes. The hybrids had greater tolerance to infection than the lines. The extent of heterosis depended on the intensity of infection: when the infection was more intense the degree of heterosis increased. Infection with a mixed suspension of the Fusarium species gave results similar to the mean values obtained after separate infection with the various species. The results of Fusarium infection confuted an earlier theory on the cause and effect relationship of infection and retarded emergence: the seeds do not become infected due to slow emergence; the infection causes the prolongation of the emergence time.