"cold" test, seed infection, seedling blight, root rot
Seedling resistance to Pythium was studied by placing maize kernels on or under a culture of Pythium growing on a semi synthetic medium. The main criteria were living plumules and roots after 14-days incubation at 12 C and 6 days at 23-27 C. Greater mortality occurred when inoculum was above the kernels than below. Surface-sterilization of kernels before exposure to Pythium increased seedling mortality, but moisture content of kernels at the start of exposure had only a slight effect on survival at 12 C. Maximum mortality occurred when the cold period was more than 8 days. Survival was greater after a short cold period of 1-2 days than if the kernels were not exposed to any cold-incubation period. Varying the length of the cold incubation introduces a genetic-incubation interaction. The critical period in exposure to Pythium at low temperatures was between 48 and 96 hours of exposure, by which time the fungus had become established in the kernels, and surface sterilization would not free them from infection. All kernels, from susceptible or resistant genotypes, were invaded in 4 days. A daily alternating incubation temperature (10-25 C) was highly variable in effect on survival. The expression of resistance was maximum in the plumule and scutellar node, which, if they survived the initial exposure to Pythium, showed near immunity. The radicle and seminal roots were never longer than 1 cm if exposed to Pythium, except in seedlings having a resistant plumule.
Proceedings of the Iowa Academy of Science
© Copyright 1980 by the Iowa Academy of Science, Inc.
Foley, D. C.
"Resistance to Pythium debaryanum in Zea mays Seedlings,"
Proceedings of the Iowa Academy of Science: Vol. 87:
, Article 7.
Available at: http://scholarworks.uni.edu/pias/vol87/iss4/7