Reaction of Germinating Maize Pollen to <i>Helminthosporium maydis</i> Pathotoxins¹

Abstract

Pollen from fertile plants of corn ( Zea mays L.), with normal and restored male‐sterile cytoplasm ( cms ), from various sources was assayed for in vitro germination on media containing Helminthosporium maydis pathotoxins extracted from infected leaves. The “pathotoxin” from H. maydis race O inhibited neither germination nor growth of pollen from any of the cms or normal cytoplasm sources tested, as compared with controls. The pathotoxin from H. maydis race T, however, inhibited in vitro germination and growth of pollen from cms‐T and cms‐P plants. Growth of pollen from cms‐C , cms‐S and normal cytoplasm sources was not inhibited by race T pathotoxin. The advantages of a pollen bioassay are discussed, as are possible special applications of this procedure.