Stalk Quality and Stalk Rot Resistance of Tropical Hybrid Maize Derivatives. R. N. Holley, Research Associate, Department of Crop Science, North Carolina State University, Raleigh 27695-7620. M. M. Goodman, Professor, Department of Crop Science, North Carolina State University, Raleigh 27695-7620. Plant Dis. 72:321-324. Accepted for publication 30 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0321.

Temperate-adapted, 100% tropical maize inbreds were evaluated as inbreds and in hybrid combination with corn belt germ plasm for stalk quality and resistance to two stalk rot pathogens, Stenocarpella maydis and Colletotrichum graminicola. Plants were inoculated with one of the two pathogens and evaluated for stalk rot resistance via internode discoloration and lodging ratings. There was a wide range of resistance among the tropical inbreds to internode discoloration caused by the two pathogens. Most tropical inbreds had relatively high levels of resistance to S. maydis but were relatively susceptible to C. graminicola. Several experimental 50% tropical hybrids were superior to the commercial checks for stalk-lodging resistance. There was no correlation between internode discoloration ratings of the inbreds or hybrids and lodging resistance. The late-season internode discoloration data were limited, however, by a natural infestation of Pythium sp. that was associated with disintegration of pith in many plants. The importance of rind strength in lodging resistance was evident by the consistency of experimental hybrid performance over different pathogen tests. Poor stalk quality has been one of the major factors limiting the use of exotic maize germ plasm. The strong performance of some tropical inbreds used in this study, however, suggests that major progress has been made in some tropical breeding programs. No significant root lodging was observed in the study.

Keyword(s): anthracnose, diplodia, Zea mays.