Wound Predisposition of Maize to Anthracnose Stalk Rot as Affected by Internode Position and Inoculum Concentration of Colletotrichum graminicola. A. Muimba- Kankolongo, Former Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908. G. C. Bergstrom, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908. Plant Dis. 76:188-195. Accepted for publication 24 July 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0188.

A 2-yr study was carried out to ascertain the nature of wound predisposition of maize to anthracnose stalk rot (ASR) relative to internode position and inoculum level. Stalks of hybrids Cornell 281 (susceptible) and CM174 × LB31 and B37 × LB31 (resistant) were inoculated with 1-ml suspensions of 10², 10⁴, 10⁶, 10⁷, and 10⁸, conidia of Colletotrichum graminicola per milliliter into wounds at midwhorl or anthesis and immediately or 6 hr after wounding. For each inoculation regime, the most severe ASR developed in the susceptible hybrid. At each inoculum level, the most severe ASR resulted from inoculation at anthesis and immediately after wounding. Disease severity increased with increasing inoculum up to 10⁷ conidia per milliliter in greenhouse-grown plants and up to 10⁶ conidia per milliliter in field-grown plants. Genotypic, ontogenic, and “wound healing” resistances to ASR were expressed in maize even at high inoculum levels of C. graminicola. Systemic ASR resulted from inoculation immediately after wounding of any of the first five internodes above the brace roots, but wound healing restricted considerably systemic ASR after inoculation of aged wounds in the lowermost stem internodes.

Keyword(s): Zea mays.