Incidence of Bipolaris and Exserohilum Species in Corn Leaves in North Carolina

Thakur, R P and Leonard, K J and Leath, S (1988) Incidence of Bipolaris and Exserohilum Species in Corn Leaves in North Carolina. Plant Disease, 72 (12). pp. 1034-1038. ISSN 0191-2917

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Samples of 42–60 corn leaves were collected without regard to disease symptoms at 2-m intervals in each of eight cornfields in western and two in eastern North Carolina in 1985. Sampling dates for the 10 fields ranged from 16 July to 8 August. The leaves were surface-sterilized and incubated in moist chambers for isolation of large-spored species of Bipolaris and Exserohilum. Incidence of B. zeicola infection was high (41–81%) in leaves from nine of the 10 fields. B. maydis and E. turcicum, which are more aggressive pathogens of hybrid corn than B. zeicola, occurred at lower incidences of 0–48% and 0–50%, respectively, in leaves from these fields at the time of sampling. This indicated that initial population densities of these aggressive pathogens were much lower than that of B. zeicola. Forty-five isolates of E. turcicum collected before 28 August were all race 1. Three isolates of race 2 were obtained later from fields of hybrids with the Ht 1 gene for resistance to race 1. All 75 isolates of B. maydis obtained from the 10 extensively sampled fields were race O; they were equally virulent on inbred line B73 with normal cytoplasm or B73 with C, S, or T male sterile cytoplasm. Frequencies of mating types of B. maydis and B. zeicola varied from field to field, with no correlation between the frequencies in the two species. Races 2 and 3 of B. zeicola, however, had similar mating type frequencies in these fields. B. sorokiniana was isolated from leaves from six of the 10 fields; the greatest incidence was 37%. E. rostratum was found in leaves from five fields at incidences up to 18%, and E. holmii occurred in leaves in one field at 11% incidence. These data indicate that a variety of species of Bipolaris and Exserohilum are able to infect green leaves of mature corn plants in the field. Thus, corn may contribute to the survival of species that are primarily pathogenic on other gramineous hosts.

Item Type: Article
Subjects: Others > Plant Pathology
Others > Entomology
Depositing User: Mr Charan Sai Ch
Date Deposited: 04 Dec 2011 12:20
Last Modified: 08 Dec 2011 05:54
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Acknowledgement: UNSPECIFIED
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