characterization of strains of dickeya zeae the causal agent of bacterial stalk rot of maize and evaluation of some maize hybrids resistant to these strains

samples with stalk rot, yellowing and stunting symptoms from maize fields in western provinces of iran were collected. after cultured of them on eosin methylen blue (emb) medium, twenty bacterial strains with metallic green color colonies on emb medium were selected for identification tests. according to the biochemical and phenotypic characteristics, these strains were identified as dickeya zeae. in order to, for evaluation of maize hybrids resistance to bacterial stalk rot, two methods including pseudostem injection and leaf puncture methods were used. in pseudostem injection method two hybrids, single cross 647 and 704, with most degree of stalk rot were placed in sensitive class (s), single cross 700 with medium resistance (mr) and single cross, 108 and 500 hybrids with least stalk rot were categorized as resistance varieties (r). the result from leaf puncture method has high correlation (r=0.93) with pseudostem injection method. hybrids single cross 704 and 647 as sensitive varieties and single cross 108 as resistant variety were introduced in this method.