Phenotypic, pathogenic, molecular and phylogenetic comparisons of bacteria causing Aloe rot from three countries

Abstract

Bacterial soft rot disease of Aloe due to heterogeneous genus Erwinia was reported from different parts of the world. In the recent past the genus underwent major taxonomic modifications. In the present study we have compared four Aloe pathogenic bacterial strains isolated from India, The Netherland and Yugoslavia. Different cultutal, biochemical, physiological and pathological characters and protein/lipid profiles indicated that the strains belonged to two different genera – Pectobacterium and Dickeya. Species specific amplification of pel gene products also supported this. Phylogenetic analysis of rRNA gene (rDNA) sequence placed these Dickeya strains close to D. dieffenbachiae and D. zeae. On the other hand, phenotypic tests suggested these to be either of D. dadanti, D. dieffenbachiae and D. zeae. On the basis of pathogeneicity of the test strains on Dieffenbachia leaves, these were placed in D. dieffenbachiae. The Yugoslavian strain was identified as P. carotovorum. Phenotypic test like lypolitic activity and protein composition also detected variation based on geographical origine of the strains. RFLP analyses of ITS and rDNA fragments deciphered variation among the same species. However, none of the six Aloe species tested in our study shoed resistance against any of the test cultures.