Molecular Diagnosis of Alternaria spp. Causing Citrus Dieback in Central Iraq

Abstract

Dieback diseases of hardwoods are a general term used to refer to a multitude of diseases primarily caused by fungal pathogens.This study was conducted to identify the genetic polymorphisms of three local species of Alternaria that isolated from infected citrus leaves,fruits,branches stains from Karbala city. One genetic locus covering a portion of the ribosomal subunit of the RNA gene was amplified in this study. A direct sequencing strategy was performed for the observed PCR amplicons in the amplified ribosomal locus. Subsequently, a comprehensive phylogenetic tree was constructed in the observed variants to assess the accurate phylogenetic distances with other relative fungal sequences. Our results indicated the presence of entire homology between our investigated samples and several species within Alternaria, namely A. alternata, A. destruens, and A.  tenuissima, while A. brassicicola was slightly tilted from the other observed variants in the comprehensive tree. Interestingly, all observed variations were taken one pattern of phylogenetic distribution, represented by the close positioning in the vicinity to A. alternata species. However,  the present tree showed that there was extremely close homology between the incorporated species of A. alternata, A. destruens, and A.  tenuissima. Furthermore, the phylogenetic tree provided further tools regarding the guaranteed identity of the investigated samples. Therefore, the utilization of PCR-sequencing strategy in three analyzed DNA samples of these local fungal species have presented a confirmed identity of these strains within the Alternaria sequences.