Cultural, morphological, pathogenic and molecular characterization of Alternaria mali associated with necrotic leaf spot of loquat

Abstract

In Pakistan, loquat (Eriobotrya japonica) in an emerging fruit and provides well economic return to growers.Percentage disease incidence of necrotic leaf spot (Alternaria mali) ranged from 25 to 46.16% in Taxila, Wahcant, Khanpur, Kalar Kahar, Choa Saiden Shan, Tret, Chatar and Murree. 48 isolates were characterized for cultural, morphological and pathogenic variations. Light to dark olivacious colonies were appraised, cottony to velvety with regular to irregular margins and variations in size and shape of conidia were observed between isolates. Length of conidiophores was ranging from 24.6 to 68.5 µm and nine was the highest septation in isolate ALT7WT1. Nucleotide sequences of inter transcribed spacer region (ITS1, 5.8S, ITS2) from 4 highly virulent isolates were submitted in the database of NCBI under accession numbersKR232489, KR232490, KT154010 and KT154011 respectively. Evolutionary history was computed with available sequences of A. mali, A. lternata, A. zinnae and A. tenuissima which were reported from Pakistan, USA, Sweden, Newzeland and India. Evolutionary tree showed4 different sub-trees and submitted sequences were observed in A. mali sub-tree. Amino acid sequences were exhibiting 100 to 99% genetic homology with A. mali isolate (FCBP1343) reported form Pakistan. Amino acid sequences were compared with FCBP1343 and differences at position number 18 (valine was replaced with glutamate), 57 (glutamine with leucine), 84 (alanine with glycine), 163 (glutamine instead of histidine) and 171 (serine was replaced with phenylalanine) were observed. Cultural, morphological, pathogenic and molecular characterization of A. mali associated with necrotic leaf spot of loquat was recorded first time in Pakistan.