Abstract

Mahsa Alimi*, Heshmatollah Rahimian, Nader Hassanzadeh, Meysam Taghinasab Darzi, Asadollah Ahmadikhah, Asghar Heydari and Giorgio Mariano Balestra

This study was conducted for detection and identification of the causal agent of blossom blight of apple, which results in blast of whole tree. During spring 2011, a newly occurring disease was observed in 4 to 5 years-old Malus domestica (cv. Mutsu) trees in Northern area of Iran. A bacterial population was repeatedly isolated from the infected plants. Koch’s postulate (pathogenicity test) was fulfilled on potted plants under controlled environmental conditions (greenhouse). Based on morphological, physiological, biochemical and pathological tests, the causal agent was identified as Pseudomonas viridiflava. Polymerase chain reaction (PCR) identification of the bacterial isolates was done based on newly designed consensus primer pair (PsV-F and PsV-R). The consensus primers were achieved by alignment of P. viridiflava 16S rRNA gene sequences available in nucleic acid data bank, National Centre for Biotechnology Information (NCBI) database. This primer set was successful for detection of P. viridiflava strains. Deoxyribonucleic acid (DNA) fragments amplified by this primer set gave a specific amplification band of ~180 bp. Sequencing was done directly (PCR products). Single bands of two isolates were extracted and sequenced for molecular characterization and compared with sequences available in Gene Bank (NCBI), using BLAST search tool. The results showed complete identity of isolates with those of the P. viridiflava strains in the databases. This to our knowledge is the first report of the occurrence of P. viridiflava on apple.