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Characterization of disease causing agent of apical necrosis of mango

Shazia Iram: Fatima Jinnah Women University, Rawalpindi

<div>Bacterial apical necrosis is observed as a major threat for healthy mango production in different mango orchards of Punjab, Pakistan during the field survey conducted in three selected districts of Punjab viz. Multan, Khanewal and Muzaffargarh in 2015. Symptoms of bacterial apical necrosis were noticed on newly buds, stems and leaves during the survey. To validate the status of mango apical necrosis thirty eight orchards were visited in these three selected districts with the objective to assess the prevalence, incidence and severity of disease and to characterize the pathogen causing the disease at molecular level. According to the results, disorder was found widely distributed with 100 % prevalence in Multan and Khanewal and 70 % in Muzaffargarh. The highest (0.9 %) bacterial apical necrosis incidence was recorded in Multan and Khanewal followed by Muzaffargarh where the lowest (0.5%) incidence was recorded. The maximum (4-5 %) severity of bacterial apical necrosis was observed in Multan and Khanewal while minimum (3-4 %) disease severity was observed in Muzaffargarh. Overall disease index in Multan (31 %), Khanewal (12 %) and Muzaffargarh (8 %) were recorded. Samples of diseased mango buds were collected from each location surveyed, isolated on Nutrient Agar and Kings’ B media. Using “toothpick method” DNA with high molecular weight was extracted and molecular based analysis was done using the primers 27F and 1492R. The strains was identified based on 16S rRNA gene analysis as <em>Pseudomonas syringae</em> strain ICMP 3023, <em>Pseudomonas syringae</em> strain NCPPB 281, <em>Pseudomonas syringae</em> strain ATCC 19310, <em>Pseudomonas syringae</em> pv. <em>tomato</em> strain DC3000, <em>Pseudomonas putida</em> strain ATCC 12633, <em>P</em><em>seudomonas savastanoi </em>strain ATCC 13522, <em>Pseudomonas syringae pv. phaseolicola </em>1448A strain.</div>