First report of Alternaria alternata causing leaf blotch and fruit spot of apple in Pakistan

Alternaria leaf blotch (ALS) or Alternaria fruit spot (AFS) on apple is a serious disease in temperate parts of the world. To determine distribution of the causal pathogen, a field survey was carried out in apple orchards of Loralai district, Balochistan province, Pakistan during 2016. Characteristic symptoms of irregular purplish-brown spots (1.5-4 cm diam.) were observed on infected leaves as well as on the fruit of 6-year-old apple trees. Representative isolates of Alternaria alternata were identified according to their preliminary morphological features and multi-locus phylogeny inferences. Pathogenicity assays revealed that isolates of A. alternata recovered from Dargai region are more highly pathogenic than isolates from Zar Karaz, producing large necrotic brown lesions on both detached leaves of Gala and fruits of Red Delicious cultivars at 9 days post-inoculation. This is preliminary information of A. alternata causing ALS and AFS in Pakistan.