M. F. Abbas

First Report of Alternaria Black Spot of Rose Caused by Alternaria alternata in Pakistan

In Pakistan, roses are commercially valuable as ornamentals and for perfumes essential oils, rose syrup, and herbal tea. During 2015-2016, circular to oval black spots (2 to 3 mm in diameter) were observed on roses in the cities of Islamabad and Rawalpindi. A total of 35 symptomatic leaves were surface sterilized with 1% sodium hypochlorite for 2 min and then rinsed three times with sterile distilled water. Excised segments (3 mm2) of surface sterilized tissue were transferred to potato dextrose agar (PDA) and incubated at 25 ± 2°C. After 5 days, white colonies developed from 25 samples and later turned black or golden brown. The conidia were borne singly or in short chains and were obpyriform to obclavate, 10-40 x 6.2-17.60 µm with 0 to 3 longitudinal and 2 to 6 transverse septa. The morphological characters matched those of Alternaria alternata (Fr.) Keissl (Simmons 2007). For confirmation of pathogenicity, three asymptomatic mature rose leaves were surface sterilized with 1% sodium hypochlorite and the...

FIRST REPORT OF CURVULARIA LUNATA CAUSING LEAF SPOTS ON LOQUAT FROM PAKISTAN

The loquat (Eriobotrya japonica Lindl.) is achieving significant value in Pakistan. During the year 2014-2015, reddish brown circular spots were observed on leaves; these spots increased in size and coalesced to form oblong lesions. Samples were cut into small pieces (3 mm2), surface sterilized with sodium hypochlorite and transferred on Malt Extract Agar (MEA). These samples were incubated at 24±2°C and dark brown colonies with large stroma were observed. Septate condiophores were unbranched or simple and geniculate with dark brown scar. Brown conidia were straight to pyriform with 3-4 cells (large and curved center cell), ranging in size from 6.9 to 20.99 μm and produced apically in a sympodial manner. Morphological characterization was similar to Curvularia lunata (Ellis, 1971). PCR was used for amplification of rDNA region (White et al., 1990) and sequences of PAK34 and PAK35 was submitted to GenBank under accession Nos. KT280007 and KT280008. Both isolates were exhibiting 99% genetic homology with previously reported C. lunata isolates (KM246260, KM246262). Spore suspension (1 × 106 spore/ml) was sprayed on healthy loquat seedlings, kept in glasshouse at 30°C and plants developed lesions similar to those observed on naturally infected plants. Isolation was performed from inoculated loquat plants and morphological characterizations were similar to naturally isolated pathogens. Curvularia leaf spot diseases caused by C. lunata have been previously found on small evergreen tree. To our knowledge, this is the first report worldwide of C. lunata causing leaf spots on loquat.