ALTERNARIA ALTERNATA CAUSING FRUIT ROT AND LEAF SPOT ON LOQUAT IN IRAN

Abstract

A fruit rot and leaf spot disease of loquat (Eriobotrya japonica) was observed in May 2013 in the Sari city of Mazandaran province (Iran) on nearly 40% of the trees planted for arboretum. Tissue fragments from surface-sterilized (75% ethanol for 1 min, and 1% sodium hypochlorite for 3 min) fruits and leaves were excised and transferred to potato dextrose agar (PDA). White fungal colonies were obtained which turned grayish-black due to abundant sporulation. Pale to light brown obpyriform conidia with a beak, showing one to seven transverse and up to three longitudinal septa, measuring 10-45 x 7-22.5 μm, were produced in long chains. Conidiophores were straight, septate, and measured 35-100 × 2-5 μm. These morphological traits conform to those of Alternaria alternata (Simmons, 2007). Leaves and fruits of 12 healthy loquat plants were inoculated by spraying to runoff a spore suspension (105 conidia/ml sterilized water) from three fungal isolates, while an equal number of control plants were atomized with sterile water. After one week, characteristic symptoms resembling those observed in the field developed on all inoculated plants; control plants were symptomless. The pathogen was re-isolated from all inoculated plants. Genomic DNA from a single-spored isolate was extracted and the major allergen of A. alternata (Alt α 1) regions was amplified and sequenced using primers Alt-for and Alt-rev (Hong et al., 2005). BLASTn analysis of a 478 bp sequence (GenBank accession No. KJ396786) showed 100% homology with A. alternata (AF288160). A. alternata is reported to infect over 48 different plants in Iran (Ershad, 2009), to which loquat can now be added.