The first report of kernel spot caused by Eremothecium coryli on Iranian hazelnut

Abstract

Brown spot formation with necrosis and sloughing off pellicle and sunken surface lesions under visibly healthy shells is one of the quality problems of Iranian hazelnuts. The symptomatic kernels were investigated for isolation of the causative bioagents. The quality attributes of infected and non-infected hazelnuts were investigated. The results showed that the total phenol content and antioxidant activity of the infected hazelnut samples were higher than non-infected samples. The infection enhanced the soluble protein content and affected the soluble protein profiles, either in the pattern or in the intensity of the protein bands. The color parameters decreased, which led to darker infected hazelnut samples. The infection also caused the alteration of the fatty acids composition of hazelnuts, which was a remarkable increment in the relative amounts of saturated fatty acids and a decrement in the unsaturated fatty acids. The optical microscopic and Scanning Electron Microscope (SEM) micrograph observation of the defective hazelnut kernel indicated the kernel parenchyma tissue had been damaged, and the microbial culture from many necrotic points revealed that this contamination due to the presence of yeast-like fungus, white to slightly creamy, round colonies with raised centers and peripheral mycelial fringes. The pathogenicity of a yeast-like fungus (isolate of NAS 201) was proved by fulfilling Koch's postulates, and the morphological and molecular identification (internal transcribed spacer region as DNA barcoding) indicated the presence of the fungal agent Eremothecium coryli. To our knowledge, this is the first report of the occurrence of yeast spots in hazelnut in Iran.