Efficacy of Cinnamon Alcoholic Extract Compared with Selected Biological, Mineral and Chemical Treatments Against Alternaria alternata Causing Foliar Spot Disease on Pepper Plants

• Mohammed Qeas Mahmood Saleh1*, Saleh Mohammed Ismail1

  Author

Foliar spot disease caused by Alternaria alternata is an important constraint to pepper production, particularly under protected cultivation where humidity can favor pathogen development. This study evaluated the efficacy of cinnamon alcoholic extract compared with selected biological, mineral and chemical treatments against A. alternata associated with foliar spot of pepper. Symptomatic leaves were collected from pepper fields in Salah al-Din Governorate, Iraq, and the causal fungus was isolated, purified and identified by morphological and molecular approaches. The representative isolate MQ-1 was deposited in NCBI under accession number PX682709.1 and showed 100% identity with A. alternata isolate NXU-LM1, while pathogenicity screening of the collected isolates identified AH2 as the most virulent isolate for greenhouse evaluation. Under in vitro conditions, cinnamon alcoholic extract was tested at 5, 10 and 15% using the poisoned food technique and compared with Bacillus subtilis filtrate, zinc, Othello Top, Caribo and Zoxis treatments. The extract showed the strongest antifungal activity, with 76.53% inhibition at 5% and complete inhibition at 10 and 15%, giving a mean inhibition of 92.18%. Under greenhouse conditions, cinnamon extract reduced disease incidence to 65.55% and disease severity to 0.283 compared with 90.00% and 0.483 in the infected control, respectively. The treatment also maintained chlorophyll content at 47.19 SPAD units and produced the highest yield per plant (624.38 g), slightly exceeding the fungicide treatment. These findings indicate that cinnamon alcoholic extract has both direct antifungal and protective physiological effects and may be integrated with other management components for reducing A. alternata foliar spot on pepper plants.

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