Detection and Morphological Identification of Alternaria alternata Associated with Juniperus phoenicea L. Seeds

Abstract

The Juniperus phoenicea L. It is evergreen perennial trees that dot the Green Mountain region, where a large percentage of the permanent vegetation cover is formed. Despite its great environmental importance in preventing erosion and preserving the soil, its seeds are sometimes exposed to fungal infection, which negatively affects their germination rates and hinders the processes of natural regeneration and plant expansion. This research is aimed at isolating and diagnosing the fungus Alternaria alternata from the seeds of infected Phoenician juniper trees, studying its morphological characteristics, using laboratory cultivation methods and microscopic examination. Infected seed samples were collected from the Wadi Al-kuf area located in the Green Mountain, an area rich in juniper trees and with favorable climatic conditions for its growth. After sterilizing the seeds and planting them on a nutrient medium (PDA), the results showed the presence of fungal colonies belonging to Alternaria alternata, a widespread pathogenic fungus, known for its ability to infect seeds and leaves, and is one of the most important causes of spotting and retrograde death in many plants. The study showed that the percentage of the appearance of mushrooms amounted to 60.72% of the total samples, and the results also showed the appearance of colonies of a dark brown-black color with velvety edges, in addition to the dark olive color of the colonies, and the presence of polymorphic dark conidial spores, divided transversely and longitudinally, clustered in short chains, which are characteristic features of the fungus Alternaria alternata identification was confirmed using the morphological characteristics of colonies and spores under the microscope, in addition to relying on the keys to the classification of fungi. The results of the study confirmed the similarity of the phenotypic qualities of the isolated fungus with what was reported in the scientific literature, indicating that the environmental conditions in the region (such as humidity and moderate temperatures) contribute to the growth and reproduction of the fungus, which makes it a source of danger to the health of Juniper seeds, and affects the natural regeneration of this ecologically and economically important tree