نشریه دانش بیماری شناسی گیاهی
سال هشتم شماره 1 (پیاپی 15، پاییز و زمستان 1397)

Pseudocercospora species are plant pathogenic fungi occurring on a wide range of herbaceous and woody plants. Since its early description of the genus, its taxonomy has always been challenging. In recent years, Multi-gene DNA sequence data have provided significant information on the accurate taxonomy of the genus Pseudocercospora. These data revealed that the species of Pseudocercospora are polyphyletic and evolved in more than one approach within family Mycosphaerellaceae, order Capnodiales, class Dothideomycetes, phylum Ascomycota. Also those species from different geographic regions but with the same morphology, symptomatology and host range, may reside in different phylogenetic clades. Accurate identification of the plant disease agent is the first step to adopt the appropriate management strategies of the diseases related to these plant pathogens. Key features of morphology and new genetic data for identifying the species of the genus are described in this article.

During recent years, citrus trees decline has becoming one of the most important factors of limiting the area of citrus orchards in the south of Iran including Fars province. Different biotic and abiotic agents were attributed to citrus decline worldwide, but it appears that some abiotic stresses including soil drought, and soil or water salinity, as well as some infectious diseases including gummosis, dieback, citrus nematode and witch’s broom are more important in Fars province. This is an attempt to gather information of the potential agents of complex diseases known as “citrus trees decline”, as well as, discussion on management strategies of citrus decline in Fars province.

Essential oils are hydrophobic, volatile and aromatic compounds that have been used as fragrances and flavors for a long time. Recent studies have shown that some plant essential oils have fungicidal effects against some important plant pathogens. For instance, the essential oil of thyme inhibits the mycelial growth of Penicillium italicum and the essential oil of lavender shows the fungistatic effect on ‎ Botrytis cinerea, Rhizopus stolonifer and Aspergillus niger. The essential oil of thyme has also been used to control the black rot of orange caused by Alternaria citri and grey mold of strawberry fruits caused by Botrytis cinerea. Antifungal activities of essential oils are mainly related to their effects on fungal cell wall, cell membrane, mitochondria and nitric oxide level. As a result of increased concern about harmful chemical pesticides, essential oils can have a good place in the market as natural fungicides. In this paper, application of essential oils as natural fungicides, their mode of actions and some safety aspects of their application have been discussed.

Pomegranate is an important fruit crop which is attacked by several pests and pathogens. Diseases caused by nematodes are of economic importance. The root knot nematodes (Meloidogyne spp.) causing considerable yield losses in pomegranate.  Root knot nematodes are sedentary endoparasite that are basically parasites of the roots, produces knots on root which cause weak root function in the absorption and transfer of water and nutrient. Above ground symptoms include dwarfing the plants, yellowing and reduction of foliage, falling leaves and yield losses. Under favorable temperature and moisture, eggs are hatching and second stage pathogenic juveniles are released. The management strategies are including sanitation, construction of nursery in healthy areas, annual plowing of garden, drip irrigation, soil solarization, organic amendment of soil and strengthen the trees.

The genus Cladosporium is one of the largest genera of fungi. Its species live in different ways: as plant pathogens, as saprobes in the soil or on decaying plant materials, or as hyperparasitic on other fungi. Morphological characteristics of conidia such as shape, formation and surface ornamentation, the features of conidiophores including shape, ramification and conidiogenous loci, and sequencing data from different regions of DNA are very important for identification of Cladosporium species. In this article the important morphological characteristics and genomic regions which are useful for identification of closely related or cryptic species of this genus, are illustrated.

In the recant decade, biopesticides with entomopathogenic nematodes (EPNs) have been developed with using different methods and materials. But the production of such biopesticides has always accompanied by some limitations such as low quality of the final product, and reducing the efficacy under field conditions. Recently, significant progress has been made in increasing in the survival time of these products. Applying two types of formulations, water dispersible granules and calcium alginate capsules, has increased the EPN survival time from 7 days to 180 days. As compare to aqueous formulation, the formulations based on the use of insect cadavers with EPNs, showed higher efficiency in pest control. New methods of the mass production of EPNs, using automated production lines and the use of new additives with better properties for field applications and methods in increasing the infectivity of these nematodes in pests are discussed in this article.