نشریه دانش بیماری شناسی گیاهی
سال پنجم شماره 2 (پیاپی 10، بهار و تابستان 1395)

Edible mushrooms that are known as the truffle are classified in apothecial ascomycetes. They are obligate ectomycorrhiza of plants and produce their fruiting bodies on or below the surface of the soil. The genus Tuber belongs to the order Pezizales, class Pezizomycets, and has numbers of species with universal distribution. So far, France, Italy, United Kingdom and New Zealand have tried for the commercial production of truffle. Among the species of edible truffle of the universe, two valuable species, the white truffle, T. magnatum, and the black truffle, T. melanosporum, are the most valuable species. Because of their economic and medicinal importance, this is necessary to perform scientific research for their accurate identification.

Cercospora leaf spot disease is one of the most important foliar diseases of sugar beet. Over one third of the sugar beet cultivation areas of the world has been affected by this disease. Cercospora beticola is the causal agent of this disease and a high level of interspecific variation of its morphology and genetics has been reported. Disease management is mainly achieved by a combination of cultural practices, cultivation of resistant varieties and application of fungicides. Due to the economic importance of the disease in Iran, some of the different aspects of Cercospora leaf spot disease, including the introduction of disease as well as the biology of the fungus, disease cycle and the efficient measures of disease management, has been reviewed in this paper.

Lime is one of the most important economic and horticultural plants in the southern part of Iran. Among the diseases of citrus in south of Iran, Witches Broom Disease of Lime (WBDL) is one of the major citrus diseases. The causal agent of WBDL is a phytoplasma with the proposed name, Candidatus Phytoplasma aurantifolia. The symptoms of disease start with appearance of witches broom at one-side of the infected tree. The disease then spread to whole parts of plant showing leaf proliferation, shortened internodes, small and pale green leaves, no formation of any spine, flower or fruit and finally death of the infected plants. To control the disease, integrated management and cultural practices has shown to be effective methods. Elimination of symptomatic trees as well of the newly emerged infected branches, chemical or mechanical weed control and a periodic spraying by systemic pesticides against the vector insect, or a combination of these methods is highly recommended. Among the control measures, chemical control of the vector has showed is very effective for reducing the disease spread and severity.

Sugar beet, is one of the basic source of the raw material for sugar industry in Iran. The beet cyst nematode, Heterodera schachtii Schmidt, 1871, is one of the most damaging pathogens of sugar beet. This nematode has a wide host range, including 218 plant species from 95 genus and 23 families, which include some of the important field crops, ornamental plants and weeds. Nematode management methods include avoiding of cultivation in highly infested soils, disease scape by early cultivation, crop rotation, using resistant varieties, application of bioagents, applying of organic fertilizers, animal manure, plant waste materials, compost, vermicompost and also soil solarization and chemical control are described here.

Rhizoctonia root rot which is caused by Rhizoctonia solani Kühn, seriously reduces the yield of bean. To prevent the widespread distribution of the disease in the main bean growing regions, it requires accurate identification of the effecting factors on disease occurrence and prevalence. Due to the lack of resistant cultivars and ineffectiveness of the chemical measures in the soil, the cultural practices play an important role in disease control. According to the findings, increasing the organic matter, improving the activity of nodule-forming rhizobia on root, avoiding of bean cultivation in sandy soils, maintaining the neutral pH level of soil, irrigation at 7-9 days interval in growing season, planting with a standard density of 30 plants per square meter, seeding at depth of 5 cm in the warm and dry climatic conditions, sprinkler irrigation, kidney beans growing in the infected fields, appropriate rotation program, applying maximum 50 kg urea /ha, weed control, seeder machine adjustment, soil application of fungicides and seed treatment with proper systemic fungicides should be considered in an integrated management program. Proper application of rhizobacteria can effectively reduce the use of chemical fertilizers as a complementary control measure.