نشریه دانش بیماری شناسی گیاهی
سال پنجم شماره 1 (پیاپی 9، پاییز و زمستان 1394)

Penicillium species have saprophytic live on plants debris, in the soil and also on some plant products, fresh and juicy damaged fruits as well as the storage fruit and grains. They can characterized by studying the features of their colony, conidiophores, phialids and conidia on selective culture media. The ability of some isolates of P. aurantiogriseum, P. bilaiae, P. chrysogenum, P. citrinum, P. funiculosus, P. glabrum, P. griseofulvum, P. oxalicum, P. purpurogenum and P. simplicissimum to control plants diseases such as Fusarium and Verticillium wilt of tomato, pulse white and gray molds, brown rot and blight twig of peach, late blight and cyst of potato has been proved. They also can act as plant growth promoter. Key morphological characteristics of these ten species of Penicillium is described in this paper. Most of these species are reported from Iran, thus identification and use of the efficient isolates of them can be suggested in management of plants diseases or in enhancement of plants growth programs.

Post- harvest rot of citrus fruits is one of the most important limiting factors that reduce the life of harvested products and are one of the most important economical diseases in world’s citrus production areas. Two most important fungi that affect the citrus fruits, are green and blue molds which are produced by Penicillium digitatum and P. italicum, respectively. The disease are mainly managed by using the synthetic fungicides, but because of environmental hazards and appearance of resistant strains of the pathogen, the biological control by the use of bacterial, fungal and yeast antagonists can be suggested. The efficiency of yeasts such as Candida guilliermondii, C. saitoan, Pichia guilliermondi and Aureobasidium pullulans; the bacteria Pseudomonas fluorescens, Bacillus subtilis, Pantoea agglomerans and the fungus Muscodor albus, in controlling the green and blue molds of citrus is reported so far. In this paper, we tried to explain the method of biological control with emphasizing on the identification of useful microorganisms and their operation.

Citrus trees are very important plants with high economic value and significant cultivation area in south of Iran. During the recent years, citrus die-back disease caused by Neofusicoccum mangiferae became one of the main treats for citrus production in tropical and sub-tropical regions of Iran. The symptoms of die- back disease are including wilting and declining of branches which start from the tip and then develop to down part of the trunk of infected tree, which sometimes has longitudinal cracks with gum exudation. Cortical layers of infected branches are sloughing off and the mass of fungal spores can be observe easily. Based on some investigations, pathogen is inactive during the winter months and its activity starts from spring and terminates at the end of summer season. The disease is more sever when it occurs in the orchards with poor disease management as well as water and nutrient deficiency. Some cultural practices like a well-managed irrigation and enough fertilizing with no pruning during the summer months, are good disease control measures, which in this paper are discussed.

Citrus greening or Huanglongbing, is one of the most devastating disease of citrus worldwide. It is common in the southeast of Asia and is also recently reported from south provinces of Iran. It is caused by Liberibacter sp. that tend to colonize in phloem vessels of the host. This bacterium affects all of the main types of citrus plants and reduces fruit production. One of the identifying challenges is that some of the disease symptoms are similar to deficiency of some nutrient such as zinc. The most important vectors of the disease causal agent are some psylla species. The only worthwhile control measure is removing the microbial inoculums from the affected tissues. Management of the disease described in this paper.

Piriformospora indica as the one of the most important soil endophytic microorganism, can increase yield of plants per unit area, by modifying the physiological characteristics of the host plants. It also provide the possibility of crop production in saline and arid soils or even in some conditions with biotic and abiotic stresses. It grants resistance to plant against diseases, through the induction of systemic resistance. Also the fungus can cause an increase in resistance to salinity and drought, through the increase in antioxidant capacity of root cells and levels of resistance proteins in their host plants. In order to adopt organic farming and achieve sustainable agriculture, this fungus can be used as a suitable alternative for chemical fertilizers and pesticides.

Ralstonia solanacearum is an important phytopathogen which reduces quantity and quality of potato. Due to its wide distribution and broad host range and in soil of different regions through irrigation water or latent infected tubers. It is generally difficult to control the damage of this bacterium. It has widely distributed in most of potato growing regions of Iran and by causing wilt and brown rot disease of potato, is a serious treat for cultivation of this crop in the country. Providing and sowing the healthy and certificated seed tubers is the most effective method of controlling the disease. For a successful strategy of disease management, a clear understanding of mode of disease distribution and epidemiology of causal agent is necessary. In this paper, recent scientific findings on this disease are described and new methods of bacterium detection and health assay of seed tubers are introduced.

During a compatible interaction, root-knot nematodes (Meloidogyne spp.) induce the root cells dedifferentiation into multinucleate feeding cells, known as giant cells. Hyperplasia and hypertrophy of the cells surrounding the head of nematode lead to the formation of a root gall. Different studies showed that the transformation of root cells into hypertrophied feeding structures, with unique morphology and functions, require some changes in the expression of a large number of genes. Previous approaches, based on differential gene expression between healthy and infected plants, analyses of known candidate genes by promoter GUS fusion or in situ hybridization and promoter trap strategies, have resulted in the characterization of about 50 genes of plant that are up regulated and 10 genes that are down regulated in giant cells. Microarray technology makes it possible to generate large-scale information about patterns of gene expression during plant–nematode interactions. A DNA microarray is a collection of microscopic DNA spots attached to a solid surface. Each DNA spot contains 10−12 moles of a specific DNA sequence, which are known as probes. These can be a short section of a gene or other DNA element that are used to hybridize a cDNA or cRNA sample that called as target. Probe-target hybridization is usually detected by detection of fluorophore or silver labeled targets.