mehdi azadvar

Gray mold, caused by Botrytis cinerea is one of the most important diseases in strawberry, causing pre– and postharvest fruit rot. One of the safe and healthy ways to reduce this disease is biocontrol and the use of biological control agents. In this study, using culture–based methods, 268 bacterial strains, and 136 fungal isolates, were isolated and purified from the phyllosphere of strawberry plants in the greenhouse and field in Jiroft city. The antagonistic effect of the isolates against the pathogen B. cinerea was investigated using dual culture and investigation of the inhibition zone, and the effect of volatile compounds under in vitro conditions, as well as the antifungal properties of the antagonistic bacteria on strawberry fruit. Identification of the selected bacterial and fungal strains was made by polymerase chain reaction, respectively, by determining the nucleotide sequence of a part of the 16S–rDNA gene and its region. The results showed that among the examined isolates, bacterial isolates UJB1, UJB3, UJB4, UJB10, UJB5, UJB6, UJB7, UJB11, UJB2, UJB8 and UJB9 and fungal isolates UJF1300, UJF1301, UJF1302, UJF1303, UJF1304, UJF1305 had an effective inhibitory effect against B. cinerea and their volatile compounds reduced pathogenic mycelium growth. In evaluating the antifungal impact of bacterial isolates on strawberry fruit, bacterial isolates UJB8, UJB2, UJB11, UJB6, UJB5, UJB10, UJB4, and UJB1 significantly increased the disease index caused by B. cinerea compared to They reduced the witness. According to morphological and molecular data, bacterial isolates belonging to the genera Delftia (isolates UJB1, UJB3, UJB4, UJB10), Bacillus (isolates UJB5, UJB6, UJB7, UJB11, and UJB2) and Stenotrophomonas (isolates UJB8 and UJB9) and fungal isolates belonging to Albifimbria verrucaria, Aspergillus terreus, Leptosphaerulina australis, Pilidium lythri, Pseudozyma flocculosa, and Seimatosporium pistaciae species.

Plant diseases play a critical and limiting role in crop production and their control by using pesticides cause serious problems regarding food safety and environmental health and increase the need for other sustainable disease management techniques. Some of plant pathogens may infect the aerial parts of plants, but spent part of their life cycle in the soil and maintained their survival. In such cases, part of the life cycle of the plant pathogen in soil may be very important, even if that microorganism does not infect the roots. Mono culturing and cultivation of crops belonging to the same family increase the potential of disease incidence. Using and applying the suitable and correct cultural practices that limit damage of root diseases is necessary for sustainable management of soil-borne pathogens. Cultural operations, including the use of cover green crops, crop rotation, organic composts, certified seeds and propagative materials, amended organic material to soil, proper tillage systems, soil solarization, resistant cultivars, mycorrhizal fungi, all are reported and confirmed as management options for long time saving soil quality and good sustainable management of soil borne diseases.

Citrus production is very important in term of economical and productivity in south of Kerman province, Iran. During recent years, occuring a new decline disease caused sever threat in citrus orchards in south part of Iran. The disease symptoms starting with significant growth retardation of infected plants. Sever  root rot can be seen easily on infected trees. In this research, the partial distribution of citrus declining disease, the population of citrus root nematode (Tylenchulus semipenetrans) and Phytophthora nicotiana were counted in bouth healthy and infected trees. The partial distribution of citrus decline was 76 percent. The results showed that the investigated samples were infected to citrus root nematode moderate to sever level. The mean of female nematode population per gram root of infected and healthy plant reported 210 and 11 respectively. The mean of 2nd larva populations per 200cm3 soil samples of infected and healthy plants were calculated 2573 and 183 respectively. The numbers of propogules of P. nicotiana in one gram soil rhizosphere of infected and healthy trees reported 13.5 and four respectively. Inoculations of bakraee seedling (rootstock) with nematode and Phyophthora showed sever root rot and nematode infection and finally death of plants. Based on the results of this research, a complex of Phytophthora and citrus nematode are involved in citrus decline disease and can affect the disease severity in south of Kerman.

Bacterial canker disease is one of the most destructive diseases of walnut trees that causes die back and plant decline and also great damages to quality and quantity of fruits. The disease can be observed in two forms, at depth and the surface of the bark which cause by two bacteria, Brenneria nigrifluens and B. rubrifaciens, respectively. The most important way of the pathogen penetration is the wounds in the trunk and branches which are occurred due to human ‎activities or mechanical harvesting equipment. The disease becomes severe with the deep irrigation and when the nutrition is insufficient and ‎temperature and humidity are high.‎ Current paper explains history, importance, symptoms, biology, host range, sampling and isolation method also differential characteristics of bacteria and methods of disease management.

During recent years, the newly emerging disease, citrus sudden decline (CSD) has destroyed many of citrus trees grafted onto bael rootstock in the south of Kerman Province. The disease is caused by Candidatus Liberibacter asiaticus and its simultaneous infection to soil born pathogens or Ca. Phytoplasma aurantifolia, or heat and drought stresses can increase the disease severity and appearance of the decline symptoms. Using the healthy and certified rootstock, using the Sour Orange or Volkamer Lemon as rootstock, control of the sucking insects at the time of flushing, optimum irrigation with appropriate distribution especially during the summer season, control of soil born fungi and nematodes, avoiding stress to plant and appropriate pruning are recommended for prevention and management of CSD disease in the south of Kerman Province.

Land-use change is one of the most important factors influencing soil microbial communities, which play a pivotal role in most biogeochemical and ecological processes. In order to determine the effect of land use on the relative abundance and composition of soil bacterial communities by using Real-time PCR, a study was carried out in three different land uses (orchard land, farmland and shrubland) in Jiroft plain, Iran. 12 surface soil samples were collected from each land use and some soil physicochemical properties were measured. The NucleoSpin® Soil kit was used for extraction and purification of DNA from soil samples. Quantitative comparison of the concentration and melting temperature of 16S rDNA amplicons, respectively, for assessment of the relative abundance and composition of soil bacterial communities in different land uses were performed by using Real-time PCR system and based on the relative standard curve method. The results related to the concentration and quality of soil DNA indicated that extraction of DNA from soil samples by using NucleoSpin® Soil kit was favorable. As the results of Kruskal-Wallis nonparametric ANOVA showed, land use had significant effect on the relative abundance and composition of soil bacterial communities at the level of 5%. Means comparison showed that the relative abundance of soil bacterial communities in orchard land use was higher than that of two other land uses. Furthermore, the composition of soil bacterial communities in orchard and farm land uses was significantly different from shrub one. It can be concluded that land-use changes in Jiroft plain from shrubland to orchard land, and from shrubland to orchard land and farmland have caused an increase in the relative abundance as well as a significant change in the composition of soil bacterial communities, respectively.

The emerged citrus quick decline disease has destroyed many of citrus plants grafted onto Bakraee rootstock in southern Kerman during recent years. Disease symptoms are included leaf wilting, root rot, and quick decline. In this project, the etiology of quick decline disease was studied. Symptomatic and asymptomatic plants were tested for the presence of plant pathogenic prokaryotes using PCR with universal and specific primers, and Miseq Illumina method. Furthermore, ELISA, RT-PCR, inoculation on index plants, and dsRNA extraction were used for detection of viruses and viroids in symptomatic and asymptomatic plants. The correlation between the presence of Tylenchulus semipenetrans, Phytophthora nicotiana, and quick decline disease was investigated by isolation and quantification of pathogens from root and rhizosphere of asymptomatic and infected plants. Overall, results indicated the association of Candidatus Liberibacter asiaticus with citrus (on Bakraee rootstock) quick decline disease in southern Kerman. In addition, drought and heat stresses and co-infection of the diseased plants by Ca. Phytoplasma aurantifolia, Phytophthora nicotiana, and Tylenchulus semipenetrans lead to severe symptoms of the disease and accelerated the decline of the infected plants.

Biological control of soil-borne diseases of plants has received serious attention among plant pathologists in recent years. In this regard, Rhizobacteria, more specifically fluorescent pseudomonads are known as an effective biocontrol of plant diseases. Pseudomonas spp. are promising agents to manage the disease caused by Sclerotinia sclerotiorum and Pythium aphanidermatum. In this study, we screened 81 bacterial isolates from cucumber rhizosphere for their antagonistic effects against the pathogens using dual culture method and investigating their ability to produce inhibiting volatile metabolites. Results indicated that isolates 19C, 21B, 24A, 33B, 33C, 38A, 42D, and 43C had significant inhibitory effects on the pathogens and their volatile metabolites significantly reduced the mycelial growth of the pathogens in comparison with controls. In greenhouse trials, isolates 19C and 24A reduced disease index of Pythium aphanidermatum more than 70% and that of Sclerotinia sclerotiorum more than 60% compared with controls. The isolates 19C, 24A, 33B, and 33C were able to produce protease. Isolate 19C was able to produce surfactin and isolates 33B and 33C were able to produce hydrogen cyanide. Molecular identification of isolates was conducted based on partial sequence of 16srDNA amplified by specific primers fD1 and rD1 thereby the isolates showed significant homology with Pseudomonas spp., Stenotrophomonas spp. and Flavobacterium spp.

Sclerotinia sclerotiorum is an important plant pathogenic fungi. Biocontrol agents such as Bacillus spp are promising to manage the disease caused by this fungi. In this study, we isolated 63 strains of Bacillus spp from cucumber rhizosphere based on morphological, physiological and biochemical characteristic. The antagonistic activity of isolates were assessed using dual culture method and the producing of volatile metabolites against pathogen. The isolates Ba17¡ Ba24¡ Ba14 and Ba29b showed the most inhibitory effects against the pathogen in dual culture method. Volatile metabolites of isolates Ba21, Ba29c, Ba10b, Ba17, Ba29b, Ba9c and Ba12a, reduced mycelial growth of the pathogen 87.14, 84.85, 83.42, 82.42, 79.14, 79.14 and 77.71%, respectively and had a significant difference with control. In greenhouse trails, isolates Ba17 ¡Ba21¡ Ba10b¡ Ba29c and Ba14 decreased the disease index of Sclerotinia stem rot, significantly. The isolates of Ba29c, Ba10b, Ba17, Ba29b, Ba24 were able to produce protease. The Isolates of Ba29c, Ba10b and Ba21 were able to produce surfactin. Molecular identification of isolates with antagonistic activity against this pathogen by partial sequencing of 16S rDNA gen which amplificated with specific primers fD1 and rD1 was performed. The isolates had homology with Bacillus cereus, B. licheniformis, B. endophyticus and Lysinibacillus sp.

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.