الهه لطفعلی نژاد

The use of biocontrol agents is a promising and safe method towards achieving environmental goals for controlling plant diseases. However, due to the lack of stability and appropriate and applicable formulations, the results obtained from the application of these agents, especially in agricultural fields, have not been sufficiently efficient. This study was conducted with the aim of developing a capsule formulation using sodium alginate to increase the viability and improve the performance of Bacillus subtilis. Capsules were prepared using the ionic gelation method. The encapsulation efficiency was estimated to be 99%. The mean size of the wet and dry capsules produced was 2600 and 1000 micrometers, respectively. The effects of ultraviolet radiation on the survival of B. subtilis showed that the bacterium in the capsule state (wet and dry) was more resistant to ultraviolet radiation compared to the non–encapsulated state. With increasing exposure time to ultraviolet light, bacterial cells resistance in the capsule state were greater than in the non–encapsulated state. The results of the thermal resistance examination at different temperatures emphasized the positive role of the capsules in increasing the survival and resistance of B. subtilis compared to the non–encapsulated state. The survival percentage of non–encapsulated B. subtilis after 60 days at 25 and 35 degrees Celsius decreased by 42% and 47%, respectively. However, for the encapsulated B. subtilis, the survival percentage decrease after the same period and temperature was estimated to be 16.5% and 26%, respectively. Greenhouse results showed that the use of B. subtilis capsule formulation reduced disease percentage compared to non–encapsulated B. subtilis and sodium alginate capsules alone. The disease percentage in plants treated with encapsulated B. subtilis was estimated to be 4.44%, while this rate was 73.33% in the control. Plants treated with encapsulated B. subtilis had significant differences in growth indices compared to the control. Growth index changes in relation to different formulations of B. subtilis (encapsulated, non–encapsulated) and sodium alginate capsules alone were significant only for root height. These results emphasize the positive role of using B. subtilis and capsule formulation in controlling damping–off caused by Rhizoctonia solani in tomato plants.

Fusarium wilt disease of tomato is caused by Fusarium oxysporum f. sp. lycopersici is reported to cause great losses in tomato production globally, and is a limiting factor to tomato production in Ramian region, Golestan province. This experiment was conducted to evaluation of soil physicochemical properties impacts on tomato Fusarium wilt.

Soil samples of tomato fields were randomly selected in the Ramian region and the physical (pH, EC) and ochemical (organic matter, N, P, K) properties were measured by titration, flame photometry and spectrophotometry methods. Disease assessment (soil inoculum, external and internal scale) also recorded in different fields. For analyzing the association between disease assessments with soil physicochemical properties, a correlation analysis was used.

The results showed a low positive, but significant correlation between pH and soil inoculum. In return, the correlations between EC, N, P, K and organic matter and soil inoculums were not statistically significant. There was a significant correlation between EC, K and soil inoculums with external scale, also a positive and negative correlation observed between internal scale with soil inoculums and with K and P, respectively. The correlation between soil inoculum with yield of first, second and total harvest were not statistically significant, but anegative significant correlation observed between soil inoculum with yield of third harvest. The correlation of internal scale and yield of first harvest was also negative and significant.Conclution: The results showed the role of plat nutrition especially K in tomato fields for wilt disease cotrol.

The effects of priming with different concentrations of indole-3-acetic acid (IAA) on physiological characteristics of three cotton cultivars (Sahel, Golestan and Varamin) as well as their effects on controlling of damping-off caused by Rhizoctonia solani were investigated in two separate experiments. To determine the effects of IAA on seed germination, IAA was used at 0, 0.1, 0.01 and 0.001 μM in plastic petri dishes. In the second experiment seeds treated with 0, 0.1, 0.01, and 0.001 μM IAA grown in infested soil with R. solani inoculum. Shoot and root growth and fresh weight were evaluated 28 days after sowing and the total phenolic content of the root extract was determined by the Folin–Ciocalteu method. The results showed that seed germination, growth of shoots, roots and fresh weight increased significantly by the application of a low concentration of IAA (0.01 and 0.001 μM). The application of 0.01 and 0.001 μM of IAA also reduced disease index caused by R. solani, 17% and 38% in Sahel and 1% and 33.5% in Golestan and Varamin, respectively. The concentrations enhanced total phenolic content in defence system. Primed seeds showed a significant effect on some physiological characteristics and disease index in three different cultivars.