ارزیابی تاثیر سودومونادها بر تحمل گیاهچه گندم به Bipolaris sorokiniana با تعیین شاخص‌های فلورسانس کلروفیل

The contamination of plants with pathogens leads to a decrease in the photosynthetic capacity by affecting the efficiency of photosystem II. The average of photosystem II quantum efficiency can be estimated using chlorophyll fluorescence technique. It is necessary to use an effective approach to maintain and increase the photosynthetic capacity of the plant to improve growth and yield of crop. Some pseudomonad rhizobacteria, due to having useful traits, can improve some responses of the plant against different plant pathogen and abiotic stresses, and increase the growth and yield of the plant in unfavorable conditions. Therefore, in this study, the effect of 104UTP, 113UTP, 110UTP and 125UTP bacterial isolates was investigated in controlling the Bipolaris sorokiniana in wheat by chlorophyll fluorescence technique. When planting the seeds, the inoculum of pathogen was mixed with the potting soil at a ratio of 5% (w:w). One ml of suspension of each bacterial isolate with a concentration of 108 cfu/ml was injected into the potting soil at the same time as planting for each seed. The pots were kept in the greenhouse at 20-23°C with light 16 h for 28 days. Chlorophyll fluorescence indices (F0, Fm, Fv, Fv/Fm) were measured in two stages (seven and 21 days after planting) using Handy PEA fluorometer. The amount of F0 index (minimum fluorescence) in the inoculated control treatment was high compared to the non-inoculated control treatment. High amount of F0 indicates disturbance in photosynthetic activities. The amount of Fm (maximum fluorescence) and Fv (variable fluorescence) indices were also different in all the treatments, and Fv and Fv/Fm (maximum photochemical efficiency of photosystem II) indices were decreased in the inoculated control compared to the non-inoculated control. According to the results, at the same time as F0 increased, the amount of Fv decreased. 104UTP and 113UTP isolates respectively had the greatest effect on Fv/Fm in the inoculated treatments, which shows that these isolates were able to moderate the pathogen effect on the wheat plant and increase the tolerance of the plant to the disease with increase the effect on the efficiency of photosystem II and the rapid start of carbon fixation. Also, the results of the disease severity evaluation showed that all isolates were able to control the disease to an acceptable extent compared to the control treatment, but the 104UTP isolate with 64.5% had the most effect in controlling the disease. The result of this study suggests 104UTP isolate as an efficient isolate for further studies.