Effect of plant growth promoting bacteria and temperature treatments on germination indices and seedling growth of safflower (Carthamus tinctorius)

Safflower (Carthamus tinctorius L.) is an annual oilseed crop that is adapted to arid and semi-arid regions and is considered an indigenous plant of Iran. Germination and seedling stage in the soil is one of the most important stages in the life cycle of plants. High germination rate and percentage increase the number of seedlings and the rapid successful establishment of seedlings in the soil also contributes to the suitable vegetative growth of the seedlings in later stages of life. Therefore, evaluation of germination indices and seedling establishment in the soil and finding more suitable conditions to improve these indices can have a direct impact on more successful plant cultivation. One of the methods used in this regard is priming.

In order to study the effect of plant growth-promoting bacteria and temperature treatments on germination indices and seedling growth of the safflower, this investigation was conducted based on a completely randomized block design with three replications at the Agricultural Research Laboratory of Yasouj University in 2016. Experimental factors were seven levels of temperature treatments (5, 10, 15, 20, 25, 30, 35°C) and seed priming with three strains of Pseudomonas fluorescens such as Pf 2, Pf 25 and CHA 0 and one strain of Bacillus subtilis and control (without inoculation).

The results showed that 20°C temperature caused the highest germination percentage, germination rate and vigor length. Also, seeds inoculated with Pseudomonas fluorescens growth-promoting bacteria strain CHA0 had the highest germination percentage (68.74), germination rate (3.49 seeds per day) and vigor length vigor (6.22). Seedling length, dry weight and vigor weight were the other parameters that showed the best results at 20 and 25°C. Also, germination and seedling growth indices decreased by an increase or decrease in the optimum temperature. The use of plant growth-promoting bacteria causes increased activity of ascorbate and catalase enzymes, which leads to a decrease in injuries related to non-optimum temperature and improved germination indices.

According to our results, to accelerate the germination rate and other parameters, it is better to inoculate seeds with bacteria strains CHA0 and 25 in the temperature range of 20-25°C.

The germination behaviour of safflower primed with bacteria varies at different temperatures.
Seeds inoculated with Pseudomonas fluorescens growth-promoting bacteria of CHA0 strain had better germination conditions.
Using the 20-25°C temperature improves germination indices.