Root formation of semi-hardwood cuttings of Vaccinium arctostaphylos L (Caucasian whortleberry) under the influence of Indole -3- butyric acid treatments and inoculation of growth promoting rhizobacteria

Vaccinium arctostaphylos L. is a forest shrub that has a great role in the formation, evolution, and improvement of the beech forest stands structure. Currently, the irregular collection and harvesting of the fruit of this species (due to its medicinal properties and high economic value) even before the fruit fully ripens in the study area, has endangered the existence of this species. Vaccinium arctostaphylos is a recalcitrant plant and therefore its propagation by conventional asexual methods is almost impossible. The aim of this research is to determine the effect of auxin and inoculation of growth promoting rhizobacteria on callus formation, root formation and growth traits cuttings.

The semi hardwood cuttings of V. arctostaphylos were collected at the end of August from the natural habitat of this species (Soha forest) located in the south-east of Ardabil Fandoghlou Forest. For surface sterilization cuttings were washed with water and 2% Benomyl fungicide solution for 15 minutes. In order to stimulate root induction, the bottom of the cuttings was scratched with a sharp knife to a length of one centimeter and a depth of approximately 2 mm. Cuttings were treated with concentrations of 0, 500, 1000, 2000, 3000 and 4000 mg/ L of Indole -3-butyric acid and then were inoculated with two bacteria including Pseudomonas putida STRAIN 169 and Enterobacter cloacae STRAIN 3, alone and together. Cuttings were planted in perlite - sand medium and then they were kept in a mist system-equipped greenhouse. After 90 days from planting, the percentage of callus formation, root formation, number of roots, root length, root dry weight, root volume, leaf area, and seedlings height were recorded.

In the control cuttings (without the application of hormones and bacteria) and the cuttings treated with 500 mg L-1 of IBA with and without P. putida and E. cloacae were treated, callus and root formation were not performed. The highest callus formation (50.20 %), root formation (41.10 %), root number (3.22), root length (3.55 cm), root dry weight (0.355 g), root volume (0.358 cm3), leaf area (8.88 cm2) and height cutting (14.07 cm) was observed in cuttings that treated by Indole -3-butyric acid 3000 mg/L and inoculated with both P. putida and E. cloacae.

The present study showed that V. arctostaphylos is one of the recalcitrant species, then, for more succeed in cuttings root induction, it is suggested that semi-woody cuttings should be collected in August and cuttings should be treated by a concentration of 3000 mg/L of Indole -3-butyric acid along with inoculation of both P. putida and E. cloacae bacteria.