The Effect of Forchlorfenuron on Bulblet Formation, Antioxidant Characteristics and Phytochemicals Compounds of Persian Shallot (Allium hirtifolium)

Allium hirtifolium commonly known as Persian shallot is an important wild medicinal plant from Alliaceae family. Persian shallot commonly known as mooseer in Iran is a perennial diploid plant that is native to Iran and grows as a wild plant throughout in the Zagross Mountains range, western and southwestern Iran. It is a bulbous herb and usually consists of a single main bulb or rarely two bulbs. Each bulb has a weight of about 8-15 times of a garlic clove. The bulbs of mooseer has been widely used as a traditional herb and spice plant, added to a variety of foods such as salads, pickles, yogurt and different sauces. Conventionally, Persian shallot propagates through bulbs and seeds but these two methods are not commercially efficient due to low growth rate of bulbs and deep dormancy, low viability and germination rate of seeds. In addition, the natural habitat of this plant is under increasing pressure as a result of excessive incorrect harvest that caused to damage the plant density in Iran rangelands. So, improving the efficiency of A. hirtifolium propagation is necessary. A number of positive effects on the growth and productivity of some plants through cytokinin application have been registered by earlier research. The current study aimed to evaluate the effects of pretreatment and foliar application of forchlorfenuron as a safe cytokinin on improving the bulb production, phytochemical compounds and antioxidant attributes of Persian shallot.
This experiment was done at research green house of Tabriz University in 2015-2016. For pretreated of Persian shallot bulbs, they were soaked in 0, 50 and 10 mg l-1 forchlorfenuron solutions for 24 h. Then they were cultured in pots contained perlite and vermicompost with 3:1 ratio. Foliar application was applied 2, 4 and 6 weeks after culture with 0, 50, 100 and 150 mg l-1 concentrations of forchlorfenuron. At the end of growth season the number of leaves, number of bublets, fresh and dry weight of bulblet were recorded. The phytochemical compound (protein, phenol and allicin), antioxidant enzymes (catalase, peroxidase, ascorbate peroxidases and superoxide dismutase) and antioxidant activity of bulbs were assayed with spectrophotometry methods.
Foliar applications of plant growth regulators such as cytokinins in agriculture crops are reported to be useful in controlling multiple physiological processes, including flower initiation, shoot elongation, bulb production, fruit set and as well as affected the quality characters of products. In this study despite the bulblets number that did not influence by treatments, pretreatment and foliar application of forchlorfenuron significantly increased the leaves number, fresh and dry weight of bulbs in comparison with control plants. The highest leaves number (4.49 per plant) was obtained from pretreatments. The highest fresh weight (91.77 g) was recorded at 5 and 10 mg l-1 pretreatment and 100 mg l-1 (91.63 g) foliar application. The interaction effect of treatments on dry weight was significant and the highest dry weight (19.75 g) was recorded at 10 mg l-1 pretreatment with 100 and 150 mg l-1 foliar application. Allicin content did not show significant variation between treatments and in average was 0.859 mg g-1 FW. Total phenol content significantly influenced by treatments and the highest phenol content (1.585 mg GAE g-1 FW) was recorded at 5 mg l-1 pretreatment with 100 mg l-1 foliar application. The antioxidant enzymes included catalase, peroxidase and ascorbate peroxidase that showed significant increasing under forchlorfenuron treatments. Due to significant effects of forchlorfenuron on antioxidant compounds and enzymes of Persian shallot bulbs, the assay of antioxidant activity also showed a significant increasing in treated bulbs. The maximum percent of antioxidant activity (74.522) was obtained from 100 mg l-1 foliar application. Exogenous application of cytokinins plays an effective role by protecting the fluidity and integrity of plant cell membranes. They properly mediate enzymatic (SOD, APX, and CAT) and non-enzymatic machinery with the result of preventing cell membrane damage by oxidative stress.
Considerable improvement in biochemical and antioxidant attributes of Persian shallot was recorded with pretreatment and foliar application of forchlorfenuron. The present data support the potential uses of the forchlorfenuron for improving the production of weighty bulbs with the high antioxidants attributes in Allium hirtifolium. Pretreated and foliar application at 5 mg l-1 and 100 mg l-1 concentrations of forchlorfenuron, respectively showed the best results and is recommendable for A. hirtifolim production.