Journal of Crop Production and Processing

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Mahmoudi M, Dadras A, Ghasemnezhad M. Investigating the Effect of Physical and Chemical Treatments on the Rate of Rooting of Iranian and Imported Olive Cultivars Cuttings under Bottom-Heat and without Bottom-Heat Conditions. Journal of Crop Production and Processing 2025; 15 (2) :19-40
URL: http://jcpp.iut.ac.ir/article-1-3312-en.html

Extended Abstract
Introduction
Olive (Olea europaea L.) encompasses numerous species and cultivars widely distributed as wild, naturalized, or cultivated trees and shrubs across vast regions of the world. Possessing a millennium-long history in Iran, this plant has been a crucial agricultural commodity and consistently holds substantial economic importance. Olive trees grow and develop well in Mediterranean climates, which feature temperate weather and mild winters .In recent years, the consumption of olives and their products has significantly increased in Iran, a trend expected to continue in the coming years. This rising demand necessitates expanding cultivation areas, developing horticultural programs, and establishing a source for producing new saplings to create new orchards and rejuvenate older ones. Propagating olive trees can be tricky, especially when it comes to rooting certain imported cultivars. This challenge has made it difficult for growers to expand production and meet demand for these popular plants. Rooting success is influenced by a mix of factors: the physical treatments applied to cuttings, the use of rooting chemicals like indole butyric acid (IBA), and environmental conditions, such as temperature. This study takes a closer look at how combining these approaches can improve rooting in four olive cultivars (Koroneiki, Koncervolia, Picual, and Zard) to make propagation easier and more reliable.

Materials and Methods
This study was conducted as two separate experiments one with bottom heat and one without at the Tarom Olive Research Station (49°05′ E longitude, 36°47′ N latitude, 350 meters above sea level). Each experiment was arranged as a factorial design within a randomized complete block design (RCBD) with three replications. The factors included cultivar (Koroneiki, Konservolia, Picual, and Zard), plant growth regulator (indole-3-butyric acid IBA at 0, 2000, and 4000 mg L⁻¹), and physical treatment of cuttings (control, basal scratching, and basal splitting). Ten cuttings were used as a sample for each replication. Semi-hardwood cuttings, 18 to 20 cm in length, were collected from the selected cultivars between early and mid-December. Each cutting retained four leaves, and the remaining leaves were removed. To prevent fungal diseases in the rooting medium, carbendazim fungicide at a concentration of 1.5 g/L was applied. The basal ends of the cuttings were disinfected by immersing them in the same carbendazim solution for 10 to 15 minutes before planting. After treatment, cuttings were rinsed thoroughly with clean water to eliminate any fungicide residue. Key parameters measured included rooting percentage, root number, root length, fresh and dry root weight, shoot number, and shoot length. The study also analyzed how the interaction of these treatments affected each cultivar’s performance.

Results and Discussion  
Initially, a test of homogeneity of variances was performed on the data with the aim of pooling it for a combined analysis. However, since the test for homogeneity of variances was significant for all traits, a combined analysis was not permissible. Consequently, the data from each experiment were analyzed separately. The analysis of variance (ANOVA) results revealed distinct outcomes between the two experimental conditions. Under without bottom heat conditions, cultivar, physical factors, and chemical factors, along with their interactions, showed significant effects on all investigated traits. The sole exception was the length of the longest root, where the interaction between cultivar and physical factor was non-significant. In contrast, under bottom heat conditions, cultivar, physical factors, and chemical factors, as well as their interactions, exerted significant effects on most of the traits examined. The findings were promising. Both the physical treatments and the chemical application of IBA significantly boosted rooting across all cultivars. Among the physical methods, scratching and splitting had the most impact, especially when combined with 4000 mg L⁻¹ IBA. Picual emerged as the top performer, achieving a 66.15% rooting rate under non-bottom-heat conditions when treated with 4000 mg L⁻¹ IBA and splitting the ends of the cuttings. On the other end of the spectrum, Koncervolia showed the lowest rooting rate (5.25%) in the control treatment under similar conditions. Adding bottom heat further enhanced rooting results. Picual excelled again, with a 69.75% rooting rate when treated with 4000 mg L⁻¹ IBA and scratching. These results highlight the importance of combining high IBA concentrations with physical treatments to maximize rooting success, particularly when bottom heat is used to create a more favorable environment for root growth.
Conclusion 
This study demonstrates how crucial it is to tailor propagation techniques for better rooting success in olive cuttings. Combining 4000 mg L⁻¹ IBA with scratching or splitting the ends of cuttings under bottom-heat conditions proved to be the most effective method, especially for the Picual cultivar. These insights provide growers with practical strategies for overcoming the challenges of rooting imported cultivars. Moving forward, researchers might want to explore other factors, like nutrient enrichment or fine-tuning environmental controls, to make olive propagation even more successful.