Document Type : Research Paper
Authors
1 Ph.D. Student, Department of Horticultural Sciences, Faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
2 Assistant Professor, Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
3 Associate Professor, Department of Biology, Faculty of Sciences, Golestan University, Gorgan, Iran
Abstract
Introduction
Strawberry is one of the most popular fruits, accordingly, its maintenance and increased quality without using harmful chemical compounds is of great concern. Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that affects plant growth activities, tricarboxylic acid cycle, production of primary and secondary metabolites, and response to biotic and abiotic stresses. Growth hormones, especially those growth regulators that increase photosynthesis and plant function, have good potential for agricultural development. The plant hormone cytokinin plays an effective role in controlling many vital processes, including plant growth and flowering. Cytokinins cause an increase in cell division, and therefore, if they are used in the initial stage of the sigmoid curve of fruit growth, when cell division is underway, they may increase the number of cells in each fruit.
Materials and Methods
The well-developed and consistent strawberry plantlets of the Camarosa cultivar were planted during October 2022 in Ramian County, Golestan province, Iran (UTM: 318446, 4092385). The foliar application of GABA solutions at 10 and 20 mM as well as control (water) was carried out at the flowering stage and 10 days later and the foliar application of forchlorfenuron )CPPU( solutions at 5 and 10 mg/L was carried out at the flowering stage. This research was conducted in the form of a complete randomized blocks design in three replications. Fruits were collected when they reached a consistent ripening stage, as characterized by change of fruit's surface color to red by more than 75% and were promptly transported to the laboratory for analysis. Root volume and weight, total sugar and leaf photosynthetic pigments, length, diameter and shape of fruit, percentage of malformed fruit, fruit firmness, total sugar, fruit color, total weight of harvested fruit and fruit cytokinin were assessed. Data analysis was done using SAS version 9.1 software and comparison of means was done through Duncan's multiple range test at the 1% probability level.
Results and Discussion
The analysis of variance of the data showed that the effect of GABA treatment at the probability level of 1% on root volume and weight, carotenoid and chlorophyll b of leaf, fruit firmness and the total weight of the harvested fruit at the probability level of 1% and on the total chlorophyll of leaf and percentage of malformed fruit at the probability level of 5% was significant. Leaf area, chlorophyll a, total leaf sugar, fruit length, diameter and length-to-diameter ratio were not affected by GABA spraying. Also, the effect of CPPU treatment was significant at 1% probability level on root volume and weight, leaf area, leaf carotenoid, fruit length and firmness, and percentage of malformed fruits, and at 5% probability level on chlorophyll a and total, fruit length to diameter ratio. Total sugar and chlorophyll b of leaf, fruit diameter and total weight of harvested fruit were not affected by CPPU solution. GABA treatment (20 mM) could increase the total weight of the harvested fruits from each experimental unit by 17%. Plants sprayed with CPPU had more leaf area compared to the control non-sprayed plants. The total chlorophyll amount of leaf increased with increasing GABA and CPPU concentration, and the highest leaf total chlorophyll was found in 20 mM GABA (1.384 mg/g) and 10 mg/L CPPU (1.430 mg/g). 10 mg/L CPPU treatment caused 107 and 59% increase in root volume and weight compared to the control, respectively. The highest fruit length (65.51 mm) and fruit length to diameter ratio (1.69) were obtained in plants sprayed with 10 mg/L CPPU. The highest firmness of the fruit tissue (1.96 N/cm2) was observed in plants sprayed with 20 mM GABA. Accordingly, GABA and CPPU treatments could significantly reduce the malformed fruit and the lowest was observed in CPPU treatment at a concentration of 10 mg/L. Also, both GABA and CPPU treatments had a significant effect on fruit color brightness index and total fruit sugar.
Conclusion
GABA and CPPU can act as a regulatory factor for plant growth and development. In general, the fruits obtained from plants sprayed with GABA and CPPU were of higher quality. Finally, according to the results, foliar spraying of Camarosa strawberry plants with 20 mM GABA and 10 mg/L CPPU is recommended in order to produce high-quality and long-lasting fruit.
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