Experiment was conducted at Melkassa Agricultural Research Center, centeral rift valley of Ethiopia from September 2008 to January 2009 with the objective to determine the effects of different concentrations and combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and gibberellic acid (GA3) spray on fruit yield and quality of tomato. The experiment consisted of two tomato varieties-one processing (Roma VF) and one fresh market (Fetan), three levels of 2,4-dichlorophenoxyacetic acid (2,4-D) (0, 5 and 10 mg l-1) and four levels of gibberellic acid (GA3) (0, 10, 15 and 20 mg l-1) arranged in 2 × 3 × 4 factorial combinations, in Randomized Completed Block Design with three replications. The result showed that increased in fruit length from 5.44 to 6.72 cm at 10 mg l-12,4-D combined with 10 mg l-1 GA3 above the control. Increased fruit weight by 13% due to 2,4-D and reduced fruit weight in single or combined application of GA3 with 2,4-D. Fruit pericarp thickness was increased by about 50% due to 2,4-D and GA3 application above the control. Titratable acidity, total soluble solids and lycopene content were also increased due to combined application of 2,4-D and GA3 spray. Lower fruit pH is another quality attributes of tomato affected by 2,4-D application while that of GA3 has no effect. Final fruit yield were significantly improved above the control even though both varieties responded deffirently. For Roma VF, GA3 at concentration of 10 and 15 mg l-1 resulted in maximum fruit yield of 69.50 and 67.92 ton ha-1, respectively in the absence of 2,4-D. For Fetan, maximum marketable fruit yield of 74.39 and 74.20 ton ha-1 was obtained from treatment combinations of 10 + 15 and 5 + 0 2,4-D and GA3, respectively. Hence, yield increment of about 35% for Roma VF and 18% for Fetan were produced at 10 mg l-1 GA3 and 10 + 15 mg l-1 2,4-D and GA3, respectively over the control. Significant increase in fruit size and weight due to 2,4-D and increased fruit number due to GA3 spray contributed to increased fruit yield. The results indicated that both PGRs are important in tomato production to boost yield and improve fruit quality under unfavorable climatic conditions of high temperature. Therefore, it is important to further investigate application methods and concentrations of the PGRs under concern in different growing conditions on different tomato cultivars.
Key words: Gibberellic acid, 2,4-dichlorophenoxy acetic acid, tomato,Lycopersicon esculentum Mill, fruit yield, quality.
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