Tomato Responses to Bioregulators Grown under Greenhouse Conditions

Abstract

Aims: Greenhouse contemporaneous horticulture demands a permanent use of new technologies directed to improve yield and fruit quality. Although, the use of bioregulators has made an important contribution to agriculture by increasing yield in vegetable and fruit crops grown under open field conditions; little is known on their effects on tomato grown in greenhouse. It would be useful to study how they may influence the behaviour of that crop. This approach could be an alternative for improving yield and fruit quality; in particular the one related to increase the antioxidant content. Prohexadione calcium (P-Ca) is a growth retardant which reduces vegetative growth and increases antioxidants content in deciduous fruit species; whereas gibberellins GA4/7 and 6-benzyl amino purine (6-BAP) stimulate flowering or fruit growth on temperate fruit crops. The effect of these hormones in tomato crop grown in greenhouse is not clear. Therefore, the aim of this research was to evaluate the effects of P-Ca, GA4/7 and 6-BAP on the growth, yield and fruit quality in saladette tomato hybrid "Raptor-F1". Study Design: A completely randomized statistical design was used with ten replicates per treatment. The results obtained were analyzed with the statistical program R version 2.14.2, for Windows version 8, and for the analysis of variance and comparison of means, the LSD (P≤0.05) test was applied.    Place and Duration of Study: The experiment was conducted at the Universidad Autónoma Agraria Antonio Narro, Saltillo, Coahuila, México, during the period April - August 2015. Methodology: When plants showed  floral primordia, a first foliar spray of treatments: control (H2O), P-Ca (50 mg L-1), GA4/7 (50 mg L-1), GA4/7 (100 mg L-1), 6-BAP (50 mg L-1), 6-BAP (100 mg  L-1), GA4/7 (50 mg L-1) + 6-BAP (50 mg L-1) and GA4/7 (100 mg L-1) + 6-BAP (100 mg L-1) was applied to run-off using a hand sprayer. A second application of same dosages was performed 15 days later. Results: P-Ca inhibited the synthesis of gibberellins A1, A4 and A7 at the apex; significantly reduced plant height and increased stem diameter, number of flowers, leaves, fruits, and ratio. GA4/7 at 100 mg L-1promoted firmness and sugar content in fruits; whereas, when combined with 6-BAP at 100 mg L-1increased the content of vitamin C and lycopene in ripen fruits. Although, the yield was not increased by bioregulators, improvement in fruit quality compensated this since the benefit : cost (B:C) ratio in these fruits had a value of 1.9, 1.9, 1.84 and 1.74 for P-Ca, GA4/7, 6-BAP and GA4/7, + 6-BAP respectively against 0.86 in control fruits as a result of a  higher market price. Conclusion: The bioregulators P-Ca, GA4/7 and 6-BAP provoke positive effects on growth, yield and fruit quality in saladette tomato hybrid “Raptor-F1” growing under greenhouse conditions.