Biostimulants on the occurrence of stenoespermocarpy in ‘Palmer’ mango¹

Bioestimulantes na ocorrência de estenoespermocarpia em frutos de manga ‘Palmer’

ABSTRACT

Stenospermocarpy in mango trees is associated with hormonal regulation and boron fertilization. However, the mode of action of plant growth regulators and boron in mango trees of the Palmer cultivar affected by this physiological disorder needs to be elucidated. In this scenario, this study aimed to evaluate the association of plant growth regulators (auxin, cytokinin, and gibberellin) and boron with the incidence of stenospermocarpic fruits in ‘Palmer’ mango. Two experiments were conducted in two consecutive crop years (2018 and 2019) in a commercial orchard. The experiment was set up in a randomized block design, with six treatments and four replicates. The treatments consisted of: T1 = water application (control); T2 = gibberellin (25 ppm, GA₃); T3 = auxin (25 ppm, naphthaleneacetic acid); T4 = cytokinin (25 ppm, 6-BA); T5 = boron (2 ppm); and T6 = boron (2 ppm) + gibberellin (25 ppm). The application of gibberellic acid during the flowering phase resulted in higher mean values for the number of stenospermocarpic fruits. The cytokinin treatment reduced the incidence of stenospermocarpic fruits and led to higher mean values for the number of productive branches. Boron, auxin, and the combination of gibberellin and boron did not reduce the stenospermocarpy indices. Hormonal balance plays a crucial role in the manifestation of stenospermocarpic fruits, with gibberellin being associated with the expression of this disorder, while cytokinin exerts an antagonistic effect. The application of boron and auxin did not have a predominant effect on the increase or reduction of stenospermy.

Key words:
Mangifera indica L.; physiological disorder; auxin; gibberellin; cytokinin

HIGHLIGHTS:

Plant hormones exert distinct influences on the stenospermocarpy of mango ‘Palmer’.

Exogenous applications of cytokinin (benzyladenine) at 20 g L^-1 reduce stenosper-mocarpy indices.

Leaf boron levels of up to 55.71 g kg^-1 do not reduce the incidence of stenosper-mocarpy.