Less Is More: A Hard Way to Get Potential Dwarfing Hybrid Rootstocks for Valencia Sweet Orange

Danilo Pereira Costa,Alécio Souza Moreira,Walter Dos Santos Soares Filho,Eduardo Sanches Stuchi,Orlando Sampaio Passos,André Luiz Vanucci Da Silva,Helton Carlos De Leão,Eduardo Augusto Girardi,Carlos Alberto Da Silva Ledo,Abelmon Da Silva Gesteira,Mauricio Antonio Coelho Filho

doi:10.3390/agriculture11040354

Abstract

As in several fruit crops, citrus trees with decreased size allow for a higher planting density, which may lead to higher productivity and facilitate operations such as harvesting and spraying. The use of dwarfing rootstocks is one of the most feasible methods for tree size control, but few commercial varieties are available to date. In this work, the long-term performance of Valencia sweet orange grafted onto 51 hybrid citrus rootstocks was evaluated in rainfed cultivation at 6.0 m × 2.5 m tree spacing in Northern São Paulo State, Brazil. About a third of the evaluated hybrids were classified as dwarfing and semi-dwarfing rootstocks, that is, respectively inducing a relative canopy volume of <40% and 40–60% compared with the standard rootstock, the Rangpur lime Santa Cruz selection. The production efficiency and soluble solids concentration were conversely related to the canopy volume. Three citrandarins of Sunki mandarin (TSKC) × Flying Dragon trifoliate orange (TRFD) were grouped within the most productive dwarfing rootstocks. Other hybrids that expressively decreased tree size were mainly sensitive to drought; therefore, the mean fruit yield was low, indicating the need for irrigation, albeit fruit quality was high. Estimated productivity on the selected TSKC × TRFD rootstocks would double to an average of 40 t·ha−1·year−1 if tree spacing was adjusted to the smaller tree size. Although the HTR-208 citrandarin and the LCR × CTSW-009 citrumelimonia were as vigorous as the Santa Cruz Rangpur lime, they induced an outstanding fruit yield due to their highest tolerance to drought and, hence, can be considered for rainfed cultivation at wider tree spacing.

Highlights

Sweet orange is one of the most cultivated fruits in the world, with a total production of around 78.7 million tons in 2019, with Brazil, China, India, USA, and Mexico being the major producers [1]
We evaluated over twelve years the tree size and survival rate, the fruit production and quality, the drought tolerance, and the graft compatibility of Valencia sweet orange (C. ×sinensis (L.) Osbeck cv
The experimental design was in randomized blocks with three replications that corresponded to a planting line each, and five trees in the plot, given a total of 765 trees evaluated

Summary

Introduction

Sweet orange is one of the most cultivated fruits in the world, with a total production of around 78.7 million tons in 2019, with Brazil, China, India, USA, and Mexico being the major producers [1]. The consumption of frozen and concentrated orange juice (FCOJ) has been decreasing since the 2000s while that of not from concentrate (NFC) orange juice has increased [2]. Intensive pest and disease management programs are necessary due to the increasing spread of various limiting pathogens [3,4]. In the era of huanglongbing epidemy, higher tree densities were associated with a lower disease incidence [8] and higher economic feasibility [9]

Methods

Results

Discussion

Conclusion