Long-term field evaluation of Pera sweet orange selections under the Brazilian humid subtropical climate

Abstract

Currently, a low number of citrus varieties are commercially planted to supply the Brazilian citrus industry demand. The diversification of citrus scion and rootstock varieties is an important strategy to prevent disease outbreaks and to obtain higher off-season profits, as well as to extend fruit supply for the citrus processing industry. The aim of this study was to evaluate 16 Pera sweet orange selections (Citrus ×sinensis Osbeck) under a humid subtropical climate in the northwest region of the state of Paraná, Brazil regarding tree development, production, and disease incidence. The experimental orchard was planted in December 2012 in a randomized block design with three replications and five trees per plot. All scions were grafted on Rangpur lime rootstock (C. ×limonia Osbeck). The evaluations were performed from 2016 through 2022, and included vegetative growth, yield, fruit quality, estimated tree density and productivity for new plantings, and incidence of diseases as citrus canker, huanglongbing (HLB), and citrus tristeza virus (CTV). All data was submitted to ANOVA and means grouped by the Scott Knott’s test (p ≤ 0.05). Pera Perão was the most vigorous variety, with the heaviest and largest fruit, and was among the selections with the highest content of soluble solids (SS), titratable acidity (TA) and juice. However, this variety showed a light-yellow juice color, and one of the lowest SS·TA−1 ratio. This selection had the lowest percentage of fruits with citrus canker but was among the selections with the highest HLB incidence. The selections Ovale, Clone 9, and Clone 42 also showed higher vegetative growth and fruit length, but lower SS content, juice yield and technological indices. All other Pera selections had lower tree height and canopy volume than Ovale, Clone 9, and Clone 42, and adequate overall fruit quality. Conversely, Pera Comprida, Dibbern, Morretes, and Seleç ão 12 scored lower cumulative fruit yield. Pera Pirangi and Comprida had the highest citrus canker incidence on fruits, while Morretes, Ovo, Pirangi, Seleç ão 12, and Seleç ão 27 had the highest HLB incidence alongside Perão. Low severity level of stem pitting was observed within the evaluated selections. The scores ranged from one (absence of stem pitting) to two (sparse surface stem pitting). IAC, Olímpia, Mel, Bianchi, and IPR 159 revealed to be the most suitable for new plantings under humid subtropical edaphoclimatic conditions, as trees had small vegetative growth, high yield performance and fruit quality, in addition to showing lower incidences of citrus canker, HLB and CTV.