Horticultural performance and huanglongbing tolerance of combinations of orange ‘valência’ grafted in different rootstock

Author(s)

Jardel Diego Barbosa Rodrigues

• Document type: Master's Dissertation
• Press: Jaboticabal. 2018-04-09.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-02-23
• Advisor: Eduardo Sanches Stuchi; Renato Beozzo Bassanezi

Abstract

Brazil is the largest producer of oranges in the world, and the huanglongbing (HLB) is the most important and devastating disease of the world citriculture. It is present in the country, more specifically in the States of São Paulo, Paraná, and Minas Gerais and has been causing severe damage to the citriculture. Until now there are no valid curative measures in HLB control, hence verification of greater tolerance of combinations scion/rootstock front HLB may contribute to advancement in the management of the disease. This work evaluated the horticultural performance of 'Valencia' orange tree grafted on 16 citrus rootstocks and tolerance of combinations to HLB, with the objective of selecting combinations that tolerate the progress of the disease. The experiment was installed in 2011 in Bebedouro-SP, at a spacing of 6.0 x 2.5 m in the rainy season. It has a completely randomized design with 16 treatments (rootstock) and 30 replications. Survival analysis studies were performed using HLB symptom assessments The horticultural performance of the different combinations scion/rootstocks was analyzed using variables of plant growth, production, productive efficiency, fruit quality and drought tolerance. The intensity of sprouting of the plants was evaluated to correlate with the variable intensity of plants with HLB symptoms. The results showed that the superiority found for fruit production and vegetative growth for 'Carrizo' tetraploid, ‘Cleopatra’ x ‘Christian’ rootstocks was equivalent to 'Cravo' and 'Swingle' rootstocks. The rootstock trifoliate ‘Flying Dragon’ showed a good aptitude for dense cultivation, introducing low vigor and higher value production efficiency plants. Hybrids with parental P. trifoliata conferred to 'Valencia' sweet orange scion production of higher quality fruits. The ‘Sunki’ x ‘Benecke’, ‘Sunki’ and 'Carrizo tretraploid' rootstocks induced medium tolerance to drought, getting behind only 'Cravo' considered as a tolerance standard. ‘Flying Dragon’ trifoliate obtained low sprouting intensity, lower incidence of the disease and high cumulative proportion of survival. Less vigorous rootstocks that confer lower crown volume had a lower incidence of HLB, resulting in less exposure to the vector of the disease-causing bacteria. The ability of plants grafted on ‘Flying Dragon’ trifoliata to present late HLB symptoms late compared to the other rootstocks studied, may be an indication of the more significant capacity of this material to tolerate the disease progression. (AU)

• FAPESP's process: 16/17480-3 - Survival analysis to HLB and horticultural performance of Valencia sweet orange grafted onto 16 rootstocks
• Grantee: Jardel Diego Barbosa Rodrigues
• Support Opportunities: Scholarships in Brazil - Master