Effects of Citrus Sudden Death Disease on Fatty Acid Profile of Orange Tree Bark

Rosilene Prestes,Nelson Antoniosi Filho,Luiz Colnago,Maria Isabel Alves,Emanuel Carrilho

doi:10.21577/0103-5053.20220012

Abstract

Citrus sudden death (CSD) is a disease that has affected millions of orange trees in Brazil, leading to economic losses in the order of billions of US dollars. This article examines the effects of CSD on the fatty acid composition of triacylglycerides (TAG) extracted from rootstock and scion bark. The fatty acid profile determined by gas chromatography showed a reduction in oleic and linolenic acids, and an increase in the saturated fatty acids and linoleic acid content, which was in line with the severity of CSD. The reduction in linolenic acid content was related to its role in the biosynthesis of jasmonic acid, which is involved in responses to abiotic and biotic stresses, as well as senescence. These alterations in the fatty acid profile were also used to classify plants both with and without CSD symptoms by using chemometric means. This method represents an alternative to support the diagnosis of CSD disease.

Highlights

Citrus sudden death (CSD) is a citrus disease that is transmitted by graft process or by aerial vector; it has only been detected in Brazil.[1,2] It has been observed in sweet orange (Citrus sinensis (L.) Osbeck), mandarin trees grafted on rangpur lime (C. limonia Osbeck), and in Citrus volkameriana rootstock.[3,4,5] CSD has not been observed in some combinations, e.g., sweet orange with Cleopatra and Sunki tangerine, Poncirus trifoliata and Citrumelo swingle, even in planting near affected orchards
The discrimination for the scion samples data set was on PC1 (56.02%), and there was no discrimination on PC2 (35.39%). This exploratory Principal component analysis (PCA) demonstrated that the fatty acid dataset of the rootstock samples (Figure 3a) contained more information to discriminate between the CON and CSD samples than the scion samples dataset
The predictions for the CSD1 and CSD2 samples were better than 83.3% for soft independent modelling of class analogy (SIMCA), and only better than 33.3% for K-nearest neighbors (KNN). These results indicate that the SIMCA model was only most efficient to classify the CSD symptoms at two levels than KNN

Summary

Introduction

Citrus sudden death (CSD) is a citrus disease that is transmitted by graft process or by aerial vector; it has only been detected in Brazil.[1,2] It has been observed in sweet orange (Citrus sinensis (L.) Osbeck), mandarin trees grafted on rangpur lime (C. limonia Osbeck), and in Citrus volkameriana rootstock.[3,4,5] CSD has not been observed in some combinations, e.g., sweet orange with Cleopatra and Sunki tangerine, Poncirus trifoliata and Citrumelo swingle, even in planting near affected orchards. These alterations in the fatty acid profile were used to classify the plants as either being with or without CSD symptoms, by using the soft independent modelling of class analogy (SIMCA) and K-nearest neighbors (KNN) chemometric methods.

Results

Conclusion