First comprehensive sanitary report of citrus-infecting viruses and viroids in Uruguay

Mj Benítez-Galeano,F Rivas,L Hernández-Rodríguez,A Bertalmío,E Bertoni,L Rubio,R Colina,D Maeso,F Dalmao

doi:10.5070/c481049181

Abstract

Citrus is the highest-value fruit crop in terms of international trade. However, citrus species are susceptible to several diseases caused by different pathogens which directly cause a decrease in production leading to economic losses. In the last half-century, the citrus industry in Uruguay has had a strong socio-economic impact and is also constantly evolving to stay competitive in world markets, by introduction of new varieties and improvement of production practices to obtain high yielding orchards. Nevertheless, despite the existence since 2014 of the Uruguayan National Citrus Sanitary and Certification Program, scarce information is available regarding the virus and viroid status of commercial citrus in Uruguay. The incidence of citrus tristeza virus (CTV), citrus psorosis virus (CPsV), satsuma dwarf virus (SDV), citrus exocortis viroid (CEVd), hop stunt viroid (HSVd), citrus dwarfing viroid (CDVd), citrus bark cracking viroid (CBCVd) and citrus bent leaf viroid (CBLVd) was investigated in this study, as well as CTV genotypes prevalent in the country. Molecular diagnostic assays were used to test 1175 samples including Valencia and Navel sweet oranges, Mandarin hybrids, Clementines and lemons, which were randomly collected from seven citrus-producing provinces. Only 6% of the samples were negative for the pathogens screened, while 93% of them were CTV positive. SDV, CBLVd and CBCVd were not detected. Co-infections were frequently detected, finding plants with up to four simultaneous pathogens, including CTV in all co-infected plants. This is the first comprehensive survey of several citrus-infecting viruses and viroids in Uruguay, as well as a determination of the CTV genotypes prevalent in the country.

Highlights

Citrus is one of the most important fruit crops worldwide, but it is susceptible to several insectborne and graft-transmissible pathogens and efficient disease management is required for competitive and sustainable production (Tennant et al 2009; Donkersley et al 2018; Spreen et al 2020)
Despite regional surveys reporting the presence of citrus tristeza virus (CTV), citrus psorosis virus (CPsV) and citrus viroids including hop stunt viroid (HSVd), citrus exocortis viroid (CEVd), citrus dwarfing viroid (CDVd) and citrus bent leaf viroid (CBLVd), a national survey was not previously conducted (Tucci et al 1965; Pagliano et al 1998; 2013)
satsuma dwarf virus (SDV), CBLVd and citrus bark cracking viroid (CBCVd) were not detected and CEVd was not widely detected in this study whilst CTV, CPsV, HSVd and CDVd were found widespread in Uruguay

Summary

Introduction

Citrus is one of the most important fruit crops worldwide, but it is susceptible to several insectborne and graft-transmissible pathogens and efficient disease management is required for competitive and sustainable production (Tennant et al 2009; Donkersley et al 2018; Spreen et al 2020). One of the main approaches to replace old varieties with new ones in established commercial fields is by means of top-working (Albrecht et al.2017). This practice shortens the production period compared to planting a new orchard, it should only be applied on healthy trees for long-term sustainability of the orchard (Sanderson et al 2007). With the threat of the global citrus industry facing Huanglongbing (HLB), a clear picture of the disease status of a country is extremely important to reinforce good management practices of the crop, especially in countries that still remain HLB-free (da Graça et al 2016; Gabriel et al.2020)

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