Abstract
Citrus plants have been extremely affected by Huanglongbing (HLB) worldwide, causing economic losses. HLB disease causes disorders in citrus plants, leading to callose deposition in the phloem vessel sieve plates. Callose is synthesized by callose synthases, which are encoded by 12 genes (calS1– calS12)in Arabidopsis thaliana. We evaluated the expression of eight callose synthase genes from Citrus in hybrids between Citrus sunki and Poncirus trifoliata infected with HLB. The objective of this work was to identify possible tolerance loci combining the expression quantitative trait loci (eQTL) of different callose synthases and genetic Single-Nucleotide Polymorphism (SNP) maps of C. sunki and P. trifoliata. The expression data from all CscalS ranged widely among the hybrids. Furthermore, the data allowed the detection of 18 eQTL in the C. sunki map and 34 eQTL in the P. trifoliata map. In both maps, some eQTL for different CscalS were overlapped; thus, a single region could be associated with the regulation of more than one CscalS. The regions identified in this work can be interesting targets for future studies of Citrus breeding programs to manipulate callose synthesis during HLB infection.
Highlights
The citrus industry plays an important role in the productivity chain in Brazilian agribusiness
Comparing the expression quantitative trait loci (eQTL) for Citrus callose synthase genes (CscalS), an important region was verified for P. trifoliata on chromosome 8 that could influence the expression of CscalS7 in plants affected by HLB
Despite the importance of eQTL mapping to provide a better understanding of the phenotypic variation, few related works exist in the literature
Summary
The citrus industry plays an important role in the productivity chain in Brazilian agribusiness. Brazil is the largest sweet orange producer, and, during the period 2017/18, its yield was approximately 397 million of boxes of 40.8 kg each (Fundecitrus, 2018). This important economic area has been challenged by Huanglongbing (HLB) (Colleta-Filho et al, 2004), which has caused great economic losses because of the fast dissemination and severity. In four years of evaluation, 50% of the scion trees showed disease symptoms, with an approximately 60% decrease in production (Fundecitrus, 2018). Other typical HLB symptoms occur, such as yellow shoots, hardened and small leaves, leaves showing zinc deficiency and corky veins, twig dieback, stunted growth, and tree decline (Bové, 2006; Wang and Trivedi, 2013)
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