Primavera otoño 2020 (Año LXIII Núms. 122-123)

horizontes@pucpr.edu Año LXIV Núm. 124-125 horizontes PRIMAVERA / OTOÑO 2021 PUCPR 60 VECTOR CONTROL OF CANDIDATUS LIBERIBACTER ASIATICUS INFECTION IN CITRUS Dargelee Joyce Laboy Gonzalez Pontifical Catholic University of Puerto Rico Biotechnology Master’s Degree Program Abstract Candidatus Liberibacter asiaticus is a disease affecting citrus plants worldwide. Researchers indicate that this disease has various vectors. There is a search for a total or partial solution for treating or curing this disease. The agriculturist must be vigilante; even the simplest detail become a risk factor for the fruits. Introduction This manuscript will discuss several recent articles related to the vectors of Candidatus Liberibacter asiaticus infection in citrus plants. Candidatus Liberibacter asiaticus was associated with several diseases, including Huanglobing globally. Many regions of the world were affected by Huanglobing disease (HLB). It was the most devastating disease affecting global citrus production. Huanglobing was a highly destructive disease in prominent citrus growing regions and was characterized by blotchiness mottling of young leaves with yellow shoots, deformed fruit, twig dieback, and tree decline. It was associated with the bacteria Candidatus Liberibacter asiaticus (CLas), a gram- negative pathogen that possesses secretion systems that deliver virulence proteins. The bacterium resided in phloem sieve cells of host plants and caused multiple pockets of necrotic phloem. CLas was detected in lemon, lime, mandarin, pummelo, rough lemon, and sweet oranges. Main analysis Zheng et al. (2020) explained that Candidatus Liberibacter asiaticus was a non- cultured protobacteria limited by phloem. It was associated with Huanglongbing, a worldwide citrus disease affecting lemon, lime, mandarin, and sweet orange from Mandalay and Myanmar, where they collected samples from infected trees. Miyata et al. (2017) suggested three different promoters directing transgenic expression in citrus phloem capable of showing pathogen-resistance characteristics. They analyzed the independence of the β-glucuronidae reporter gene of specific phloem promoters, including phloem-specific promoters Arabidopsis thaliana phloem protein 2, A. thaliana sucrose transporter 2, and citrus phloem protein 2. Bacterial concentration correlated with the activation of each promoter reacting to the presence of CLas, indicating that the phloem-specific promoters Arabidopsis thaliana phloem protein 2 were correlated with CLas concentration. This promoter combined pathogen-inducibility and tissue-specificity, so were appropriate for transgenic plant development. CLas appeared to cause disease by disrupting the function of the phloem, the essential vascular tissue transporting sugar and the other nutrients from the leaves. Clark et al. (2020) suggested that adult plants of A. thaliana that expressed sec-delivered effector 1 exhibited a yellow leaf color associated with HLB. Sec-delivered effector 1 expression in citrus fruits confirmed that it accelerated and improved the cellular process related to aging. Senescence was a possible mechanism supporting the progression of HLB which obstructed the phloem and the accumulation of starch. Vasconcelos et al. (2020) suggested that cells containing CLas were distributed within the foliar tissues, then branch tissues, feeder roots, trunk, and structural roots. Samples of branches, leaves, trunks, feeder roots, and structural roots represented the metabolic load of CLas in the different organs. They found 1,164 x 106 CLas cells/leaf, which meant they were approximately 104 times less than typical apoplastic bacterial pathogens. Apoplastic