First report of a 16SrIII‐X phytoplasma associated with <i>Lactuca sativa</i> witches’‐broom in Argentina

During the summer of 2022, symptoms witches’-broom, flowering malformation and redness were observed in lettuce plants (Lactuca sativa) fields Cordoba Province, Argentina (Fig. 1a). In same fields, garlic (Allium sativum) exhibiting phyllody 1b-c) also observed. To confirm presence phytoplasma, leaf samples from two diseased three collected. As negative controls, symptomless (one garlic) Total DNA was extracted each sample using CTAB method quantified by spectrophotometry a NanoDrop-1000 (Thermo Scientific, USA). The used as template for PCR reactions 16Sr RNA universal phytoplasmas primers, P1/P7 (Deng & Hiruki, 1991; Schneider et al., 1995) R16F2n/R16R2 (Gundersen Lee, 1996) direct nested (P1/P7, dilution 1:20) reactions, respectively. Amplicons expected size (c. 1.8 1.2 kb, respectively) obtained all but not samples. Nested amplicons (R16F2n/R16R2) subjected to restriction MseI, HhaI RsaI enzymes (NEB, USA) according manufacturer's instructions. RFLP profile indistinguishable 16SrIII-X subgroup, while that 16SrIII-J subgroup (Galdeano 2013). named LWB-Arg1 (Lettuce Witches’ Broom) GarPhy-Arg1 (Garlic Phyllody) cloned sequenced. Consensus sequences deposited GenBank with Accession Nos. ON623076 (GarPhy-Arg1) ON623077 (LWB-Arg1). silico classification iPhyClassifier (https://plantpathology.ba.ars.usda.gov/) showed has an identical reference strain (KC412026) (AF147706). Phylogenetic inference determined partial 16S rRNA this work, representative X-disease group selected ‘Ca. Phytoplasma species’ employing IQ-TREE software (http://www.iqtree.org/) under maximum likelihood (1000 bootstraps). tree branches subgroups 2) confirming affiliations virtual RFLP. Garlic decline phytoplasma (subgroup 16SrIII-J) reported previously association disease (Conci 1998). However, is first time associated have been reported. our knowledge, report affecting worldwide. Previous work different species weeds region 2013; Fernández 2020) which may suggest common insect vector polyphagous feeding behaviour. This supported grant Instituto Nacional de Tecnología Agropecuaria (INTA): INTA/2019-PD-E4-I090-001 FONCyT PICT 2016-0862.