Phytoplasma of the 16SrIII-J subgroup associated with cabbage stunt and spatial pattern analysis of the disease
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Phytoplasma of the 16SrIII-J subgroup associated with cabbage stunt and spatial pattern analysis of the disease Ana Paula Amaral Mello 1 & Lilian Amorim 2 & Ivan Paulo Bedendo 2 Received: 6 September 2019 / Accepted: 12 November 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Abstract The aim of this study is the molecular characterization of a phytoplasma associated with cabbage stunt and spatial analyses of symptomatic plants in the field. Detection by nested PCR, sequencing of 16S rRNA gene and conventional and virtual RFLP, as well as phylogenetic analysis revealed that a 16SrIII-J phytoplasma was associated with cabbage plants that exhibited stunting, reduced size, malformation or failure to form head, reddening leaves, sprout proliferation and vessel necrosis. The spatial analyses demonstrated that the dispersion pattern of symptomatic plants was aggregated and the pathogen introduced from adjacent areas. Phytoplasmas of 16SrIII group were also detected in leafhoppers of the species Atanus nitidus collected from cabbage fields and adjacent areas, evidencing that these insects are possibly potential vectors of this fastidious bacteria found in cabbage plants. These findings confirmed that a subgroup 16SrIII-J phytoplasma is associated with cabbage stunt. In addition, the spatial analyses indicated that the disease emerges from primary foci located in external areas and progress toward the center of the fields. The discovery of the etiological agent of the cabbage stunt together with the type of dispersion of the disease represent a relevant contribution to improve the management strategies aiming harm reduction. Keywords Mollicutes . Epidemiological analysis . Brassicas, yellows
Cabbage (Brassica oleracea var. capitata) is among the most important vegetable crops in Brazil and the State of São Paulo (SP) is the main producer with 305.340 tons harvested in over 7611 ha (Instituto de Economia Agrícola 2018). Since the 1990s, a disease, here denominated cabbage stunt, has been observed in cabbage fields located in the region of the green belt of the city of São Paulo, SP (Mello and Bedendo 2005). Incidence levels of up to 70% have caused significant losses due to low yield and low quality of the production. The diseased plants exhibit various types of symptoms such as stunting, reduced size, malformation of the head, red or purple coloration of the leaves, leaves growing outward from the stem (resulting in the absence of a head), sprout proliferation at the base of the stem, and vessel necrosis evidenced by a circular dark ring when the stem is crosscut (Mello 2007).
* Ivan Paulo Bedendo [email protected] 1
Agricultural Science Center, University of São Carlos, Araras, Brazil
2
Department of Plant Pathology and Nematology – ESALQ, University of São Paulo, Piracicaba, Brazil
In some countries this kind of cabbage disease have been prevalently associated with phytoplasmas belonging to the 16SrI group, which induce distinct types of symptoms as numerous sprouts and purple col
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