Biological and molecular evidence for the transmission of aster yellows phytoplasma to French marigold (Tagetes patula) by the flatid planthopper Metcalfa pruinosa

Abstract

AbstractAster yellows (AY) phytoplasmas (Candidatus Phytoplasma asteris) are associated with a number of plant diseases throughout the world. Several insect vectors are responsible for spreading AY diseases resulting in wide distribution and low host specificity. Because the role of sucking insects as vectors of phytoplasmas is widely documented, and the citrus flatid planthopper Metcalfa pruinosa is a phloem feeder, it has been incriminated as a possible vector of phytoplasmas. However, its ability to transfer phytoplasma has not been confirmed. The present work shows that M. pruinosa (Hemiptera: Flatidae), a polyphagous planthopper, is able to vector Ca. P. asteris to French marigold (Tagetes patula). Transmission experiments were conducted in 2017 and 2018 in central Hungary by two approaches: (a) AY‐infected M. pruinosa were collected from an area with severe incidence of the disease on T. patula and caged on test plants for an inoculation‐access period of 2 weeks, and (b) presumably phytoplasma‐free insects were collected from apparently healthy grapevines (Vitis vinifera L.) and fed on AY‐infected T. patula plants for 2 weeks prior to being caged on test plants. AY disease symptoms developed on 4 out of 10 and 10 out of 15 test plants, respectively. All phytoplasma‐positive marigold and M. pruinosa samples showed identical RFLP patterns and shared 100% 16S rDNA sequence identity with each other and with the aster yellows phytoplasma strain AJ33 (GenBank accession number MK992774). These results indicated that the phytoplasma belonged to the phytoplasma subgroup 16SrI‐B Ca. P. asteris. Therefore, the work presented here provides experimental evidence that M. pruinosa is a vector of a 16SrI‐B subgroup phytoplasma to T. patula.