Transmission of “Candidatus Phytoplasma pruni”‐related strain associated with broccoli stunt by four species of leafhoppers

Abstract

A disease known as broccoli stunt, associated with “Candidatus Phytoplasma pruni”‐related strain, has been responsible by significant economic losses in crops grown in the State of São Paulo, Brazil. Previous investigations evidenced some species of leafhoppers observed in broccoli fields as potential vectors of the phytoplasma. In this study, the six species more frequently found in broccoli crops were collected to confirm that evidence. Group of five insects of each species were confined per broccoli seedling for an inoculation access period (IAP) of 48 hr. After the IAP, each group was tested for detection of phytoplasma. Evaluation of plants was performed 60 days after inoculation based on the presence of phytoplasma in their tissues. When transmission was positive, genomic fragments corresponding to 16S rDNA were sequenced both for the infected plants and its respective group of insects. The results revealed that the species Agallia albidula, Agalliana sticticollis, Atanus nitidus and Balcluta hebe were able to transmit phytoplasma to broccoli seedlings. Based on the estimates of transmission probability by single insects (P), the highest transmission rate was observed for A. nitidus (24.2%) and the lowest for B. hebe (1.9%). The sequencing of 16S rDNA revealed complete similarity between the sequences of the phytoplasma transmitted to broccoli test plants and the sequences of the phytoplasma found in the field‐collected leafhoppers. These findings support the inclusion of those species as vectors of phytoplasmas belonging to 16SrIII group in broccolis, providing additional information to improve management of this important disease of endemic occurrence.

‘Ca. Phytoplasma pruni’ and ‘Ca. Phytoplasma meliae’ are affecting plum in Argentina

“…Interestingly, the presence of phytoplasmas from this subgroup in association with peaches has been previously reported in the same area where the plum samples were collected (Fernández et al 2013). Although potential vector insects have been identified for phytoplasmas of the X-disease group in the region (Eckstein et al 2013;Kreyci et al 2017), further investigations are necessary to define the role that these insects play in the spread of the disease. In this work, plum is showed as new host for the 'Ca.…”