Haplaxius crudus (Hemiptera: Cixiidae) Transmits the Lethal Yellowing Phytoplasmas, 16SrIV, to Pritchardia pacifica Seem. & H.Wendl (Arecaceae) in Yucatan, Mexico.

Lethal yellowing (LY) affects several palm species in the Americas. It is caused by 16SrIV group phytoplasmas. In Florida (USA), LY was shown to be transmitted by the planthopper Haplaxius crudus ( Van Duzee ) (Hemiptera, Cixiidae) to different palm species, including Pritchardia pacifica Seem . & H. Wendl . (Arecaceae) in insect-proof cage experiments in the 1980s, a result that had never been reproduced later. LY has destroyed many coconut plantations as well as other palm species in the Caribbean and Mexico. In order to evaluate if H. crudus is a vector of LY phytoplasmas in Mexico, experiments were carried out in Yucatan (Mexico). Several H. crudus from palms infected by LY in the field were introduced into cages containing young P. pacifica palms. These insects were able to transmit 16SrIV group phytoplasmas to P. pacifica palms. According to DNA sequences comparative analysis, virtual restriction fragment length polymorphism, and phylogenetic analysis, the phytoplasmas detected in these infected P. pacifica were of subgroups A and D. All of ten P. pacifica palms infected with the subgroup D phytoplasmas developed symptoms of LY and died, whereas only one of two palms infected with subgroup A developed LY symptoms and died. This is the first time, more than 30 years later, that the role of H. crudus as a vector of LY is confirmed.

Derbid Planthoppers (Hemiptera: Fulgoroidea: Derbidae) Associated with Coconut and Oil Palm in Brazil.

We present surveys of derbid planthoppers associated with coconut (Cocos nucifera L.) and oil palm (Elaeis guineensis Jacq.) collected in Northeastern (Sergipe) and North (Pará and Roraima) Brazil. The surveys were intended to contribute to our knowledge of possible vectors of phytoplasmas or other phloem-restricted plant pathogens. Eight derbid taxa were found, two in the subfamily Cedusinae, tribe Cedusini (Cedusa yipara Kramer and C. yowza Kramer) and six in the subfamily Derbinae, tribe Cenchreini: Herpis sp., Persis pugnax Stål, Omolicna anastomosa (Caldwell), O. nigripennis (Caldwell), and two new species in the genus Agoo Bahder & Bartlett are described here. Genus-level features between Omolicna and Agoo are discussed and a key to the species of Agoo is provided.

Occurrence in Brazil of Haplaxius crudus (Hemiptera: Cixiidae), Vector of Coconut Lethal Yellowing.

The lethal yellowing (LY) is a major phytoplasma causing disease seriously threatening coconut plantations worldwide, with imminent risk of entering Brazil. The LY phytoplasma is restricted to the phloem and transmitted by the planthopper Haplaxius crudus (Van Duzee) (Cixiidae). In this study, Auchenorrhyncha were collected on the leaves of Dwarf vs. Dwarf hybrids and Brazilian Green Dwarf Jiqui in the Brazilian northern state of Para using yellow adhesive traps in May of 2016. The planthopper H. crudus was found in coconut plantations of Brazilian Green Dwarf Jiqui, accounting for 87% of the individuals captured. This is the first report of vector H. crudus in Brazilian coconut plantations. These findings are of great scientific relevance since H. crudus could negatively impact the Brazilian coconut industry and this knowledge could be used in contingency measures in the case of LY be introduced in the country.

The spliced leader RNA gene array in phloem-restricted plant trypanosomatids (Phytomonas) partitions into two major groupings: epidemiological implications.

The arbitrary genus Phytomonas includes a biologically diverse group of kinetoplastids that live in a wide variety of plant environments. To understand better the subdivisions within the phytomonads and the variability within groups, the exon, intron and non-transcribed spacer sequences of the spliced leader RNA gene were compared among isolates of the phloem-restricted members. A total of 29 isolates associated with disease in coconut, oil palm and red ginger (Alpinia purpurata, Zingibreaceae) were examined, all originating from plantations in South America and the Caribbean over a 12-year period. Analysis of non-transcribed spacer sequences revealed 2 main groups, I and II; group II could be further subdivided into 2 subgroups, IIa and Ilb. Three classes of spliced leader (SL) RNA gene were seen, with SLI corresponding to group I, SLIIa to group lIa, and SLIIb to group IIb. Two isolates showed some characteristics of both major groups. Group-specific oligonucleotide probes for hybridization studies were tested, and a multiplex amplification scheme was devised to allow direct differentiation between the 2 major groups of phloem-restricted Phytomonas. These results provide tools for diagnostic and molecular epidemiology of plant trypanosomes that are pathogenic for commercially important flowers and palms.

Adenylyl cyclase and G-proteins in Phytomonas.

Phytomonas sp. membranes have an adenylyl cyclase activity which is greater in the presence of Mn2+ than with Mg2+. The Mg2+ and Mn2+ activity ratio varies from one membrane preparation to another, suggesting that the adenylyl cyclase has a variable activation state. A[35S]GTP-gamma-S-binding activity with a Kd of 171 nM was detected in Phytomonas membranes. Incubation of these membranes with activated cholera or pertussis toxin and [adenylate 23P]NAD+ led to incorporation of radioactivity into bands of about 40-44 kDa. Crude membranes were electrophoresed on SDS-polyacrylamide gels and analyzed, by Western blotting, with the 9188 anti-alpha[s] antibody and the AS/7 antibody (anti-alpha[i], anti-alpha[i1], and anti-alpha[i2]. These procedures resulted in the identification of polypeptides of approximately 40-44 kDa. Phytomonas adenylyl cyclase could be activated by treatment of membrane preparations with cholera toxin, in the presence of NAD+, while similar treatment with pertussis toxin did not affect this enzyme activity. These studies indicate that in Phytomonas, adenylyl cyclase activity is coupled to an unknown receptor entity through G alpha[s] proteins.

Characterization and detection of plant trypanosomatids by sequence analysis of the small subunit ribosomal RNA gene.

The complete sequences of the genomic small subunit ribosomal RNA gene from two Phytomonas isolates: one associated with palm pathologies (P. cocos FGuiana) and one found in lactiferous plants with no apparent pathology (P. Euphorbe Senegal), were analyzed. Partial sequences from a number of other Phytomonas isolates were also determined. The sequences obtained were used to determine the phylogenetic relationships between Phytomonas and other trypanosomatids as well as within the genus Phytomonas. The analysis showed that the intraphloemic isolates associated with pathologies in palm trees formed a homogeneous group that diverged from the more heterogeneous group of non-pathogenic isolates found in latex plant. Sequence comparisons of the full and partial SSU rRNA gene, identified sequences which are specific to the genus Phytomonas and an EcoRI restriction nuclease site which specifically identifies the Phytomonas isolates associated with diseases in palm trees.