Recilia banda Kramer (Hemiptera: Cicadellidae), a vector of Napier stunt phytoplasma in Kenya

Abstract

Napier grass (Pennisetum purpureum) is the most important fodder crop in smallholder dairy production systems in East Africa, characterized by small zero-grazing units. It is also an important trap crop used in the management of cereal stemborers in maize in the region. However, production of Napier grass in the region is severely constrained by Napier stunt disease. The etiology of the disease is known to be a phytoplasma, 16SrXI strain. However, the putative insect vector was yet unknown. We sampled and identified five leafhopper and three planthopper species associated with Napier grass and used them as candidates in pathogen transmission experiments. Polymerase chain reaction (PCR), based on the highly conserved 16S gene, primed by P1/P6-R16F2n/R16R2 nested primer sets was used to diagnose phytoplasma on test plants and insects, before and after transmission experiments. Healthy plants were exposed for 60 days to insects that had fed on diseased plants and acquired phytoplasma. The plants were then incubated for another 30 days. Nested PCR analyses showed that 58.3% of plants exposed to Recilia banda Kramer (Hemiptera: Cicadellidae) were positive for phytoplasma and developed characteristic stunt disease symptoms while 60% of R. banda insect samples were similarly phytoplasma positive. We compared the nucleotide sequences of the phytoplasma isolated from R. banda, Napier grass on which these insects were fed, and Napier grass infected by R. banda, and found them to be virtually identical. The results confirm that R. banda transmits Napier stunt phytoplasma in western Kenya, and may be the key vector of Napier stunt disease in this region.

Opportunities for Napier Grass (Pennisetum purpureum) Improvement Using Molecular Genetics

“…The primary mode of transmission of the disease is by vegetative propagation of infected planting material or by phloem-feeding insects belonging to the families Cicadellidae (leafhoppers), Delphacidae (planthoppers) and some psyllids (Psylloidea) [124,125]. Obura et al [126] identified Maiestas banda Kramer (Hemiptera:Cicadellidae) as a vector for Napier grass stunt disease phytoplasma in Kenya and Leptodelphax dymas and Exitianus spp. have been recorded in Ethiopia [127].…”

“…have been recorded in Ethiopia [127]. However, so far no vector has been identified in Uganda [126]. The vector-phytoplasma-host plant three-way interaction plays an important role in determining the spread of the disease [128].…”

“…Therefore, efficient diagnostic tools (serological or molecular) could offer a valuable asset for the early detection and diagnosis of the disease and to monitor its spread for improved management and containment. A number of studies have been undertaken towards the identification of the pathogen, possible vectors and disease severity for an outbreak of Napier grass stunt disease in Kenya [118,126,148]. However, further studies will be required to elucidate factors involved in the plant-host-vector three-way interaction related to the spread of stunt disease in Ethiopia and Uganda.…”

Seasonal abundance of Maiestas banda (Hemiptera: Cicadellidae), a vector of phytoplasma, and other leafhoppers and planthoppers (Hemiptera: Delphacidae) associated with Napier grass (Pennisetum purpureum) in Kenya

“…Often the whole stool is affected with a complete loss in yield and eventual death. The Ns-disease has been reported in Kenya, Uganda, and Ethiopia, posing a serious negative effect on both dairy and cereal production in the predominantly mixed crop-livestock farming systems in the region (Jones et al 2004(Jones et al , 2007Nielsen et al 2007;Arocha et al 2009;Obura et al 2009). According to phylogenetic analysis of 16S rDNA sequences, the phytoplasmas associated with Ns-disease in Kenya and Uganda are classified into the 16SrXI group (Candidatus Phytoplasma oryzae or rice yellow dwarf) (Jones et al 2004;Nielsen et al 2007), while those occurring in Ethiopia are classified into the 16SrIII group (X-disease) (Jones et al 2007).…”

“…Since there is no parasitic plant associated with Napier grass, the primary means of Ns-disease spread are the introduction of infected plant material (i.e., cane cuttings or clump splits) by farmers and/ or insect vectors carrying the phytoplasma. Recently, Obura et al (2009) tested the Ns-phytoplasma transmission ability of five leafhopper and three planthopper species and identified the leafhopper Maiestas banda (Kramer) [recently transferred from genus Recilia, Webb and Viraktamath (2009)] as a vector of Ns-phytoplasma in Kenya. However, despite that several different insect species are able to transmit the same kind of phytoplasma (Weintraub and Beanland 2006), little is known about fauna of leafhoppers/planthoppers on Napier grass in Africa.…”