Fig 1 - uploaded by Maheswarappa H.P
Content may be subject to copyright.
Symptoms of lethal wilt disease (LWD). a Nut fall. b Inflorescence necrosis. c Shedding of male flowers. d Leaf yellowing. e Bronzing, drying and drooping of leaves. f Death
Source publication
Lethal wilt disease of coconut, reported as a disease of unknown etiology as early as 2007, was for the first time found consistently in association with a phytoplasma in diseased coconut trees in Thanjavur, Thiruvarur and Pudukkottai districts in Tamil Nadu on the southeastern coast of India. Nested PCR with phytoplasma-specific universal primers...
Contexts in source publication
Context 1
... primary visible symptom of the disease is shedding of nuts of all stages within 3-5 days (Fig. 1a), followed by inflorescence necrosis and shedding of male flowers (Fig. 1b, c). As the inflorescence necrosis progresses, yellowing starts from the outer whorls of leaves and expands to the inner whorls (Fig. 1d). The chlorotic leaves then turn brown and necrotic, with the dried leaves hanging intact on the crown (skirting of leaves ...
Context 2
... primary visible symptom of the disease is shedding of nuts of all stages within 3-5 days (Fig. 1a), followed by inflorescence necrosis and shedding of male flowers (Fig. 1b, c). As the inflorescence necrosis progresses, yellowing starts from the outer whorls of leaves and expands to the inner whorls (Fig. 1d). The chlorotic leaves then turn brown and necrotic, with the dried leaves hanging intact on the crown (skirting of leaves around the trunk) for a few days before detachment from the trunk (Fig. 1e). In ...
Context 3
... primary visible symptom of the disease is shedding of nuts of all stages within 3-5 days (Fig. 1a), followed by inflorescence necrosis and shedding of male flowers (Fig. 1b, c). As the inflorescence necrosis progresses, yellowing starts from the outer whorls of leaves and expands to the inner whorls (Fig. 1d). The chlorotic leaves then turn brown and necrotic, with the dried leaves hanging intact on the crown (skirting of leaves around the trunk) for a few days before detachment from the trunk (Fig. 1e). In the advanced stage of the disease, necrosis, and rotting are seen on spear leaves and growing points (Fig. 1f). Eventually, the entire ...
Context 4
... male flowers (Fig. 1b, c). As the inflorescence necrosis progresses, yellowing starts from the outer whorls of leaves and expands to the inner whorls (Fig. 1d). The chlorotic leaves then turn brown and necrotic, with the dried leaves hanging intact on the crown (skirting of leaves around the trunk) for a few days before detachment from the trunk (Fig. 1e). In the advanced stage of the disease, necrosis, and rotting are seen on spear leaves and growing points (Fig. 1f). Eventually, the entire crown dies, leaving a bare trunk. Affected palms die within 3-5 months after the initial nut fall. The symptoms of this emerging disease completely differ from all other diseases reported so far on ...
Context 5
... and expands to the inner whorls (Fig. 1d). The chlorotic leaves then turn brown and necrotic, with the dried leaves hanging intact on the crown (skirting of leaves around the trunk) for a few days before detachment from the trunk (Fig. 1e). In the advanced stage of the disease, necrosis, and rotting are seen on spear leaves and growing points (Fig. 1f). Eventually, the entire crown dies, leaving a bare trunk. Affected palms die within 3-5 months after the initial nut fall. The symptoms of this emerging disease completely differ from all other diseases reported so far on coconut palms from India. Because the disease is lethal and affected palms show wilting symptoms, the disease is ...
Similar publications
Coconut (Cocos nucifera) cultivation, the main coastal crop in Côte d'Ivoire, is compromised by the coconut lethal yellowing disease. Nedotepa curta (Homoptera: Cicadellidae) carries the phytoplasma responsible for this disease. This study focused on the life history of this potential vector and the seasonal impact on some of its biological paramet...
Citations
... Insect pests and diseases remain as key factors in the decline in global coconut production (Gruber et al., 2021). This has been demonstrated in the recent outbreak of coconut scale insect: Aspidiotus rigidus Reyne in the Philippines (Caoili et al., 2014); the reported newly invasive coconut rhinoceros beetle populations that threatens the Pacific Island regions (Paudel et al., 2021); the occurrence of coconut malformation caused by Fusarium proliferatum in Southern Iran (Goudarzi et al., 2019); and the association of Candidatus Phytoplasma asteris with lethal disease of coconut (Babu et al., 2020). Pest infestation and disease occurrence in coconut can be efficiently dealt with should there be a holistic integrated pest management (IPM) framework based on modern science. ...
The integrated pest management (IPM) approach was introduced to alleviate the negative effects of synthetic pesticide use in any agroecosystem. Initially, IPM is proposed as a multidisciplinary environmentally-sensitive approach that utilizes biological, cultural, genetics, mechanical, physical, and other artificial techniques to manage the pest population. The IPM concept has evolved with various reported history as well as definitions and has been adopted to solve pest problems in different agroecosystems including coconut. This paper revisits the different approaches of IPM in coconut pests as well as the conceptual framework for IPM introduced by Stenberg (2017) and the new integrated pest management paradigm for modern age conceptualized by Dara (2019) to come up with a holistic IPM framework for the efficient control of pests and diseases of coconut for adoption of coconut-producing countries in the region.
... The LY disease is present in American, African, and also in Asian countries where coconut is being grown commonly and have caused the death of millions of palms during the twentieth century. Although 16SrIV group of phytoplasma was associated with LY diseases (Gurr et al., 2016), in Asian coconut trees phytoplasma diseases belong to 16SrI-B, -IV, -XI, -XIV, and -XXXII groups and were reported in Indonesia, Malaysia, India, and Sri Lanka (Sitepu et al., 1988;Nejat et al., 2009Nejat et al., , 2013Edwin and Mohankumar, 2007;Manimekalai et al., 2010Manimekalai et al., , 2014Perera et al., 2012;Babu et al., 2021). ...
... Recently, a lethal wilt disease of coconut killing palms within 5 months has been reported in Thanjavur, Thiruvarur, and Pudukkottai districts in Tamil Nadu on the southeastern coast of India and association with a 'Ca. P. asteris' (16SrI-B) group phytoplasma was confirmed (Babu et al., 2021). ...
... Phytoplasmas are primarily identified based on the 16S rRNA genes, but the use of housekeeping genes is also very useful in the characterization of specific strains (Martini et al. 2019). Phytoplasma strains associated with several diseases of economically important crops in India were characterized using multilocus genes, such as brinjal little leaf (Azadvar and Baranwal 2012), coconut lethal wilt (Babu et al. 2021), chickpea stunt (Reddy et al. 2021), rose and marigold phyllody (Rihne et al. 2021;Panda et al. 2021). ...
Symptoms of leaf roll, swollen nodes, flat branch and witches’ broom were observed in five cultivars of sweet cherry from Srinagar, Jammu and Kashmir province, India, during 2019–2021. Phytoplasmas association were confirmed by amplifying 16S rRNA, secA, rp, tuf and secY genes with phytoplasma-specific primers in all symptomatic sweet cherry cultivars in nested PCR assays. Pairwise sequence comparison, phylogeny and virtual RFLP (16S rRNA gene) analyses confirmed the presence of ‘Candidatus Phytoplasma asteris’ and ‘Ca. P. trifolii’ strains in the sweet cherry samples. The incidence of flat branch and witches’ broom symptoms associated with ‘Ca. P. trifolii’ varied from 5.8 to 25% in cultivars Bigarreau Nepoleon (Double), Bigarreau Noir Grossa and CITH-Cherry-9. However, incidence of leaf rolling, swollen nodes and bud proliferation associated with ‘Ca. P. asteris’ was recorded 7.5% in cultivar Stella and 10% in Sunburst, respectively, in the surveyed area. The multigene characterization of sweet cherry phytoplasma strains confirmed the validity of these molecular markers for identification of phytoplasmas enclosed in 16SrI and 16SrVI groups. The presence of phytoplasmas in sweet cherry is the first report from India.
... Witches' broom symptoms of Tephrosia purpurea could be induced by 16SrII-V and 16SrII-M subgroup phytoplasmas [42]. The phytoplasma strains belonging to different 16Sr groups, including 16SrI, 16SrIV, 16SrXI, 16SrXIV, 16SrXXII and 16SrXXXII, were associated with lethal yellow-type diseases in coconut [5,44,45]. Areca palm yellow leaf disease could be induced by the phytoplasma strains belonging to the 16SrI, 16SrXI and 16SrXIV groups [38,39,46,47]. The phytoplasma strains associated with papaya diseases belonged to six distinctly classified 16Sr groups containing 16SrI, 16SrII, 16SrXII, 16SrXIII, 16SrXV and 16SrVII [48]. ...
The pathogens associated with citrus Huanglongbing symptoms, including yellowing and mottled leaves in Citrus maxima, an important economic crop on Hainan Island of China, were identified and characterized. In the study, detection, genetic variation and phylogenetic relationship analysis of the pathogens were performed based on 16S rRNA and β-operon gene fragments specific to phytoplasma and Candidatus Liberibacter asiaticus. The results indicated that the pathogens—such as phytoplasma strains of CmPII-hn belonging to the 16SrII-V subgroup and CmPXXXII-hn belonging to the 16SrXXXII-D subgroup, as well as Candidatus Liberibacter asiaticus strains CmLas-hn—were identified in the diseased plant samples, with numbers of 12, 2 and 6 out of 54, respectively. Among them, mixed infection with the 16SrII-V subgroup phytoplasma and Candidatus Liberibacter asiaticus was found in the study, accounting for 7.4% (four samples). The phytoplasma strains of CmPII-hn—Tephrosia purpurea witches’ broom, Melochia corchorifolia witches’ broom and Emilia sonchifolia witches’ broom—were clustered into one clade belonging to the 16SrII-V subgroup, with a 99% bootstrap value. The phytoplasma strains of CmPXXXII-hn and Trema tomentosa witches’ broom belonging to 16SrXXXII-D, and the other 16SrXXXII subgroup strains were clustered into one clade belonging to the 16SrXXXII group with a 99% bootstrap value. There were 16 variable loci in the 16S rRNA gene sequences of the tested 16SrXXXII group phytoplasma strains, of which two bases had an insertion/deletion. The strains of Candidatus Liberibacter asiaticus, identified in the study and the strains that had been deposited in GenBank, were in one independent cluster with a 99% bootstrap value. To our knowledge, this is the first report showing that Citrus maxima can be infected by 16SrII-V and16SrXXXII-D subgroup phytoplasmas in China. Moreover, this is also the first report in which the plants are co-infected by 16SrII-V subgroup phytoplasmas and Candidatus Liberibacter asiaticus. More comprehensive and detailed identification and characterization of the pathogens associated with the diseased symptoms in Citrus maxima on the island in China would be beneficial for epidemic monitoring and for the effective prevention and control of related plant diseases.
Phytoplasmas are associated with many plant diseases. In palms, lethal bronzing disease, Texas Phoenix palm decline, and coconut lethal yellowing decline are some of them. In Sri Lanka, coconut leaf wilt decline has been reported in the Weligama area of the Southern province, and the disease is called Weligama coconut leaf wilt disease (WCLWD). Unlike other phytoplasma diseases of palms, WCLWD shows slow disease progress. Pathogen detection entirely relies on nested polymerase chain reaction (PCR). However, inconsistencies in pathogen detection have been experienced, i.e., symptomatic plants often produce negative results. The objectives of this study were to reconsider the choice of primers and to determine the best sampling tissue types for consistent detection of the pathogen. Among the six universal primer combinations tested, P1/Tint nested with fU5/rU3 produced consistent results. BLASTn searches of the sequences showed 99-100% similarity to sugarcane white leaf disease (SWL) or grassy shoot (SGS) disease-causing phytoplasma. The optimized nested PCR protocol was successful, with the minimum success rating of 88% and 100% specificity. Midribs of milky white bud leaf samples were the best tissue type for rapid detection. Systemic movement of the pathogen and a tentative latent period were also reported. The findings are helpful in the early detection of the disease.
Coconut (Cocos nucifera L.) is an economically important plantation crop grown widely in tropical and sub-tropical regions and coastal ecosystems worldwide. The impact of global warming on agriculture, in general, and perennials such as plantation crops, in particular, warrants the application of novel genomics-based approaches to safeguard the crops against abiotic and biotic stressors. Unlike the seasonal or annual crops, the damage of pests and diseases in coconut plantations is a serious threat to the coconut-based economy owing to the perennial nature of the crop. Against this backdrop, adopting genomic approaches for designing biotic stress tolerant coconut genotypes is inevitable. Coconut molecular breeding has witnessed the application of DNA markers in genetic diversity analysis and mapping of quantitative trait loci (QTLs). Further advancements in genome sequencing and transcriptome profiling have opened enormous avenues for utilising coconut-derived ‘big data’ in developing biotic stress-tolerant cultivars. This chapter discusses the important diseases and pests of coconut, genetic resources of coconut, approaches in conventional breeding to develop resistant genotypes, molecular mapping of resistance genes, QTLs and marker-assisted breeding, association mapping, glimpses of genome assemblies, and RNA-Seq approaches to develop disease and pest resistant genotypes.
Coconut lethal yellowing (LY) diseases caused by phytoplasmas are devastating diseases for coconut cultivation, seriously threating the coconut industry around world. The phytoplasmas associated with the LY diseases belonged to 6 16Sr groups containing 16SrI, 16SrIV, 16SrXI, 16SrXIV, 16SrXXII and 16SrXXXII, with comparatively higher variable level. Conserved regions of the 16S rRNA genes of LY phytoplasmas belonging to the 6 16Sr groups were obtained in the study. Based on the conserved region sequences of 16S rRNA genes, 2 sets of LAMP primers, Co-4 and Co-6, were designed and screened, and the rapid and visual detection methods universal for different groups LY phytoplasmas were established. The entire detection reactions of the universal detection methods could be completed by only 30-40 minutes of constant temperature amplification at 64 °C, and the detection results were judged by the color changes of the reaction systems, which are convenient and quick. For the 6 groups phytoplasmas, the estimated minimum detection limit range of the universal detection primers Co-4 and Co-6 were identical, 4.8×101- 4.8×107 copies per 200 μL. The universal detection methods for the LY phytoplasmas established in the study are of great significance for the rapid diagnosis and identification, the efficient monitoring and early warning as well as the port inspection and quarantine of the LY phytoplasmas and their related diseases.
