Tomato and Jute Mallow are two new hosts of papaya bunchy top phytoplasma, a 'Candidatus phytoplasma convolvuli'-related strain in Nigeria

Authors: Inaba, Junichi; KAZEEM, SHAKIRU, ADEWAL - Nigeria Agricultural Quarantine Service; Zhao, Yan; ZWOLINSKA, AGNIESZKA - Institute Of Plant Protecton - National Research Institute; OGUNFUNMILAYO, AKINDELE - Nigeria Agricultural Quarantine Service; AROGUNDADE, OLAWALE - National Horticultural Research Institute; Wei, Wei

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2022
Publication Date: 6/14/2023
Citation: Inaba, J., Kazeem, S.E., Zhao, Y., Zwolinska, A., Ogunfunmilayo, A.O., Arogundade, O., Wei, W. 2023. Tomato and Jute Mallow are two new hosts of papaya bunchy top phytoplasma, a 'Candidatus phytoplasma convolvuli'-related strain in Nigeria. Plant Disease. https://doi.org/10.1094/PDIS-09-22-2192-PDN.
DOI: https://doi.org/10.1094/PDIS-09-22-2192-PDN

Interpretive Summary: Tomato is widely cultivated in Nigeria for its edible fruit and high vitamin C content. Jute mallow is a staple vegetable in Nigeria because of its edible and nutritional young shoots. Since 2020, symptomatic tomato and jute mallow plants have been observed in Ibadan, Oyo State, Nigeria, where Nigerian papaya bunchy top phytoplasma (NGPBT) disease has been reported. The affected tomato and jute mallow plants exhibited little leaf, yellowing, and stunted growth, which ARS scientists in Beltsville, Maryland suspected were caused by phytoplasma infection. In collaboration with Nigerian scientists, ARS scientists conducted molecular diagnostic analysis by using three genetic markers unique to phytoplasma and demonstrated that tomato and jute mallow were two novel hosts of NGPBT phytoplasma. This is the first time that phytoplasma infection was detected in tomato and jute mallow in Nigeria because phytoplasma diseases were only found in coconut palms and papaya in the country. Such results strongly suggest the presence of insect vectors that transmit NGPBT phytoplasma in the region. As both tomato and jute mallow are important vegetable crops in Nigeria, the findings from the study are crucial for local growers and extension personnel.

Technical Abstract: Nigerian papaya bunchy top (NGPBT) phytoplasma, which was first discovered in Ibadan, Oyo State, Nigeria, is a 'Candidatus Phytoplasma convolvuli'-related strain and represents a subgroup lineage, 16SrXII-O. In 2020, tomato and jute mallow plants growing near where NGPBT disease was found also developed symptoms of yellowing, little leaf, and stunting, which were suspicious of phytoplasma infection. DNAs extracted from the diseased plants were subject to the molecular diagnostic assays including nested PCR with phytoplasma-specific primers, and multilocus sequence analysis (MLSA) of three genetic loci of phytoplasma (16S rRNA, rplV-rpsC and rplO-secY-adk). The results showed that phytoplasmas strains associated with the diseased papaya, tomato, and jute mallow plants shared 100% nucleotide sequence identities in their 16S rRNA, rplV-rpsC and rplO-secY-adk gene fragments. This demonstrates that tomato and jute mallow are two new hosts of NGPBT phytoplasmas. This also marked the first time that phytoplasma diseases were identified in tomato and jute mallow in Nigeria, as prior to this study, phytoplasma diseases had only been found in coconut palm and papaya in the country. In addition, the findings from the study also strongly suggest the presence of insect vector(s) for the transmission of the NGPBT phytoplasma in this region. Screening and identification of insect vectors in the future will help understand the epidemiology of NGPBT phytoplasma disease and effectively control the disease.