Tomato and Jute Mallow are Two New Hosts of Papaya Bunchy Top Phytoplasma, a 16SrXII-O Subgroup Strain in Nigeria.

Nigerian papaya bunchy top (NGPBT) phytoplasma was first identified in diseased papaya plants growing in Ibadan, Oyo State, Nigeria (Kazeem et al. 2021). The NGPBT phytoplasma is a 'Candidatus Phytoplasma convolvuli'-related strain and represents a subgroup lineage, 16SrXII-O (the accession number of the reference strain is MW530522, Kazeem et al. 2021). The present communication reports that NGPBT phytoplasma can also infect tomato (Solanum lycopersicum) and jute mallow (Corchorus olitorius). Since May 2020, tomato and jute mallow grwn in Ibadan have been observed to develop yellowing, little leaf, and stunting symptoms (Fig. 1). Because the symptomatic plants occurred in the region approximately 1 km adjacent to where the NGPBT disease was reported, and the symptoms of infected plants resembled those of phytoplasma infection, molecular diagnostic assays for phytoplasma detection were deployed. Total DNAs were extracted from symptomatic plants, including four tomato plants and three jute mallows, as well as from asymptomatic two tomato and two jute mallow plants. The DNA samples were subjected to semi-nested PCR using phytoplasma 16S rRNA gene-specific primers P1A and P7A, followed by P1A and 16S-SR (Lee et al. 2004). An amplicon of 1.5 kb was obtained from each of the symptomatic plants, while no amplicon resulted from DNA samples of asymptomatic plants or negative controls without DNA templates (water and PCR reagents only). PCR products were cloned into the TOPO TA cloning vector (Invitrogen, Carlsbad, CA, USA), and three clones were chosen for each sample for Sanger sequencing (Psomagen Inc., Rockville, MD, USA). The nearly full-length 16S rRNA gene sequences (1.53kb) derived from tomato (OP123558) and jute mallow (OP123559) samples were identical. Based on the iPhyClassifier phytoplasma classification web tool (Zhao et al. 2009) and the BLAST search against the NCBI nucleotide database, these phytoplasma strains showed 100% sequence identity in 16S rRNA gene with the NGPBT phytoplasma (16SrXII-O, MW530522). Moreover, two additional genetic loci including ribosomal protein genes rplV-rpsC, and rplO-secY-adk were also amplified by nested PCR or semi-nested PCR with specific primers rpStolF/rpStolR followed by rpStolF2/rpStolR (Martini et al. 2007), and SecYF1a (Xll)/MapR-703-a, followed by SecYF2a (Xll)/MapR-703-a (Lee et al. 2010). Gene fragments of rplV-rpsC (1238bp) and rplO-secY-adk (2064bp) were amplified from DNAs of diseased papaya, tomato, and jute mallow plants. The obtained sequences were deposited into GenBank, respectively: rplV-rpsC (OP123560, OP123562, and OP123563) and rplO-secY-adk (OP123565, OP123567, and OP123568). Multilocus sequence analysis (MLSA) indicated that the sequences of phytoplasmas amplified from three different plant hosts were also identical in rp, secY, and adk genes. The MLSA results demonstrate that tomato and jute mallow are two new hosts of NGPBT phytoplasmas. This also marks the first time that phytoplasma diseases are associated with tomato and jute mallow in Nigeria, as prior to this study, phytoplasma diseases were only reported in coconut palm and papaya in the country (Osagie et al. 2016; Kazeem et al. 2021). Results from the present study suggest that insect vector(s) for the transmission of the NGPBT phytoplasma are present in the region. Since both tomato and jute mallow are important vegetable crops in Nigeria, timely dissemination of emerging disease information is needed to alert growers and extension personnel in the region. In addition, ongoing incidence, and prevalence surveys of NGPBT disease indicate that more infected papaya and tomato plants have been observed in the region than in previous years. A better understanding of the NGPBT phytoplasma disease epidemiology will help devise strategies to control the diseases associated with the NGPBT phytoplasma.

Occurrence and distribution of pepper veinal mottle virus and cucumber mosaic virus in pepper in Ibadan, Nigeria.

Viral diseases constitute obstacles to pepper production in the world. In Nigeria, pepper plants are primarily affected by pepper veinal mottle virus (PVMV), Cucumber mosaic virus (CMV), Pepper leaf curl Virus (TLCV), Tobacco mosaic virus (TMV), Pepper mottle virus (PMV) and a host of other viruses. The experiment was carried out with a diagnostic survey on the experimental field of the National Horticultural Research Institute, Ibadan, Nigeria and on pepper farms in six local government areas within Ibadan Oyo State, Nigeria, forty samples were collected from each of the farms. Diseased samples were obtained from the field and taken to the laboratory for indexing. In ELISA test some of the samples from the pepper farms showed positive reaction to single infection with PVMV (36.79%), CMV (22.14%) while some others showed positive reaction to mixed infection of the two viruses (10%) but some also negative reaction to PVMV and CMV antisera (31.07).

Effects of Cowpea mottle virus and Cucumber mosaic virus on six Soybean (Glycine max L.) cultivars.

The study was carried out to determine the comparative pathogenic response of six cultivars of soybean; TGx 1844-18E, TGx 1448-2E, TGx 1910-8F, TGx 1019-2EN, TGx 1910-8F and TGx 1876-4E to single and mixed infections with cowpea mottle virus and cucumber mosaic virus. The experiment was conducted in the screenhouse at the crop production pavilion, Faculty of Agriculture, University of Ilorin, Ilorin, Kwara state Nigeria. The results of the experiment revealed that all soybean cultivars were susceptible to single and mixed infection of the two viruses but to seemingly different extent. The single infection with cowpea mottle virus (CMeV), however, caused the most severe symptoms on the soybean cultivars. Cucumber mosaic virus (CMV) alone was not as severe as the CMeV. The mixed infection of CMeV and CMV did not cause higher severity than CMeV alone indicating that there was little or no synergistic effect between the two viruses on soybean.