No abstract

Watermelon, Citrullus lanatus, (Thunb.) is an annual crop in the Cucurbitaceae family grown for it fruits. It nutritional and medical uses helps in combating some illnesses and maintaining good health. The production of this crop in Nigeria is seriously under threat by virus disease. A survey of some farms in Adim, Biase Local Government Area of Cross River State, Nigeria during the 2019 planting season revealed mosaic and chlorotic symptoms. Mechanical inoculation was performed on young seedlings of Cucumeropsis mannii from watermelon samples showing viral symptoms and latter tested against the universal potyvirus antiserum and further detected by RT-PCR assay using cylindrical inclusion (CI) primer. The amplified cDNA was cloned and the nucleotide sequence determined. The serology result showed that there was positive reaction against the potyvirus antiserum confirming it to be a potyvirus. The gene sequence analysis revealed 86% sequence identity with Algerian watermelon mosaic virus. This is the first report of Algerian watermelon mosaic virus strain infecting watermelon in Nigeria.

Trichosanthes cucumerina L is a tropical or subtropical fruit bearing crop of the Cucurbitaceae family.  Field survey during 2020 planting season in Akamkpa, Southern Cross River State, Nigeria revealed widespread virus infection of the crop. Symptoms observed included severe leaf malformation/reduction and rugosity. This research was therefore aimed at identifying viruses infecting Trichosanthes cucumerina in this location. Infected leaf samples were collected and virus maintained on young seedlings of T. cucumerina in the Botanical Garden of University of Calabar, Nigeria. Diagnostic tools included ACP-ELISA and gene sequence analysis.  The ELISA result revealed two viruses belonging to the genus Cucumovirus and Potyvirus. The identity of the viruses were determined after virus sequences were compared with other viruses available in the GenBank of National Centre for Biotechnology Information (NCBI) using the basic local alignment search tool (BLASTn). The result revealed the Cucumovirus to be Cucumber mosaic virus (CMV) while the Potyvirus was revealed to be Potato virus Y (PVY). This is the first report of mixed virus infection on Trichosanthes cucumerina in Nigeria.

Cucurbits are group of plants which belonged in the Cucurbitaceae family and constitute one of the most important vegetables for human consumption throughout the world. A survey conducted between January to March 2021 across major cucurbit-growing area in Cross River State revealed wide spread virus infection of these crops, surveyed plants showed mosaic, mottle and leaf deformation symptoms. This research was aimed at identifying viruses infecting some cucurbits in the study areas. Twenty four samples showing virus like symptoms were collected and tested against ACP-ELISA and RT-PCR. Result obtained from ACP-ELISA showed that 20 out of 24 samples collected tested positive to universal potyvirus antisera, the gene sequence analysis revealed that samples were predominantly infected with Algerian watermelon mosaic virus representing 40% of total viruses detected followed by Morroccan watermelon mosaic virus representing 15% of total viruses detected followed by Papaya ringspot virus, Zucchini tigre mosaic virus, Watermelon mosaic virus and Soybean mosaic virus representing 10% each for total viruses detected and finally Potato virus Y representing 5% of total virus detected. This survey is an accurate and timely detection and will form the basis for mitigating yield losses resulting from virus infection on cucurbits. This is the first report of wide scale detection of viruses infecting cucurbits in Nigeria.

Leaf samples of Ocimum gratissimum (L.) exhibiting vein banding, mosaic and chlorotic spots were collected randomly from the field. The symptomatic samples reacted positively to specific CMV antibody in antigen coated plate enzyme linked immunosorbent assay and to confirm the presence of CMV, RT-PCR was performed using CMV-specific primers that amplify a 519 bp region from the viral coat protein gene. The expected amplicon shared homology of 97.06% with a Nigerian isolate MH178110. Phylogenetic tree constructed revealed the isolate in close association with CMV strains belonging to subgroup II. This is the first molecular evidence of CMV in O. gratissimum in Nigeria and adds to the list of natural host for the virus.