Variation in seed transmission of cowpea viruses between single and multiple infections.

Seed transmission (ST) plays an important role in virus dispersion and disease epidemiology. Many viruses infecting cowpea are known to be seed-transmitted. This study evaluated the rate of virus ST in cowpea varieties inoculated under screenhouse conditions (SC) with bean common mosaic virus-blackeye cowpea mosaic strain (BCMV-BlCM), Southern bean mosaic virus (SBMV) and cucumber mosaic virus (CMV) under single and multiple-infections. Up to 50 seeds harvested from the virus-infected plants of each variety per treatment were used for the grow-out test under insect-proof SC. Data were recorded on seed germination (SG), symptoms in seedlings, and virus ST. The leaf samples were tested for viruses by enzyme-linked immunosorbent assay (ELISA) and reverse-transcription polymerase chain reaction (RT-PCR). The SG rate was 78 ± 2.8-100 ± 0% in all treatments. A total of 1.5% of 1,604 seedlings infected singly showed symptoms, whereas in diagnostics testing, viruses were detected in 2.6% of plants, indicating occurrence of asymptomatic ST. The highest rate of transmission observed for single infections was 17% CMV in IT98K-133-1-1, 17.1% BCMV-BlCM in IT98K-503-1, and 2.3% SBMV in IT99K-1060. The highest CMV frequency under coinfection was 22.2% in plants inoculated (PI) with SBMV + CMV, 4.2% for BCMV-BlCM in PI with BCMV-BlCM + CMV and 2.3% for SBMV in PI with BCMV-BlCM + SBMV + CMV. This study indicated high variation in the rates of ST based on cultivar and virus type, and for each virus under mixed-infection conditions. Diagnostic confirmation detected a higher percentage of seed-transmitted viruses compared to visual assessment, warranting the need for diagnostics for the reliable detection of seed-transmitted viruses.

Supplementary information: The online version contains supplementary material available at 10.1007/s13337-024-00899-2.