Pollen and seed transmission of Cucumber green mottle mosaic virus in cucumber

Cucumber green mottle mosaic virus (CGMMV) is transmitted mechanically in cucurbits, but whether it is transmitted via pollen to healthy plants and onto the subsequent generation of seedlings is unknown. Greenhouse experiments were conducted to investigate the importance of this route of infection. Cucumber seedlings at the 3-true-leaf stage were mechanically inoculated with CGMMV. At anthesis, scanning electron microscopy (SEM) and reverse transcription polymerase chain reaction (RT-PCR) were used to verify the presence of CGMMV. Pollen was collected from the flowers of the infected plants and used to fertilize non-inoculated plants. The rate of CGMMV transmission to the resulting fruits ranged from 171 to 512% compared with 333-100% for mechanically inoculated plants. Seeds were harvested from the cucumber fruits of both treatments and tested for the presence of CGMMV by RT-PCR. The CGMMV-positive seeds harvested from the two treatments were sown separately. The seed transmission rates for the inoculated and non-inoculated plants were 167-100% and 128-767%, respectively. It was concluded that CGMMV can be transmitted both horizontally via cucumber pollen and vertically, to the next generation, in infected seeds. In addition the rate of seed transmission was much higher than previous reports. These findings have important implications for the disease management of CGMMV.