Seed and pollen transmission of tomato leaf curl New Delhi virus, tomato leaf curl Taiwan virus, and tomato yellow leaf curl Thailand virus in cucumbers and tomatoes

Understanding the seed-borne nature of plant viruses is essential for developing disease control strategies and is impactful to the seed market. Here, we investigated seed transmissibility of tomato leaf curl New Delhi virus-cucumber isolate (ToLCNDV-CB) and -oriental melon isolate (ToLCNDV-OM) in cucumber and seed transmissibility of tomato leaf curl Taiwan virus (ToLCTV) and tomato yellow leaf curl Thailand virus (TYLCTHV) in tomato. Parent plants were inoculated using agroinfiltration with virus infectious clones, and virus infection was confirmed by PCR with virus-specific primers. ToLCNDV-CB and ToLCNDV-OM were detected in different parts of the female and male flowers and the fruits of cucumbers. ToLCNDV-CB and ToLCNDV-OM were also detected in cucumber seed coats and seedlings with an infection rate higher than 79%. Similar results were observed with ToLCTV and TYLCTHV as they were detected in different parts of the female and male flowers and fruits of three tomato cultivars. ToLCTV and TYLCTHV were also detected in tomato seed coats and seedlings with an infection rate higher than 36%. In addition, pollen-mediated transmission assays of these four begomoviruses were conducted with pollen derived from virus-infected plants to healthy plants. Results showed that ToLCNDV-CB and ToLCNDV-OM were detected in cross-pollinated cucumber progenies with an infection rate higher than 70%. ToLCTV and TYLCTHV were [also] detected in cross-pollinated tomato progenies with an infection rate higher than 77%. Our results indicated that ToLCNDV, ToLCTV, and TYLCTHV can be transmitted via seeds or pollens of cucumber and tomato plants. To our knowledge, this is the first report documenting the pollen-mediated transmission of begomoviruses.