Large-Scale Seedling Grow-Out Experiments Do Not Support Seed Transmission of Sweet Potato Leaf Curl Virus in Sweet Potato

Abstract

Sweet potato leaf curl virus (SPLCV) threatens global sweet potato production. SPLCV is transmitted by Bemisia tabaci or via infected vegetative planting materials; however, SPLCV was suggested to be seed transmissible, which is a characteristic that is disputed for geminiviruses. The objective of this study was to revisit the validity of seed transmission of SPLCV in sweet potato. Using large-scale grow-out of sweet potato seedlings from SPLCV-contaminated seeds over 4 consecutive years, approximately 23,034 sweet potato seedlings of 118 genotype entries were evaluated. All seedlings germinating in a greenhouse under insect-proof conditions or in a growth chamber were free of SPLCV; however, a few seedlings grown in an open bench greenhouse lacking insect exclusion tested positive for SPLCV. Inspection of these seedlings revealed that B. tabaci had infiltrated the greenhouse. Therefore, transmission experiments were conducted using B. tabaci MEAM1, demonstrating successful vector transmission of SPLCV to sweet potato. Additionally, tests on contaminated seed coats and germinating cotyledons demonstrated that SPLCV contaminated a high percentage of seed coats collected from infected maternal plants, but SPLCV was never detected in emerging cotyledons. Based on the results of grow-out experiments, seed coat and cotyledon tests, and vector transmission experiments, we conclude that SPLCV is not seed transmitted in sweet potato.

Seed Transmission of Begomoviruses: A Potential Threat for Bitter Gourd Cultivation

“…Contrary to our expectation, market seeds were more infected than seeds collected from the field, indicating variation in the amount of virus inoculum in seeds. Conflicting results obtained for the same cultivar from two different sources in our study are similar to previous results [ 11 , 26 , 27 , 28 , 29 ]. This discrepancy in the virus detection between different sources, different batches of the same cultivar, and different cultivars of the same host may explain the ambiguity recorded in seed transmission of some of the begomoviruses.…”

Emerging evidence of seed transmission of begomoviruses: implications in global circulation and disease outbreak

“…The seed to seedling transmission rate was reported to be 21.21% and further confirmed the SPLCV replication in seedlings through Southern blot hybridization. On the contrary, in another study, Andreason et al (2021) concluded that SPLCV was not seed transmissible. They observed the presence of SPLCV only on the seed coat but not on any new germinated cotyledons after testing the infected seeds in Petri dishes.…”

Begomoviruses: what is the secret(s) of their success?

“…By contrast, other studies generally carried out more recently were not able to detect seed transmission of a number of begomoviruses, some of them previously reported as being transmissible. These include sweet potato leaf curl virus in sweet potatoes, TYLCV in tomatoes and Nicotiana benthamiana, TYLCSV in tomatoes, ToLCNDV in melons, tomato mottle virus in tomatoes, tomato golden mosaic virus in tomatoes, and bhendi yellow vein mosaic virus in okra [80][81][82][83][84][85][86].…”