Citation: Gomathi Devi, R.; Jothika, C.; Sankari, A.; Lakshmi, S.; Malathi, V.G.; Renukadevi, P.Seed Transmission of Begomoviruses: A Potential Threat for Bitter Gourd Cultivation. Plants 2023, 12, 1396. https://doi.org/10.3390/ plants12061396 Academic Editors: Munir Mawassi and Sergey Morozov Received: 4 February 2023 Revised: 13 March 2023 Accepted: 15 March 2023 Published: 21 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Article Seed Transmission of Begomoviruses: A Potential Threat for Bitter Gourd Cultivation Ravisankar Gomathi Devi 1 , Chinnaraj Jothika 1 , Arjunan Sankari 2 , Sethuraman Lakshmi 3 , Varagur Ganesan Malathi 4 and Perumal Renukadevi 1, * 1 Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India 2 Department of Vegetable Science, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India 3 Departmentof Seed Science and Technology, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India 4 Retired Scientist, ICAR-IARI, GI, Sree Kumaran Hill Crest Apartment, Coimbatore 641046, Tamil Nadu, India * Correspondence: renukadevi.p@tnau.ac.in Abstract: Bitter gourd (Momordica charantia L.), one of the valued vegetable crops in India, is severely affected by yellow mosaic disease caused by two begomoviruses, tomato leaf curl New Delhi virus (ToLCNDV) and bitter gourd yellow mosaic virus (BgYMV). The symptoms are yellowing, distortion of leaf, puckering, and malformed fruits. Increased incidence of the disease and appearance of symptoms even in young emerging seedling stage were suggestive of seed transmission of the viruses, which was examined in detail. To study the seed transmission, two sources—seeds of elite hybrids H1, H2, H3, H4, and Co1 procured from a seed market; and seeds from infected plants in the farmer’s field were tested. Detection of the virus by DAS-ELISA using polyclonal antibody indicated embryo infection up to 63%, 26%, 20%, and 10% in hybrids H1, H2, H3, and H4, respectively, for market-procured seeds. In PCR analysis with primers specific for ToLCNDV and BgYMV, infection by ToLCNDV was as high as 76% and mixed infection was 24%. In contrast, in seeds derived from field-infected plants, the percentage detection was less. Grow-out tests with market-procured seeds revealed no transmission for BgYMV compared with 5% transmission for ToLCNDV. Whether seed-borne inocula could serve as an inoculum for new infection in a field and further progress of the disease was investigated in a microplot study. The study clearly revealed variation in seed transmission between different sources, lots, cultivars, and viruses. The virus present in symptomatic and asymptomatic plants was easily transmitted by whitefly. In another microplot experiment, the potential of seed-borne virus as inoculum was proved. There was 43.3% initial seed transmission in the microplot, increasing to 70% after release of 60 whiteflies. Keywords: Momordica charantia L. embryo; grow-out test; microplot; ToLCNDV; BgYMV 1. Introduction Emergence of diseases caused by begomoviruses is the major challenge in improving productivity of food, feed, fiber, and ornamental crops. The genus Begomovirus, which belongs to the family Geminiviridae, contains nearly 450 virus species affecting a large number of economically important crops. Virus members of this family have a circular single-stranded genome of 2.7–3 kb length, encapsidated by twinned para-icosahedral virion particles (22 × 38 nm). On the basis of genome organization, vector, and host range, the family is divided into 14 genera—Becurtovirus, Begomovirus, Capulavirus, Curtovirus, Eragrovirus, Grablovirus, Mastrevirus, Topocuvirus, Turncurtovirus, Citlodavirus, Maldovirus, Mulcrilevirus, Opunvirus, and Topilevirus [1–4]. Of all the ssDNA viruses, the genus Bego- movirus infects economically important dicotyledonous hosts, and is transmitted by the whitefly, Bemisia tabaci, in a circulative persistent manner. The begomoviruses have either a bipartite (DNA A and DNA B) or monopartite genome (DNA A) encapsidated within gem- inate particles. The transcription is bidirectional, and genes encoded in virion-sense and Plants 2023, 12, 1396. https://doi.org/10.3390/plants12061396 https://www.mdpi.com/journal/plants