Garlic Potyviruses Are Translocated to the True Seeds through the Vegetative and Reproductive Systems of the Mother Plant

Abstract

Garlic lost its ability to produce true seeds millennia ago, and today non-fertile commercial cultivars are propagated only vegetatively. Garlic viruses are commonly carried over from one generation of vegetative propagules to the other, while nematodes and arthropods further transmit the pathogens from infected to healthy plants. A recent breakthrough in the production of true (botanical) garlic seeds resulted in rapid scientific progress, but the question of whether viruses are transmitted via seeds remains open and is important for the further development of commercial seed production. We combined morpho-physiological analysis, fluorescence in situ hybridization (FISH), and PCR analysis to follow potyvirus localization and translocation within garlic fertile plants and seeds. Spatial distribution was recorded in both vegetative and reproductive organs. We conclude that garlic potyviruses are translocated to the seeds from the infected mother plant during flower development and post-fertilization, while pollen remains virus-free and does not contribute to seed infection. Therefore, the main practical goal for virus-clean seed production in garlic is the careful maintenance of virus-free mother plants. Although garlic pollen is free of potyviral infection, the male parents’ plants also need to be protected from contamination, since viral infection weakens plants, reducing flowering ability and pollen production.

Pathogen Eradication in Garlic in the Phytobiome Context: Should We Aim for Complete Cleaning?

“…Plant viruses are transmitted both horizontally and vertically, and similar to other vegetatively propagated crops (e.g., potato) [ 57 ], garlic viruses are spread within and between plant populations by aphids and thrips and during clonal propagation. Our recent studies have shown that garlic viruses are also transmitted by true seeds from infected mother plants and that some of them might even be integrated into the garlic genome [ 58 ]. Potyviruses are regarded as pathogenic agents in garlic [ 13 ], but our analysis of transcriptome-associated viruses shows a predominant presence of the Allexiviruses, while Poty- or Carla viruses were identified only by PCR analysis ( Figure 6 and Figure 7 ).…”

Incidence of main viruses infecting local garlic in Java, Indonesia

“…We also noted that titter of OYDV, GCLV, and SLV on bulbil was the lowest than other propagation materials even though the virus incidence was not quite different. Previous study indicated that bulbil might become a good planting material due to its pathogens (bacteria and fungi) free and less virus infection (Bushal et al, 2021;Fan et al, 2017;Shemesh-Mayer et al, 2022;Sulastiningsih et al, 2020). To date, only Potyvirus that was found on true-seeds garlic (Shemesh-Mayer et al, 2022).…”

“…Previous study indicated that bulbil might become a good planting material due to its pathogens (bacteria and fungi) free and less virus infection (Bushal et al, 2021;Fan et al, 2017;Shemesh-Mayer et al, 2022;Sulastiningsih et al, 2020). To date, only Potyvirus that was found on true-seeds garlic (Shemesh-Mayer et al, 2022). Recent study suggested that the presence of potyvirus on the young developing flowers occurred either through cellto cell movement or phloem tissue (Shemesh-Mayer et al, 2022).…”

“…To date, only Potyvirus that was found on true-seeds garlic (Shemesh-Mayer et al, 2022). Recent study suggested that the presence of potyvirus on the young developing flowers occurred either through cellto cell movement or phloem tissue (Shemesh-Mayer et al, 2022).…”

“…Virus mix infection on individual plant plays an important role on each virus pathogenicity and disease severity (Perotto et al, 2010;Takaichi et al, 1998). The data on the virus incidence implied that all propagative materials (except pollen) have been already infected by potyviruses and may contribute as primary inoculum in the field (Shemesh-Mayer et al, 2022). Therefore, it is highly recommended to use virus-free bulbs as initial planting material despite the difficulties to provide commercial virus-free planting material in large numbers.…”