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The number of viruses known to be transmitted vertically from seeds to seedlings has increased to over 200, and is dominated by about 30 members of the <i>Potyvirus</i> genus, with a few viruses in the Bromoviridae (<i>Alfalfa mosaic virus, Cucumber mosaic virus, </i>and<i> Peanut stunt virus</i>), <i>Fabavirus</i>, and <i>Carlavirus</i>. These viruses and potyviruses are also transmitted horizontally by aphids in a non-persistently or stylet-borne manner. Transmission of filamentous potyviruses is known to be mediated by interaction between specific motifs of two viral-encoded proteins, HCPro and CP, which function in attachment and release of virus particles from stylet tips.  About half of the potyviruses infect and are seed-transmitted in legumes in the family <i>Fabaceae</i>, with up to three viruses infecting each of six other dicot families (<i>Asteraceae</i>, <i>Brassicaceae</i>, <i>Caricaceae</i>, <i>Cucurbitaceae</i>, <i>Rosaceae</i>, <i>Solonaceae</i>) and two monocot families (<i>Amaryllidaceae</i>, <i>Poaceae</i>). Aphids of both colonizing and non-colonizing species of host plants can usually transmit each virus, with varying efficiency.  Efforts to understand pollen, ovule, and embryo infection, and manage these seed-borne viruses, will be discussed for important pathogens of lettuce and legume crops. New approaches to confirm vertical and horizontal transmission of <i>Zucchini yellow mosaic virus</i>, an emerging disease of cucurbits spread globally via infected seed, and to reveal significant genome diversity, will be discussed.