The Man'yoshu (meaning "collection of ten thousand leaves") is the oldest anthology of poetry in Japan. One poem, written by the Empress Koken in 752 AD, describes the unusual autumnal appearance of eupatorium plants during the summer — they exhibit a characteristic yellow leaf pattern on their leaves, attributed to the presence of a geminivirus called eupatorium yellow-vein virus (EpYVV). In a Brief Communication in the April 24 Nature, Keith Saunders and colleagues at The John Innes Centre, Norwich, UK, show that a geminivirus and accompanying satellite component are responsible for the foliar patterns of eupatorium plants. This finding suggests that the poem also represents the first known record of a plant virus (Nature, 422:831, April 24, 2003).

Saunders et al. investigated the possibility that, in addition to EpYVV, a DNA β-satellite component was required for the aetiology of eupatorium plants. Cloned tandem repeats of β-satellite DNA components and of geminiviruses were used to infect wild-type eupatorium plants. Diseased plants exhibited the characteristic phenotype, and analysis confirmed that both the β-satellite DNA and the EpYVV DNA were required. In addition, the disease and phenotype could be transmitted between plants by the whitefly Bemisia tabaci.

"[This] implies that such disease complexes were prevalent before the advent of modern intensive agriculture practices. Similar disease complexes have now been found in weeds, ornamental plants, and economically important crops throughout Africa and Asia, indicating that they are diverse and widespread, and represent a serious threat to agriculture in the Old World," conclude the authors.