Global Plant Virus Disease Pandemics and Epidemics

Abstract

The world’s staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. This situation is becoming increasingly serious because of the human population’s growing food requirements and increasing difficulties in managing virus diseases effectively arising from global warming. This review provides historical and recent information about virus disease pandemics and major epidemics that originated within different world regions, spread to other continents, and now have very wide distributions. Because they threaten food security, all are cause for considerable concern for humanity. The pandemic disease examples described are six (maize lethal necrosis, rice tungro, sweet potato virus, banana bunchy top, citrus tristeza, plum pox). The major epidemic disease examples described are seven (wheat yellow dwarf, wheat streak mosaic, potato tuber necrotic ringspot, faba bean necrotic yellows, pepino mosaic, tomato brown rugose fruit, and cucumber green mottle mosaic). Most examples involve long-distance virus dispersal, albeit inadvertent, by international trade in seed or planting material. With every example, the factors responsible for its development, geographical distribution and global importance are explained. Finally, an overall explanation is given of how to manage global virus disease pandemics and epidemics effectively.

The Phylogeography of Potato Virus X Shows the Fingerprints of Its Human Vector

“…Potato virus X (PVX, genus Potexvirus, family Alphaflexiviridae) [1,2] was one of the first potato (Solanum tuberosum) viruses described [3][4][5][6]. It is one of over 50 viruses now found infecting potato crops around the world and, historically, has been the subject of much research [7][8][9][10][11][12][13]. It is spread by contact between healthy and infected foliage or roots of potato, tobacco and tomato plants.…”

“…No specific PVX vectors have been found despite a wide range of invertebrate species being tested, and it is not transmitted via true seeds of infected potato plants. However, non-specific transmission by biting insects has been reported [13]. Long-distance spread within regions or worldwide depends on the movement of virus-infected plant materials, usually in the trade of infected seed potato tubers [7][8][9][10][11][12][13][14].…”

“…However, non-specific transmission by biting insects has been reported [13]. Long-distance spread within regions or worldwide depends on the movement of virus-infected plant materials, usually in the trade of infected seed potato tubers [7][8][9][10][11][12][13][14]. PVX strains differ in virulence, mostly causing mild leaf mosaic symptoms, but severe strains cause obvious mosaics [3,[6][7][8]13,15,16].…”

“…Long-distance spread within regions or worldwide depends on the movement of virus-infected plant materials, usually in the trade of infected seed potato tubers [7][8][9][10][11][12][13][14]. PVX strains differ in virulence, mostly causing mild leaf mosaic symptoms, but severe strains cause obvious mosaics [3,[6][7][8]13,15,16]. PVX infection usually depresses the yield of potato tubers by 5-20%, but up to 40% with severe PVX strains [8][9][10][11][12][13]17,18].…”

“…In potato plants, mixed infections of PVX with potato virus A (PVA) or potato virus Y (PVY), both potyviruses (family, Potyvirideae), causes the classic severe foliage diseases 'crinkle' (PVX + PVA) and 'rugose mosaic' (PVX + PVY), and much greater tuber yield losses [8,13,19,20]. Mixed infection of PVX with potato virus S (PVS; genus, Carlavirus, family, Betaflexiviridae) also increases the severity of potato foliage symptoms [21].…”