Agriculture Reference
In-Depth Information
emerge as potato is increasingly grown in
warmer, food-insecure parts of the world. It
then discusses what is currently known about
the likely influences of climate change in ex-
acerbating the future incidence of potato virus
diseases and altering their distributions in dif-
ferent potato growing regions. An analysis is
provided of the current disagreement between
biological and phylogenetic nomenclature sys-
tems for different strains of common potato
viruses and how to approach a resolution, es-
pecially regarding Potato virus Y (PVY) strain
group classification. The chapter then focuses
on the reasons for the recent upsurge of prob-
lems with PVY in potato crops in many coun-
tries and what can be done to address this. Fi-
nally, it emphasizes areas where research on
potato viruses is needed in the future, the need
for surveillance over the emergence of add-
itional potato viruses, and the importance of
improving the effectiveness of seed potato
health, especially in developing countries.
of novel viruses capable of invading potato
crops (e.g. Jones, 2009; Navas-Castillo et  al .,
2011; Jones and Barbetti, 2012).
Well-known potato viruses
Some of the well-known potato viruses found
in most parts of the world where potatoes are
grown have become less common over time, for
example Potato virus M and Potato virus A
(PVA), or rare, for example Potato aucuba mosaic
virus and Potato yellow dwarf virus . However,
PVY, Potato leaf roll virus (PLRV), Potato virus X
(PVX), and Potato virus S (PVS) continue to
occur commonly on a global basis ( Table 12.1 ).
PLRV and PVY both cause substantial yield and
tuber quality losses in many countries (e.g.
Valkonen, 2007). When present alone, PVX
and PVS normally cause minor yield losses, but
become more important when present in mixed
infections with each other, or especially when
PVX co-infects plants with PVY (rugose mo-
saic), PVA (crinkle) or PLRV (Wright, 1977; de
Bokx and van der Want, 1987; Stevenson et al .,
2001; Valkonen, 2007; Nyalugwe et al ., 2012).
In the past, PLRV was generally considered the
most important potato virus, especially when
potato crops were grown in warmer climates
(e.g. de Bokx and van der Want, 1987; Jones et
al ., 2009). This continues to be the case in
many regions with warmer climates, such as
Australia (e.g. Holmes and Teakle, 1980; Wil-
son and Jones, 1990; Holland and Jones,
2005). In many other regions, however, PVY
has recently overtaken PLRV in importance
(e.g. Blanchard et al ., 2008; Rolland et al .,
2008; Gray et al ., 2010).
12.1 Viruses Infecting Potato
Like most vegetatively propagated crops, po-
tato becomes infected with many virus dis-
eases. These are of two main types: (i) those
that primarily infect potato, and (ii) those that
predominantly infect other plants but also in-
vade potato. The first group coevolved with
wild potato species in the Andean region and
then invaded cultivated potatoes during their
early domestication. Most of the second group
only spread to the potato when it was intro-
duced following its dispersal to new locations
after European colonization of South America
(e.g. Jones, 1981a, 2009; Valkonen, 2007). Cur-
rently, about 50 viruses and one viroid, Potato
spindle tuber viroid , are known to infect the crop
globally (Table 12.1 ) . As the technology avail-
able for virus identification becomes increas-
ingly sophisticated (e.g. Boonham et al ., 2003,
2014; Donaire et al ., 2009; Kreuze et al ., 2009;
Jones, 2014), the numbers found are expected
to continue to increase. Compounding this ef-
fect, climate change is projected to increase
new encounters between introduced crops and
native flora, increasing the rate of emergence
Viruses causing tuber necrosis
Viruses causing potato tuber necrosis, including
necrotic rings, continue to cause serious damage
in some parts of the world. In regions with
warmer climates, for example in southern Aus-
tralia, South Africa, Brazil, and Argentina, Tomato
spotted wilt virus (TSWV) is an important cause
of tuber necrosis ( Table 12.1 ) (e.g. Wilson, 2001;
Jones et al ., 2009). In regions with cold climates,
 
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