Postharvest Factors Affecting Potato Quality and Storability - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 409

mol/m 3 ) concentration, sprouting was delayed in tubers for
25 weeks. Ethylene treatment results in uniform sprouting from all eyes when the tubers are
reconditioned at room temperature. Ethylene has been registered as “Eco Sprout Guard TM ”
as a potato tuber sprout-suppressant in Canada (Daniels-Lake et al., 2005).
Prange et al. (1998) hypothesized that continuous treatment of ethylene terminates
bud rest at biochemical and cellular levels but stops further cellular differentiation and
elongation. Sprouts that are formed after treating with ethylene are easy to detach from
tuber compared to untreated tubers. Ethylene exposure increases polyamine levels in tubers
(Jeong, 2002). Increased levels of spermidine in stored tubers produce more smaller-size
tubers (Pedros et al., 1999). Daniels-Lake et al. (2005) tested different concentrations of
ethylene on fry color. All the ethylene treatments in storage darkened the fry color com-
pared to CIPC treatment (Prange et al., 2001; Daniels-Lake et al., 2005). This darkening
is due to increase in polyamine levels in tubers. Application of 1-methylcyclopropene (1-
MCP) as a pretreatment before applying ethylene improved fry color (Prange et al., 2001,
2005). 1-MCP is applied at 1

treatment at 4 μ L/L (166 μ

L/L for 2 days prior to ethylene treatment. Some culti-
vars (Shepody) require multiple treatments of 1-MCP during storage to reduce fry color
darkening.
Endogenous ethylene plays an important role in microtuber endodormancy (Suttle,
1998a, b). Dose-dependent treatments using an ethylene noncompetitive antagonist such as
silver nitrate (AgNO 3 ) and a competitive antagonist such as 2,5-norbornadiene (NBD) initi-
ated sprouting in potato tubers. Premature tuberization was 98% when treated with AgNO 3
at the 50

μ

M concentration, and 85% when treated with NBD at 5 ppm concentration.
Ethylene inhibitors are effective in inducing sprouting if tubers are treated early. This led to
the hypothesis that ethylene is required only to initiate endodormancy in microtubers. Ethy-
lene can reverse these changes, which further confirms the role of ethylene in promoting
dormancy.
Hydrogen peroxide-based materials suppress the sprouting by causing physical damage
to the sprout tips and buds (Afek et al., 2000). These materials are applied with an atomizing
system after wound healing in potatoes. Afek et al. (2000) compared sprout inhibition
activity of CIPC with hydrogen peroxide. Four times treatment with 10% hydrogen peroxide
resulted in 0% sprouting even after 6 months of storage (Afek et al., 2000). Lopez-Delgado
et al. (2005) showed spraying hydrogen peroxide in field increased starch concentration in
tubers to 6-30%, and it will be highly interesting to see how these tubers perform in storage.

μ

19.6 Conclusions

In summary, there are considerable advances made in understanding the biology of dor-
mancy and sprouting in plant systems. Additionally, the practical benefit in understanding
the biological process behind wound healing, CIS, and physiological aging will be enor-
mous. The key is to understand how different plant hormones interact together to orches-
trate these biological phenomena. Gaining a complete understanding of the genetics of such
complex traits is central to our ability to use biotechnology for the improvement of potato.
More information on specific plant hormone roles and their cross talk in these processes
will help in developing new environmental-friendly technologies to manipulate both dor-
mancy and sprouting. Using multiparallel technologies such as genomics, proteomics, and
metabolomics can give us new insights to manipulate metabolites.