Procedures for Standard
Evaluation and Data
Management of Advanced
Potato Clones
Module 4.
Assessment of Dormancy and Sprouting
Behavior of Elite and Advanced Clones
International Cooperators’ Guide
1
International Potato Center (CIP)
MTP Project 3
Output 1 Target 2
Assessment of dormancy and sprouting behavior of elite and advanced clones
C. Carli, E. Mihovilovich, and M. Bonierbale
Introduction
In potato breeding and selection, storability or keeping quality of potatoes should be
regarded as equally important as yield, disease resistance, and quality. It is one of the
considerations that need to be evaluated before releasing any variety so that farmers are
able to store their produce for a desired period of time at their farm under traditional
storing conditions or in refrigerated storage infrastructure, depending whether the end-use
is for fresh consumption, processing, or planting as seed. For estimating keeping quality of
a particular potato clone, its dormancy period, sprouting behavior, and weight loss are
major criteria that should be documented before any promising clone is released.
The present protocol is formulated to support the assessment and documentation of the
dormancy period, sprout growth and weight loss of CIP’s elite and advanced potato
clones. This information will guide farmers to manipulate sprouting to occur only when it
is desirable.
Review of literature
Dormancy is a physiological state characterized by a period during which autonomous
sprout growth will not occur even under optimal sprouting conditions, i.e., darkness, 15
to 20 C, relative humidity about 90% (Wiersema, 1985). Dormancy should be regarded
as the period in the tuber life cycle from initiation to the time when sprouting starts
(Burton 1989). However, since this period is difficult to determine, post harvest
dormancy is used for practical purposes and defined as the period from dehaulming to the
time 80% of tubers show sprouts at least 2 mm long.
Dormancy is considered to be a varietal character yet influenced by environmental and
management conditions. Since dormancy is not related to earliness of varieties, it is
possible to breed late varieties with relatively short dormancy and early varieties with
relatively long dormancy (Beukema and van der Zaag, 1979). Dormancy period depends
on soil and weather conditions during growth, tuber maturity at harvest, storage
conditions, and whether the tuber is injured or not (Ezequiel and Singh 2003). High
temperatures, low soil moisture and fertility during tuber growth accelerate physiological
development and reduce the dormant period. On the other hand, tubers harvested at an
immature stage have a longer post-harvest dormancy than tubers harvested at maturity.
Regarding storage, fluctuating storage temperatures shorten dormancy more than constant
high temperatures. Therefore, storage temperatures should remain as consistent as
possible when retarding sprout development is desired. Finally, tuber injuries caused by
harvest or by diseases and pests, can result in earlier sprouting.
2
Sprouting is a physiological stage that commence when dormancy is broken. It is the
major visible milestone in determining tuber physiological age. The earliest observable
stage of sprouting is characterized by visible small white buds, often termed “pipping” or
“peeping” (Daniels-Lake and Prangel, 2007). The physiological age of the tuber has a
great effect on the pattern of sprout growth but the basis is genetic. In turn, the
physiological age of the tuber is greatly influenced by growing conditions, storage
conditions, and length of storage period.
Patterns of sprout growth:
Apical dominance: This is a physiological phenomenon characterized by the exhibition
of a dominant bud over the others, that is suppressing the sprouting of other buds
(Pavlista, 2004). The suppressing bud is at the apical end of the tuber, which is the
furthest bud from where the tuber was attached to the vine. Physiological young tubers
exhibit apical dominance and thus the apical sprout will need to be removed (desprouted) for the other buds to develop sprouts.
Multiple sprouting: This pattern develops gradually in time as apical dominance
diminishes, and is characterized by the appearance of several
buds sprouting along the tuber. The duration of apical
dominance as well as the number of sprouts per tuber is a
varietal characteristic (Sunoschi 1981, van Es and Hartmans
1987).
Middle aged tubers exhibit multiple sprouts, and are at the
optimum stage for planting. However, as mentioned before, this
pattern can be induced in young tubers by removing the apical
sprout, although apical dominance may be reinstated by
growing of the next bud closest to the apical end (Pavlista,
2004). In such a situation, a second de-sprouting will be
necessary for inducing more sprouts (Beukema and van der Zaag, 1979).
Branching This pattern appears as middle aged tubers age further. Since sprouts are
comprised of multiple nodes with meristematic tissue and leaf
primordia at each node, branching occurs when apical dominance
within the sprouts is overcome, either after the sprouts are sufficiently
large because of tuber senility, or following damage to the apex.
These branches are referred to as “hairy” because they tend to be
weak. Even more, old tubers may also show a proliferation of small
stolons (Daniels-Lake and Range, 2007).
3
Effect of tuber size on sprout growth: Since the sprout depends on the tuber for the
materials for growth, if there are several sprouts on the tuber, an inter-sprout competition
for growth factors will be imposed by the size of the tuber (Burton, 1989). With fairly
large tubers, no effect of size will be noticeable, but with decreasing size, a point can
clearly be reached at which growth will be impaired. This competition has been shown to
be independent of the distance between the competing sprouts, suggesting that it is not a
local matter but of growth factors distributed throughout the tuber (Morris, 1966; cited by
Burton, 1989).
Additional considerations
 Tubers grown in warm regions have shorter dormancy than those of the same
variety grown in a cooler region (Wiersema, 1985).
 Tubers grown in short days tend to have a somewhat shorten dormant period
(earlier maturing of the crop) than those of the same cultivar grown under long
days (Beukema and van der Zaag, 1979)
 Tubers of cultivars with short dormant period reach their physiologically old-stage
earlier than those with a long dormant period (Beukema and van der Zaag, 1979)
 Cultivars with prominent apical dominance show faster rate of growth of their
apical sprout whereas those with more number of sprouts show a slower rate of
growth of their apical sprout (Pande et al., 2007).
 Potato sprouts in the light are shorter and sturdier than those grown in the dark
(Beukema and van der Zaag, 1979)
 Once, apical dominance is broken and multiple sprouting starts, storage between
16 and 20oC are the optimum temperature for sprout growth (Wiersema, 1985).
Weight loss: This trait determines the longevity of tubers’ storability and hence their
keeping quality. Variations in weight loss among cultivars are attributed to either their
periderm characteristics and/or their sprouting behavior. Weight loss in unsprouted tubers
occurs through the periderm and for a minimum proportion through the lenticels. Hence
varieties with a thicker periderm (a greater number of cell layers in the periderm) and
lesser number of lenticels on the tuber surface lose less weight than their counterparts
(Ezekiel et al., 2004 and Pande et al., 2007). On the other hand, sprouted tubers loose
much more weight than unsprouted tubers. After the onset of sprouting the rate of sprout
growth and number of sprouts determine the weight loss in potatoes (van Es and
Hartmans, 1987). Greater water loss with sprout growth occurs because of the high
permeability of sprout wall to water vapor. A significant correlation between weight loss
and both, the length of the longest sprout and number of sprouts per tuber was
encountered by Pande et al. (2007).
Physiology of tuber dormancy and sprouting.
Dormancy and sprouting are controlled by the interactions of major plant growth
regulators, predominantly the ratio of gibberellin (GA) and abscisic acid (ABA). ABA
has been suggested as important to maintain dormancy, whereas the role of GA has been
4
clearly determined in dormancy breakdown (Fernie and Willmitzer, 2001). On the other
hand, some evidence has also implicated indole acetic acid (IAA), an auxin, in sprouting.
IAA has been suggested to mediate the suppression of sprouting of lateral axillary buds
by apical dominance (Pavlista, 2004).
Quantitative trait loci (QTL) analyses have indicated that tuber dormancy is controlled by
at least nine distinct loci (van den Berg et al., 1996). The potential role of ABA in
dormancy has also been supported by the observation of three of these QTL influencing
ABA levels (Classens and Vreugdenhil, 2000).
Sprouting is associated with many physiological changes including the conversion of
starch to sugars, respiration, water loss, and glycoalkaloid content (Burton, 1989).
Although cool temperatures during storage can prolong the dormancy period, they
generally result in an increase in reducing sugar content, primarily glucose, which is
undesirable in the processing industry due to darkening of fried products. Low
temperature storage is not appropriate for potatoes destined for the processing market. On
the other hand, visible sprouts on potatoes are unacceptable to consumers.
Materials
Use at least 30 tubers of a calibre ranging from approximately 50 to 70 mm (Category 2)
per test clone. Try to select tubers of uniform size within clones. Tubers with bruises or
skinning damage must be avoided for storage
Procedures
Harvest practices
 Follow the practice of dehaulming i.e, cutting of haulms, by sickle or killing by
chemicals (e.g. Gramoxone), 10-15 days before crop harvesting.
 Stop irrigation about two weeks before dehaulming.
 Select tubers without bruises or skinning damage to make them less susceptible to
rot diseases during storage.
 Clean tubers from excess of soil or debris which can promote rot. It is
recommended to clean them carefully by hand. Do not wash potatoes, dampness
can cause decay.
Post-harvest practices
Dry the harvested tubers and cure skin at 10 to 20oC and 85 to 95% relative
humidity for 15 to 20 days. Avoid temperatures above 25oC. This period will allow
wound healing and promote maturity of tubers.
5
Storage
Clean and repair your storage before potatoes are introduced. Equipment in the cold store
should be examined for satisfactory storage operations.
Storability of the selected clones should be assessed under traditional storage (at ambient
temperature) and cold storage conditions at 2-4°C and 95% relative humidity (RH).
Maintaining this RH will minimize shrinkage of tubers.
Assessment of dormancy and sprouting pattern parameters of advanced and elite
clones at CIP-Headquarters is performed under diffused light storage with natural
ventilation and cold storage conditions.
The trial should last 4 months under diffused light storage and 6 under cold storage.
However, this depends on the expected duration of the dormancy period of test clones
and the location. A period of at least 45 days is required after dormancy is released1 to
allow for assessment of sprout growth pattern. Under traditional storage, in areas where
diffused light storage cannot be implemented due to the presence of strong winter as in
the temperate geographic area, the trial may last up to 6 months depending on storage
temperatures. Also in this case we should allow a period of 45 days to assess sprout
growth for the clone(s) with the longest dormancy period before the end of the trial.
Experimental design
Experimental units should consist of 10 to 15 tubers that may be placed on trays. If
available, you may use experimental units of up to 20 tubers. Tubers should be identified
by enumerating them on the skin using a permanent marker. Treatments (test clones) are
replicated twice (two experimental units/test clone). Replications of treatments should be
randomized at the storage site following a completely randomized design (CRD).
The weight of tubers should be recorded before storage.
Data recording
a) Tuber growing conditions
Since dormancy and sprouting of a given cultivar are greatly influenced by the
geographic location and growing season, it is required to indicate the geographical
growing area and weather conditions under which the tubers were grown. Data
recommended for recording:
 Eco-geographic growing conditions, example Tropical lowlands, Temperate
highlands or lowlands, etc..
 Photoperiod (daylight hours)
1
Dormancy is considered released when 80% of the tubers have at least one sprout longer than 2 mm (van
Ittersum and Scholte, 1992)
6




Monthly average maximum and minimum air temperatures (oC)
Monthly average relative air humidity (%)
Monthly average precipitation (mm)
Soil temperature (10 cm depth) (oC)
b) Storage conditions
 Storage system (cold store, diffused light store, cellars, etc.)
 Temperature (monthly average): Maximum, minimum and mean (oC)
 Relative humidity (RH) (monthly average)
c) Additional information




Number of days from planting to haulm-cutting
Number of days from haulm-cutting to harvest
Number of days after harvest and before entering store (period of skin curing)
Storage dates (beginning-end)
d) Evaluation parameters
Dormancy period (DORPD)
The dormancy period should be counted as number of days from haulm cutting to
sprouting of 80% of the tubers ( 8 to 12 tubers depending on the size of the
experimental unit) with at least one sprout longer than 2 mm. Tubers should be
checked at 10 day-intervals for monitoring sprouting initiation and growth, and to
accurately record the dormancy period
Tuber weight
 Initial tuber weight (g) (ITW): Measure the weight of each tuber before the tubers
are put into storage
 Intermediate tuber weight (g) (INTW): Measure the weight of each tuber when
dormancy is released
.
 Final tuber weight (g) (FTW): Measure the weight of each sprouted tuber of a test
clone 45 days after dormancy release in trials conducted under diffused light
storage and 60 days in trials conducted under cold storage. Prior to weighing each
tuber, remove sprouts carefully.
Sprout growth
Variables for sprout growth should be recorded in each test-clone 45 days after
dormancy release under diffused light storage, and 60 days under cold storage.
7
 Number of sprouts per tuber (NSP): Count the number of sprouts per tuber
 Length of the longest sprout (mm) (LGLNSP): Measure the longest sprout of each
tuber
 Length of lateral axillary sprouts (mm) (LGLATSP): Measure the length of each
lateral axillary sprout of each tuber (mm). Then take the average of lateral axillary
sprout length per tuber, i.e, sum the length of the lateral axillary sprouts and divide
them into the total number of lateral axillary sprouts.
 Sprout thickness (mm): Measure the thickness of the apical sprout (THASP) and of
one or two lateral axillary sprouts (THLSP1, THLSP2) (if present, measure the
thickness of the longest ones) of each tuber. Then take the average of sprout thickness
per tuber (AVTHSP).
Data analysis
Tuber weight loss
Calculate per tuber, the percentage of weight loss through periderm and lenticels,
also known as “weight loss percentage of unsprouted tubers” (PW_USPT)
% of weight loss-_unsprouted tuber = initial_tuber-weight - intermediate_ tuber-weight x 100
initial_tuber-weight
Estimate mean percentage of weight loss of unsprouted tubers per test clone and
replication (PW_USPT_mean)
Mean % of weight loss_unsprouted tubers =
15
00
Σ (%_wt-loss_unsprt-tub )
0
n=1
15
Calculate per tuber, the percentage of weight loss due mainly to number of
sprouts and sprout growth, also known as “weight-loss percentage of sprouted
tubers” (PW_SPT)
% of weight loss_sprouted tubers = initial_tuber-weight - final_ tuber-weight x 100
initial_tuber-weight
8
Estimate mean percentage of weight loss of sprouted tubers per test clone and
replication (PW_SPT_mean)
15
Σ (%_wt-loss_sprt-tub )
Mean % of weight loss_ sprouted tuber =
n=1
15
Sprout growth
Estimate the mean per clone and replication of each sprout growth variable.
Example for “length of lateral sprouts”
15
Mean length of lateral__sprouts =
Σ (length of lateral_axillary_sprouts)
n=1
15
Analysis of Variance
Use the data “number of days from haulm cutting to sprouting (dormancy
period)”, and means per test clone and replication of “percentage of weight loss of
unsprouted tubers”, “percentage of weight loss of sprouted tubers”, “number of
sprouts per tuber”, “length of the longest sprout”, “length of lateral axillary
sprouts” and “sprout thickness” to perform the ANOVA for a CRD. Estimate the
means and standard errors of the analyzed variables for each test clone. It could
be of interest to compare means between test clones for some variables. LSD can
be used for this purpose. The analysis can be run in R or in any other statistical
software.
Data Interpretation
Dormancy period: Tubers stored at low temperatures such as cold storage (2-4oC)
have longer period of dormancy than those stored at higher temperatures such as
diffused light storage at ambient temperature (18-20oC). Accordingly, three
categories could be suggested to document test-clones for their dormancy period
(Table 1). However, ranges of dormancy period within each category may vary
depending on tuber growing conditions, and temperature conditions under other
storage systems i.e. traditional storage.
9
Table 1. Categories and dormancy periods suggested for documenting advanced
clones
Storage system
Category
Short dormancy
Medium dormancy
Long dormancy
Diffused light (days)
Cold storage (days)
 75
> 75 -  95
> 95
 95
> 95 -  125
> 125
Weight loss
Cultivars with longer dormancy period are believed to perform better under nonrefrigerated storage conditions. Consequently, cultivars with a long dormancy
period and significantly lower percentages of weight loss of unsprouted tubers
could be suitable for fresh consumption or processing after long periods of storage
(up to 3 months or somewhat longer). Comparison of test clones should be
performed for this variable.
Weight loss of sprouted tubers is of great concern as cultivars with a high
percentage of weight loss age faster and consequently show disadvantages over
young seed during their growing season, such as less vigor, shorter tuber bulking
and smaller tubers (Pavlista, 2004). Documenting this variable along with
dormancy period provide a good reference for deciding the best storage
conditions and time for planting of new varieties. Comparison of test clones
should be performed for this variable. Clones with less percentage of weight loss
of sprouted tubers maintain an adequate condition for planting for a longer time.
Sprouting patterns (SPPATT)
A single apical sprout or an average less than 2 sprouts per tuber observed at the
end of the test indicate the prevalence of an apical dominance, even if the
additional sprout shows a growth rate almost similar to that of the apical sprout.
An average of less than 3 developed sprouts, of which one is the apical, may still
be considered a partial dominance, while an average number of 3 or more sprouts
per tuber indicates the absence of apical dominance or a pattern of multiple
sprouts.. However, remember that the number of sprouts per tuber is a genetic
characteristic. Multiple sprouting cultivars are desired over those with apical
dominance as they give rise to plants with several stems and consequently with
greater yields. On the other hand, the presence of multiple sprouts is usually
accompanied by greater weight loss of sprouted tubers, thus this latter parameter
should be taken into account in multiple sprouting cultivars for deciding best
storage conditions or storage period.
10
Length of the longest sprout along with mean length of lateral axillary sprouts are
good indicators for determining the sprout pattern of a cultivar, viz, a negative
correlation exist between number of sprouts and length of the longest sprout
(Singh and Ezekiel, 2003). Pande et al. (2007) observed examples of cultivars
with prominent apical dominance that clearly showed a faster rate of growth of
their apical sprout and of multiple sprouting cultivars that observed a slower rate
of growth of their longest sprout.
Finally, mean sprout thickness though not correlated with sprout number, nor with
length of the longest sprout or dormancy period is not less important, as vigorous
sprout growth is associated with a greater resistance to infection to certain
diseases such as Rhizoctonia and blackleg. Since sprouts under diffused light
storage are generally more vigorous, measure of sprout thickness is better
recommended under this storage system.
Implementing dormancy and sprouting pattern protocol – Experiences from
Uzbekistan
A preliminary trial was conducted in Tashkent (Uzbekistan) for assessing dormancy
period and sprouting pattern of 17 clones comprising 12 advanced and elite CIP clones,
and 5 varieties from INTA, Argentina. The growing season was from the first week of
July to mid-October 2008 (second season at Tashkent, starting with long and ending with
short photoperiods, and high to mild temperatures).
Identification data
Project Name and Code
Year
CIP Region
Country
Locality
Environment
Altitude (masl)
Latitude
Longitude
2008
SWCA
Uzbekistan
Tashkent
Temperate lowlands
476
47° 18' 59.76"
69° 15' 0"
The crop was dehaulmed 100 days after planting and harvested 10 days later. Tubers
were cured for 14 days.
The trial was performed under two storage systems: Traditional storage (cellar storage)
with monthly mean maximum temperatures ranging from 14oC to 11oC, and minimums
from 7oC to 4oC, and cold storage (2-4oC).
Ninety tubers of each of 17 clones were allocated to experimental units of 30 tubers
placed in trays and randomized in three replications following a random complete block
design (RCBD). A RCBD was chosen because the experiment‘s objectives were to test
associations between variables in addition to documenting. The trial lasted 3.8 months in
cellar storage and 5.7 months in cold storage.
11
Performance of clones under cellar and cold storage are shown in tables 2 and 3,
respectively.
Table 2. Dormancy period and sprouting behavior of 17 clones under
cellar storage (Tmax range 11-14oC Tmin range 4-7oC )
Length of
Mean
Weight loss of
Dormancy
the longest number of
sprouted
period
sprout
sprouts per
tubers
(days)
(mm)
tuber
(%)
CIP-Number
Maturity
397099.4
Early
102
12
2.3
5.8
388615.22
Early
98
14
2.0
6.5
390478.9
Early
98
18
3.3
5.9
720087
Early
107
10
2.7
5.6
720141
Early
107
12
5.7
5.9
720148
Early
108
8
2.3
5.0
388676.1
Mid-early
91
21
1.7
6.5
390663.8
Mid-early
95
20
6.3
6.1
391180.6
Mid-early
98
15
2.3
5.1
392797.22
Mid-early
77
9
4.7
7.0
397035.26
Mid-early
95
16
3.3
6.1
397073.16
Mid-early
87
23
1.7
8.0
397069.11
Medium
95
16
2.0
6.1
397077.16
Medium
89
14
3.7
5.9
388611.22
Medium
91
16
3.3
7.1
720139
Medium
107
9
3.0
6.1
720150
Medium
115
8
1.7
6.3
Mean
97.6
14
3.06
6.2
CV (%)
1
8
17
3
LSD (0.05)
1.6
18
0.9
0.3
12
Table 3. Dormancy period and sprouting behavior of
17 clones under cold storage (2-4oC )
Weight loss of
sprouted
tubers
(%)
CIP-Number
Maturity
Dormancy
period
(days)
397099.4
Early
139
6.0
388615.22
Early
174
7.5
390478.9
Early
104
6.9
720087
Early
174
6.2
720141
Early
174
6.3
720148
Early
174
5.8
388676.1
Mid-early
109
4.6
390663.8
Mid-early
174
6.9
391180.6
Mid-early
99
4.8
392797.22
Mid-early
114
4.8
397035.26
Mid-early
99
7.5
397073.16
Mid-early
99
5.9
397069.11
Medium
104
6.7
397077.16
Medium
129
8.8
388611.22
Medium
99
5.8
720139
Medium
124
5.6
720150
Medium
174
6.8
Mean
133
6.3
CV (%)
4
3
LSD (0.05)
8
0.3
13
Dormancy period under cellar storage ranged from 77 to 115 days while that under cold
storage ranged from 99 to 174 days. There was a relatively high positive correlation
(0.61) for dormancy period between storage systems indicating that clones with longer
and shorter dormancy period under one system will also be those with longer and shorter
dormancy under the other system. However this was not always the case. Clone 390663.8
that was among those with longest dormancy period under cold storage was not among
those with the same tendency under cellar storage (see tables 2 and 3 for comparison).
Dormancy periods of the test clones under cellar storage were well suited to the ranges
proposed for dormancy categories under diffused light in Table 1. According to those
categories, the test clones could only be grouped into medium and long dormancy.
Likewise, under cold storage, the test clones fell into the same categories, which agrees
with the positive correlation found between dormancy period of the test clones under the
two storage conditions. Clone 390663.8 was the exception as it was categorized as
medium dormant under cellar storage and long dormant under cold-storage.
As opposed to the lack of correlation found between dormancy period and bulking
maturity in previous studies (Beukema and van der Zaag, 1979), a low but statistically
significant negative correlation (-0.40 under cold storage, and -0.20 under cellar storage)
was found in this study. This result indicates that there is some tendency toward long
dormancy in early bulking clones. However, further studies need to be performed to
confirm this observation as very few clones were tested.
Mean sprout number per tuber was only assessed under the cellar storage system. This
variable ranged from 1.7 to 6.3 sprouts per tuber. No statistical differences for mean
number of sprouts were found among clones with 1.7 to 2.3 sprouts per tuber indicating
that apical dominance was prevalent among them (see yellow cells for mean number of
sprouts per tuber in table 2). On the other hand, clones with more than a mean number of
2.3 sprouts per tuber showed complete absence of apical dominance. Genetic differences
may account for the number of sprouts per tuber among clones with absence of apical
dominance.
A relatively high negative correlation (-0.51) was found between dormancy period and
length of the longest sprout, indicating that clones with shorter dormancy often show a
greater length of their longest sprout. However, this was not the case of the clone with the
shortest dormancy period, 392797.22, whose longest sprout reached barely 9mm by the
time the trial was over. The short length of its longest sprout can be attributed to the
multiple sprouting pattern of the clone (4.7 sprouts/tuber). It has been shown in previous
studies that multiple sprouting cultivars observe a slower rate of growth of their longest
sprout (Pande et al., 2007). Despite these observations, no correlation was found between
number of sprouts and length of the longest sprout in the present work. The negative
correlation found between dormancy period and length of the longest sprout may have
contributed to the absence of correlation between these two variables. For instance, clone
720150 that had the longest dormancy period under cellar storage was, as expected,
among those with shortest length of their longest sprout. On the other hand, based on its
apical sprouting pattern (1.7 sprouts/tuber) (Table 3), a faster rate of growth of their
14
apical sprout would also have been expected, but because of its longest dormancy period,
the growth of its apical sprout was initiated late and barely reached 8 mm by the time the
trial was over (Table 3). A different case was observed for clone 388676.1 that despite its
multiple sprouting pattern (6.3 sprouts/tuber) was among those with longest length of its
longest sprout (20mm) (Table 3). The relatively short dormancy of this clone (95 days)
may account for its long length of its longest sprout by the time the trial was over.
However, since length of lateral sprouts were not recorded in this trial, it was not possible
to discern if the apical sprout growth was slow or fast based upon the difference between
length of the longest sprout and mean length of lateral sprouts. The influence of the
number of sprouts on the length of the longest sprout can be better observed by
estimating the difference between mean length of lateral sprouts and length of the longest
(apical) one. When in addition to the apical sprout there are one or two lateral sprouts in
some or several tubers of a clone, this difference allows determination of prevalence of
apical dominance. Measurement should be performed on every lateral sprout of a tuber
and an average calculated to then estimate mean length of lateral sprouts in an
experimental unit.
Finally, percentage of weight loss per tuber showed similar ranges in both storage
systems, from 5.0 to 8.0% in cellar storage and from 4.6 to 7.5% s in cold storage.
Considering that 80% of the tuber content is water these values can be disregarded.
Weight of sprouted tubers in this trial was measured without removing the sprouts, which
may have contributed significantly to the final weight of the tuber. Hence, as proposed in
the present protocol, weight of sprouted tubers must be measured after removing sprouts
carefully.
The trial conducted under traditional and cold storage in Tashkent contributed to the
characterization of dormancy period and sprouting pattern of 17 advanced and elite
clones and to document them as shown in table 4.
15
Table 4. Dormancy and sprouting pattern behavior of 17
advanced and elite clones (Tashkent, Uzbekistan)
Bulking
CIP-Number
Maturity
Dormancy
period
Number
of
sprouts
per tuber
Sprouting
pattern
397099.4
Early
Long
2
Apical
388615.22
Early
Long
2
Apical
390478.9
Early
Medium
3
Multiple
720087
Early
Long
3
Multiple
720141
Early
Long
6
Multiple
720148
Early
Long
2
Apical
388676.1
Mid-early
Medium
2
Apical
390663.8
Mid-early
Long
6
Multiple
391180.6
Mid-early
Medium
2
Apical
392797.22
Mid-early
Medium
5
Multiple
397035.26
Mid-early
Medium
3
Multiple
397073.16
Mid-early
Medium
2
Apical
397069.11
Medium
Medium
2
Apical
397077.16
Medium
Medium
4
Multiple
388611.22
Medium
Medium
3
Multiple
720139
Medium
Long
3
Multiple
720150
Medium
Long
2
Apical
16
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http://www.cipotato.org/csd/materials/cipp5w5.pdf
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