Abstract Potato is an important food and cash crop in Eastern Ethiopia; however, its productivity is low for a number of constraints. Shortage of quality planting material and poor tuber sprouting due to long dormancy period of improved varieties at planting are two of the factors known to affect production cycle and productivity of the crop in Eastern Ethiopia. Two separate experiments were conducted from November 2013 to June 2014, to assess the effect of Gibberellic acid and storage condition on seed tuber dormancy breakage of two potato varieties. The treatments in the first experiment consisted of two potato varieties (‘Bubu’ and ‘Bate’) and three levels of Gibberellic acid (GA3) (0, 10, and 20 ppm) kept under three storage methods: in diffused light store (DLS), in pit, and in farmyard manure (FYM) heap. The experiment was laid out as a randomised complete design with four replications and conducted in the horticulture laboratory of Haramaya University. The second experiment consisted of the same treatments laid out in the field to study the effects of the treatments on the subsequent growth, yield, and yield-related traits. The experiment was laid out in a randomised complete block design with three replications and conducted on a farmer’s field. The results of the experiments showed that genotypes, exogenous application of GA3, and storage conditions, as well as the interaction between them, significantly affected seed tuber dormancy period, sprouting characteristics, and subsequent tuber yield. Dormancy period, sprouting percent, sprout length, length of lateral axillary sprouts, and sprout vigour were significantly affected by the treatments. However, parameters such as days to 50% emergence, days to 50% flowering, and number and weight of very small and small tubers showed highest values for seed tubers, either treated with GA3 or not, and stored under FYM heap and pit storage conditions when compared with tuber treated and stored in DLS. In general, the study indicated that the interaction between genotypes, exogenous application of GA3, and storage conditions resulted in early dormancy termination, early emergence of shoots, and high marketable tuber yield. Gemeda Mustefa

1. Programme on Integrated Seed Sector Development in Ethiopia
EFFECTS OF DORMANCY-BREAKING METHODS
ON SEED TUBER SPROUTING AND SUBSEQUENT
TUBER YIELD OF POTATO CULTIVARS
1Gemeda Mustefa, 1Wassu Mohammed, 1Nigussie Dechessa and
1Dandena Gelmesa
1Haramaya University, College of Agricultural and Environmental
Sciences School of Plant Sciences. Dire Dawa, Ethiopia
10th Triennial APA Conference, 10th-13th October 2016, Addis Ababa

2. Potato in Eastern Ethiopia
• 2nd most important crop next to
chat in Easter Ethiopia (Hararghe)
• 759% increase in income over
sorghum in Hararghe
• Is high potential food security crop
• The possibility of year-round
production has made the crop
become an import commodity in
eastern Ethiopia.
• For local and export markets (Dire
Dawa, Somali, Hargessa, Yemen,
etc)

3.  Little time gap between tuber harvesting and re-
planting.
 Timely availability of well-sprouted seed potato
tubers is a pre-requisite for year round production
and attaining high yield.
 All improved potato varieties released in
Ethiopia have more than 2 months dormancy
period
 Most farmers cultivars have a dormancy
period of 45-70 days and largely preferred for
production

4. Short dormancy period varieties are largely
preferred for production
 Farmers’ potato varieties have a short dormancy period (a
month and little more than a month).
 Study on dormancy breaking methods and its subsequent
effect on tuber yield and quality is important to benefit
farmers from potato production year round.
??
Farmers Practices
different dormancy
breaking methods

5. Priority breeding/research areas
not important important moderately
important
extremely
important
Freq % Freq % Freq % Freq %
Improving yield and quality of potato 0 0 4 3 23 17.2 107 79.9
Improving quality seed supply 0 0 6 4.5 37 27.6 91 67.9
Developing early maturing Varieties 0 0 12 9.0 27 20.1 95 70.9
Developing drought tolerant Varieties 0 0 19 14.2 26 19.4 88 65.7
Developing biotic stress tolerant Varieties 0 0 21 15.7 33 24.6 74 55.2
Disease management techniques 0 0 21 15.7 38 28.4 72 53.7
Developing appropriate agronomic practice 6 4.5 62 46.3 17 12.7 30 22.4
Developing short dormancy period varieties 3 2.2 27 20.1 44 32.8 77 57.5
Developing long dormancy period varieties 58 43.3 35 26.1 7 5.2 2 1.5
Improving shelf life of potato 13 9.7 28 20.9 23 17.2 47 35.1
Developing varieties for processing 19 14.2 33 24.6 34 25.4 25 18.7
Developing varieties for boiling and stew 8 6.0 32 23.9 41 30.6 45 33.6
Developing high dry matter content varieties 4 3.0 46 34.3 37 27.6 35 26.1
Developing better nutritional value varieties 5 3.7 24 17.9 29 21.6 60 44.8
Top potato breeding/research areas prioritized by farmers
(n=134) in eastern Ethiopia, 2016 survey data

6.  To assess the effects of GA3 and storage
methods on dormancy breaking of potato
varieties
 To study the effects of GA3 and storage
methods on the subsequent growth, yield
and yield related traits of potato varieties
Objectives

7. MATERIALS AND METHODS
Dormancy breaking experiment
 Conducted at Haramaya University research site, Ethiopia
from Nov to December 2013.
 Located at 9 °29' N latitude, 42 °7' E longitudes and altitude of
2022 m.a.s.l.
 The mean annual rainfall is 700mm and the average annual
maximum and minimum temperature is 25.4 °C and 8.6 °C.
 Three storage methods (Diffused light store (DLS), Pit and
FYM and
 Three concentration of GA3 (0, 10 and 20 ppm) were used

8.  Bubu-improved variety released by Haramaya University
having 90 days dormancy period.
 Bate-farmers variety obtained from rare Hora seed
producer cooperative, having 45 days dormancy period.
 RCBD with 4 replications were used
 Selected tubers of each potato cultivars dipped
initially for 20 min in GA3 solutions at different
concentrations and stored under different storage
methods.
Two potato variety used for the experiment

9. Pit digging Seed tuber treated with GA3 and
placed in the pit
Covered with soil

10. Field Experiment
 The same treatments with dormancy breaking methods were
used.
 Randomized Complete Block Design with three replications used
 The land were prepared as per the recommended practices and
sprouted potato tubers obtained from the dormancy breaking
experiment.
 Field management were also performed as per the research
recommendations.
 (t ha-1) etc.
 The field experiment was conducted at Haramaya woreda, five km
from Haramaya University, on farmer field (Rare Hora seed
producer cooperative site) from January to June 2014.

11. • Days to dormancy
period;
• Number of sprouts per
tuber,
• Sprout length (mm),
• Sprout thickness
(mm),
• Sprout vigor (score 1-
5 point)
• Sprout thickness
(mm),
• Dry weight of sprouts
• Tuber weight loss etc.
Data collection
• Days to 50% flowering and
maturity,
• Tuber number per hill,
• Average tuber weight,
• Number of main stem per
hill,
• LAI, ATN and ATW,
• Marketable tuber yield
• Specific gravity of tubers
• Tuber dry matter content
• Total soluble solids (0Brix
• pH content

12. Data analysis
• The data were subjected to analysis of variance
using Gen Stat, 13th Edition (VSN Ltd, Oxford UK)
statistical software package.
• Least significant difference (LSD) test at 5%
probability was used to separate means

13. Results and discussion
 The results of the experiments showed that,
genotypes, exogenous application of GA3 and storage
conditions as well as the interaction between them
significantly affected
 seed tuber dormancy period,
 sprouting percent,
 sprout length,
 Sprout thickness & sprout vigor,
 Tuber yield and other tuber quality attributes

14. Figure 1. Interaction effect of GA3 and storage
methods on number of sprout per tuber of potato
0 ppm GA3 treated and
stored in pit
20 ppm GA3 treated
and stored in pit

15. Table 1. Interaction effects of GA3, storage condition and potato cultivars on
dormancy period, sprouting percentage and sprout vigor of potato cultivars
Character Dormancy period (days) Sprouting percentage Sprout vigour (score)
Storage methods
Cultivar
GA3
(ppm) DLS Pit storage FYM DLS
Pit
storage FYM DLS
Pit
storage FYM
0 102.50a 48.25e 46.75ef 91.67d 90.83d 92.50d 2.59gh 2.71g 2.03i
Bubu 10 83.00b 43.00g 41.00gh 99.17ab 95.84c 98.34ab 3.51c 3.24def 3.33cde
20 70.50c 39.50h 36.50i 100a 99.17ab 100a 4.50a 3.92b 3.96b
0 54.25d 35.00ij 33.25jk 91.67d 85.00e 95.84c 2.37h 1.75j 1.34k
Bate 10 46.00f 34.00jk 32.00kl 95.84c 97.50bc 99.17ab 3.05f 2.51gh 2.00i
20 39.50h 31.00l 31.00l 100a 100a 100a 3.36cd 3.17ef 2.54gh
LSD (5%) 2.22
2.32
0.25
CV (%) 3.30
1.70
6.00

16. Table 2. Interaction effect of GA3, storage condition and cultivar
on marketable and unmarketable tuber yields
Character Marketable tuber yield t ha-1 Unmarketable tuber yield t ha-1
Treatment combinations DLS Pit storage FYM DLS Pit storage FYM
Cultivar GA3 (ppm)
Bubu
0 25.98e 26.00e 26.20e 6.60c 5.80e 5.50f
10 30.50c 29.80d 29.80d 5.40f 5.10g 4.98g
20 34.20a 33.70b 33.60b 3.70h 3.20jk 3.00k
Bate
0 12.90j 13.30i 13.10i 10.50a 9.90b 9.90b
10 19.90h 20.50h 20.00h 6.30d 5.80e 5.80e
20 24.97f 23.70g 23.70g 2.50l 3.40i 3.32ij
LSD (5%) 0.23 0.25
CV (%) 16 2.50

17. Quality parameter Variety
GA3 (ppm)
0 10 20
LSD
(5%)
CV
(%)
Specific gravity
Bubu 1.090b 1.095a 1.099a
0.002 0.200
Bate 1.077d 1.085c 1.090b
DM (%)
Bubu 25.20e 26.28c 27.00a
0.10 0.20
Bate 24.30f 25.30d 26.34b
pH
Bubu 5.70b 5.74b 5.88a
0.03 0.50
Bate 5.50d 5.60c 5.70b
TSS (oBrix)
Bubu 5.60c 5.70b 5.83a
0.05 0.90
Bate 5.12e 5.20d 5.23d
Interaction effect of variety and GA3 on tuber
quality parameters

18.  In many potato cultivars, natural dormancy progression
occurs over a period of many months.
 Breaking of tuber dormancy through different Chemicals
and storage methods could enable farmers for year round
potato production
 Treatment combinations (GA3 application) and storage
methods (both modern and traditional) could offer the
farmers for early tuber sprouting used for potato production
especially in areas where two to three round potato
production per year with out no significant yield decline.
CONCLUSIONS

19. Thank you