The influence of genotype by pre-treatment interaction on dormancy eggplant ( Solanum
melongena L.) seed
Zdravković Milan1, Mladenović Jelena3, Pavlović Nenad2 and Jasmina Zdravković2
1 Institute of Soil Science, 7, Teodora Drajzera st., 11000 Belgrade, Serbia
2Institute for Vegetable Crops, 71, Karadjordjeva St., 11420 Smederevska Palanka, Serbia
3University of Kragujevac, Faculty of Agriculture, 34, Cara Dušana st., 32000 Cacak, Serbia
*Corresponding author E-mail: soils.mzdravkovic@gmail.com
Key words: dormancy, gibberellic acid, KNO3, eggplant
Publication date 31/05/2020, http://m.elewa.org/Journals/about-japs/
1 SUMMARY
Eggplant is a vegetable with seed dormancy. Initially inactive seeds are prevent germination during inadequate ecological surrounding in order to avert low seedling survival. Accelerated senescence of seed appears to be in genotypes that passed the dormant period. The aim of this research was to establish which treatment had the highest effect on germination with the highest stability comparing to natural dormancy period and what possibilities of shortening are. In this study we used 5 genotypes, 2 selected lines (33 and 34), and 3 genotypes from Institute for Vegetable Crops (2 - 02619, 7 – 00568 and 12 – 00823). These genotypes were treated with: (a) four previous low temperature treatments (HLS at 4oC) for 96 hours (4 days), 72 hours (3 days) and 48 hours (2 days).
(b) hormonal treatments with gibberellic acid (GA3) in three concentrations i.e. 5 ml/100ml, 15 ml/100ml and 25 ml/100ml. (c) potassium nitrate treatment KNO3 with 0.5%, 1% and 1.5%
solution for 24 hours. (d) Time treatment, in order to naturally overcome the dormancy was Kon-3, Kon-6, Kon-12 and control observed for 3, 6 and 12 months. The lowest stability, i.e. the highest AMMI’s stability value (ASV) value was recorded in selected line L33. This line expressed the highest seed dormancy and low germination (18.5%), and it did not reach its full germination even 12 months after seed extraction (88.5%).The lowest value of ASV coefficient was with KNO3 1%
treatment, where the percentage of germination of all studied genotypes was the most uniformed.
2 INTRODUCTION
Eggplant seed dormancy shortly after the extraction is a complex feature and causes very complicated assessment of seed quality in a year following extraction from the fruit. This vegetable has a seed variety that belongs to a less energetic seed (Barbosa et al., 2011).
Therefore, Finch-Savage and Leubner-Matzger (2006) divided the dormancy, as a phenomenon, in two groups: physiological (dormancy of embryo, dormancy of endosperm and seed coat) and morphological (morpho- physiological, physical and combined –
complex dormancy). Mechanism of seed inaction after extraction from the fruit is different in every genotype and very complex, which is considered to be genetically directed (Zdravković et al., 2013). Furthermore, Padmini et al. (2008) reported cytoplasmatic (maternal effect) in F1 generation and monogenetic dominant, two-gene-complementary and recessive genetic effect in F2 generation.
Having in mind the potential of the existing eggplant genetic found, selection processes for shortening the dormancy could be successful
(Gisbert et al., 2011). Breakage of dormancy by applying hormones exogenously or by cooling the seed improves the germination. Cleaning of seed or pre-treatments could obtain higher germination. Exogenous hormonal treatment with chemical agencies during the cooling treatment, demonstrate mechanism for overcoming the dormancy (Yogeesha et al., 2006). Treatment of fresh eggplant seed with acetone solution of gibberellic acid increased the germination from 81% to 100% (Gisbert et al., 2011). The number of days from seeding to harvesting mature fruits is a very important factor for seed dormancy right after extraction (Demir et al., 2002; Passam et al., 2010). Other varieties of Solanum used as food have similar seed dormancy (Hayati et al., 2005). Breaking the dormancy by applying pre-treatments would be a significant contribution in determination of reliable average germination of seed lot of eggplant. Seed processed this way, have lower risk of fault assessment of germination of fresh seed, and have the quality that suits the norms
determined by local referential document (SFRY Government, 1987). Quality norms and conditions for seed germination, Regulation on the quality of agricultural plants Official Gazette of SFRJ br.47/87). After passing the phase of dormancy in storage, the eggplant seed reaches balanced quality level and viability (Demir et al., 2009). AGBO and Nwosu (2009) studied the dormancy of eggplant seed from the fruits picked in different phases of maturation.
They reported that the germination of just extracted seed from the fruits was 70% and three months later 90%. The aim of this study was to determine which pre-treatment has the greatest impact and the most stabile effects of eggplant seed germination comparing to natural period of dormancy in order to obtain most precise results of germination immediately after seed extraction, as well as the possibility of shortening the period of dormancy. The screening of available genotypes could be the beginning of line selection for obtaining the genotypes with short dormancy or without it.
3. METHODOLOGY
3.1 Genotypes: In this study, five genotypes were used:
- Two selected lines (33 and 34). These lines originated from the Institute for Vegetable Crops and were obtained as sister lines from crossing Domaci srednje dugi (DSD) and Junior.
Both lines have large fruits with intensive colour. Line 34 was not dormant, while line 33 was;
- Three genotypes from Institute for Vegetable Crops eggplant germplasm collection: 2 - 02619, 7 - 00568, 12 - 00823.
Genotype no. 2 was not dormant, while others were.
3.2 Seed extraction: Seeds were extracted by hand, from the mature fruits, 73 days after flowering. Hand extraction meant cutting the fruits and washing it. The seed was dried to 10% of humidity. Prepared seeds were preserved in paper bags. Five days later, the cooling treatments started.
3.3 Pre treatments: Cooling pre- treatments (HL) were performed at 4oC for 96 hours (4 days), 72 hours (3 days) and 48 hours (2 days) continually. Hormonal pre-treatments with gibberellic acid (GA3) were performed in three concentrations: 5 ml/100ml; 15 ml/100ml and 25 ml/100ml, for 24 hours. Chemical pre- treatments were performed with potassium nitrate KNO3 in concentrations: 0.5%, 1% and 1.5% solution for 24 hours. Control treatments were set for natural overcoming of dormancy:
Kon-3, Kon-6 and Kon-12, i.e. the germination was checked after 3, 6 and 12 months. Control was set at the same time when the other varieties were pre-treated.
3.4 Germination: Germination was tested by applying standard methods ISTA (2003), sowing 100 seeds on filter paper in Petri dishes, with 4 replications for all treatments and control. Germination energy was calculated after 7 days and the total germination results were calculated 14 days from sowing.
3.5 Data analysis
3.5.1 Trends in controlled measurements:
Dynamics of change of average values of germinations in time has been followed by trend line and represents the average motion of observed phenomena in time:
Curvilinear - parabolic trend (second-degree parabola) was used (Franić and Kumrić, 2005):
YC =a+bX +cX2 Where:
a
Y X X YX
N X X X
= ⋅ − ⋅
⋅ −
4 2⋅ 2
4 2 3 , the expected value of the trend at the point indicated by zero
b
XY
=
X
2 , an average increase or decrease of the phenomenon per unit time (slope)c
N YX X Y
N X X X
= ⋅ − ⋅
⋅ − ⋅
2 2
4 2 2, coefficient that determines the direction, i.e., if positive than the phenomena grows, and if negative phenomena decreases. The representativeness
of the trend was determined by the coefficient of determination (R2), where R2> 0.6. The trends were observed at the time serials of germination testing (Kon) after seed extraction and periodical research (Kon3, Kon-6 and Kon12).
3.5.2 AMMI model: The interaction of genotypes and treatments for comparing increased germination energy and germination (breaking of dormancy) were analysed by AMMI model (Additive Mean Effects and Multiactive Interaction – model of main effects and multiply correlation), Zobel et al.,1988.
Analysis the residual from interaction used model PCA (Gauch, 1988). AMMI’s stability value (ASV) was calculated in order to rank genotypes in terms of stability using the formula (Purchase, 1997):
AMMI stability value (ASV) = [SSIPCA1/SSIPCA2(IPCA1score]2 +[IPCA2score]2 Where:
SS= sum of squares
IPCA1= interaction principal component axis 1 IPCA 2 = interaction principal component axis 2
For statistical analysis R software (version 2.14.0, A Language and Environment Copyright, 2011) was used.
4 RESULTS AND DISCUSSION Genotype 2 had high germination constantly in all cooling treatments and treatments with KNO3 and GA (in all concentrations), due to a low percentage of dormant seed in this genotype. Maximal percentage of germination was accomplished in treatments with gibberellic acid (GA). The increase of concentration of gibberellic acid had no effect since in concentration GA-5, germination was maximal (Table 1. and Fig 1 A). Condition R2 points to a
fact that 98.2% of square sum deviation value belongs to parabolic model trend. Expansion of trend in the first trimester (Kon-3) was a result of passing the inaction phase and low percentage of dormant seeds in this genotype.
After growing trend, stagnation occurred, which proves stabile germination in this period.
Negative sign of “c” coefficient proves the decreasing of the phenomena, i.e. the senescence of seed (Fig 1. A).
Table 1: The average values of seed germination per pre-treatment and control
Pre Treatments
genotypes
34 12 7 33 2
KNO3 0.5% 98.50 84.75 54.00 48.00 99.00
KNO3 1% 99.25 91.50 62.50 59.75 98.75
KNO3 1.5% 98.75 92.00 58.80 67.25 99.25
LSD for G 0.05 4.68 LSD T 0.05 3.31 LSD 0.05 GxT 8.12
0.01 5.77 0.01 4.08 0.01 9.99
GA 5 ml/100ml 93.50 75.00 41.50 41.75 100.00
GA 15 ml/100ml 98.75 97.50 78.5 83.00 99.75
GA 25 ml/100ml 99.25 98.00 94.25 98.00 99.75
LSD for G 0.05 5.23 LSD T 0.05 3.70 LSD 0.05 GxT 9.07
0.01 6.44 0.01 4.56 0.01 11.16
Hl - 96 92.25 58.75 31.5 27.75 100.00
Hl - 72 91.50 50.00 36.50 28.25 99.25
Hl - 48 94.00 63.00 45.00 36.50 99.25
LSD for G 0.05 5.14 LSD T 0.05 3.64 LSD 0.05 GxT 8.91
0.01 6.33 0.01 4.47 0.01 10.96
control 81 59.25 21.5 18.5 96.75
Kon-3 99.00 49.75 72.00 63.25 99.75
Kon-6 99.50 58.50 72.25 72.00 100.00
Kon12 98.25 78.25 88.75 88.50 97.25
LSD for G 0.05 3.738 LSD T 0.05 2.639 LSD 0.05 GxT 6.465
0.01 4.594 0.01 3.249 0.01 7.958
In genotype L-12, the determinacy coefficient was R2=0.992. The value is close to 1, which proves the representativeness of trend line. The intersection of the trend line and the line of mean values at the end the first trimester indicates that the current decreasing trend of germination gradually passes into growing.
Negative sign of “b” coefficient proves that average decrease of germination in time unit, and changes i.e. the growth of germination in observed period was the consequence of dormancy, for which the treatments proved to be present in high percentage in this genotype (Fig 1. B). Twelve months later, the average germination of samples was close to results obtained by treatment G-5. Results coincide for data obtained from pre-treatments with GA-15 and GA-25, as well as K-1 and K-1.5, which means that the increase of concentration in these cases had no effect (Tab 1). Maximal
value of germination of L-7 was obtained by applying pre-treatment GA-25 and was 94%
(Tab 1). Genotype L-7 had determination coefficient (R2 > 0.6 (0.891 close to 1) which gives the representative trend line (Fig 1C).
Increased trend in the first trimester and high percentage of seed germination was a consequence of passing the dormancy phase in large number of seeds of L-7 during 3-6 months. A little bit higher variation of average values from the trend line was a consequence of harder impact of residual factor on germination of this genotype. Dormancy of seed for 3-6 months led to stagnation of germination (Kon-3 was 72%, Kon-6 was 72.25%), and after this period germination began to grow (Kon-12 was 88.75%) – Tab 1.
The intersection point of the trend line and movement properties after twelve months, indicate that the initial trend after a year
decreases (Fig 1C). Genotype L-33 had a dynamic of change of germination, as well as genotype 7. The only difference that can be spotted here is a low impact of residual factors because the deviations of average values from tendency parabola were lower. The impact of residual factors in genotype 33 was lower than in genotype 7 (Fig 1D). Genotype 34 had decreasing trend line in treatment times (coefficient with X2 was negative). Germination increase in the first trimester due to a passing through dormancy period. Intersection of lines of average values and trend line after five months, points to gradual transition from growth phase and the beginning of the period of stagnation. During this period, stability of germination was maximal for this genotype.
After twelve months, the direction of the current trend changed to declining. The expected decrease of germination after a period of one year was the consequence of seed senescence (Fig 1E). Period of overcoming the dormancy was different for each genotype.
According to Gisbert et al. (2011), there are three physiological mechanisms that define dormancy: (1) seed coverings that restrict water intake, embryo growth, gas permeability; (2) chemical inhibitors and growth regulators and (3) morphological aspect, such as small and undeveloped embryos. The researched genotypes with germinating inhibition did not belong to the same seed type. After one year of storage, Genotype 7 did not have the germination he had after treating with GA-25 immediately after the seed extraction. Vigour of eggplant seed in the second year after storage can be improved. Liu et al. (2007) improved the average germination with different chemical
compounds. Trend line of Genotype 34 went downward after storage of seed for one year although this genotype had high average value of germination after extraction. From the third to twelfth month, germination was stable.
Decreasing trend pointed to, eventually, rapid senescence of seed of dormant genotypes.
These results coincide with those obtained by Torres and Negreiros (2008), especially after temperature treatments. Physiological aspect of maturing and pre-treatment that should shorten the inhibition periods could cause certain number of degenerative changes that in the end lead to decreased germination (Alves et al.
2012). Rapid seed senescence after treatment does not necessarily have to appear. Rongqing et al. (2001) found significant effects in promoting rapid germination and improvement of seed vitality, as favourable physiological effects on commercial seed, 6 months after storage. The seed has been treated with GA. In this study, we researched the fully mature seed (according to the number of days from anthesis to harvesting). Seeds of some genotypes reached the physiological balance after extraction and storage. Tendency of growth of average germination during storage, stagnation and increase/decrease, was different regardless to the fact whether the genotypes were breeding lines or belonged to exotic germ plasm. Ristić et al. (2013) found that eggplant seed had high germination after dormancy.
They also found that germination decreased which is a usual trait of seed senescence.
Therefore, not only that yield time impacts the beginning of dormancy, but also impacts the time necessary for obtaining maximal germination of non-dormant lines.
A B
C D
E
Fig. 1: Parabolic trends of average germination in treatment time / natural dormancy: A) genotype, B) genotype 12, C) genotype 7, D) genotype 33 E) genotype 34.
4.1 AMMI analyse: AMMI model proved significant differences among genotypes, treatments and its interactions to germination.
Square sum of genotypes makes more than a half of total square sum (52.85%) and it is double higher that square sum of treatments.
Square sum of treatments (24.49%) participates in total square sum equally as square sum of interaction GxE (20.13%). AMMI variance analysis proves significance of the first and the second main component (PC1 and PC2), where square sums of the first and the second
component (PC1 and PC2) make 98.30% of interaction square sums, of which the first component (PC1) forms 72.71%. Other components were not significant, so AMMI
model with the first and the second main component was the best mode (Zobel et al., 1988) - Tab 2.
Table 2: Analysis of variance for the AMMI model
Source of variation df SS SS% MS F
Genotype (G) 4 84638 52.85 21159.50 1121.07**
REP (ENV) 39 1108 0.69 28.40 1.51
Treatment (E) 12 39220 24.49 3268.30 115.00**
GxE 48 32238 20.13 671.60 35.58**
PC1 (72.7%) 15 23440.52 72.71 1562.70 82.79**
PC2 (25.6%) 13 8257.86 25.62 635.22 33.66**
PC3 (1.1%) 11 367.51 1.14 33.41 1.77
PC4 (0.5%) 9 172.13 0.53 19.13 1.01
PC5 (0%) 7 0 0 0 0
Error 156 2944 1.84 18.90
Total 259 160148
* indicates 5% significance
** indicates 1% significance
The lowest ASV, i.e. the highest stability had genotypes L12 and L34. These two genotypes belong to non-dormant group. Genotype L34 was second in the stability range and had high average germination (95.65%). The lowest
stability and the highest ASV had line L33. This line was highly dormant right after extraction.
Germination was low (18.5%) both at the start and 12 months after extraction (88.5%) - Tab 3.
Table 3: Mean AMMI stability values and ranking orders of stability – Genotypes No Genotype Germination
PC1 PC2 ASV
Mean Rank Value Rank
1 L12 73.56 3 -1.1023 5.9000 6.68 1
2 L2 99.02 1 -4.8011 -1.9655 13.77 4
3 L33 56.31 5 5.0807 -0.2777 14.42 5
4 L34 95.65 2 -3.2036 -1.8259 9.28 2
5 L7 58.14 4 4.0262 -1.8309 11.57 3
The lowest ASV had treatment KNO31%, where the germination of all researched genotypes was the most uniform. Besides this treatment other two KNO3 (KNO30.5% and KNO31.5%) distinguished with their low ASV (rang 3, i.e. 2). The lowest stability and the highest ASV had treatment GA25% and Kon- 12, where the germination was tested one year
after extraction. Cooling treatments had different level of stability and the largest stability coefficient (8.54, rang 10) had treatment with the shortest cooling (48 hours), while the 96 hours cooling treatment had ASV coefficient 5.15 (rang 4) treatment with high stability (Tab 4.).
Table 4: Mean AMMI stability values and ranking orders of stability – Environments No Environments Germination
PC1 PC2 ASV
Mean Rank Value Rank
1 K-0,5 76.85 7 -1.0479 1.5572 3.36 3
2 K-1,0 82.25 5 0.0329 2.0031 2.01 1
3 K-1,5 83.15 4 0.3359 2.1788 2.38 2
4 GA-5 70.35 9 -1.8332 0.9907 5.30 5
5 GA-15 91.50 2 2.3225 1.9691 6.88 8
6 GA-25 97.85 1 4.1183 1.2876 11.76 13
7 Hl-48 62.05 11 -3.0021 -0.5806 8.54 10
8 Hl-72 61.10 12 -2.5015 -1.8588 7.34 9
9 Hl-96 67.55 10 -1.7987 -0.6641 5.15 4
10 kon 55.40 13 -3.4745 0.5365 9.88 11
11 kon-3 76.75 8 1.3469 -3.7587 5.36 6
12 kon-6 80.25 6 1.7256 -2.7767 5.63 7
13 kon-12 89.90 3 3.7756 -0.7841 10.75 12
AMMI 2 biplot shows the ratio of the first (PC1) and the second (PC2) main component (Fig 2). Treatments were circularly arranged and have arrows associated with the item PC1, PC2 (0.0). The length of an arrow refers to stability, i.e. adaptability of a certain treatment. GxE treatment with longer arrows is emphasized and the other way around, short arrows represent small interaction with GxE. Angle among arrows explains the similarity of treatments: the smaller the angle among the treatments, more similar was the interaction of genotype with this
treatment. The closer the genotypes were to a certain treatment, the more stable they were in those treatments. Just as ASV values did, the AMMI 2 biplot also proved that the treatments with KNO3, that with HL-96 and GA-5, had the shortest arrows and the most stabile values and the lowest GxE interaction. L12 had the best interaction with KNO3 treatments, while the second (L-34) and the fourth in the range (L-2) grouped with cooling treatments. L7 had the best results in control treatments (Fig 2).
Fig 2. AMMI 2 biplot
AMMI 1 biplot (Fig 3) shows four groups of treatments that had a positive impact of eggplant genotypes. They were grouped according to their impact on germination. One group of treatments were GA-25, GA-15 and Kon-12 that distinguished in the upper, right quadrant of biplot. These treatments caused higher than the average germination, however those values were not uniform and these treatments were highly unstable (PC1 value = 2.3225 - GA-15, 4.1183 -GA-25, 3.7756 - Kon- 12). Treatments Kon-6 and Kon-3, as well as K-0.5 had high germination and stability, i.e.
interaction GxE was lower, comparing to previous group of treatments. The most stabile results were obtained with treatments K-1.0
and K-1.5 with very high germination (82.25, i.e. 83.15%). Cooling treatments groups: Hl-48, HL-72 and Hl-96, than GA-5 and Kon had an unfavourable reaction and lower germination.
In addition, the results were unstable and GxE interaction was high. Genotypes were grouped in L33 and L7 in left upper quadrant as extremely dormant, L34 and L2 in lower right quadrant, as non-dormant or with low dormancy (Tab 1.). Genotype L12, all of the observed genotypes, was the closest to PC1 axis, which proves his stability comparing to other genotypes in this experiment.
Germination of this genotype (73.56%) was close to average (76.54%).
Fig 3. AMMI 1 biplot
Eggplant has high dormancy, which could be a problem in testing the quality of seed right after the yield. Baskin and Baskin (2004) found that brakeage of dormancy in Solanaceae is influenced by endogen hormones in class non-deep level for Angiospermae. A large number of researches conducted in order to improve the germination of eggplant deal with level of maturity of the fruit carrying the seed, which is justified by the fact that only the seed of the completely mature fruits can be hormonally balanced (Angelovici et al., 2010). Dormancy of selected eggplant genotypes is very rare Yogeesha et al. (2006). In our study, dormancy was established on one selected genotype (genotype 33), while the other genotype (genotype 34) had high germination right after the yield. Other three genotypes belong to exotic germplasm and had the average germination from deep dormancy
(genotype 7) to non-dormancy (genotype 2).
Finch-Savage and Leubner-Matzger (2006) found that dormancy is caused by ABA and GA ratio and their role in seed maturation.
Exogenous intake of GA initiated deeply dormant seed of genotype 33 and 12. Although the impact of GA was efficient, the AMMI values were low (GA5, GA15, GA25 i.e. 5, 8, 13). This, practically, means that GA in 25ml/100ml concentration treatments for 24 hours caused the highest germination, but not with high stability. Similarly to the effect of the pre-treatment Kumar (2005), found higher germination: 92% of controlled sample; and maximal germination with GA3 (200ppm) and KNO3 (2%) treatments. These researches prove that pre-treatments in different concentrations improved the germination.
Treatment with potassium nitrate gave,
according to ASV coefficient, the most stabile effect (KNO3 0.5%, KNO3 1.0%, KNO3 1.5%, in range 3, 1, 2). Many researchers reported that potassium nitrate positively influenced the germination of eggplant (Geetharani and Ponnuswamy 2002) and improved the vigour of plant. Cooling of seed had high impact on single genotype regarding the break of dormancy and increase of germination. The assumption is that this happened due to significant divergence of eggplant genotypes (Zdravković et al., 2013). Cooling of seed for 96 hours gave stable ASV rang (4) which confirm
the fact that moisture seed should be cooled longer in order to get a stabile germination growth and break the inhibition in. Hayati et al.
(2005) reported that this cooling should be performed for 1-5 days. AMMI 2 biplot gave vector display of treatment and genotype interaction and a large number of, conditionally, similar reactions, although there were many interactions of seed and treatment that influenced the germination. Lower angle among interaction vectors represents higher similarity in their interaction (Babić, et al. 2010).
6 CONCLUSION
Pre-treatments with highest stability of effects on seed germination comparing to physiological (time) duration of dormancy of eggplant seed have been established. The lowest stability was observed in Line 33. The seed of this line was highly dormant immediately after extraction (germination 18.5%), and it did not reach its full germination even 12 months later, when it was 88.5%. The lowest ASV was found in treatment with KNO3 1%, where the germination percent of all researched genotypes was the most uniform. Cooling treatments
showed different levels of stability. The highest stability coefficient (8.54, rang 10) had a treatment with the shortest cooling period (48 hours), while 96 hours cooling treatment had ASV coefficient 5.15 (rang 4) which means high stability. Genotype 34 had large average germination after extraction and was stabile during storage. After one year of storage germination begun to decrease. This could be the proof of rapid senescence of seed that went through dormant period.
7 ACKNOWLEDGEMENT
Financial support for this research was given by Ministry of Education, Science and Technological development, trough grant
TR31059. Integrating biotechnology approach in breeding vegetable crops for sustainable agricultural systems, 2010-2020.
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