Data on selected seed quality parameters and seedling characteristics were recorded during the course of the study. The results of the study are presented and discussed sequentially as follows.
The study results revealed that all seed physiological characteristics were significantly influenced by the extraction methods along with duration of time (Table 1).
Weight of 1000 seeds
Results revealed that means of weight of 1000 seeds extracted with fermentation and HCl acid methods with different time duration were significantly (P< 0.01) different. Maximum weight of 1000 seeds (4.277g) was recorded at 1% of HCl dipping for 30 minutes even if statistically similar with 2% HCl for 30 minutes, fermentation for 24 hours, 1% HCl for 60 minutes, 2% HCl for 60 minutes and 1% HCl for 90 minutes (Table 1). As shown in Fig.3. (A) dominantly higher seed weight in 1% HCl across all time lengths as compared with higher concentrations of HCl. The minimum weight (1.440 g) was obtained from 3% HCl for 90 minutes. Generally, weight of 1000 seeds decreased with increasing concentration of HCl. Maximum weight of 1000 seeds at lower HCl concentrations might probably be due to partial removal of mucilage and presence of gelatinous substance adhered to the seeds (Vishwanath et al., 2006).
Table 1. Effects of different seed extraction methods and time length on weight of 1000 seeds and seed mycoflora
Treatments
|
Weight of 1000 seeds (g)
|
Seed mycoflora (%)
|
Fermentation for 24 hrs
|
4.140ab
|
22.67c
|
Fermentation for 48 hrs
|
3.107d
|
29.33b
|
Fermentation for 72 hrs
|
1.727e
|
36.00a
|
1% HCl for 30 min
|
4.277a
|
17.33d
|
1% HCl for 60 min
|
4.037ab
|
9.33e
|
1% HCl for 90 min
|
3.940ab
|
1.33fg
|
2% HCl for 30 min
|
4.233a
|
4.00f
|
2% HCl for 60 min
|
4.007ab
|
0.00g
|
2% HCl for 90 min
|
3.350cd
|
0.00g
|
3% HCl for 30 min
|
3.653bc
|
1.33fg
|
3% HCl for 60 min
|
2.843d
|
0.00g
|
3% HCl for 90 min
|
1.440e
|
0.00g
|
Significance
|
**
|
***
|
LSD (5%)
|
0.514
|
3.370
|
CV (%)
|
4.0
|
19.8
|
Means within a column sharing common letter(s) are not significantly different at 5% level of significance; * = significant at p<0.05; LSD=Least significant difference; CV=Coefficient of variation.
Seed mycoflora
The percent mycoflora detection was significantly (P< 0.001) affected by seed extraction methods and time length. The highest percentage of mycoflora (36%) observed from fermentation method for 72 hours followed by fermentation for 48 hours (29.33) (Table 1). On the other hand, mycoflora load drastically decreased as HCl concentration as well as time length increased (Fig. 2. B). No mycoflora was detected from higher concentration (2% and more HCl) and time length (60 minutes and longer time). As par with this result Vishwanath et al., (2006) also reported highest mycoflora load from fermentation extraction and lowest load from higher concentration of (2.5% HCl) acid extraction methods. It has been evidenced that fusarium, root nematodes and verticillum pathogens resided deep within seed coats and fuzzes usually emerge during germination could be disinfected by acid extraction method (Vishwanath et al., 2006; Dick and Dick, 2014; and Alabi, 2019).
First count germination
The analysis of variance showed that first count germination was significantly (P< 0.001) affected by treatment effects. The highest first count germination (93.3%) was recorded at 2% HCl for 60 minutes whereas the lowest (23%) was recorded from seeds extracted with 72 hours fermentation (Table 2). On the contrary, Ankitet al. (2016) reported highest first count germination (93.33%) from 1% HCl for 30 minutes over fermentation and NaCO3 method of tomato seed extraction. In contrast, the current study showed that lower concentration (less than 2% HCl) and shorter length of time (shorter than 60 minutes) resulted lower first count germination percent. The difference might be due to difference in fruit mesocarp thickness of the varieties.
Germination percentage
Seed extraction methods and time length showed a significant (P < 0.001) influence on germination percent of seeds both in laboratory and open field pot trials (Table 2). The highest germination percent (99.33 and 89.76% in laboratory and open field pot experiments respectively) was obtained at 2% HCl for 60 minutes followed by 2% HCl for 90 minutes (94.67% and 81.99% in lab and open field pot experiments respectively). However, the lowest germination percent (30.67) was shown at fermentation process for 72 hours and lower concentration (less than 2% HCl) as well as 2% HCl for 30 minutes. This finding is supported by Demir and Samit (2001).
Germination percent highly declined when fermentation period prolonged from 24 to 48 then to 72 hours (Fig. 4. B). Darken and swollen (imbibed) seed coat was also observed (Fig. 1. C). Extended period of fermentation likely imposed seeds to germinate during extraction process and protruded radicle killed during seed drying process. Nemati et al., (2010) also reported analogous findings. As shown in Fig. 4. (B), the lower germination in lower concentration (1% HCl) and shorter dipping time (less than 60 minutes) might probably be due to presence of inhibitors in the gelatinous substance adhered to the seeds (Vishwanath et al., 2006).
Table 2. Effects of different seed extraction methods and time length on first count germination, germination percentage and seed emergence
Treatments
|
First count germination (%)
|
Germination percentage (%)
|
Seed emergence (%) (open field in pot)
|
Fermentation for 24 hrs
|
75.00 bcd
|
85.00 cd
|
81.00 bc
|
Fermentation for 48 hrs
|
59.33 e
|
69.67 f
|
69.08 de
|
Fermentation for 72 hrs
|
23.00 f
|
30.67 g
|
33.71 f
|
1% HCl for 30 min
|
72.67 cd
|
76.33 e
|
68.79 de
|
1% HCl for 60 min
|
76.00 bcd
|
81.33 d
|
73.36 cd
|
1% HCl for 90 min
|
78.00 bcd
|
85.33 cd
|
76.46 bcd
|
2% HCl for 30 min
|
82.00 bc
|
86.67 c
|
78.72 bc
|
2% HCl for 60 min
|
93.33 a
|
99.33 a
|
89.76 a
|
2% HCl for 90 min
|
83.33 b
|
94.67 b
|
81.99 ab
|
3% HCl for 30 min
|
79.67 bc
|
88.67 c
|
79.48 bc
|
3% HCl for 60 min
|
75.33 bcd
|
81.67 d
|
73.33 cd
|
3% HCl for 90 min
|
69.33 d
|
73.33 ef
|
64.10 e
|
Significance
|
***
|
***
|
***
|
LSD (5%)
|
9.802
|
4.632
|
8.508
|
CV (%)
|
8.1
|
3.5
|
7.0
|
Means different letter within a column are significantly different at 5% level of significance; LSD=Least significant difference; CV=Coefficient of variation.
Lengthening the time from 60 into 90 minutes or increasing the concentration of HCl from 2% into 3% also resulted significantly reduced germination percentage (94.67%) and (88.67%), respectively. This might also be due to corrosive effect of acid over prolonged period (Vishwanath et al., 2006; Nemati et al., 2010; França et al., 2013; and Ankit et al., 2016).
Seeds emergence
Significantly maximum (89.76%) seeds emergence was obtained from 2% HCl for 60 minutes followed by 2% HCl for 90 minutes (81.99%). The lowest seeds emergence (33.71%) was found at fermentation for 72 hours (Table 2).The lowest germination might be either the seeds were damaged by fungal pathogens or seeds were germinated during extended fermentation time thus failed to germinate during germination test. This finding is in conformity with the results of Evera and Vanangamudi (2006) and Nemati et al., (2010) who reported that decreased seed emergence due to fermentation longer than 48 hours. This might be due to premature sprouting and reduced germination from extended fermentation period.
Seedling length
Among all extraction methods, significantly (P< 0.01) maximum seedling length (14.00 cm) was recorded at 2% HCl for 60 minutes followed by 1% HCl for 90 minutes (13.50 cm). The minimum seedling length 10.77 cm and 10.83 cm recorded at fermentation for 72 hours and 3% HCl for 90 minutes respectively (Table 3 and Fig. 4. B). Quite the reverse, Ankit et al., (2016) testified a maximum seedling length (13.49 cm) from 24 hours fermentation. On the contrary, Nemati et al., (2010) reported no significant difference between short-term fermentation and severe plant height reduction with long-term fermentation. In the current study, difference in seedling length might be due to difference in date of germination. Earlier germinated seedlings probably had longer periods for root and shoot growth.
Seedling fresh weight
Seedling fresh weight was significantly (P < 0.01) affected by the treatment effects. Maximum fresh weight (558.1g) found at 2% HCl for 30 minutes which is statistically at par with 2% HCl for 60 minutes (556.2g) (Table 3).
Seedling dry weight
Seedling dry weight was significantly (P< 0.01) influenced by seed extraction methods. The highest seedling dry weight (26.73 g) was observed from 2% HCl for 60 minutes followed 1% HCl for 30 minutes (24.85 g) time length. Minimum dry weight (13.71g) and (15.4 g) was recorded from 72 hours fermentation and 3% HCl for 90 minutes (Table 3).
Table 3. Effects of different seed extraction methods and length of time on seedling length, seedling fresh weight and seedling dry weight
Treatments
|
Seedling length (cm)
|
Seedling fresh weight (g)
|
Seedling dry weight (g)
|
Fermentation for 24 hrs
|
13.13 abc
|
541.6 ab
|
24.16 b
|
Fermentation for 48 hrs
|
11.93 ef
|
490.6 d
|
19.06 d
|
Fermentation for 72 hrs
|
10.77 g
|
437.1 e
|
13.71 e
|
1% HCl for 30 min
|
12.15 def
|
518.2 c
|
21.82 c
|
1% HCl for 60 min
|
12.95 bcd
|
531.4 bc
|
23.14 bc
|
1% HCl for 90 min
|
13.50 ab
|
541.6 ab
|
24.16 b
|
2% HCl for 30 min
|
13.05 bc
|
558.1a
|
24.85 b
|
2% HCl for 60 min
|
14.00 a
|
556.2 a
|
26.73 a
|
2% HCl for 90 min
|
12.60 cdef
|
544.8 ab
|
24.31 b
|
3% HCl for 30 min
|
12.73 bcde
|
538.5 abc
|
23.85 b
|
3% HCl for 60 min
|
11.73 f
|
484.2 d
|
19.09 d
|
3% HCl for 90 min
|
10.83 g
|
450.7 e
|
15.40 e
|
Significance
|
**
|
**
|
**
|
LSD (5%)
|
0.8913
|
22.45
|
1.821
|
CV (%)
|
4.2
|
2.6
|
5.0
|
Means different letter within a column are significantly different at 5% level of significance; LSD=Least significant difference; CV=Coefficient of variation.
Vigour indices
Both vigour index I and II were significantly affected by extraction method and time length at P < 0.001 and P < 0.01 respectively. The highest vigour index I (1391) and Vigour Index II (2655) were obtained from dibbing of the crashed tomato fruits in 2% HCl for 60 minutes while the lowest vigour index I (329) and Vigour Index II (417) were recorded from fermentation for 72 hours (Table 4).
There was a severe increase in seed vigour indices with increasing HCl concentration and time length up to 2% HCl for 60 minutes then radically decreased beyond that point (Fig. 5. A and B). However, CAFT (2017) recommended 3% HCl for 30 minutes to get the best vigour and seed quality of tomato. But, in this study seed vigour was reduced over 2% HCl. This might be due to differences in pulp thickness. On the other hand, Demir and Samit (2001) reported that best seed vigour can be obtained from 2 and 3% HCl acid extraction.
Table 4. Effects of different seed extraction methods and length of time on seed vigour index I and vigour index II
Treatments
|
Seed vigour index I (unit)
|
Seed vigour index II (unit)
|
Fermentation for 24 hrs
|
1116 bc
|
2054 c
|
Fermentation for 48 hrs
|
832 fg
|
1329 f
|
Fermentation for 72 hrs
|
329 h
|
417 h
|
1% HCl for 30 min
|
929 ef
|
1666 e
|
1% HCl for 60 min
|
1054 cd
|
1883 d
|
1% HCl for 90 min
|
1153 bc
|
2062 c
|
2% HCl for 30 min
|
1132 bc
|
2154 bc
|
2% HCl for 60 min
|
1391 a
|
2655 a
|
2% HCl for 90 min
|
1194 b
|
2301 b
|
3% HCl for 30 min
|
1129 bc
|
2115 c
|
3% HCl for 60 min
|
959 de
|
1560 e
|
3% HCl for 90 min
|
794 g
|
1128 g
|
Significance
|
***
|
**
|
LSD (5%)
|
109.4
|
170.8
|
CV (%)
|
6.5
|
5.7
|
Means different letter within a column are significantly different at 5% level of significance; LSD=Least significant difference; CV=Coefficient of variation.