Estimation of plant growth parameters, biomass and phosphorus measurement
The results also indicated that growth parameters of the plants inoculated with AMF significantly were higher as compared to the non-inoculated control group. In detail, the mean height, number of leaves, stem diameter and leaf area in AMF treated plants were 56%, 41% and 24% higher (p < 0.05) (Table 1). Similarly, the dry weight of root, dry weight of aerial parts and root volume of the plants treated with AMF were 28%, 28%, 61% and 55% higher, respectively. The results indicated that tomato inoculation with the mixture of four fungal species had significant effects on phosphorous content at the 0.05 level. These results demonstrated that mycorrhizal plants contained 67% more phosphorous than the control non-inoculated plants (Table 1).
Table 1
Effect of AMF on the growth parameters (Mean ± SE) and root phosphorus )P) content of Solanum lycopersicum
Treatment
|
Control
|
AMF
|
T
|
df
|
Plant height (cm)
|
61.32 ± 0.03b
|
138.57 ± 0.04a
|
-417.11
|
53.39
|
Number of leaves
|
24.5 ± 0.03b
|
45.7 ± 0.02a
|
-79.25
|
55.54
|
Leaf area (cm2/plant)
|
210.24 ± 0.2b
|
322.33 ± 0.3a
|
-557.18
|
57.96
|
Root volume (cm3/plant)
|
3.5 ± 0.3b
|
5.4 ± 0.2a
|
-7.8
|
56.22
|
Stem diameter (mm)
|
3.22 ± 0.13b
|
4.35 ± 0.33a
|
-6.49
|
58
|
Root weight (gr/plant)
|
10.8 ± 0.14b
|
14.85 ± 0.38a
|
-119.98
|
51.1
|
Shoot weight (gr/plant)
|
28.15 ± 0.1b
|
39.14 ± 0.1a
|
-21.96
|
58
|
P content (mg/g root)
|
0.3 ± 0.25b
|
0.9 ± 0.11a
|
-13.82
|
29
|
Root colonization (%)
|
0b
|
71.32 ± 0.01a
|
-468.05
|
29
|
The mean values with different superscript letters in each column are significantly different (p < 0.05)
Effect of AMF and B. tabaci on PAL activity of tomato leaf material
As shown in Fig. 2, in all treatments (AMF*BT, AMF, BT) the PAL activity was higher than control, but the enzyme activity was increased in AMF*BT faster (Time 1; day 10 after release of B. tabaci) and it was significantly higher than the other treatments. In AMF and BT the increase was lower and happened more slowly. Likewise, on day 20, the PAL activity in AMF*BT (2.458 ± 0.22 /min/g fresh leaf) was higher as compared to all treatments.
Bars with different lowercase letters indicate significant differences between different treatments at the same time.
Bars with different capital letters indicate significant differences between different times with the same treatments at P ≤ 0.05 by LSD test.
Day zero corresponds to 10 weeks after tomato planting and AMF inoculation.
Effect of AMF and B. tabaci on PPO activity of tomato leaf material
The trend of changes in PPO activity on sampling days in the various treatments is shown in Fig. 3. In all selected times, the enzyme activity in mycorrhizal treatments were significantly higher than non-mycorrhizal treatments. Although, 20 days after release of B. tabaci the PPO activity increased both in the mycorrhizal plants with or without whiteflies. Still, no significant increase was observed in enzyme activity in the BT treatment. The highest PPO activity (1.354 ± 0.08/min/g fresh leaf) was recorded in AMF*BT on 20 days after the insects were released.
Time 0, 1, and 2 are 0, 10 and 20 days after release of B. tabaci respectively). C, Control; AMF, arbuscular mycorrhizal fungi; BT, B. tabaci.
Bars with different lowercase letters indicate significant differences between different treatments at the same time.
Bars with different capital letters indicate significant differences between different times with the same treatments at P ≤ 0.05 by LSD test.
Day zero corresponds to 10 weeks after tomato planting and AMF inoculation.
Effect of AMF and B. tabaci on PO activity of tomato leaf material
In all three sampling times, the PO activity in the mycorrhizal treatments was higher than in the non-mycorrhizal treatments. Although the BT treatment was not inoculated with fungi, a significant increase in enzyme activity was recorded faster on 10 day (even if this increase was not continuous). In the mycorrhizal treatments (with or without whiteflies), a significant increase in the enzyme activity was observed on the 20th day. Although the enzyme activity was higher in the mycorrhizal treatments than in the non-mycorrhizal treatment, this enhanced effect required more time to appear as compared to BT treatment. Moreover, the largest PO content (0.966 ± 0.08/min/g fresh leaf) was recorded in the mycorrhizal treatment with whiteflies on day 20 after they were released (Fig. 4).
Time 0, 1, and 2 are 0, 10 and 20 days after release of B. tabaci respectively). C, Control; AMF, arbuscular mycorrhizal fungi; BT, B. tabaci.
Bars with different lowercase letters indicate significant differences between different treatments at the same time.
Bars with different capital letters indicate significant differences between different times with the same treatments at P ≤ 0.05 by LSD test.
Day zero corresponds to 10 weeks after AMF inoculation.
Effect of AMF and B. tabaci on phenolic content of tomato leaf material
In treatments inoculated with AMF, the phenolic content of plants increased as the time of exposure to B. tabaci was increased. Even though AMF and BT treatments produced significant quantities of phenolics compared to the control, the effect was highest in the AMF*BT treatment. The maximum phenolic content of 2.212 ± 0.19/min/g fresh leaf was observed in AMF (AMF*BT)-inoculated plants after 20 days of B. tabaci exposure (Fig. 5).
Time 0, 1, and 2 are 0, 10 and 20 days after release of B. tabaci respectively). C, Control; AMF, arbuscular mycorrhizal fungi; BT, B. tabaci.
Bars with different lowercase letters indicate significant differences between different treatments at the same time.
Bars with different capital letters indicate significant differences between different times with the same treatments at P ≤ 0.05 by LSD test.
Day zero corresponds to 10 weeks after AMF inoculation.
Effect of AMF on B. tabaci growth, development and reproduction
The mean durations of the growth stages and the results obtained from their statistical analysis are presented in Table 2. On average, the oviposition period of adult whiteflies began after 1.95 ± 0.16 days on non-mycorrhizal tomato and after 40 ± 11 days on mycorrhizal tomato. These results showed that the mycorrhizal and non-mycorrhizal tomato plants differed significantly in adult pre-oviposition period (APOP) (P < 0.05). In addition, the total pre-oviposition period (TPOP) of adult females was 28.86±0.22 days and 26±0.21 days on mycorrhizal and non-mycorrhizal plants, respectively, indicating that these two types of tomato plants differed significantly in this regard (P < 0.05). The shortest adult insect life span (24.57±0.42 days) was recorded in mycorrhizal plants, which was significantly different from that of non-mycorrhizal plants (25.77 ± 0.37 days). The shortest total life span (43.29 ± 2.25 days) was that of the mycorrhizal plants, which was significantly different from that of the non-mycorrhizal plants (45.62 ± 1.95). Nonetheless, no significant differences was observed between the mycorrhizal and non-mycorrhizal plants in nymphal stages.
Table 2
The mean duration (± SE) of different life stages of whiteflies of Bemisia tabaci on tomato plants without (Control) and with AMF
Stage (days)
|
Control
|
AMF
|
p-value
|
Egg
|
7.45 ± 0.08a
|
7.53 ± 0.08a
|
0.54
|
Nymph stages
|
10.78 ± 0.21a
|
10.97 ± 0. 1a
|
0.42
|
Pupa
|
5.13 ± 0.12b
|
5.60 ± 0.17a
|
0.027
|
Pre-adult
|
24.09 ± 0.23a
|
23.63 ± 0.25b
|
0.17
|
Adult
|
25.77 ± 0.37a
|
24.57 ± 0.42b
|
0.031
|
Life cycle
|
45.62 ± 1.95a
|
43.29 ± 2.25b
|
0.033
|
APOP
|
1.95 ± 0.16b
|
4.00 ± 0.11a
|
0.003
|
TPOP
|
26.00 ± 0.21b
|
28.86 ± 0.22a
|
0.0001
|
Different letters in each row show significant differences among treatments at 5% level.
The results showed that the mycorrhizal and non-mycorrhizal treatments differed significantly in net reproduction rate (R0), intrinsic rate of population increase (rm), finite rate of population increase (λ) and generation time (T) of B. tabaci (Table 3).
Table 3
Life table parameters (mean ± SE) of whiteflies of Bemisia tabaci on tomato plants without (Control) and with AMF
Parameter
|
Control
|
AMF
|
p-value
|
Intrinsic rate of increase (rm) (d− 1)
|
0.17 ± 0.005a
|
0.13 ± 0.005b
|
0.0001
|
Finite rate of increase (\(\lambda\)) (d− 1)
|
1.18 ± 0.006a
|
1.14 ± 0.006b
|
0.0001
|
Net reproductive rate (R0) (offspring)
|
209 ± 34a
|
102 ± 16b
|
0.003
|
Mean generation time (T) (d)
|
31.08 ± 0.31b
|
33.62 ± 0.32a
|
0.0001
|
Control (n=35) and AMF (n=40)
Means in the same row followed by different letter are significantly different (paired bootstrap test at 5% level).