A pathogenicity study, conducted under pot culture conditions, revealed that M. incognita had pathogenic effects on muskmelon when the inoculum concentration reached 500 J2 (second-stage juveniles) per plant or greater. There was a noticeable and consistent reduction in the shoot and root length of the muskmelon plants when the inoculum level was maintained at or above 500 J2 per plant, with this effect observed at each of the specified time intervals (15, 30, 45, 60, and 90 days) following inoculation. Furthermore, a decrease in various other plant growth parameters, including shoot and root length, as well as fresh and dry shoot weights, was evident in muskmelon plants inoculated with 500 J2 at each time interval after inoculation. In contrast, the plants in the control group (T1) consistently exhibited the maximum shoot and root length at each of the specified day intervals from the date of inoculation.
15 days after inoculation
At 15 days post-inoculation, compared with those of the controls, the initial inoculation levels of 500 J2 and above per plant significantly increased the fresh weight of the roots by 17.3%, 40.1%, and 48.7% respectively. Similar trends were observed for root dry weight, attributed to severe galls. Conversely, shoot and root growth parameters, as well as shoot fresh and dry weight, decreased significantly across all inoculum levels, notably at 2000 and 5000 J2 per plant (Table 2 & Graphs A-F). Uninoculated plants showed no root-knot nematode females, while the highest female count (28) occurred at 5000 J2/plant, followed by 2000 J2/plant (21.66). The lowest female count (6.66) was at 100 J2/plant. The egg masses mirrored this pattern, with the highest count (16.33) occurring at 5000 J2/plant and the lowest (6.33) occurring at 100 J2/plant. The increase in nematode population in roots and soil was correlated with the inoculum concentrations. The gall index peaked at 4 for 5000 J2 and was 3 for 2000 J2/plant. The reproduction rate varied, with the highest (3.5) occurring at 100 J2/plant and the lowest (0.98) occurring at 5000 J2/plant (Table 3).
Inoculation level (J2/2 kg soil)
|
Shoot Length
(cm)
|
Root Length
(cm)
|
Shoot Fresh Weight
(g)
|
Root Fresh Weight
(g)
|
Shoot Dry Weight
(g)
|
Root Dry Weight
(g)
|
T1 (0)
|
24.2
|
5.6
|
3.944
|
0.308
|
0.154
|
0.015
|
T2 (100)
|
22.9
(- 5.28)
|
5.3
(- 4.82)
|
3.782
(- 4.10)
|
0.373
(+ 6.5)
|
0.142
(- 7.79)
|
0.019
(+ 4.00)
|
T3 (500)
|
21.6
(- 10.8)
|
5.1
(- 7.85)
|
3.698
(- 6.23)
|
0.437
(+ 12.9)
|
0.132
(- 14.28)
|
0.024
(+ 9.00)
|
T4 (1000)
|
17.7
(- 26.7)
|
4.9
(- 11.9)
|
3.654
(- 7.35)
|
0.481
(+ 17.3)
|
0.126
(- 18.18)
|
0.027
(+ 12.00)
|
T5 (2000)
|
12.6
(- 47.9)
|
4.8
(- 13.7)
|
3.548
(- 10.04)
|
0.709
(+ 40.1)
|
0.114
(- 25.9)
|
0.041
(+ 26.00)
|
T6 (5000)
|
10.8
(- 55.3)
|
3.6
(- 35.7)
|
3.234
(- 18.00)
|
0.795
(+ 48.7)
|
0.104
(- 32.4)
|
0.055
(+ 40.00)
|
S.E.(d)
|
0.384
|
0.252
|
0.051
|
0.004
|
0.003
|
0.003
|
C.D(P=0.05)
|
0.847
|
0.556
|
0.023
|
0.003
|
0.007
|
0.007
|
*Figures in parentheses are percent decrease (-) /increase (+) compared with the control.
Table 2: Effect of the population density of M. incognita on the plant growth parameters of muskmelon 15 days after inoculation.
Inoculum level (Pi)
|
No. of female/ 5 g root
|
No. of egg masses/ 5 g root
|
Root-Knot Index
|
Final nematode population/ 250 g of soil (Pf)
|
Reproduction factor (Pf/Pi)
|
T1 (0)
|
0.00
|
0.00
|
0.00
|
0.00
|
0.00
|
T2 (100)
|
6.66±0.882
|
3.33±0.33
|
2
|
351.66±6.692
|
3.51
|
T3 (500)
|
9.00±1.0
|
5.33±0.882
|
2
|
1582.33±19.150
|
3.16
|
T4 (1000)
|
9.66±1.45
|
6.33±0.882
|
2
|
2332.33±2.995
|
2.33
|
T5 (2000)
|
21.66±0.667
|
15.33±1.764
|
3
|
3582.33±17.294
|
1.79
|
T6 (5000)
|
28.00±2.082
|
16.33±0.882
|
4
|
4915.00±18.230
|
0.983
|
S.E.(d)
|
1.700
|
1.361
|
-
|
18.721
|
-
|
C.D(P=0.05)
|
3.744
|
2.998
|
-
|
41.242
|
-
|
Table 3: Effect of population density of M. incognita on nematode reproduction factors in muskmelon 15 days after inoculation.
30 days after inoculation
At 30 days post-inoculation, muskmelon plants showed significant reductions in various growth parameters when inoculated with 500 J2 or more per plant. Maximum shoot and root lengths (95.76 cm and 16.76 cm, respectively) were observed in the absence of nematodes (T1). Despite reductions in secondary and tertiary roots, total root weight increased with increasing M. incognita inoculum. All treatments increased the fresh and dry root weights compared to those of the controls, with the highest increase (54.7% and 51.2%, respectively) occurring at 5000 J2/plant, consistent with the 15-day results (Table 4 & Graphs A-F). The highest female and egg mass counts (63.33 and 53.66, respectively) occurred at 5000 J2/plant, followed by 2000 J2 and 1000 J2/plant, while the lowest counts occurred at 100 J2/plant (6.66 and 3.33, respectively). The soil nematode population increased with each inoculum level. The root-knot index peaked at 5 with 5000 and 2000 J2/plant and was lowest at 100 J2/plant. The maximum reproduction rate (18.32) occurred at 100 J2/plant, while the minimum (1.33) occurred at 5000 J2/plant, consistent with 15-day findings (Table 5).
Inoculation level (J2/2 kg soil)
|
Shoot Length
(cm)
|
Root Length
(cm)
|
Shoot Fresh Weight
(g)
|
Root Fresh Weight
(g)
|
Shoot Dry Weight
(g)
|
Root Dry Weight
(g)
|
T1 (0)
|
91.6
|
16.7
|
10.66
|
2.153
|
1.293
|
0.194
|
T2 (100)
|
88.6
(- 7.41)
|
14.2
(- 15.09)
|
8.33
(- 21.8)
|
2.771
(+ 22.3)
|
0.915
(- 29.2)
|
0.221
(+ 12.21)
|
T3 (500)
|
83.7
(- 12.53)
|
12.8
(- 23.2)
|
7.498
(- 29.6)
|
3.18
(+ 32.2)
|
0.757
(- 41.4)
|
0.274
(+ 29.1)
|
T4 (1000)
|
68.6
(- 28.2)
|
10.9
(- 34.9)
|
6.933
(- 34.9)
|
3.54
(+ 39.1)
|
0.551
(- 57.3)
|
0.295
(+ 34.2)
|
T5 (2000)
|
56.2
(- 41.2)
|
8.7
(- 47.9)
|
5.83
(- 45.3)
|
4.46
(+ 51.7)
|
0.437
(- 66.2)
|
0.363
(+ 46.5)
|
T6 (5000)
|
46.2
(- 51.6)
|
6.7
(- 59.6)
|
5.23
(- 50.9)
|
4.76
(+ 54.7)
|
0.377
(- 70.8)
|
0.398
(+ 51.2)
|
S.E.(d)
|
0.395
|
0.247
|
0.279
|
0.024
|
0.006
|
0.013
|
C.D(P=0.05)
|
0.869
|
0.545
|
0.615
|
0.052
|
0.012
|
0.029
|
*Figures in parentheses are percent decrease (-) /increase (+) compared with the control.
Table 4: Effect of population density of M. incognita on plant growth parameters of muskmelon 30 days after inoculation.
Inoculum level (Pi)
|
No. of female / 5 g root
|
No. of egg masses/ 5 g root
|
Root-Knot Index
|
Final nematode population/ 250 g of soil (Pf)
|
Reproduction factor (Pf/Pi)
|
T1 (0)
|
0.00
|
0.00
|
0.00
|
0.00
|
0.00
|
T2 (100)
|
15.66±1.202
|
8.66±0.882
|
3
|
1832.33±20.624
|
18.32
|
T3 (500)
|
23.33±1.453
|
18.33±0.667
|
4
|
3165.00±34.962
|
6.33
|
T4 (1000)
|
40.00±1.528
|
20.66±1.202
|
4
|
4582.33±15.907
|
4.58
|
T5 (2000)
|
61.00±1.528
|
48.00±1.528
|
5
|
5665.00±91.882
|
2.83
|
T6 (5000)
|
63.33±2.728
|
53.66±0.882
|
5
|
6665.00±20.421
|
1.33
|
S.E.(d)
|
2.285
|
1.388
|
-
|
59.891
|
-
|
CD (P=0.05)
|
5.034
|
3.057
|
-
|
131.937
|
-
|
Table 5: Effect of the population density of M. incognita on nematode reproduction factors in muskmelon 30 days after inoculation.
45 days after inoculation
After 45 days of root-knot nematode (RKN) inoculation, the study confirmed the pathogenicity of M. incognita to muskmelon at inoculum levels of 500 J2 and above per plant, resulting in a significant reduction in plant length and various growth parameters. Despite the reductions in secondary and tertiary roots, the total fresh and dry root weights increased with increasing M. incognita inoculum levels, except at 5000 J2/plant (Table 6 & Graphs A-F). The infected plants displayed stunting, leaf yellowing, and wilting, while the uninoculated plants remained free of RKN females. The highest female count (48.66) was at 2000 J2/plant, followed by 1000 J2 (41.66) and 500 J2 (36.66), with the lowest (20.66) at 100 J2/plant. However, T6 (5000 J2) had a reduced female nematode count (30.66/5 g root) and egg mass. The nematode population in the soil doubled compared to that at 15 days post-inoculation. The maximum (14.15) and minimum (1.383) reproduction rates occurred at 100 J2 and 5000 J2, respectively. The root-knot index was 5 for all inoculum levels except T2 (100 J2/plant) (Table 7).
Inoculation level (J2/2 kg soil)
|
Shoot Length
(cm)
|
Root Length
(cm)
|
Shoot Fresh Weight
(g)
|
Root Fresh Weight
(g)
|
Shoot Dry Weight
(g)
|
Root Dry Weight
(g)
|
T1 (0)
|
116.9
|
17.8
|
18.93
|
3.966
|
2.097
|
0.386
|
T2 (100)
|
91.5
(- 21.6)
|
17.3
(- 3.13)
|
16.73
(-11.62)
|
4.313
(+ 8.04)
|
1.620
(- 22.7)
|
0.417
(+ 7.43)
|
T3 (500)
|
84.7
(- 27.54)
|
16.6
(- 6.88)
|
14.93
(- 21.13)
|
4.653
(+ 14.76)
|
1.536
(- 26.7)
|
0.453
(+ 14.7)
|
T4 (1000)
|
69.9
(- 40.17)
|
14.6
(- 18.08)
|
11.23
(- 40.67)
|
4.699
(+ 15.59)
|
0.950
(- 54.6)
|
0.481
(+ 19.7)
|
T5 (2000)
|
62.8
(- 46.22)
|
9.1
(- 48.71)
|
7.51
(- 60.32)
|
5.146
(+ 22.93)
|
0.545
(- 74.01)
|
0.540
(+ 28.5)
|
T6 (5000)
|
56.1
(- 55.60)
|
8.6
(- 51.84)
|
6.13
(- 67.61)
|
3.821
(- 3.656)
|
0.358
(- 82.9)
|
0.374
(- 3.108)
|
S.E.(d)
|
1.598
|
0.395
|
0.144
|
0.212
|
0.024
|
0.014
|
C.D(P=0.05)
|
3.520
|
0.870
|
0.317
|
0.466
|
0.053
|
0.031
|
*Figures in parentheses are percent decrease (-) /increase (+) compared with the control.
Table 6: Effect of the population density of M. incognita on the plant growth parameters of muskmelon 45 days after inoculation.
Inoculum level (Pi)
|
No. of female / 5 g root
|
No. of egg masses/ 5 g root
|
Root-Knot Index
|
Final nematode population/ 250 g of soil (Pf)
|
Reproduction factor (Pf/Pi)
|
T1 (0)
|
0.00
|
0.00
|
0.00
|
0.00
|
0.00
|
T2 (100)
|
20.66±2.028
|
11.33±0.667
|
4
|
1415.00±21.0
|
14.15
|
T3 (500)
|
36.66±1.856
|
22.00±1.0
|
5
|
2915.00±29.816
|
5.83
|
T4 (1000)
|
41.66±2.028
|
25.33±1.667
|
5
|
5416.66±17.291
|
5.41
|
T5 (2000)
|
48.66±1.453
|
32.33±1.764
|
5
|
6082.33±15.181
|
3.04
|
T6 (5000)
|
30.66±0.0882
|
17.66±0.882
|
5
|
6915.00±23.438
|
1.38
|
S.E.(d)
|
2.203
|
1.644
|
-
|
28.337
|
-
|
CD (P=0.05)
|
4.852
|
3.622
|
-
|
62.424
|
-
|
Table 7: Effect of the population density of M. incognita on nematode reproduction factors in muskmelon 45 days after inoculation.
60 days after inoculation
After 60 days of M. incognita inoculation, significant reductions in shoot and root growth were observed at inoculum levels of 500 J2 and above per plant. Muskmelon plants inoculated with 500 J2 or more displayed decreased shoot length, root length, and fresh and dry weights. The maximum reduction in root length (66.1) occurred at 5000 J2/plant. Conversely, compared with those of the uninoculated controls. the initial inoculum levels of 100, 500, 1000, and 2000 J2/plant increased the fresh root weight by 6.32%, 10.80%, 23.41%, and 29.21%, respectively. However, plants inoculated with 5000 J2/plant exhibited a 7.74% decrease in root fresh weight (Table 8 & Graphs A-F). Uninoculated plants showed no RKN females. The highest female count (41.66) occurred at 2000 J2/plant, followed by 1000 J2 (37.66), while the lowest (27.66) was at 100 J2. The maximum egg mass count (28.66) was at 2000 J2/plant, followed by 1000 J2 (21.33), 500 J2 (16.66), and 100 J2 (15.00). The root-knot nematode population increased in soil for all treatments, with severe galling (index of 5). Maximum (16.65) and minimum (1.283) reproduction rates occurred at 100 J2 and 5000 J2, respectively (Table 9).
Inoculation level (J2/2 kg soil)
|
Shoot Length
(cm)
|
Root Length
(cm)
|
Shoot Fresh Weight
(g)
|
Root Fresh Weight
(g)
|
Shoot Dry Weight
(g)
|
Root Dry Weight
(g)
|
T1 (0)
|
142.7
|
18.4
|
21.95
|
5.33
|
3.439
|
0.576
|
T2 (100)
|
132.8
(- 6.89)
|
15.3
(- 16.6)
|
17.53
(- 20.1)
|
5.69
(+ 6.32)
|
2.936
(- 14.62)
|
0.595
(+ 3.19)
|
T3 (500)
|
128.5
(- 9.92)
|
10.9
(- 40.4)
|
15.47
(- 29.5)
|
5.97
(+ 10.80)
|
2.760
(- 19.74)
|
0.749
(+ 23.09)
|
T4 (1000)
|
122.4
(- 14.2)
|
8.5
(- 53.3)
|
14.33
(- 34.7)
|
6.96
(+ 23.41)
|
2.233
(- 35.06)
|
0.841
(+ 31.51)
|
T5 (2000)
|
103.9
(- 27.1)
|
7.4
(- 59.6)
|
11.59
(- 47.1)
|
7.53
(+ 29.21)
|
1.388
(- 59.63)
|
0.991
(+ 41.87)
|
T6 (5000)
|
95.0
(- 33.3)
|
6.2
(- 66.1)
|
9.62
(- 56.1)
|
4.91
(- 7.748)
|
1.264
(- 63.24)
|
0.503
(- 12.67)
|
S.E.(d)
|
1.130
|
0.601
|
0.644
|
0.276
|
0.038
|
0.035
|
C.D(P=0.05)
|
2.490
|
1.324
|
1.418
|
0.609
|
0.083
|
0.077
|
*Figures in parentheses are percent decrease (-) /increase (+) compared with the control.
Table 8: Effect of the population density of M. incognita on the plant growth parameters of muskmelon 60 days after inoculation.
Inoculum level (Pi)
|
No. of female / 5 g root
|
No. of egg masses/ 5 g root
|
Root-Knot Index
|
Final nematode population/ 250 g of soil (Pf)
|
Reproduction factor (Pf/Pi)
|
T1 (0)
|
0.00
|
0.00
|
0.00
|
0.00
|
0.00
|
T2 (100)
|
27.66±1.85
|
15.00±1.52
|
5
|
1665.00±28.43
|
16.65
|
T3 (500)
|
34.33±1.76
|
16.66±1.45
|
5
|
3082.33±14.31
|
6.16
|
T4 (1000)
|
37.66±1.85
|
21.33±2.02
|
5
|
4332.33±30.76
|
4.33
|
T5 (2000)
|
41.66±1.33
|
28.66±2.60
|
5
|
6165.00±20.88
|
3.08
|
T6 (5000)
|
29.00±3.60
|
14.33±0.882
|
5
|
6415.00±13.05
|
1.28
|
S.E.(d)
|
2.874
|
2.317
|
-
|
29.251
|
-
|
CD (P=0.05)
|
6.331
|
5.105
|
-
|
64.439
|
-
|
Table 9: Effect of the population density of M. incognita on nematode reproduction factors in Muskmelon 60 days after inoculation.
90 days after inoculation
After 90 days of M. incognita inoculation, the pathogenicity study confirmed its impact on muskmelon, especially at inoculum levels of 500 J2 and above per plant. Significant reductions in plant length and various growth parameters, including shoot and root length, and fresh and dry shoot weight were observed. The reductions in root systems were consistent across treatments, highlighting the high pathogenicity of M. incognita to muskmelon. Initial inoculum levels of 100, 500, 1000, and 2000 J2/plant resulted in increases in fresh root weight of 27.11%, 39.10%, 42.21%, and 16.93%, respectively, compared to those of the controls (Table 10 & Graphs A-F). However, at 5000 J2/plant, there was a 6.35% reduction in fresh root weight. Plants inoculated with 2000 and 5000 J2 displayed significant growth reductions, including stunting, leaf yellowing, and wilting. There were no RKN females on the uninoculated plants. The highest female count (34.66) was at 500 J2/plant, followed by 31.33 at 1000 J2/plant. The lowest (21.66) was at 5000 J2, followed by 24.66 at 2000 J2/plant. The maximum egg mass count (23.33) was at 1000 J2/plant, followed by 21.66 at 500 J2, 17.66 at 100 J2, 16.33 at 2000 J2, and 13.33 at 5000 J2/plant. The nematode population in roots and soil increased with increasing inoculum. A severe increase in the root-knot index (5) was observed across treatments, indicating significant root damage. The maximum (19.92) and minimum (0.901) reproduction rates were at 100 J2 and 5000 J2, respectively (Table 11).
Inoculation level (J2/2 kg soil)
|
Shoot Length
(cm)
|
Root Length
(cm)
|
Shoot Fresh Weight
(g)
|
Root Fresh Weight
(g)
|
Shoot Dry Weight
(g)
|
Root Dry Weight
(g)
|
T1 (0)
|
267.2
|
24.5
|
35.62
|
7.697
|
4.545
|
1.175
|
T2 (100)
|
223.0
(- 16.53)
|
14.5
(- 41.37)
|
29.47
(-17.26)
|
10.56
(+ 27.11)
|
3.859
(- 15.09)
|
1.661
(+ 29.25)
|
T3 (500)
|
206.8
(- 22.58)
|
11.6
(- 53.22)
|
26.45
(- 25.47)
|
12.64
(+ 39.10)
|
3.550
(- 21.89)
|
1.884
(+ 37.63)
|
T4 (1000)
|
181.0
(- 32.24)
|
9.5
(- 61.57)
|
23.35
(- 34.44)
|
13.32
(+ 42.21)
|
2.95
(- 35.09)
|
2.195
(+ 46.46)
|
T5 (2000)
|
158.0
(- 40.84)
|
7.5
(- 69.63)
|
21.63
(- 39.27)
|
9.26
(+ 16.93)
|
2.641
(- 41.89)
|
1.48
(+ 20.60)
|
T6 (5000)
|
124.6
(- 53.35)
|
6.6
(- 73.30)
|
18.39
(- 48.37)
|
7.209
(- 6.353)
|
1.799
(- 60.41)
|
0.947
(- 19.40)
|
S.E.(d)
|
1.613
|
0.407
|
0.294
|
0.084
|
0.039
|
0.049
|
C.D(P=0.05)
|
3.553
|
0.897
|
0.649
|
0.185
|
0.085
|
0.109
|
*Figures in parentheses are percent decrease (-) /increase (+) compared with the control.
Table 10: Effect of the population density of M. incognita on the plant growth parameters of muskmelon 90 days after inoculation.
Inoculum level (Pi)
|
No. of female / 5 g root
|
No. of egg masses/ 5 g root
|
Root-Knot Index
|
Final nematode population/ 250 g of soil (Pf)
|
Reproduction factor (Pf/Pi)
|
T1 (0)
|
0.00
|
0.00
|
0.00
|
0.00
|
0.00
|
T2 (100)
|
29.33±1.45
|
17.66±0.882
|
5
|
1992.00±5.50
|
19.92
|
T3 (500)
|
31.33±2.02
|
21.66±0.667
|
5
|
3665.00±7.21
|
7.33
|
T4 (1000)
|
34.66±1.76
|
23.33±1.20
|
5
|
4620.00±10.01
|
4.62
|
T5 (2000)
|
24.66±1.85
|
16.33±1.66
|
5
|
7740.00±22.74
|
3.87
|
T6 (5000)
|
21.66±3.75
|
13.33±0.882
|
5
|
4509.33±15.91
|
0.901
|
S.E.(d)
|
2.994
|
1.440
|
-
|
17.834
|
-
|
CD (P=0.05)
|
6.595
|
3.173
|
-
|
39.286
|
-
|
Table 11: Effect of population density of M. incognita on nematode reproduction factors in muskmelon 60 days after inoculation.