Guava (
The population of
In total, 100 ppm of 1 litre salicylic acid solution was prepared by adding 0.1g of salicylic acid with 500ml of water and few pellets of sodium bicarbonate (to dissolve salicylic acid with water). Final volume of one litre was prepared by adding water to the dissolved solution.
Methyl jasmonate solution was prepared by diluting 0.1g of methyl jasmonate in 20ml of ethanol. In total, 980ml of water was added after complete dilution of methyl jasmonate in ethanol and make up to 1 litre of the total solution.
In total, 1,000 ppm of 1 litre Indole 3 Butyric acid solution was prepared by weighing 1g of crystalline Indole 3 Butyric acid and dissolved in 20 milliliters of alcohol. The prepared mixture was then added with 980 milliliters of water to make 1,000 ppm of 1 litre Indole 3 Butyric acid solution.
In total, 0.5g of solid Mepiquat chloride was weighed and dissolved in 1,000ml of water to prepare 1 litre of 500 ppm Mepiquat chloride solution.
One litre of 500 ppm Chloromequat chloride solution was prepared by dissolving 0.5g of solid Chloromequat chloride in 1 litre of water.
The effect of plant growth regulators on the growth of guava seedlings inoculated with root knot nematode,
Plant height | – | The plant height of guava plants was measured from the ground level to the tip of the most stretched leaf in each replication. The mean values were expressed in cm |
Root length | – | The plant was uprooted along with its roots causing lower damage and its length was measured and expressed in cm |
Fresh root biomass | – | The roots of guava plants at 45, 75, 105 DAP were uprooted, washed and cleaned to remove the adhering water and soil particles and fresh root weight and was measured and expressed as g plant-1 |
Dry root biomass | – | The roots of guava plants at 45, 75, 105 DAP were uprooted, cleaned and air dried initially followed by oven drying at 65 ± 5oC till a constant weight was attained and root weight was measured and expressed as g/plant |
Chlorophyll index | – | SPAD meter |
Photosynthetic rate | – | Portable photosynthesis system (LI-6400XT, Licor Inc, Nebraska, USA) |
Transpiration rate | – | Portable photosynthesis system (LI-6400XT, Licor Inc, Nebraska, USA) |
Stomatal conductance | – | Portable photosynthesis system (LI-6400XT, Licor Inc, Nebraska, USA) |
Chlorophyll fluorescence | – | Chlorophyll fluorescence meter (Opti-sciences OS5p) |
Total phenols | – | Malick and Singh (1980) |
Peroxidase | Rad et al. (2007) | |
Polyphenol oxidase | Mayer et al. (1966) | |
Acid phosphatase | Dickerson et al. (1984) | |
Phenylalanine ammonia lyase | Dickerson et al. (1984) |
The nematode
Variety | : | Luknow-49 |
Design | : | Randomized block design |
Treatments | : | Seven |
Replications | : | Ten |
Spacing | : | 3.0 m × 3.0 m |
Field trial-I | Field trial-II | ||
---|---|---|---|
Date of planting | : | 20.12.2017 | 12.08.2017 |
Date of treatment imposed | : | 03.01.2018 | 03.04.2018 |
Date of harvest | : | 04.02.2019 | 09.01.2019 |
Soil type | : | Red loamy | Sandy loam |
The data generated from various experiments of the present study were analyzed following Gomez and Gomez (1984) method. The package used for analysis was IRRISTAT version 91-1 developed by International Rice Research Institute, Biometrics unit, Philippines.
The Lucknow 49 Guava seedlings were treated with plant growth regulators viz., Salicylic acid, Jasmonic acid, Indole 3-Butyric Acid, Mepiquat chloride, Chlormequat chloride alone and in combination by quick dipping method. Morphological, physiological, biochemical, and nematode population measurement parameters of the Guava plants were analyzed at 45, 75, and 105 days after planting. The data presented in Figure 1A–N show that the plant growth regulators significantly influenced the growth (morphological, physiological, and biochemical parameters and showed a reduction in nematode population, egg masses, and female population (
Influence of different plant growth regulators in guava infected by
Effect of plant growth regulators in guava (Lucknow-49) infested with root knot nematode,
Nematode population in 5g of root | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Nematode population in 200cc of soil (days) | No of egg masses (days) | No of females (days) | No of eggs/egg masses (days) | ||||||||||
Treatments | 0 | 45 | 75 | 105 | 45 | 75 | 105 | 45 | 75 | 105 | 45 | 75 | 105 |
T1 – SA 100ppm | 169.33bc | 167.66cd (0.99) | 166.00cd (0.99) | 164.66c (0.81) | 24.67c | 23.33d (5.42) | 22.00d (5.70) | 26.67bc | 24.66bc (7.53) | 24.00bc (2.68) | 212.33bc | 219.66b ( |
206.33a (6.07) |
T2 – JA 100ppm | 176.00abc | 174.66abcd (0.76) | 173.33bcd (0.76) | 172.00bc (0.77) | 24.67c | 23.66d (4.08) | 22.33d (5.62 | 28.67cd | 25.00c (12.79) | 24.33bc (2.68) | 198.66a | 204.33ab ( |
218.66f ( |
T3 – IBA 1000ppm | 181.33a | 178.66abc (1.47) | 176.00abc (1.49) | 173.33abc (1.52) | 23.33bc | 21.66cd (7.17) | 19.66c (9.23) | 26.33bc | 23.66bc (10.15) | 22.66b (4.23) | 209.66abc | 212.33ab ( |
217.33ef ( |
T4 – SA100ppm +JA 100ppm + IBA 1000ppm | 184.33a | 180.33ab (2.17) | 175.66abc (2.59) | 171.00bc (2.65) | 20.00a | 17.66a (11.70) | 14.66a (16.99) | 22.00a | 19.66a (10.64) | 16.66a (15.26) | 214.33c | 208.00ab (2.95) | 206.66a (0.64) |
T5 – SA 100ppm+JA 100ppm | 177.00abc | 175.33abcd (0.94) | 173.66abcd (0.95) | 172.33bc (0.77) | 24.67c | 23.33d (5.42) | 21.66d (7.16) | 26.67bc | 24.66bc (7.53) | 24.33bc (1.34) | 200.33ab | 203.66ab ( |
209.66bc ( |
T6 – JA100ppm + IBA1000ppm | 181.33c | 164.33d (1.79) | 161.33d (1.83) | 158.00c (2.06) | 23.00b | 21.00bc (8.70) | 18.66c (11.14) | 26.00b | 23.66bc (9.00) | 22.66b (4.23) | 219.66c | 218.66b (0.46) | 219.33f ( |
T7 – SA100ppm + IBA1000ppm | 167.33abc | 170.33bcd (1.92) | 167.00cd (1.96) | 163.33c (2.20 | 21.33a | 19.00ab (10.94) | 16.33b (14.05) | 23.33a | 20.33a (12.87) | 18.33a (9.84) | 215.33c | 204.33ab (5.11) | 209.66bc ( |
T8 – Mepiquat chloride 500 ppm | 179.00ab | 182.66a ( |
186.00a ( |
189.33a ( |
26.33d | 27.33e ( |
28.66e ( |
29.33de | 28.66d (2.30) | 30.66d ( |
207.33abc | 200.33a (3.38) | 208.33ab ( |
T9 – Chlormequat chloride 500 ppm | 174.66abc | 179.33abc ( |
183.66ab ( |
187.66ab ( |
27.33d | 28.33e ( |
29.00ef ( |
31.33e | 30.00de (4.26) | 32.00d ( |
219.66c | 217.66b (0.91) | 219.66f ( |
T10 – Untreated control | 176.66abc | 181.66ab ( |
186.00a ( |
190.00a ( |
27.67d | 29.00e ( |
30.33f ( |
29.67e | 31.33e ( |
32.33d ( |
218.66c | 219.66b ( |
212.33d (3.34) |
The results showed that plant height measured at 45, 75, and 105 days after planting showed a significant increase in all the treatments and the maximum plant height was recorded at 105 days. The plant height measured for plants treated with two plant growth regulators was higher than the single plant growth regulator treatment. Comparatively, the combination of three plant growth regulators (T4) showed a statistically higher value compared to all treatments and untreated control (T10) (Fig. 1A) (Plate 1). The root length in all the treatments from T1 to T9 was significantly higher than the untreated control. Root length of all the treated and untreated plants increased from 45 to 105 days. The results were statistically significant compared to the untreated control (Fig. 1B). Fresh and dry root biomass of all treatments weighed in 45, 75, and 105 days after planting were statistically and significantly lower than the plants in the untreated control (T10). The fresh root biomass of T10 plants increased from 11.17 g in 45 days to 17.67 in 105 days. Similarly, the dry root biomass of T10 plants increased from 2.69 to 3.81 grams (Fig. 1C, D).
T4 – Salicylic acid (100 ppm) + Jasmonic acid (100 ppm) + Indole 3-Butyric Acid (1,000 ppm) vs T10 – Untreated control.
All plant growth regulators used in this study significantly influenced the physiological parameters such as chlorophyll index, photosynthetic rate, transpiration rate, stomatal conductance, and Chlorophyll fluorescence in all treatment and untreated control. The chlorophyll index measured at 105 days was high in T3 compared to T1 and T2. The chlorophyll index was high in T7 compared to T5 and T6 (
The induction of peroxidases, polyphenol oxidase, phenylalanine ammonia-lyase, acid phosphatase, and total phenols linking to the defence mechanism of the nematode infected plants treated with plant growth regulators were analyzed (Fig. 1J–N). Treatments from T1 to T7 significantly produced a high percentage of peroxidase compared to T8, T9 and untreated control T10 (Fig. 1J). The analysis of polyphenol oxidase (PPO) activity of plant growth regulator treated plants indicated that the result of T3 plant was higher than T5, similar to T6 and lower than T4 and T7. All the single and combined plant growth regulator treated plants showed higher PPO activity than T8, T9 and untreated control (
All the biochemical parameters tested were on the raising side when the treated plants were analyzed 45, 75, and 105 days after application of plant growth regulators. The highest value was recorded by T4 followed by T7 and significantly influenced the growth, physiological, and biochemical parameters compared to other treatments and untreated control.
Treatment with plant growth regulator viz., salicylic acid and Jasmonic acid effectively reduced the nematode population in the soil. A combination of three followed by two plant growth regulators showed high percentages of reduction in nematode population compared to single plant growth promotor application. Reduction of nematode population noted in T3 treated with Indole Butyric Acid at 1,000 ppm concentration was high compared to T1, T2, and untreated control T10. Application of Salicylic acid and Indole butyric acid in combination (T7) effectively reduced the nematode population in soil compared to other plant growth regulator combinations (T5 and T6). The result of the three plant growth regulators (Salicylic acid + Jasmonic Acid + Indole Butyric Acid) combined at a particular concentration specified in this study reduced the nematode population at a high percentage compared to single and combination of two plant growth regulators as well as untreated control. Among T8 and T9, Chlormequat chloride at 500 ppm concentration showed a high percentage of increase in nematode population in the soil in 105 days (Table 1).
Nematode population parameters such as number of females, number of eggs, and egg masses are calculated for 5 gram of root sample collected from Guava plants treated with plant growth regulators in single and in combinations of two and three. A reduction in the number of egg masses was noted from 45th day to 105th day. The highest reduction in egg masses was observed in T3 plants treated with IBA at a concentration of 1,000 ppm. When the plant growth regulators were used in combination (T5, T6, T7), SA + IBA showed a high percentage of reduction in egg mass.
The highest reduction in egg mass was noted in T4 (SA + JA + IBA) combination. The results of T8, T9, and T10 indicated an increase in egg masses. The highest increase was noted in T8 compared to T9 and T10 (Table 1).
Reduction in the female nematode population was noted in T3 in single plant growth regulator treatments and T7 in combined plant growth regulator treatments. Subsequently, an increase in the female population was noted in T8, T9, and T10. The analysis of eggs per egg masses showed that Salicylic acid reduced the number of egg per egg masses, while T2 and T3 resulted in an increased number of eggs/egg mass. The treatments T5, T6, T7, T8, and T9 showed an increase in the number of eggs per egg mass (Table 1).
All biocontrol agents significantly reduced the nematode population both in soil and plant roots compared to the untreated control. In total, 10 guava plants infested with the root-knot nematode,
A high percentage of reduction in nematode population was noted in the plants treated
Effect of biocontrol agents in guava (Lucknow-49) infested with root knot nematode,
Nematode population in 200cc of soil | ||||||||
---|---|---|---|---|---|---|---|---|
Treatments | Initial population | 30 days | 60 days | 90 days | 120 days | 150 days | 180 days | 210 days |
Experiment-1 | ||||||||
|
189.32b | 180.46b (4.68) | 171.24a (9.55) | 162.87c (13.97) | 151.58a (19.93) | 140.32b (25.88) | 131.25b (30.67) | 123.87c (34.57) |
|
196.45bc | 190.09bc (3.24) | 183.26b (6.71) | 172.59b (12.15) | 163.34b (16.85) | 154.16d (21.53) | 140.42c (28.52) | 131.52d (33.05) |
|
177.78a | 169.21a (4.82) | 160.53a (9.70) | 155.65cd (12.45) | 151.68a (14.68) | 145.67c (18.06) | 137.67bc (22.56) | 122.74c (30.96) |
|
247.54d | 210.78d (14.85) | 188.39bc (23.90) | 174.87e (29.36) | 153.65a (37.93) | 132.82a (46.34) | 101.34a (59.06) | 86.87a (64.91) |
|
255.25d | 224.45e (12.07) | 190.23bc (25.47) | 188.54d (26.14) | 169.19bc (33.72) | 153.46d (39.88) | 129.87b (49.12) | 94.48b (62.99) |
|
201.23c | 193.84c (3.67) | 188.41bc (6.37) | 179.98f (10.56) | 174.34c (13.36) | 168.28e (16.37) | 163.56d (18.72) | 159.29e (20.84) |
Untreated control | 196.32bc | 197.87c (0.78) | 198.65c (1.17) | 199.83a (1.76) | 204.25d (3.88) | 207.58f (5.42) | 210.71e (6.83) | 229.45f (14.44) |
Experiment-2 | ||||||||
|
285.36b | 262.87b (7.88) | 248.54c (12.90) | 220.83c (22.61) | 199.18b (30.20) | 172.37b (39.60) | 158.43c (44.48) | 141.84c (50.29) |
|
278.48ab | 257.64b (7.48) | 249.25c (10.50) | 224.84c (19.26) | 201.13b (27.78) | 184.23b (33.84) | 165.87d (40.44) | 150.62c (45.91) |
|
300.97c | 289.13c (3.93) | 270.24d (10.21) | 258.45d (14.13) | 237.78c (21.00) | 219.55c (27.05) | 196.60e (34.68) | 173.75d (42.27) |
|
269.35a | 230.92a (14.27) | 200.45a (25.58) | 180.06a (33.15) | 157.36a (41.58) | 132.48a (50.81) | 98.09a (63.58) | 64.28a (76.14) |
|
280.42ab | 259.58b (7.43) | 215.26b (23.24) | 194.64b (30.59) | 165.92a (40.83) | 140.47a (49.91) | 112.64b (59.83) | 79.85b (71.52) |
|
300.97d | 289.13d (3.93) | 270.24e (10.21) | 258.45d (14.13) | 237.78c (21.00) | 219.55c (27.05) | 196.60f (34.68) | 173.75e (42.27) |
Untreated control | 278.97ab | 285.52c (2.29) | 290.48e (3.96) | 296.31e (5.85) | 298.52d (6.55) | 301.26d (07.40) | 305.95g (8.82) | 308.72f (9.64) |
The analysis of the plant roots in 0, 30, 90, 150, and 210 days after the application of biocontrol agents showed that
The untreated control plants showed a increase trend for the same parameters tested, i.e. the number of egg masses increased from 16.94 to 23.48 egg masses/5g of the root, similarly increase in female population from 29.26 to 36.42 females was observed. The number of eggs per egg mass increased from 158.23 to 175.53 in Experiments I and II (Table 3).
Effect of biocontrol agents in guava (Lucknow-49) infested with root knot nematode,
Nematode population in roots (5g) | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
No of egg masses (days) | No of females (days) | No of eggs/egg masses (days) | |||||||||||||
Treatments | 00 | 30 | 90 | 150 | 210 | 00 | 30 | 90 | 150 | 210 | 00 | 30 | 90 | 150 | 210 |
Experiment-1 | |||||||||||||||
|
17.32b | 13.45a (22.34) | 11.89c (31.35) | 09.83c (43.24) | 07.39b (57.33) | 30.48a | 22.23b (27.07) | 19.23c (36.91) | 16.52c (45.80) | 13.66b (55.18) | 149.98a | 145.65a (2.89) | 141.42a (5.71) | 138.43b (7.70) | 135.32b (9.77) |
|
19.54d | 15.68d (19.75) | 12.32cd (36.95) | 10.42c (46.67) | 09.26c (52.61) | 29.19a | 25.12c (13.94) | 22.74d (22.10) | 20.34d (30.32) | 17.51c (40.01) | 172.38d | 160.54c (6.87) | 154.57bc (10.33) | 151.63c (12.04) | 148.07c (14.10) |
|
16.38a | 14.56b (11.11) | 12.63d (22.89) | 10.35c (36.81) | 09.34c (42.98) | 34.52c | 30.09d (12.83) | 25.82e (25.20) | 21.84e (36.73) | 18.48d (46.47) | 163.34bc | 160.94c (1.47) | 157.32c (3.69) | 154.81c (5.22) | 152.29c (6.77) |
|
18.37c | 14.84bc (19.22) | 10.95b (40.39) | 04.64a (74.74) | 02.86a (84.43) | 34.87c | 21.32ab (38.86) | 14.09b (59.59) | 07.56a (78.32) | 03.98a (88.59) | 163.87bc | 152.42b (6.99) | 140.75a (14.11) | 129.43a (21.02) | 115.35a (29.61) |
|
19.65d | 15.26cd (22.34) | 10.12a (48.50) | 05.64b (71.30) | 02.85a (85.50) | 32.35b | 20.54a (36.51) | 12.45a (61.51) | 09.39b (70.97) | 04.54a (85.97) | 159.56b | 151.5ab 8(5.00) | 145.39ab (8.88) | 136.24ab (14.62) | 129.48b (18.85) |
|
20.46e | 18.23e (10.90) | 16.43e (19.70) | 14.65d (28.40) | 12.62d (38.32) | 37.98d | 32.94e (13.27) | 30.64f (19.33) | 26.98f (28.96) | 23.76e (37.44) | 167.67cd | 162.32c (3.19) | 158.24cd (5.62) | 155.85c (7.05) | 153.68c (8.34) |
Untreated control | 16.94ab | 19.56f (13.39) | 21.65f (21.76) | 22.32e (24.10) | 23.48e (27.85) | 29.26a | 30.29d (3.40) | 32.38g (9.64) | 35.63g (17.88) | 36.42f (19.66) | 158.23b | 164.09c (3.57) | 167.83d (5.72) | 171.34d (7.65) | 175.53d (9.86) |
Experiment-2 | |||||||||||||||
|
21.24bc | 16.20b (23.73) | 12.57b (40.82) | 08.90b (58.10) | 06.41b (69.82) | 30.38ab | 22.08ab (27.32) | 19.81b (34.79) | 14.61c (51.91) | 10.64c (64.98) | 163.42ab | 155.45ab (4.88) | 151.73b (7.15) | 144.24b (11.74) | 135.54b (17.06) |
|
22.89e | 18.34c (19.88) | 15.78d (31.06) | 12.06c (47.31) | 07.59c (66.84) | 36.87d | 28.46d (22.81) | 20.24bc (45.10) | 16.35d (55.66) | 11.73d (68.19) | 172.76c | 163.31cd (5.47) | 152.85b (11.52) | 139.68b (19.15) | 132.36b (23.39) |
|
20.45a | 17.81c (12.91) | 13.69c (33.06) | 11.51c (43.72) | 08.34d (59.22) | 30.37ab | 24.34c (19.86) | 20.92c (31.12) | 16.09d (47.02) | 12.44e (59.04) | 165.62bc | 161.45bc (2.52) | 156.43b (5.55) | 150.53c (9.11) | 147.62c (10.87) |
|
21.68cd | 14.50a (33.12) | 10.80a (50.18) | 05.84a (73.06) | 02.57a (88.15) | 29.35a | 20.78a (29.20) | 14.28a (51.35) | 09.52a (67.56) | 04.94a (83.17) | 157.47a | 149.39a (5.13) | 138.65a (11.95) | 129.04a (18.05) | 123.50a (21.57) |
|
22.24d | 16.20b (27.16) | 13.57c (38.98) | 08.90b (59.98) | 03.41c (84.66) | 31.38bc | 23.08bc (26.45) | 19.81b (36.87) | 10.61b (66.19) | 08.64b (72.47) | 167.42bc | 162.45cd (2.97) | 154.73b (7.58) | 142.24b (15.04) | 131.54b (21.43) |
|
20.89ab | 19.34d (7.42) | 16.78e (19.67) | 13.06d (37.48) | 11.59e (44.52) | 31.87c | 28.46d (10.70) | 25.24d (20.80) | 22.35e (29.87) | 19.73f (38.09) | 170.78bc | 168.78de (1.17) | 165.85c (2.89) | 161.68d (5.33) | 155.36d (9.03) |
Untreated control | 23.72f | 26.43e (10.25) | 29.26f (18.93) | 32.02e (25.92) | 34.56f (31.37) | 35.46d | 37.82e (6.24) | 40.24e (11.88) | 43.52f (18.52) | 45.68g (22.37) | 171.76c | 172.31e (0.32) | 176.54d (2.71) | 178.34e (3.69) | 179.54e (4.33) |
All the plants treated with commercial biocontrol agents at regular intervals during the year 2018 significantly enhanced the plant growth and yield of guava plants under natural field conditions. Application of
Field observations on application of different biocontrol agents.
Effect of biocontrol agents on Plant growth parameters of guava cv. Lucknow-49 challenged with root knot nematode,
Yield parameters | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
At vegetative stage | At fruiting stage | |||||||||||
Treatments | Tree height (m) | Girth of stem (cm) | Leaf area (cm2) | Tree height (m) | Girth of stem (cm) | Leaf area (cm2) | No. of fruits/tree (nos) | Fruit length (cm) | Shoots diameter (cm) | Average fruit weight (g) | Fruit yield/tree (kg tree
|
Fruit yield t/ha |
Experiment-1 | ||||||||||||
|
1.36b | 12.29b | 74.12b | 1.74b | 12.41b | 74.24b | 40.00b | 7.41b | 8.22bc | 278.12b | 11.12c | 10.91c |
|
1.34bc | 12.00b | 72.67bc | 1.72b | 12.14b | 72.77b | 39.60b | 7.30bc | 8.09cd | 264.00bc | 10.45d | 10.25d |
|
1.29cd | 11.42c | 70.00c | 1.68bc | 11.56c | 70.11bc | 38.40bc | 7.11bc | 7.93d | 259.00c | 9.95e | 9.76e |
|
1.80a | 16.00a | 82.10a | 2.14a | 16.19a | 82.24a | 45.20a | 8.68a | 8.59a | 336.20a | 15.20a | 14.91a |
|
1.78a | 15.91a | 79.27a | 2.11a | 16.04a | 79.39a | 43.60a | 8.61a | 8.47ab | 321.10a | 14.00b | 13.73b |
|
1.24de | 11.26cd | 66.21d | 1.59c | 11.40cd | 66.32cd | 37.10c | 6.89c | 7.62e | 231.00d | 8.57f | 8.41f |
Untreated control | 1.19e | 10.84d | 64.00d | 1.43d | 11.00d | 64.10d | 34.10d | 6.20d | 7.36e | 165.00e | 5.63g | 5.52g |
Experiment-2 | ||||||||||||
|
1.44b | 12.38b | 75.31b | 1.89c | 12.45b | 75.54b | 37.16c | 7.36b | 8.44ab | 261.06b | 9.70c | 9.52c |
|
1.39bc | 12.17bc | 74.70b | 1.83c | 12.24bc | 75.09b | 34.37d | 7.31bc | 8.35b | 239.14c | 8.22d | 8.06d |
|
1.32cd | 11.61cd | 68.84c | 1.71d | 11.67cd | 70.05c | 32.04e | 7.08c | 8.31bc | 259.00b | 8.30d | 8.14d |
|
1.86a | 16.18a | 82.07a | 2.49a | 16.29a | 82.25a | 43.02a | 8.43a | 8.69a | 310.40a | 13.35a | 13.10a |
|
1.81a | 16.02a | 80.89a | 2.28b | 16.17a | 81.16a | 41.01b | 8.39a | 8.63a | 304.20a | 12.48b | 12.24b |
|
1.28de | 11.39d | 63.13d | 1.60e | 11.44d | 65.17d | 30.03f | 6.72d | 8.29c | 220.03d | 6.61e | 6.48e |
Untreated control | 1.21e | 11.02d | 62.18d | 1.42f | 11.09d | 63.09d | 26.11g | 6.04e | 8.23d | 149.01e | 3.89f | 3.82f |
Further, this study showed that treating the
Current study results showed that the application of plant growth regulators in combination increased plant growth parameters of Lucknow-49, Guava plants and resulted in producing enormous new root proliferation and reduced the nematode infection. Among different treatments, the use of combined plant growth regulators such as Salicylic acid (100 ppm) + Jasmonic acid (100 ppm) + Indole 3-Butyric Acid (1,000 ppm) showed a positive influence on plant height, root length, root number, and promoted the formation of the tertiary roots. Previous studies on these plant growth regulators such as Salicylic acid and Jasmonic acid-enhanced plant resistance against plant parasitic-nematodes (Charehgani et al., 2014; Oka et al., 1999). Salicylic acid played its role in enhancing the physiological plant defence responses against plant pathogens through systemic acquired resistance (Molinari and Baser, 2010).
Results from glasshouse showed that the application of salicylic acid, Jasmonic acid and Indole 3-Butyric Acid at specific combination increased the activity of total phenols, peroxidase, polyphenol oxidase, acid phosphatase, and phenylalanine ammonia-lyase at different intervals. Such an increase in biochemical compounds enhanced the development of resistance against root-knot nematodes. The rise in biochemical compounds may be due to the rapid breakdown of bound phenols leading to the formation of lignin that offers resistance to nematodes. The enzyme peroxidase plays a significant role in the defence mechanism, catalyzes the process of condensation phenols into lignin leading to a hypersensitive reaction and an activated resistance against the invading pathogen (Dignum et al., 2001). In general, an increase in peroxidase activity at the later stages of the infection process activates the free radicals that inhibit the activities of the pathogen (Hammerschmidt et al., 1982).
Acid phosphatase is an enzyme closely linked with the Mi gene, confers resistance against root-knot nematodes (Williamson and Colwell, 1991). It catalyzes the process of hydrolysis of inorganic phosphates from phosphomonoesters at reduced pH level and offers resistance to plants against nematodes. Increased Phenylalanine ammonia-lyase enzyme induces the activation of defence compound, trans-cinnamic acid and initiates the lignin biosynthetic pathway involved in the resistance against nematodes (Brueske, 1980).
Soil is home to still unknown organisms with antagonistic potential (Sikora et al., 2003). Many of these organisms are responsible for the reduced nematode infestation (Sikora et al., 2003). Based on this concept, several biocontrol agents were developed and used as root-knot nematode controlling agents. For example, the egg-parasitic fungi
In India, Lucknow 49 Guava is a popular and widely cultivated variety grown as a commercial crop. It is highly susceptible to nematode infestation and causing an economic loss at nurseries and in the established orchards of Tamil Nadu. Management practices are insignificant to control the nematodes. The nematode
For the standing Guava crop, the application of
Further, this study suggests that treating the guava seedlings with plant growth regulators before transplantation reduced the