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Full Research Article

Impact of Antixenotic Mechanism of Mungbean on the Incidence of Thrips (Megalurothrips sp.) and Aphid (Aphis cacccivora) in the Gangetic Plains of West Bengal

N
Neha Mahato1
S
Soumita Bera1
S
Sabyasachi Ray1
S
Snigdha Samanta2
S
Srijani Maji3
A
Arpita Das4
A
Amitava Banerjee3,*
1Department of Agricultural Entomology, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.
2School of Smart Agriculture, Adamas University, Barasat, Kolkata-700 126, West Bengal, India.
3All India Coordinated Research Projects on Mungbean, Urdbean, Lentil, Lathyrus, Rajmash, and Fieldpea, Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.
4Department of Genetics and Plant Breeding, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.

  • Submitted13-09-2025|

  • Accepted18-02-2026|

  • First Online 13-03-2026|

  • doi 10.18805/LR-5568

ABSTRACT

Background: At every stage of crop cycle, from seedling to storage, insect pests attack green gram or mungbean (Vigna radiata L.), the third most important pulse crop in India following chickpea and pigeonpea and severely reduce crop productivity. This situation along with the increased use of toxic chemicals for their management prompts the researchers to divert their efforts to Integrated Pest Management (IPM) which includes the use of resistant varieties. Specific genotype of any crop bears distinguished biophysical and biochemical parameters which have definite impact on the occurrence and distribution of pests of pulse crops. In this context, an experiment was undertaken on five germplasms of green gram viz. BCM 20-46, BCM 20-47, BCM 21-133, Sukumar and Virat to study the impact of crop morphology on the incidence of key insect pests attacking mungbean.

Methods: The present study has been carried out at District Seed Farm (AB Block) of BCKV Mohanpur, Kalyani, Nadia, West Bengal during pre-kharif season of 2022 and 2023. Statistical design followed was RBD, with 4 replications and 5 germplasms as treatments.

Result: Major insect pests recorded during the investigation were aphid, thrips, spotted pod borer and gram pod borer. Among them thrips and aphid played vital role. Incidence of flower thrips was significantly and negatively correlated with trichome density on leaf and pod along with plant height, whereas total no. of pods and primary branches exhibited significant positive correlation. Similarly, significant negative associations were observed between aphid infestation and trichome density on leaf and pod; total number of pods; and plant height, whereas total number of primary branches was positively and significantly correlated. Regression studies revealed that, total number of primary branches and trichome density on leaf described flower thrips population up to 85% and 86% during 2022 and 2023, respectively.  While, in case of aphid infestation, trichome density on leaf and on pod exhibited most influence up to 85% and 81% during the same, respectively.

INTRODUCTION

Greengram [Vigna radiata (L.) Wilczek] is one of the most extensively grown leguminous, versatile and drought resistant pulse crops of India. It is also considered as “Golden Bean” because of its nutritive values and ability to increase soil fertilty by adding nitrogen to the soil. It is primarily a kharif season crop but with the development of early maturing varieties, it has also proved to be an ideal crop for spring and summer seasons (Dhakal et al., 2016; Raghu et al., 2016; Sowmya et al., 2023). Production of mungbean in India was 3.10 million tonnes, during 2024 from an area of 5.19 million ha with a productivity of 598 kg/ ha (Pratap, 2025). Like other crops, green gram also suffers from different production constraints. Among them, biotic stress is an important factor. Insect pests infest mungbean in all stages of crop cycle from seedling to maturity, which can lead to heavy losses in crop productivity. While some insect pests cause direct crop harm, others serve as disease vectors that spread viruses. Whitefly, aphid, thrips, stem fly, spotted pod borer, gram pod borer and bruchids are recognized as the major pests of green gram worldwide (Panda and Raju, 1972; Chhabra et al., 1979; Chiang and Talekar, 1980; Prakit et al., 2007; Zahid et al., 2008; Singh et al., 2017). Reliance on synthetic pesticides for pest management has led to challenges such as insecticide resistance, environmental concerns and adverse effect on non-target organisms, highlighting the need for sustainable alternatives. Among these, host plant resistance offers a promising and eco-friendly strategy for reducing pest pressure. Specific crop genotypes possess distinct biophysical and biochemical traits and earlier studies confirm that these factors significantly influence pest occurrence and distribution in pulse crops (Hossain et al., 2008; Girija et al., 2008; Haralu et al., 2018; Golla et al., 2018). The information regarding the effect of crop morphology (biophysical factors) on the abundance of insect pests associated with green gram is scarce and understanding these relationships is essential for developing resistant varieties. In this context, an experiment has been planned in the lower Gangetic plains of West Bengal to evaluate the antixenotic effect of green gram on flower thrips and aphid and to figure out the sources of resistance among the tested green gram germplasms.

MATERIALS AND METHODS

The field experiment was carried out at District Seed Farm (AB Block) of Bidhan Chandra Krishi Viswavidyalaya, Kalyani, Nadia, West Bengal (Latitude: 22o87’N, Longitude: 88o20’E), during two consecutive pre-kharif seasons of the year 2022 and 2023. Five gremplasms of green gram were taken, of which Sukumar and Virat were popular varieties of the zone and BCM 20-46, BCM 20-47 and BCM 21-133 were advanced lines. The study was conducted in an experimental setup following randomized block design (RBD) involving five treatments with four replications. Observations were recorded starting three weeks post-sowing at weekly intervals upto crop maturity. Five plants were randomly selected per plot. For counting thrips, ten flowers per plant were tapped on white paper and the number of thrips was counted. Population of aphid was recorded by visual counting method. The total number of adults (both alate and apterous forms) and nymphs of aphid were counted from 10 cm apical twigs. A hand-held magnifying lens (10x) was used to count the insects in the field. Aspirator was used to collect necessary sample insects for further identification. Mean population was worked out in case of both the insects.
       
In this study, different morphological parameters were considered to evaluate antixenotic mechanism of mungbean against incidence of insect pests. Trichome density on leaf was assessed by collecting uniformly developed leaflets from three sample plants of each treatment during the pod developing stage when the pest load was high. From each leaf a bit of 1 mm2 was cut and observed under binocular microscope at 100x magnification and number of trichomes was counted (Karthik and Vastrad, 2018). Same procedure was followed to determine trichome density on pod. Other parameters such as no. of primary branches and plant height were recorded at 50% flowering stage. Pod length and width was measured during maturity and total no. of pods was counted at the time of harvest.
       
The experimental data were analyzed using appropriate statistical methods. Correlation between mean pest population and crop morphological parameters were worked out to find out the effect of the crop morphology on tolerance or susceptibility of different varieties of green gram against flower thrips and aphid. Further multiple step wise linear regression analysis was conducted between incidence of insect pests, per cent pod damage and the above-mentioned morphological parameters (Gomez and Gomez, 1984).

RESULTS AND DISCUSSION

Morphological characterization of different green gram germplasms
 
Trichome density on leaf
 
Number of trichomes per unit area of leaves of different green gram gremplasms differed significantly, ranging from 9.8/ mm2 to 17.6/ mm2 (Table 1). The highest density of trichome was recorded in Sukumar (17.6/ mm2) followed by BCM 20-47 (15.8/ mm2) and BCM 21-133 (15.4/ mm2). Minimum density of trichome on leaf was found in Virat (9.8/ mm2) followed by BCM 20-46 (11.4/ mm2).

Table 1: Morphological parameters of different green gram gremplasms.


 
Trichome density on pod
 
Density of trichomes per unit pod area differed significantly across various germplasms ranging from 11.4/ mm2 to 18.4/ mm2 (Table 1). Maximum density of trichomes on pod was found in Sukumar (18.4/ mm2) followed by BCM 20-47 (15.8/ mm2) and BCM 21-133(14.8/ mm2). Minimum density of trichome on pod was recorded from BCM 20-46 (11.4/ mm2) followed by Virat (13.4/ mm2).
 
Total number of primary branches
 
Gremplasms were significantly differed in number of primary branches ranging from 4.6 to 5.6 (Table 1). Maximum and minimum number of primary branches was observed in Virat (5.6) and Sukumar (4.6), respectively.
 
Plant height
 
Plant height was non-significantly variable across different gremplasms of mungbean ranging from 39.0 cm to 49.0 cm (Table 1). The tallest gremplasms was BCM 20-47 (49.0 cm) followed by Sukumar (48.4 cm) and BCM 21-133 (48.0 cm). Whereas Virat (39.0 cm) and BCM 20-46 (43.0 cm) having medium length.
 
Pod length
 
The significantly highest pod length was recorded from BCM 20-46 (9.18 mm) followed by BCM 20-47 (8.68 mm) and Sukumar (8.42 mm) (Table 1). Minimum pod length was recorded from Virat (6.78 mm) followed by BCM 21-133 (7.78 mm).
 
Pod width
 
Significant variation in pod width was found in different green gram gremplasms ranging from 0.39 mm to 0.53 mm (Table 1). Maximum pod width was found in BCM 21-133 (0.53 mm) followed by BCM 20-46 (0.46 mm), Virat (0.46 mm) and BCM 20-47 (0.45 mm). The shortest pod width was found in Sukumar (0.39 mm).
 
Total no. of pods/ plant
 
Total no. of pods/ plant varied significantly among the tested gremplasms ranging from 7.85 to 9.25 (Table 1). Maximum pod count per plant was observed in Virat (9.25) followed by BCM 20-46 (9.12). Moderate number of pods was present in BCM 21-133 and BCM 20-47 whereas, the lowest number of pods was recorded from Sukumar (7.85).
 
Effect of crop morphology on Megalurothrips sp. population recorded on green gram
 
Effect of different morphological characters of green gram on incidence of Megalurothrips sp. is presented in Table 2. Total no. of primary branches was significantly and positively correlated with flower thrips population in both the years (r = 0.934 and 0.917 during 1st and 2nd year, respectively) which indicates that the pest preferred the gremplasms having dense canopy with more branches. Plant height showed significant negative correlation in both the years of experimentation (r = -0.923 and -0.946 during 1st and 2nd year, respectively) revealing the non-preference of the pest towards taller gremplasms. Pod length exhibited non-significant negative correlation during both the years of experimentation (r = -0.295 and -0.303 during 1st and 2nd year, respectively) which also signifies the less preference of the pests to larger pods. While, pod width exhibited non-significant positive correlation (r = 0.236 and 0.247 during 1st and 2nd year, respectively). Number of trichomes of leaf per unit area exhibited significant negative correlation (r = -0.926 and -0.952 during 1st and 2nd year, respectively) with thrips population. Trichome number on pods per unit area also showed significant negative correlation (r = -0.875 and -0.883) in both the years. Both these results clearly suggest that flower thrips prefers green gram gremplasms having leaves and pods with less trichomes. On the contrary total no. of pods/plant (r = 0.852 and r = 0.868) exhibited significant positive correlation with thrips population which means thrips prefer gremplasms having more pods per plant. According to Tamta and Jha (2021), the lowest incidence of thrips was reported in SSME 21-70 (1.52 thrips/10 flowers) germplasm having highest trichome length (1357µm) and highest trichome density on both upper (193.0 ) and lower surface  (215.6 ) per 5 mm2 followed by SSME 21-53 (1.80) as compared to PM 05 (3.69 thrips/10 flowers) which had the lowest trichome length (918 µm) and lowest trichome density on both upper (104.3) and lower (118.3) surface per 5 mm2. Yasmin et al., (2022) recorded that, thrips population showed significant negative associations with trichome density, the lower incidence was linked to plants having higher trichome density. Revathi and Selvanarayanan (2024) also found that the resistant accession IC-329039-1 exhibited the highest trichome density, followed by the tolerant accession IC-39380, while the susceptible accession IC-103862 showed the lowest density. A negative correlation was observed between trichome density of mungbean and the colonization of M. distalis, another thrips species. These results corroborate the present findings.

Table 2: Correlation of Megalurothrips sp. population with crop morphological parameters.


 
Regression studies among Megalurothrips sp. population and crop morphological parameters
 
The equation found from the multiple step wise linear regression analysis are Y = 1.84 - 0.041X* and Y = 2.28- 0.208X* in 2022 and 2023, respectively (Table 3). The results reveal that thrips population was significantly influenced by different plant morphological characters. Among them, total number of primary branches became the major governing factor on incidence and population of Megalurothrips sp. in 1st season, but in second season trichome density of leaf became the major governing factor for describing thrips population. The regression coefficient (R2) values for the year 2022 and 2023 were 0.85 and 0.86, respectively which indicates that the total number of primary branches and trichome density on leaf described the thrips population up to 85% and 86% during 2022 and 2023, respectively.

Table 3: Multiple step-wise linear regression analysis between population of Megalurothrips sp. and crop morphological traits.


 
Effect of crop morphology on Aphis craccivora population recorded on green gram
 
Effect of different morphological characters of green gram on incidence of Aphis craccivora is presented in Table 4. Total no. of primary branches was significantly and positively correlated with aphid population in both the years (r = 0.898 and 0.907 during 1st and 2nd year, respectively) which indicates that the pest preferred the gremplasms having dense canopy with more branches. Plant height showed significant negative correlation in the both the years (r = -0.896, -0.910 in 2022 and 2023, respectively). Pod length exhibited non-significant negative correlation during both the years (r = -0.012 and -0.005, respectively) while, pod width exhibited non-significant positive correlation (r = 0.132 and 0.174 during 1st and 2nd year, respectively). Number of trichomes on leaf per unit area exhibited significant negative correlation (r = -0.922 and -0.915 during 1st and 2nd year, respectively) with aphid population. Trichome density on pods also significantly and negatively correlated (r = -0.912 and -0.926) in both the years. Total pod count (r = -0.884 and -0.908) also exhibited significant negative correlation with incidence of aphid. All these observations reveal the aphid’s non-preference towards green gram gremplasms having taller height, larger pod, dense trichome density on both leaves and pods.

Table 4: Correlation of Aphis craccivora population with crop morphological parameters.


       
Tamang et al. (2017) recorded that the green gram variety Samrat (PDM 24-139) possessing the lowest trichome density (13.5 and 18.0/ cm2) showed considerably greater aphid incidence during consecutive two cropping seasons. Mulwa et al., (2023) found that among the three conditions, leaf moisture content (R2 0.18) and leaf area (R2 0.32) was positively connected with pest infestation, whereas leaf hair density (R2 0.30) and leaf wall thickness (R2 0.54) were negatively correlated with pod borer and aphid counts. All these earlier findings are in accordance with our results.
 
Regression studies among Aphis craccivora population and crop morphological parameters
 
The equation found in multiple step wise linear regression analysis are Y = 3.49 – 0.115X* and Y= 3.43- 0.009X* in 2022 and 2023, respectively (Table 5). The results reveal that aphid population was significantly influenced by different plant morphological characters. Among the different morphological characters, trichome density on leaf became the major governing factor on incidence of Aphis craccivora in 1st year, but in second year trichome density on pod became the major governing factor. The regression coefficient (R²) values were 0.85 and 0.81 which indicates that the trichome density on leaf and trichome density on pod described the aphid population up to 85% and 81% during 2022 and 2023, respectively.

Table 5: Multiple step-wise linear regression analysis between population of Aphis craccivora and crop morphological traits.

CONCLUSION

From this experiment, it can be concluded that trichome density on leaves and pods showed significant negative correlations with the populations of thrips and aphids, indicating that these pests prefer green gram gremplasms with less trichomes like, Virat and BCM 20-46. Influence of pod length on thrips and aphid population was non-significant and negative which also signifies the less preference of the pests to larger pods whereas, it was non-significant and positive in case of pod width. Gremplasms having more branches and dense canopy like Virat and BCM 20-46 showed highly positive effect on load of both the pests. The population build-up of thrips and aphid was negatively influenced by plant height and gremplasms with medium stature, such as Virat and BCM 20-46, were more susceptible to infestation while, taller gremplasms like, Sukumar and BCM 20-47 were less preferred. Total pod count exhibited significant positive correlation with thrips population and in contrast, it showed significant negative correlation with aphid population. Aphid prefer the gremplasms having more number of pods like Virat and BCM 20-46. Overall, both pests tend to avoid green gram gremplasms characterized by taller plant height, larger pods and dense trichome coverage on leaves and pods. Among all the studied morphological traits, total number of primary branches and trichome density on leaf were the major influencing factor in case of thirps during 2022 and 2023, respectively, while, in case of aphid, trichome density on leaf and trichome density on pod were the major governing factors during the same. The morphological characters of green gram specially trichome density on leaves and pods which showed the non-preference of pests particularly thrips and aphid may act as an important tool for the green gram breeders to develop pest resistant varieties where the gremplasms like Sukumar and BCM 20-47 may play vital role.

ACKNOWLEDGEMENT

The authors express their sincere gratitude to the teaching and non-teaching staff of the AICRP on MULLaRP, Mohanpur Centre, BCKV, for their support and cooperation throughout the study.
 
Disclaimer
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

CONFLICT OF INTEREST

The authors declare that there are no conflicts of interest regarding the publication of this article.

REFERENCES


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    Full Research Article

    Impact of Antixenotic Mechanism of Mungbean on the Incidence of Thrips (Megalurothrips sp.) and Aphid (Aphis cacccivora) in the Gangetic Plains of West Bengal

    N
    Neha Mahato1
    S
    Soumita Bera1
    S
    Sabyasachi Ray1
    S
    Snigdha Samanta2
    S
    Srijani Maji3
    A
    Arpita Das4
    A
    Amitava Banerjee3,*
    1Department of Agricultural Entomology, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.
    2School of Smart Agriculture, Adamas University, Barasat, Kolkata-700 126, West Bengal, India.
    3All India Coordinated Research Projects on Mungbean, Urdbean, Lentil, Lathyrus, Rajmash, and Fieldpea, Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.
    4Department of Genetics and Plant Breeding, Bidhan Chandra Krishi Viswavidyalaya, Nadia-741 252, West Bengal, India.

    • Submitted13-09-2025|

    • Accepted18-02-2026|

    • First Online 13-03-2026|

    • doi 10.18805/LR-5568

    ABSTRACT

    Background: At every stage of crop cycle, from seedling to storage, insect pests attack green gram or mungbean (Vigna radiata L.), the third most important pulse crop in India following chickpea and pigeonpea and severely reduce crop productivity. This situation along with the increased use of toxic chemicals for their management prompts the researchers to divert their efforts to Integrated Pest Management (IPM) which includes the use of resistant varieties. Specific genotype of any crop bears distinguished biophysical and biochemical parameters which have definite impact on the occurrence and distribution of pests of pulse crops. In this context, an experiment was undertaken on five germplasms of green gram viz. BCM 20-46, BCM 20-47, BCM 21-133, Sukumar and Virat to study the impact of crop morphology on the incidence of key insect pests attacking mungbean.

    Methods: The present study has been carried out at District Seed Farm (AB Block) of BCKV Mohanpur, Kalyani, Nadia, West Bengal during pre-kharif season of 2022 and 2023. Statistical design followed was RBD, with 4 replications and 5 germplasms as treatments.

    Result: Major insect pests recorded during the investigation were aphid, thrips, spotted pod borer and gram pod borer. Among them thrips and aphid played vital role. Incidence of flower thrips was significantly and negatively correlated with trichome density on leaf and pod along with plant height, whereas total no. of pods and primary branches exhibited significant positive correlation. Similarly, significant negative associations were observed between aphid infestation and trichome density on leaf and pod; total number of pods; and plant height, whereas total number of primary branches was positively and significantly correlated. Regression studies revealed that, total number of primary branches and trichome density on leaf described flower thrips population up to 85% and 86% during 2022 and 2023, respectively.  While, in case of aphid infestation, trichome density on leaf and on pod exhibited most influence up to 85% and 81% during the same, respectively.

    INTRODUCTION

    Greengram [Vigna radiata (L.) Wilczek] is one of the most extensively grown leguminous, versatile and drought resistant pulse crops of India. It is also considered as “Golden Bean” because of its nutritive values and ability to increase soil fertilty by adding nitrogen to the soil. It is primarily a kharif season crop but with the development of early maturing varieties, it has also proved to be an ideal crop for spring and summer seasons (Dhakal et al., 2016; Raghu et al., 2016; Sowmya et al., 2023). Production of mungbean in India was 3.10 million tonnes, during 2024 from an area of 5.19 million ha with a productivity of 598 kg/ ha (Pratap, 2025). Like other crops, green gram also suffers from different production constraints. Among them, biotic stress is an important factor. Insect pests infest mungbean in all stages of crop cycle from seedling to maturity, which can lead to heavy losses in crop productivity. While some insect pests cause direct crop harm, others serve as disease vectors that spread viruses. Whitefly, aphid, thrips, stem fly, spotted pod borer, gram pod borer and bruchids are recognized as the major pests of green gram worldwide (Panda and Raju, 1972; Chhabra et al., 1979; Chiang and Talekar, 1980; Prakit et al., 2007; Zahid et al., 2008; Singh et al., 2017). Reliance on synthetic pesticides for pest management has led to challenges such as insecticide resistance, environmental concerns and adverse effect on non-target organisms, highlighting the need for sustainable alternatives. Among these, host plant resistance offers a promising and eco-friendly strategy for reducing pest pressure. Specific crop genotypes possess distinct biophysical and biochemical traits and earlier studies confirm that these factors significantly influence pest occurrence and distribution in pulse crops (Hossain et al., 2008; Girija et al., 2008; Haralu et al., 2018; Golla et al., 2018). The information regarding the effect of crop morphology (biophysical factors) on the abundance of insect pests associated with green gram is scarce and understanding these relationships is essential for developing resistant varieties. In this context, an experiment has been planned in the lower Gangetic plains of West Bengal to evaluate the antixenotic effect of green gram on flower thrips and aphid and to figure out the sources of resistance among the tested green gram germplasms.

    MATERIALS AND METHODS

    The field experiment was carried out at District Seed Farm (AB Block) of Bidhan Chandra Krishi Viswavidyalaya, Kalyani, Nadia, West Bengal (Latitude: 22o87’N, Longitude: 88o20’E), during two consecutive pre-kharif seasons of the year 2022 and 2023. Five gremplasms of green gram were taken, of which Sukumar and Virat were popular varieties of the zone and BCM 20-46, BCM 20-47 and BCM 21-133 were advanced lines. The study was conducted in an experimental setup following randomized block design (RBD) involving five treatments with four replications. Observations were recorded starting three weeks post-sowing at weekly intervals upto crop maturity. Five plants were randomly selected per plot. For counting thrips, ten flowers per plant were tapped on white paper and the number of thrips was counted. Population of aphid was recorded by visual counting method. The total number of adults (both alate and apterous forms) and nymphs of aphid were counted from 10 cm apical twigs. A hand-held magnifying lens (10x) was used to count the insects in the field. Aspirator was used to collect necessary sample insects for further identification. Mean population was worked out in case of both the insects.
           
    In this study, different morphological parameters were considered to evaluate antixenotic mechanism of mungbean against incidence of insect pests. Trichome density on leaf was assessed by collecting uniformly developed leaflets from three sample plants of each treatment during the pod developing stage when the pest load was high. From each leaf a bit of 1 mm2 was cut and observed under binocular microscope at 100x magnification and number of trichomes was counted (Karthik and Vastrad, 2018). Same procedure was followed to determine trichome density on pod. Other parameters such as no. of primary branches and plant height were recorded at 50% flowering stage. Pod length and width was measured during maturity and total no. of pods was counted at the time of harvest.
           
    The experimental data were analyzed using appropriate statistical methods. Correlation between mean pest population and crop morphological parameters were worked out to find out the effect of the crop morphology on tolerance or susceptibility of different varieties of green gram against flower thrips and aphid. Further multiple step wise linear regression analysis was conducted between incidence of insect pests, per cent pod damage and the above-mentioned morphological parameters (Gomez and Gomez, 1984).

    RESULTS AND DISCUSSION

    Morphological characterization of different green gram germplasms
     
    Trichome density on leaf
     
    Number of trichomes per unit area of leaves of different green gram gremplasms differed significantly, ranging from 9.8/ mm2 to 17.6/ mm2 (Table 1). The highest density of trichome was recorded in Sukumar (17.6/ mm2) followed by BCM 20-47 (15.8/ mm2) and BCM 21-133 (15.4/ mm2). Minimum density of trichome on leaf was found in Virat (9.8/ mm2) followed by BCM 20-46 (11.4/ mm2).

    Table 1: Morphological parameters of different green gram gremplasms.


     
    Trichome density on pod
     
    Density of trichomes per unit pod area differed significantly across various germplasms ranging from 11.4/ mm2 to 18.4/ mm2 (Table 1). Maximum density of trichomes on pod was found in Sukumar (18.4/ mm2) followed by BCM 20-47 (15.8/ mm2) and BCM 21-133(14.8/ mm2). Minimum density of trichome on pod was recorded from BCM 20-46 (11.4/ mm2) followed by Virat (13.4/ mm2).
     
    Total number of primary branches
     
    Gremplasms were significantly differed in number of primary branches ranging from 4.6 to 5.6 (Table 1). Maximum and minimum number of primary branches was observed in Virat (5.6) and Sukumar (4.6), respectively.
     
    Plant height
     
    Plant height was non-significantly variable across different gremplasms of mungbean ranging from 39.0 cm to 49.0 cm (Table 1). The tallest gremplasms was BCM 20-47 (49.0 cm) followed by Sukumar (48.4 cm) and BCM 21-133 (48.0 cm). Whereas Virat (39.0 cm) and BCM 20-46 (43.0 cm) having medium length.
     
    Pod length
     
    The significantly highest pod length was recorded from BCM 20-46 (9.18 mm) followed by BCM 20-47 (8.68 mm) and Sukumar (8.42 mm) (Table 1). Minimum pod length was recorded from Virat (6.78 mm) followed by BCM 21-133 (7.78 mm).
     
    Pod width
     
    Significant variation in pod width was found in different green gram gremplasms ranging from 0.39 mm to 0.53 mm (Table 1). Maximum pod width was found in BCM 21-133 (0.53 mm) followed by BCM 20-46 (0.46 mm), Virat (0.46 mm) and BCM 20-47 (0.45 mm). The shortest pod width was found in Sukumar (0.39 mm).
     
    Total no. of pods/ plant
     
    Total no. of pods/ plant varied significantly among the tested gremplasms ranging from 7.85 to 9.25 (Table 1). Maximum pod count per plant was observed in Virat (9.25) followed by BCM 20-46 (9.12). Moderate number of pods was present in BCM 21-133 and BCM 20-47 whereas, the lowest number of pods was recorded from Sukumar (7.85).
     
    Effect of crop morphology on Megalurothrips sp. population recorded on green gram
     
    Effect of different morphological characters of green gram on incidence of Megalurothrips sp. is presented in Table 2. Total no. of primary branches was significantly and positively correlated with flower thrips population in both the years (r = 0.934 and 0.917 during 1st and 2nd year, respectively) which indicates that the pest preferred the gremplasms having dense canopy with more branches. Plant height showed significant negative correlation in both the years of experimentation (r = -0.923 and -0.946 during 1st and 2nd year, respectively) revealing the non-preference of the pest towards taller gremplasms. Pod length exhibited non-significant negative correlation during both the years of experimentation (r = -0.295 and -0.303 during 1st and 2nd year, respectively) which also signifies the less preference of the pests to larger pods. While, pod width exhibited non-significant positive correlation (r = 0.236 and 0.247 during 1st and 2nd year, respectively). Number of trichomes of leaf per unit area exhibited significant negative correlation (r = -0.926 and -0.952 during 1st and 2nd year, respectively) with thrips population. Trichome number on pods per unit area also showed significant negative correlation (r = -0.875 and -0.883) in both the years. Both these results clearly suggest that flower thrips prefers green gram gremplasms having leaves and pods with less trichomes. On the contrary total no. of pods/plant (r = 0.852 and r = 0.868) exhibited significant positive correlation with thrips population which means thrips prefer gremplasms having more pods per plant. According to Tamta and Jha (2021), the lowest incidence of thrips was reported in SSME 21-70 (1.52 thrips/10 flowers) germplasm having highest trichome length (1357µm) and highest trichome density on both upper (193.0 ) and lower surface  (215.6 ) per 5 mm2 followed by SSME 21-53 (1.80) as compared to PM 05 (3.69 thrips/10 flowers) which had the lowest trichome length (918 µm) and lowest trichome density on both upper (104.3) and lower (118.3) surface per 5 mm2. Yasmin et al., (2022) recorded that, thrips population showed significant negative associations with trichome density, the lower incidence was linked to plants having higher trichome density. Revathi and Selvanarayanan (2024) also found that the resistant accession IC-329039-1 exhibited the highest trichome density, followed by the tolerant accession IC-39380, while the susceptible accession IC-103862 showed the lowest density. A negative correlation was observed between trichome density of mungbean and the colonization of M. distalis, another thrips species. These results corroborate the present findings.

    Table 2: Correlation of Megalurothrips sp. population with crop morphological parameters.


     
    Regression studies among Megalurothrips sp. population and crop morphological parameters
     
    The equation found from the multiple step wise linear regression analysis are Y = 1.84 - 0.041X* and Y = 2.28- 0.208X* in 2022 and 2023, respectively (Table 3). The results reveal that thrips population was significantly influenced by different plant morphological characters. Among them, total number of primary branches became the major governing factor on incidence and population of Megalurothrips sp. in 1st season, but in second season trichome density of leaf became the major governing factor for describing thrips population. The regression coefficient (R2) values for the year 2022 and 2023 were 0.85 and 0.86, respectively which indicates that the total number of primary branches and trichome density on leaf described the thrips population up to 85% and 86% during 2022 and 2023, respectively.

    Table 3: Multiple step-wise linear regression analysis between population of Megalurothrips sp. and crop morphological traits.


     
    Effect of crop morphology on Aphis craccivora population recorded on green gram
     
    Effect of different morphological characters of green gram on incidence of Aphis craccivora is presented in Table 4. Total no. of primary branches was significantly and positively correlated with aphid population in both the years (r = 0.898 and 0.907 during 1st and 2nd year, respectively) which indicates that the pest preferred the gremplasms having dense canopy with more branches. Plant height showed significant negative correlation in the both the years (r = -0.896, -0.910 in 2022 and 2023, respectively). Pod length exhibited non-significant negative correlation during both the years (r = -0.012 and -0.005, respectively) while, pod width exhibited non-significant positive correlation (r = 0.132 and 0.174 during 1st and 2nd year, respectively). Number of trichomes on leaf per unit area exhibited significant negative correlation (r = -0.922 and -0.915 during 1st and 2nd year, respectively) with aphid population. Trichome density on pods also significantly and negatively correlated (r = -0.912 and -0.926) in both the years. Total pod count (r = -0.884 and -0.908) also exhibited significant negative correlation with incidence of aphid. All these observations reveal the aphid’s non-preference towards green gram gremplasms having taller height, larger pod, dense trichome density on both leaves and pods.

    Table 4: Correlation of Aphis craccivora population with crop morphological parameters.


           
    Tamang et al. (2017) recorded that the green gram variety Samrat (PDM 24-139) possessing the lowest trichome density (13.5 and 18.0/ cm2) showed considerably greater aphid incidence during consecutive two cropping seasons. Mulwa et al., (2023) found that among the three conditions, leaf moisture content (R2 0.18) and leaf area (R2 0.32) was positively connected with pest infestation, whereas leaf hair density (R2 0.30) and leaf wall thickness (R2 0.54) were negatively correlated with pod borer and aphid counts. All these earlier findings are in accordance with our results.
     
    Regression studies among Aphis craccivora population and crop morphological parameters
     
    The equation found in multiple step wise linear regression analysis are Y = 3.49 – 0.115X* and Y= 3.43- 0.009X* in 2022 and 2023, respectively (Table 5). The results reveal that aphid population was significantly influenced by different plant morphological characters. Among the different morphological characters, trichome density on leaf became the major governing factor on incidence of Aphis craccivora in 1st year, but in second year trichome density on pod became the major governing factor. The regression coefficient (R²) values were 0.85 and 0.81 which indicates that the trichome density on leaf and trichome density on pod described the aphid population up to 85% and 81% during 2022 and 2023, respectively.

    Table 5: Multiple step-wise linear regression analysis between population of Aphis craccivora and crop morphological traits.

    CONCLUSION

    From this experiment, it can be concluded that trichome density on leaves and pods showed significant negative correlations with the populations of thrips and aphids, indicating that these pests prefer green gram gremplasms with less trichomes like, Virat and BCM 20-46. Influence of pod length on thrips and aphid population was non-significant and negative which also signifies the less preference of the pests to larger pods whereas, it was non-significant and positive in case of pod width. Gremplasms having more branches and dense canopy like Virat and BCM 20-46 showed highly positive effect on load of both the pests. The population build-up of thrips and aphid was negatively influenced by plant height and gremplasms with medium stature, such as Virat and BCM 20-46, were more susceptible to infestation while, taller gremplasms like, Sukumar and BCM 20-47 were less preferred. Total pod count exhibited significant positive correlation with thrips population and in contrast, it showed significant negative correlation with aphid population. Aphid prefer the gremplasms having more number of pods like Virat and BCM 20-46. Overall, both pests tend to avoid green gram gremplasms characterized by taller plant height, larger pods and dense trichome coverage on leaves and pods. Among all the studied morphological traits, total number of primary branches and trichome density on leaf were the major influencing factor in case of thirps during 2022 and 2023, respectively, while, in case of aphid, trichome density on leaf and trichome density on pod were the major governing factors during the same. The morphological characters of green gram specially trichome density on leaves and pods which showed the non-preference of pests particularly thrips and aphid may act as an important tool for the green gram breeders to develop pest resistant varieties where the gremplasms like Sukumar and BCM 20-47 may play vital role.

    ACKNOWLEDGEMENT

    The authors express their sincere gratitude to the teaching and non-teaching staff of the AICRP on MULLaRP, Mohanpur Centre, BCKV, for their support and cooperation throughout the study.
     
    Disclaimer
     
    The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

    CONFLICT OF INTEREST

    The authors declare that there are no conflicts of interest regarding the publication of this article.

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