Correlation of biochemical traits with resistance to pod borer infestation in pigeonpea

Introduction

Pigeon pea, [Cajanus cajan (L.) Millspaugh] (2 n = 22) is an important pulse crop mainly grown under rain-fed condition s in the tropics and subtropics. In Asia, Africa and Latin America, pigeon-pea seeds have become the main source of protein especially for the vegetarians. Guandul in Latin America, Gungo peas in the Anglo Caribbean and Congo pea in Sub Saharan Africa are the names given to the pigeon pea (Carney and Rosomoff, 2009) [11] . In India, it is known by a variety of names including arhar, red gram, tur and tomarapayaru (Anonymous,). Pigeon-pea appears to have originated in Peninsular India, with its nearest wild relative (Cajanus cajanifolia) growing in tropical deciduous woodlands (Van der Maeson). Pigeon pea is grown in over 25 tropical and subtropical nations, either as a stand-alone crop or in combination with cereals such as sorghum and maize, or other legumes such as peanuts. Pigeon pea is the most adaptable edible legume, with a wide range of use including food, feed, fodder and fuel. Grain comes in a variety of forms, including green seeds as vegetables and reconstituted dried split seeds. It is a rich source of protein and fulfils a major protein requirement of vegetarian population of the country. It is a major source of dietary protein in South Asian vegetarian civilizations. Pigeon-pea provides 50% of all protein ingested by Indians in some areas (Ryan et al. 1984) [12] . The food value of pigeon-pea is due to its protein content (22.3%) along with iron, iodine and essential amino acids like lysine, cystine arginine, vitamins and minerals. It has better quality of fiber, 7 g/100 g of seeds (Kandhare, 2014) [13] ." A wide range of constraints (abiotic and biotic) are responsible for reduction in productivity of the country's pigeon pea. Among them biotic factors which include insect pests are the most notable threat to the crop's potential yield. The havoc caused by insect pests is critical (Mishra et al. 2012) [14] . Though pigeon pea is inundated by more than 250 species of insect pests belongings to 8 orders and 61 families that appear at various growth stages of the crop in India, only a few of these cause consistent and significant damage to the crop (Lateef and Reed, 1990 and Gopali et al. 2010) [15,16] . Worldwide, over 30 species of Lepidoptera feed on pods and seeds of pigeon pea (Shanower et al. 1999) [17] .

The pod borer complex, which comprises Helicoverpa armigera, Etiella zinckenella and Maruca vitrata, has been identified as a significant threat to pigeon pea crop causing significant losses in grain yield ranging from 30 to 100% by targeting the reproductive sections of the plant. The insect pod borer complex has a significant impact on the production of most pulses. Among these the H. armigera (Hübner) is the major pest in most parts of the country and it has attained the key pest prominence due to its direct attack on fruiting bodies, voracious feeding habits, high mobility, fecundity, multivoltine and overlapping generation with facultative diapauses, nocturnal "bahaviour, migration, host selection and propensity for acquiring resistance against insecticides (Satpute and Sarode, 1995) [18] . It accounts for 90-95% of total damage. A single larva can damage 25-30 pods of gram in its life time. It feeds on tender shoots and young seeds. It makes holes in pods and inserts half of its body inside the pod to eat developing seeds "(Ojha et al. 2017) [19] .

Materials and Methods

Biochemical characters conferring resistance against pod borers in pigeon pea genotypes during kharif 2023-2024 and 2024-2025. For the study of biochemical parameters viz. total nitrogen and total protein contents, total phenols, total soluble sugars, reducing sugar and chlorophyll were estimated on three randomly selected samples from each genotypes (in total 22 genotypes) and data were correlated with the damage of pod borers. "The procedures adopted for the estimation of biochemical parameters are described as under: 1. Total nitrogen content: Nitrogen in plant sample was determined by employing KELPLUS Digestion and Distillation systems as described by Subbiah and Asija (1956). 2. Total protein content: Total protein content was estimated by "Nitrogen-Protein (N: P) conversion factor". Firstly total nitrogen content of each genotype was analyzed by KELPLUS unit by Subbiah and Asija and then the total nitrogen content was multiplied with Nitrogen-Protein (N: P) conversion factor '6.25'.

Total protein content = Total nitrogen × 6.25

Total phenols:

The total phenols present in pods of twenty two pigeon pea genotypes were estimated as per the method developed by Sadasivam and Manickam (1996) [20] .

Total soluble sugar (TSS):

The concentrations of total soluble sugar (TSS) were determined by Anthrone method of Dubois et al. 1951 [21] . 5. Reducing sugar: For the estimation of reducing sugar, the dinitro salicyclic acid method (Miller, 1972) [22] was used.

Chlorophyll extraction protocol given by Arnon, D.I. 1949 was followed.

Results and Discussion

The nitrogen content obtained ranged from 2.18 to 3.19% in the pods of different pigeon pea genotypes. Considerable differences were recorded in the nitrogen content among all the genotypes of pigeon pea tested for the resistance to pod borers. Maximum nitrogen content was recorded in highly susceptible genotype RP5-2016-45 of 3 1). Correlation analysis of nitrogen and protein per cent with per cent pod damage caused by pod borers conferred positively significant with r value 0.781* and 0.782* (Table 2). This indicated s that with the increase in nitrogen and protein per cent, there will be an increase in infestation level too.

The present findings are in coordination with Parre et al.

(2018) [6] , who had reported that the protein content showed positive correlation with percent of pod borer damage (0.8035) indicating that genotypes with more protein content are more susceptible to Helicoverpa infestation. Similarly, Mamta et al. (2023) [4] who also reported that analysis of protein per cent and per cent pod damage caused by pod borers depicted positively and highly significant correlation with r value 0.914*. This indicates that with increase in protein per cent, there will be an increase in the infestation level.

The phenol content showed significant variation among different genotypes of pigeon pea. The total phenol content of different genotypes varied from 2.41 -4.16 mg/g, in the pods of pigeon pea genotypes (Table 1 Correlation studies between phenolic content and total per cent pod damage by pod borers showed highly significant but negative correlation with r value (-0.670*) which clearly shows that high phenol content exhibits critical role in offering resistance to pod borers in field condition (Table 2). The current findings are in accordance with earlier researchers such as, Rashmi et al., (2020) [7] and Tyagi et al.

(2021) [10] who reported that the correlation between the pod damage and phenol content in pods of different genotypes was negative and significant, indicating that increase in phenol content resulted in less pod damage. The present results are in total agreement with the findings of Sahoo and Patnaik (2002) [8] , Anantharaju and Muthiah (2008) [1] , Sharma et al. (2009) [9] , Bommesha et al. (2012) [2] and Jagtap et al. (2012) [3] who had reported that low protein and sugar content and high phenol content in pod coats and seeds were responsible for the resistance of pigeon pea varieties against pod borers. These present results are also in accordance with the findings of Vageesh Pandey et al.

(2011) [5] and Mamta et al. (2023) [4] stating that the genotypes with more phenol content suffered less pod and grain damage by pod fly.

Considerable differences in the TSS among all the tested genotypes of pigeon pea were depicted for the resistance to pod borers and varied from 4.88 to 11.99 mg/g, (Table 1 [6] who reported that the Total sugars (0.8045) i.e., reducing and non-reducing sugars showed positive association with the percent of pod borer damage indicating that genotypes having more sugars are highly preferred by Helicoverpa species. The present results are in agreement with the findings of Mamta et al. (2023) [4] .

Considerable differences in the presence of reducing sugar content were revealed among all the tested genotypes of pigeon pea for the resistance to pod borers and the values varied from 0.43 to 1.24mg/g, as presented in (Table 1). Maximum reducing sugar content was estimated in RP5-2016-45 as 1.24 mg/g followed by RP5-2016-31, RP5-2016-16 and RP5-2016-25 as 1.15, 1.11 and 1.03 mg/g respectively, whereas minimum reducing sugar content was observed in RP5-2016-72 as 0.43 mg/g followed by RP5-2017-16, RP5-2016-44 and RP5-2017-33 as 0.45, 0.46, 0.46 mg/g respectively (Table 1).

Correlation studies between reducing sugar content and total per cent pod damage by pod borers showed significant but positive correlation with r value (0.657*) which clearly shows that high reducing sugar content exhibit critical role in offering resistance to pod borers in field condition (Table 2). The present findings are in match with Parre et al. (2018) [6] who reported that the total sugars (0.8045) i.e., reducing and non-reducing sugars showed positive association with the percent pod borer damage indicating that genotypes having more sugars are highly preferred by Helicoverpa species. Similar findings were also reported by Siva Kumar et al.

(2015) [23] who documented that the correlation between the reducing sugars and pod damage due to pod fly was positive and significant, which indicated that increase in reducing sugar increased the incidence of pest infestation.

5.

Chlorophyll content (mg/g) Significant differences in the chlorophyll content among all the tested genotypes of pigeon pea for resistance to pod borers and varied from 0.14 to 1.11 mg/g, as presented in (Table 1). Maximum chlorophyll content was measured in RP5-2016-72 as 1.11 mg/g followed by RP5-2017-16, RP5-2016-44 and RP5-2016-42 as 1.01, 0.91 and 0.78 mg/g. respectively, whereas minimumchlorophyll content was observed in RP5-2016-45 as 0.14 mg/g followed by RP5-2016-31, RP5-2016-25 and RP5-2016-17 as 0.20, 0.30, 0.33 mg/g respectively. Correlation studies between chlorophyll content and pod damage by pod borers showed highly significant but negative association with r value (-0.742*) which clearly shows that high chlorophyll content exhibits critical role in attracting pod borers and susceptibility in field condition (Table 2). Chlorophyll a and chlorophyll b contents were also estimated separately. Chl. (a) content varied from 0.10 to 0.39 mg/g whereas, Chl. (b) content varied from 0.12 to 0.72 mg/g, as presented in (Table 1). These findings are in agreement with those of Patel et al.

(2015) [24] , who reported that higher chlorophyll levels in pigeon pea pods could attract more oviposition by H. armigera, possibly due to greener pods acting as visual cues or offering a better nutritional substrate. Similarly, Rani and Srivastava (2010) [25] suggested that insect herbivores tend to prefer plant parts with higher chlorophyll content due to enhanced palatability and nitrogen content associated with photo synthetically active tissues. Further, Kumari et al.

(2017) [26] reported that in pigeon pea and chickpea, varieties with darker green foliage were more prone to insect pest attacks, particularly by H. armigera and Spodoptera litura. This observation aligns and agrees with the present results, where genotypes with lower chlorophyll content (such as RP5-2016-45 and RP5-2016-31) exhibited lower pod damage, indicating a potential role of chlorophyll content as a marker trait for tolerance or resistance.

Conclusion

Maximum nitrogen per cent was recorded in RP5-2016-45 (3.19%) while least was recorded in RP5-2017-16 (2.18%). Correlation of nitrogen per cent and per cent pod damage was positively significant (r = 0.781*). Highest protein per cent was recorded in RP5-2016-45 (19.95%) while. least in RP5-2017-16 (13.65%). Correlation analysis of protein per cent and damage caused by pod borers was positively significant (r = 0.782*).

Highest phenol content was determined in genotype RP5-2016-72 (4.16 mg/g), whereas lowest was observed in RP5-2016-31 (2.41 mg/g). Correlation studies between phenolic content and pod damage by pod borers showed significant negative association. (r = -0.670*) Maximum TSS was recorded in susceptible genotype RP5-2016-31 (11.99 mg/g), whereas the least was recorded in moderately resistant genotype RP5-2016-72 (4.88 mg/g).

References

1. Anantharaju P, Muthiah AR. Biochemical basis of resistance to pod borers in pigeon pea. Legume Research. 2008;31(1):55-58.
2. Bommesha M, Prasad YG, Reddy KR, Savithri P. Influence of pod biochemical constituents on pod fly damage in pigeon pea. Indian Journal of Plant Protection. 2012;40(2):125-129.
3. Jagtap DR, Chavan BN, Mahapatro GK. Biochemical constituents associated with pod fly resistance in pigeon pea. Annals of Plant Protection Sciences. 2012;20(1):210-213.
4. Mamta K, Singh V, Sharma N. Biochemical parameters conferring resistance against pod borer complex in pigeon pea. Journal of Food Legumes. 2023;36(2):5561.
5. Pandey V, Katiyar R, Singh R. Role of phenols in imparting resistance to pod fly in pigeon pea. International Journal of Plant Protection. 2011;4(2):318-321.
6. Parre B, Reddy DDR, Rao MS. Influence of biochemical constituents on pod borer incidence in pigeon pea. Journal of Entomological Research. 2018;42(3):331-336.
7. Rashmi M, Reddy CN, Sridevi V. Phenolic compounds governing pod borer resistance in pigeon pea. Plant Archives. 2020;20(1):1024-1030.
8. Sahoo BK, Patnaik HP. Biochemical evaluation of pigeon pea genotypes for resistance to pod borers. Orissa Journal of Agriculture Research. 2002;15(2):6772.
9. Sharma SP, Yadav MS, Singh D. Chemical basis of resistance to pod borers in pigeon pea. Indian Journal of Pulses Research. 2009;22(1):89-92.
10. Tyagi S, Singh K, Verma A. Role of biochemical traits in resistance of pigeon pea to pod borer complex. Legume Research. 2021;44(3):335-340.
11. Carney J, Rosomoff RN. In the shadow of slavery: Africa's botanical legacy in the Atlantic world. Univ of California Press; 2009.
12. Ryan DE, Iida S, Wood AW, Thomas PE, Lieber CS, Levin W. Characterization of three highly purified cytochromes P-450 from hepatic microsomes of adult male rats. Journal of Biological Chemistry. 1984 Jan 25;259(2):1239-50.
13. Kandhare AD, Shivakumar V, Rajmane A, Ghosh P, Bodhankar SL. Evaluation of the neuroprotective effect of chrysin via modulation of endogenous biomarkers in a rat model of spinal cord injury. Journal of natural medicines. 2014;68(3):586-603.
14. Reed W, Lateef SS. Pigeon pea: pest management. 1990, 349-374.
15. Gopali JB, Raju Teggelli RT, Mannur DM, Suhas Yelshetty SY. Web-forming lepidopteran, Maruca vitrata (Geyer): an emerging and destructive pest in pigeon pea; 2010, 35-38.
16. Shanower TG, Romeis JM, Minja EM. Insect pests of pigeon pea and their management. Annual review of entomology. 1999;44(1):77-96.
17. Awchar SL, Satpute US, Sarnaik DN, Sarode DB. Effect of certain chemical and botanical insecticides on some beneficial insects associated with mustard. Journal of Biological Control. 1995;9:3-15.
18. Sadasivam S. Biochemical methods. New age international; 1996.
19. Miller RL. Ultrafine-grained microstructures and mechanical properties of alloy steels. Metallurgical Transactions. 1972;3(4):905-12.
20. Siva G, Sivakumar S, Premkumar G, Kumar TS, Jayabalan N. Enhanced production of psoralen through elicitors treatment in adventitious root culture of Psoralea corylifolia L. International Journal of Pharmacy and Pharmaceutical Sciences. 2015;7(1):146149.
21. Srivastava UR. Shift work related to stress, health and mood states: a study of dairy workers. Journal of Health Management. 2010 Jun;12(2):173-200.
22. Kumari B, Kumar V, Sinha AK, Ahsan J, Ghosh AK, Wang H, et al. Toxicology of arsenic in fish and aquatic systems. Environmental chemistry letters. 2017;15(1):43-64.