Biochemical bases of resistance against stem borer in sorghum

Introduction

Sorghum is a vital cereal crop, serving as both food and fodder for some of the world's most vulnerable populations. In 2022-23, global sorghum grain production was 55.09 million tonnes, with India as the top producer, followed by Mexico and Nigeria. Sorghum is the third most consumed cereal in India, after rice and wheat, with kharif (2022-23) production estimated at 1.69 million tonnes from 2.94 million hectares (Anon., 2022) [1] . The spotted stem borer (Chilo partellus), a major pest from the family Crambidae and order Lepidoptera, causes significant damage to sorghum and other crops such as maize, sugarcane, rice, and finger millet. This pest damages the crop from the vegetative stage to maturity, leading to substantial yield losses. Its life cycle, lasting 3-4 weeks, supports multiple generations under favorable conditions (Saranya and Samiayyan, 2017) [6] . Host plant resistance is one of the most sustainable methods for managing stem borer infestations. Key biochemical traits in sorghum significantly influence pest resistance. For instance, phenolic compounds act as natural deterrents, discouraging pest feeding and reproduction. The role of nitrogen is dual-while excessive levels may promote pest growth, optimal levels can enhance plant defense. Similarly, protein content can impact the development of the pest, and moisture levels in plant tissues influence pest establishment and survival. Given the variability in resistance across sorghum genotypes, identifying varieties with robust resistance mechanisms is crucial. Incorporating biochemical factors such as phenols, nitrogen, proteins, and moisture into screening programs can help develop more resilient sorghum lines, offering a long-term solution for managing C. partellus.

Objective

Biochemical bases of resistance against stem borer in sorghum

Methodology

The investigations on "Biology, population dynamic and management of stem borer, Chilo partellus (Swinhoe) on grain sorghum (Sorghum bicolor L.)" were carried out at Agronomy Instructional Farm, C. P. College of Agriculture, S. D. Agricultural University, Sardarkrushinagar during kharif seasons of year 2021 and 2022. The material used and methodology adopted during the course of investigation are described under here. The investigation on biochemical parameters was carried out at the Center for Oilseeds Research Station, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar. Thirty five days old leaves and were collected from each genotypeand subjected to biochemical analysis to assess the total soluble sugar (TSS), total phenol, protein, nitrogen and moisture content using various laboratory equipment. The correlation study was carried out between pest infestation and biochemical parameters.

Results and Discussion

Biochemical bases of resistance against stem borer in sorghum Phenol

The perusal of data on phenol content from leaves of different genotypes of pearl millet are presented in Table 1. The total phenol content was observed between 1.09 to 2.11 mg/g in various genotypes. The genotype, IS-2205 held highest amount of total phenol (6.59 mg/g) whereas the Varity, GJ43 (2.20 mg/g) held lowest amount of total phenol with an average of 3.79 mg/g. Rest of the genotypes revealed total phenol content in the range from 4.80 to 2.45 mg/g.

Total soluble sugar

The results on TSS from leaves of genotypes of sorghum are presented in Table 1 and graphically displayed in Fig. 4.8. The minimum amount of TSS was detected in genotype, IS-2205 (7.48 mg/g) whereas, it was maximum in genotype, Swarna (10.98 mg/g). The TSS content in rest of the genotypes recorded between 10.56 and 7.58 mg/g. The average TSS content in leaf of all the varieties/genotypes was 9.03 mg/g.

Total nitrogen

The results on total nitrogen content in the leaves of different genotypes of pearl millet are presented in Table 1 The results revealed that minimum nitrogen was found in genotype, IS-2205 (3.18%) whereas, it was maximum in genotype, DJ-6514 (4.48%). The remaining genotypes revealed the total nitrogen content in the leaf from 3.23 to 4.43 (Av. 3.87%). [2] at Hyderabad recorded 91.04 to 92.43 percent moisture content, 23.24 to 25.44 percent protein and 2.70 to 3.16 total soluble sugar from leaf of sorghum. Patel et al.

(2021) reported that the phenol in leaf of sorghum varied from 2.75 to 7.12 mg/g and total soluble sugar in the different genotypes ranged between 6.37 to 8.34 mg/g. Patil and Bagde (2017) [5] revealed that leaf of sorghum exhibited 81.45 to 90.39 percent moisture at Kolhapur, Maharashtra. Patel et al. (2021) at Anand, Gujarat, reported that nitrogen and protein content in leaf of sorghum varied between 1.47 to 3.06 and 9.16 to 19.12 percent, respectively. Thus, present findings are in range reported by earlier worker.

Correlation between stem borer on sorghum varieties/ genotypes and biochemical parameters Total phenol

The correlation analysis between total phenol content and dead hearts by stem borer presented in table 2. Reveling stem borer infestation (r = -0.803**) exhibited highly significant and negatively correlation with total phenol content. Patel et al. (2021) revealed that total phenol had highly significant but negative correlation with stem borer infesting sorghum. Hence, the outcome of present study is consist with the finding of former workers.

Total soluble sugar

From the correlation analysis (Table 2) it could be seen that stem borer infestation expressed highly significant and positive relationship (r = 0.823**) with TSS content of different genotypes of the sorghum varieties/ genotypes. Earlier, At Hisar, Haryana, Lokesh and Mehla (2017) [3] noticed that TSS content from leaves of maize established highly significant and positive relationship with stem borer incidence. Hence, the findings of present investigations are very close with the findings on relation of TSS and stem borer infested as observed by above worker.

Moisture

The results of correlation study presented in table 2 revealed that moisture content of leaf expressed highly significant positive relationship with stem borer incidence (r = 0.849**). At Anand, Gujarat, Patel et al. (2021) [4] revealed that moisture had highly significant and positive correlation with stem borer infesting sorghum. Hence, the outcome of present study are same as finding of former workers.

Total nitrogen

Correlation analysis between stem borer infesting various varieties/ genotypes of sorghum and biochemical parameters presented in table 2 revealed that stem borer infestation had highly significant positive correlation (r = 0.839**) with total nitrogen content of leaf. Patel et al. (2021) reported that total nitrogen had highly significant and positive correlation with stem borer infesting sorghum. Hence, the outcome of present study are matching with the finding of former workers.

Total protein

The results of correlation study presented in table 2 revealed that total protein content of leaf expressed highly significant positive relationship with stem borer incidence (r = 0.839**). In past, at Anand, Patel et al. (2021) observed that the protein content had highly significant and positive correlation with stem borer infesting sorghum. Hence, the outcome of present study are matching with the finding of former workers.

Conclusion

The study confirms that biochemical traits significantly impact sorghum's resistance or susceptibility to stem borer infestation. Higher moisture, nitrogen, protein, and TSS levels were positively correlated with greater infestation, suggesting these factors favor pest growth and development. Conversely, higher phenol content was associated with reduced pest incidence, demonstrating its role in enhancing plant defense. Genotype IS-2205 showed the most promising resistance due to its optimal biochemical composition, while DJ-6514 and Swarna were the most susceptible. These findings provide valuable insights for breeding programs aimed at developing sorghum genotypes with improved resistance to stem borers.

References

1. Anonymous. Crop outlook reports of Andhra Pradesh. Acharya N. G. Ranga University, Andhra Pradesh; 2022. p. 1.
2. Chamarthi SK, Sharma HC, Sahrawat KL, Narasu LM, Dhillon MK. Physio-chemical mechanisms of resistance to shoot fly, Atherigona soccata in sorghum, Sorghum bicolor. Journal of Applied Entomology. 2010;135(6):446-455.
3. Lokesh, Mehla JC. Study on morphological and biochemical features associated with maize (Zea mays L.) resistance against Chilo partellus. International Journal of Pure and Applied Bioscience. 2017;5(4):1011-1021.
4. Patel CT, Patel CC, Varma CB. Bio-chemical basis of resistance to stem borer, Chilo partellus (Swinhoe) infesting forage sorghum, Sorghum bicolor (L.) Moench. Journal of Entomology and Zoology Studies. 2021;9(1):834-839.
5. Patil SP, Bagde AS. Physio-chemical resistance mechanism of sorghum genotypes against shoot fly (Atherigona soccata Rondani). International Journal of Current Microbiology and Applied Sciences. 2017;6(9):2742-2746.
6. Saranya VSL, Samiayyan K. Study of the biology of Chilo partellus (Swinhoe) on artificial and natural diets. Journal of Entomology and Zoology Studies. 2017;5(2):721-724.