Effect of chemicals and bio agents on seed germination, vigour & seedling growth of custard apple (Annona squamosa L.) under net house condition

Introduction

Custard apple (Annona squamosa L.) is also known as Sitaphal, Sugar apple, sharifa, sweet soap etc. which is grown in tropical and subtropical climates. It belongs to the Annonaceae family and is a native of the West Indies, but it has long been cultivated in Central America and Southern Mexico. There are more than 100 species in the genus, five of which have edible fruits species which includes Annona squamosa L. (Custard Apple), Annona muricata L. (Soursop), Annona reticulata L. (Bullock Heart, Ramphal), Annona atemoya L. (Lakshman phal) and Annona cherimola L. (Hanu-manphal). Among all the species Custard apple is the most popular monoecious fruit in India. According to Department of Agriculture and farmers welfare 2023-24 presently, in India custard apple grown in area of 52,000 ha. with production of 460,000 MT. Madhya Pradesh is 2 nd largest producer of Custard Apple with area of 9.602 thousand ha. production of 116.27 thousand MT of fruit production (Anonymous, 2022-23) [2,3] . Seed germination marks the initial phase of plant development, signifying the reactivation of embryo growth leading to the emergence of a young plant. The dormancy in seeds can be attributed to factors such as a tough and impermeable seed coat, germination inhibitors and irregular embryo development. The hard seed coat of custard apple seeds requires 35-50 days for natural germination. To enhance and ensure successful germination, pre-sowing treatments are essential. These treatments facilitate early germination and the growth of robust seedlings. To speed up the germination process, presowing treatments like GA 3 , cow urine and dung slurry, potassium nitrate, NAA, thiourea, HCl and H 2 SO 4 are used to break dormancy and promote germination. Cow urine is emerging as a viable option that could potentially revolutionize the current scenario. GA 3 breaks seed dormancy by activating gluconeogenic enzymes. Potassium nitrate enhances germination by improving nutrient absorption and water uptake. NAA promotes germination and seedling growth at low concentrations. Thiourea boosts seed germination, while HCl helps break the seed coat to reduce dormancy.

Materials and Methods

The experiment was carried out in Department of Horticulture, College of Agriculture Rewa. The experiment was laid out in CRD design with three replications. The experiment comprised of fifteen treatments consisting of T 1Control distilled water, T 2 -KNO 3 1%, T 3-KNO 3 2%, T 4 -Thiourea 1 %, T 5-Thiourea 2 %, T 6-Cow urine 10 %, T 7Cow urine 20 %, T 8-Cow dung slurry 10 %, T 9 -Cow dung slurry 20 %, T 10-GA 3 100 ppm, T 11-GA 3 200 ppm, T 12NAA 100 ppm, T 13-NAA 200 ppm for 24 hours, T 14-HCl 0.1 % and T 15-H 2 SO 4 0.1 % for 2 minutes. For sowing of custard apple seeds, black polybags (9 cm × 12 cm) were used. To promote drainage and aeration poly bags were punctured and then filled with media, made of three part of soil and one part of FYM. Fully ripe, uniformsized custard apple fruits were collected and seeds were extracted, washed and dried in the shade for an hour. The seeds were then placed in a bucket of water for whole night. Non-viable floating seeds were discarded, while viable seeds that sank were kept for sowing. The viable extracted seeds were soaked in Pre-sowing treatment solutions prepared by dissolving specific quantities of each substance in 100 ml of distilled water. For KNO₃, 1% and 2% solutions were made by dissolving 1 g and 2 g respectively. Similarly, thiourea solutions of 1% and 2% were prepared using 1 g and 2 g of thiourea. Cow urine treatments at 10% and 20% concentrations were prepared by adding 1 ml and 2 ml of cow urine, respectively. Cow dung slurry solutions of 10% and 20% were made by dissolving 1 g and 2 g of slurry. GA₃ solutions of 100 ppm and 200 ppm were prepared by dissolving 1 mg and 2 mg of GA₃, respectively.

NAA solutions of 100 ppm and 200 ppm were similarly prepared using 1 mg and 2 mg of NAA. For acid treatments, 0.1% solutions of HCl and H₂SO₄ were prepared by adding 0.01 ml of each acid to 100 ml of distilled water. All measurements were carried out using an electronic balance to ensure precision and then seed sowing was done on 20-09-2023. For analysis Statistical software use was OPSTAT.

Results and Discussion

Seed Germination Parameters

Pre-sowing treatments significantly impacted seed germination parameters represented in table 01. Seeds soaked in GA3 @ 200 ppm for 24 hours had the shortest time to start (21.51 days) and complete germination (49.73 days). The control group (T1) showed the longest times, with 38.97 days to start and 72.36 days to complete germination. The highest germination percentage (78.26%) was in GA3 @ 200 ppm for 24 hours, while the control had the lowest (61.76%). The highest seedling vigour index (769.29) was noted under the chemicals and bio-agents treatment combination of GA 3 @ 200 ppm (T 11 ) Whereas lowest seedling vigour index (459.49) was observed under the treatment of control (T 1 ). The findings are consistent with those reported by Dhoran and Gudadhe (2012) [7]. The acceleration of specific enzymes such as α-amylase by GA 3 could be responsible for increasing the availability of starch assimilation, leading to early germination. Several researchers have extensively documented the significant impact of GA 3 on seed germination, particularly in overcoming seed dormancy. Garge et al. (2011) [9] demonstrated this effect in custard apple, while Krishnan and Kulasekaran (1984) [11] , Ghosh and Sen (1988) [10] observed it in ber. [12] . The increased production of leaves in seedlings may be attributed to both enhanced seedling growth and the activity of GA 3 at the apical meristem, resulting in greater synthesis of nucleoprotein responsible for increasing leaf initiation (Sen and Ghunti, 1976) [16] .

Physiological Parameters

Pre-sowing treatments significantly impacted physiological parameters represented on table 03. Seeds treated with GA 3 at 200 ppm for 24 hours (T 11 ) had the highest fresh weight of leaves (2.83 g), dry weight of leaves (0.25 g), and leaf area index (31.15 cm²) at 120 DAS. In contrast, the control group (T 1 ) showed the lowest values: 1.33 g, 0.09 g, and 15.67 cm².The accelerated transportation of water and nutrients likely facilitated increased production of photosynthetic products, which were then translocated to different plant parts, potentially leading to enhanced seedling growth, and consequently increased fresh weight. These outcomes are consistent with the findings reported by Dhankhar and Singh (1996) [6] in Aonla and Anjanwe et al.

(2013) [1] in Papaya. Similar observations to these findings have been documented by Vachhani et al. (2014) [19] in khirnee and Ashiya and Tank (2015) [4] in mango. Rahemi and Baninasab (2000) [15] . The increased root length resulting from the GA 3 treatment on seeds could be attributed to cell multiplication and elongation in the meristematic region of the roots. These findings align with previous studies by Pampanna and Sulikeri (2001) [13] in Sapota, Dhaka and Pal (2009) [5] in sour lime, Supe et al.

(2012) [17] in Aonla, Anjanwe et al. (2013) [1] in papaya and Parvin et al. (2015) [14] in black walnut seeds.

Conclusion

Based on the findings of the present investigation, it can be concluded that treatment with GA 3 at a concentration of 200 ppm for 24 hours resulted in early and maximum seed germination, increased height, stem diameter, number of leaves, leaf area, fresh weight and dry weight of leaves and root, and a seedling vigour of seedlings and minimum value is found in control. However, these findings serve as indicators and necessitate further experimentation to establish more consistent and conclusive results before being conveyed to growers.

Acknowledgement

AcknowledgmentThe authors gratefully acknowledge the Department of Horticulture, College of Agriculture, Rewa, for their invaluable support and for providing the necessary infrastructure and resources that facilitated this research work.

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