Effect of different grafting time in naturally ventilated condition on success of wedge grafting in custard apple (Annona squamosa L.) cv. Sindhan

Introduction

Custard apple (Annona squamosa L.) is a dryland fruit crop of economic importance in India. Native to the tropical Americas, particularly the West Indies and South America. In India, it is cultivated mainly in Andhra Pradesh, Bihar, Madhya Pradesh, Maharashtra, Tamil Nadu, Gujarat and Odisha, covering 51.73 thousand ha with 548.27 thousand tonnes production (Anon., 2023) [2,3] . In Gujarat, it occupies 7,900 ha with 79.56 thousand tonnes yield, predominantly in Bhavnagar district. Belonging to the family Annonaceae (40 genera, 120 species, only five edible), it is known as the "poor man's fruit" for its suitability to marginal soils. Major production constraints include a shortage of improved planting material and lack of standardized propagation techniques. Seed propagation is common but unsuitable for maintaining varietal traits due to the crop's heterozygous nature. Wedge grafting is preferred for producing true-to-type plants, ensuring genetic fidelity and higher yields. Grafting can be done in shade nets, naturally ventilated polyhouses and fan-and-pad polyhouses. Naturally ventilated polyhouses use passive airflow for temperature and humidity control, reducing stress on grafted seedlings. Success depends on climatic conditions and season, with March-May being optimal in South Gujarat (Chauvatia & Singh, 1999) [6] , though precise timing is crucial. Wedge grafting offers better scion-rootstock compatibility, rapid establishment and higher survival rates. Considering the need for timely production and the future demands of the industry, standardizing the ideal grafting period under North Gujarat's conditions will ensure timely availability of quality planting material, meet the rising demand for improved varieties and enhance productivity in custard apple cultivation. This would further enhance the effectiveness of propagation techniques and improve overall productivity in the region.

Materials and Methods

The experiment was conducted during the summer season of 2024 (February-July) at the College Farm, College of Horticulture, Sardarkrushinagar Dantiwada Agricultural

The grafted plants were maintained under growing environments naturally ventilated polyhouse. Irrigation was provided manually and plant protection measures were applied as required. Uniform length, pencil thickness, healthy scion were used for grafting. The scion sticks were selected from mature shoots of current year growth from terminal portion of the mother plants of cultivar 'Sindhan' and were defoliated 10 days prior grafting. The grafting was done at 15 days intervals through wedge grafting.

Observations were recorded after 30, 45 and 90 days after grafting. Formula used to analyse Survival percentage (%)

Total number of grafts success Survival percentage = × 100 Total number of grafts prepared

The experiment involved a series of treatment combinations, outlined in the details below. [21,10,6] . Delayed sprouting in May grafts could be attributed to reduced stored food materials, slowing callus formation and bud break (Giri & Lenka, 2008) [8] , in agreement with findings in guava (Abbas et al., 2013; Padmapriya et al., 2021) [1,20] and jackfruit (Kumar et al., 2022) [17] .

Sprouted grafts at 30 days after grafting (DAG)

T 3 produced the highest sprouted grafts (18.67%), at par with T 4 (18.00%), while T 6 recorded the lowest (11.00%) at 30 DAG, (Table 2a). Higher sprouting in March grafts was attributed to optimal temperature, relative humidity and assimilate availability, which enhanced meristematic activity and graft union healing (Nithya et al., 2022) [19] , These findings align closely with those reported in guava (Gotur et al., 2017; Kholia et al., 2022) [9,15] and tamarind (Deshmukh and Bhagat, 2018) [7] .

Number of fully opened leaves at 45 and 90 days after grafting (DAG)

At 45 DAG, T 3 recorded the highest leaf count (16.67), which was statistically at par with T 2 (15.27) and at 90 DAG, T 3 (22.47) was recorded highest number of fully opened leaves, which was statistically at par with T 4 (20.53). In contrast, T 6 had the lowest leaf counts (8.53 and 12.07, respectively at 45 and 90 DAG), (Table 2a). Early grafting favoured rapid bud break, leaf flushing and graft union formation under optimal temperature and humidity, whereas extreme conditions in May impeded callus formation and nutrient translocation (Bhandari et al., 2021), These findings aligning with Panchal et al., (2022) [21] in custard apple.

As presented in table 2b, T 3 showed maximum scion length (54.53 cm at 45 DAG and 61.86 cm at 90 DAG), which was statistically at par with T 2 and T 4 , whereas T 6 showed lowest scion length (43.22 cm at 45 DAG and 49.06 cm at 90 DAG). Greater length in early grafts was attributed to early sprouting, faster union formation and improved nutrient absorption (Nithya et al., 2022) [19] , This results are consistent with reports given by Syamal et al., 2012 [25] , Sweeti et al., 2016 [24] Barathkumar, 2017 [4] in aonla and Karna et al., 2018 [14] in mango.

T 3 showed maximum girth of scion at 45 and 90 DAG (8.99 mm and 11.51 mm, respectively), which was statistically at par with T 4 . In contrast, T 6 had the lowest girth (6.48 mm and 9.14 mm at 45 and 90 DAG), (Table 2b). Increased girth in early grafts was linked to higher carbohydrate reserves, early sprouting, greater leaf production and better photosynthate supply, which also correlated with greater plant height (Hiwale et al., 2008) [11] , in agreement with findings in custard apple (Kudmulwar et al., 2008; Kamble et al., 2024) [16,13] and mango (Thutte et al., 2020) [26] .

Graft survival percent at 90 days after grafting (DAG) Maximum survival percentage was observed in T 3 (93.33%), was statistically at par with T 4 (90.00%), while T 6 recorded the lowest (55.00%), (Table 2b). High survival percentage in March-April grafts was due to favourable climatic conditions and higher carbohydrate content in physiologically active plants. Majumder et al. (1972) [18] reported 90 percent success on grafting using scions taken from non-flowering shoots compared with 70 percent success from flowering shoots. Similar results are observed by Singh and Sengupta (1996) [23] in mango, Joshi et al.

(2000) [12] , Giri and Lenka (2008) [8] and Panchal et al.

(2022) [21] in custard apple.

Conclusion

Based on results obtained from present investigation, it may thus be concluded that the 3 rd week of March represents the most suitable period for wedge grafting in custard apple under naturally ventilated conditions, ensuring improved graft establishment, accelerated growth and higher survival rates, thereby offering significant potential for enhancing nursery efficiency and grower profitability.

References

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