Effect of months on softwood grafting in carambola (Averrhoa carambola l.)

Introduction

Carambola (Averrhoa carambola L.), often known as the "star fruit" or "five finger" fruit, also important fruit of warm tropics and sub tropics region of world which belongs to Oxalidaceae family. In climatic region in Konkan region carambola is flowering and fruiting thrice so this crop can be used as boundary crop which may additionally provide income to the farmers. Traditionally, carambola plants have been propagated through seeds; however, seed propagation often results in high genetic variability among the progeny. Due to their heterozygous nature, seedlings are unlikely to have fruit that closely resembles that of the mother tree. (Sonawane et al., 2012) [9] . As a result, seedling plants may vary significantly in terms of fruit size, shape, taste, yield and other characteristics. To overcome this issue and ensure uniformity and quality in commercial orchards, vegetative propagation methods such as air layering and softwood grafting have been adopted. Grafting enables the production of true-to-type plants that faithfully replicate the genetic and phenotypic characteristics of the elite mother plant. This technique not only ensures uniformity in fruit quality and maturity but also shortens the juvenile phase allowing for earlier fruiting compared to plants grown through seeds. Among various vegetative methods, softwood grafting is effective in carambola due to its relatively high success rate and ease of implementation. nowadays demand for carambola grafts is increasing day by day for which studies on propagation was done in which softwood grafting and air layering was practiced but now as per the changing climatic condition softwood grafting from August to September month was conducted with following objective Effect of months on softwood grafting in carambola (Averrhoa carambola L.)

Material and Methods

The experiment was conducted in 2024-2025, at nursery of Department of Fruit Science, College of Horticulture, Dapoli. The experiment was carried out in randomized block design with 8 treatments of I st and II nd fortnight of August to November month which were replicated three times. Carambola seeds were collected from ripe fruits and sown in trays with a 2:1:2 mixture of soil, cocopeat and compost. After germination (20-25 days), seedlings were transplanted into polybags. Healthy seedlings (25-30 cm tall, 0.25-0.30 cm thick) were selected as rootstocks. Scion sticks were taken from 3-4-month-old shoots, defoliated and left on the tree for 8-12 days before use. Grafting involved inserting a wedge-shaped scion into a V-slit on the rootstock and tying it with a polythene strip. Grafts were kept in shade, watered every 3-4 days, and covered with polythene bags, which were removed after sprouting began. The observation was recorded till 180 days after grafting with 30 days interval. All the Sprouting percentage, Survival percentage and growth parameters (height, height from graft union, rootstock girth, graft union girth, scion girth). [8] in mango where maximum sprouting (%) was observed in September month in softwood grafting.

The treatment maximum survival (%) (73.33) of grafts was recorded in Treatment T 3 (Grafting in I st Fortnight of September) which was followed by T [8] , Karna et al.

(2017) [5] and Kuree et al. (2024) [6] in mango where maximum survival (%) was found in September month for softwood grafting.

The data related to height and per cent increase in height was recorded at 180 DAG and is presented in Table 2. The statistically highest percent increase in height (14.94%) of carambola grafts was found in T1 treatment which was at par with T 2 (Grafting in II nd Fortnight of August) (14.58%), T 6 (Grafting in II nd Fortnight of October) (14.04%) and T 3 (Grafting in I st Fortnight of September) (13.31%). The lowest percent increase in height (11.09%) was noted in T 5 (Grafting in I st Fortnight of October) treatment. Grafting success, particularly graft height, is significantly influenced by climatic conditions. Grafting during late monsoon (August-September) and early winter (October-November) proved optimal. Consistent moisture in the air and media, a congenial temperature range of 24-26 ℃ and increasing light intensity during initial growth (T 1 , T 2 , T 3 ) facilitated better height development. Successful graft union enabled efficient nutrient and water transfer, promoting photosynthesis and subsequent growth. Similar results were found by Chander et al. (2016) [3] in jamun and Karna et al.

(2017) [5] and Kuree et al. (2024) [6] in mango where maximum height was noted in September month for softwood grafting.

The data related to height from graft union and per cent increase in height from graft union was recorded at 180 DAG is presented in Table 2. The highest percent increase in height from union of carambola graft (16.30%) was recorded in T1 (Grafting in I st Fortnight of August) which was at par with T 2 (Grafting in II nd Fortnight of August) (16.18%) and T 4 (Grafting in II nd Fortnight of September) (13.54%) while the lowest percent increase in height from union of carambola graft (10.02%) was found in T 5 (Grafting in I st Fortnight of October) treatment. Successful cambium union facilitates the vital exchange of nutrients, water and food between rootstock and scion. The favourable climatic conditions during the growth period, as mentioned in section 3.2, likely enhanced photosynthate production, ultimately boosting scion growth and height. Similar results were found by Bhavya et al. (2018) [1] in karonda and Karna et al. (2017) [5] and Kuree et al. (2024) [6] in mango where maximum height was noted in September month for softwood grafting.

The data related to rootstock girth (mm) was recorded at 180 DAG is presented in [4] and Chander et al. (2016) [3] in jamun noted maximum girth in September month of softwood grafting.

The data related to graft union girth (mm) was recorded at 180 DAG is presented in Table 2. the maximum graft union (7.18 mm) was recorded in T3 (Grafting in I st Fortnight of September) treatment which was at par with T 4 (Grafting in II nd Fortnight of September) (7.03 mm), T 6 (Grafting in II nd Fortnight of October) (6.82 mm) and T 5 (Grafting in I st Fortnight of October) (6.67 mm). The minimum graft union girth (5.92 mm) was found in T 8 treatment. Increased girth at the graft union suggests robust wound healing and growth. Rapid callus tissue development likely formed a strong vascular connection, ensuring uninterrupted water, mineral, and assimilate translocation, thereby promoting radial growth and increased graft girth. Similar results were found by Ghojage et al. (2009) [4] and Chander et al. (2016) [3] in jamun noted maximum girth in September month of softwood grafting.

The data related to scion girth was recorded at 180 DAG is presented in Table 2. The maximum scion girth (5.39 mm) was recorded in T3 (Grafting in I st Fortnight of September) treatment which was at par with T 1 (Grafting in I st Fortnight of August) (5.33 [4] and Chander et al. (2016) [3] in jamun noted maximum girth in September month of softwood grafting.

Conclusion

From the present investigation, considering the higher ranking of treatment in various parameter under study, it can be concluded that grafting in September month especially in I st fortnight resulted the superior efficacy in enhancing the plant growth parameters i.e. sprouting (%), rootstock girth, graft union girth, scion girth, survival (%). Climatic conditions during grafting and further growth plays an important role in success and

References

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