Propagation studies in miracle fruit [Synsepalum dulcificum (Schumach. and Thonn.) Daniell

Abstract

Miracle fruit [Synsepalum dulcificum (Schumach. & Thonn.) Daniell] is an exotic evergreen shrub belonging to the family Sapotaceae, native to West Africa. The fruit is renowned for its unique taste-modifying property attributed to the glycoprotein miraculin, which temporarily converts sour taste into sweet. In addition to this remarkable sensory feature, various parts of the plant possess notable pharmacological properties, including antioxidant, antidiabetic, anticancer, and antihyperuricemic activities, attributed to its rich composition of bioactive compounds such as flavonoids, phenolics, and triterpenoids. These attributes make miracle fruit a promising functional and nutraceutical crop with growing global demand. Despite Kerala’s favourable agro- climatic conditions, the commercial cultivation of miracle fruit remains limited, as its propagation presents considerable challenges affecting large-scale multiplication. Hence, the present study entitled “Propagation Studies in Miracle Fruit [Synsepalum dulcificum (Schumach. & Thonn.) Daniell]” was conducted during 2024–2025 in the Department of Fruit Science, College of Agriculture, Vellanikkara, with the objective of standardizing efficient propagation methods of miracle fruit suitable for Kerala conditions. The research programme comprised two major experiments viz standardization of media for seed propagation and evaluation of vegetative propagation techniques. The first experiment on seed propagation was conducted in CRD with five treatments and three replications, using ten seeds per replication. The media evaluated were: soil (T₁–control), soil + cocopeat + FYM (2:1:1) (T₂), soil + cocopeat + vermicompost (1:1:1) (T₃), sawdust (T₄), and sawdust + vermicompost (1:1) (T₅). Results revealed that seeds sown in T₅ significantly outperformed other treatments, recording the earliest germination (12.00 days), highest germination percentage (53.33%), maximum seedling height (7.51 cm) and seedling weight (0.80 g), 90 DAS. Meanwhile, T₃ was superior in vegetative growth parameters, producing the highest number of branches (3.83, 120 DAS), leaves (4.17, 90 DAS), and stem girth at 10 cm height (0.20 cm, 120 DAS). In contrast, soil + cocopeat + FYM (2:1:1) (T₂) recorded the lowest germination rate, while soil alone (T₁) and sawdust (T₄) required the maximum days for germination and exhibited poor seedling development. The experiment on terminal cuttings was conducted in CRD with eight treatments, three replications, and ten cuttings per replication. Various growth regulators and natural rooting substances were tested to assess their effect on root induction and growth: 400 ppm IBA (T₁), 800 ppm IBA (T₂), 500 ppm NAA (T₃), 1000 ppm NAA (T₄), Rootex (T₅), Aloe vera gel (T₆), dry control (T₇), and wet control (T₈). Results revealed significant variation among treatments in their rooting response. Cuttings treated with 800 ppm IBA (T₂) recorded the maximum number of rooted cuttings (6.66), roots per cutting (2.86), root length (11.96 cm), and survival rate (44.40%) at 120 days after planting. In contrast, dry and wet controls (T₇ and T₈) showed poor rooting performance. However, no sprouting, leaf emergence, or shoot formation was observed in any of the treatments during the experimental period. The air layering experiment was conducted with six different media treatments, arranged in CRD with three replications and five air layers per replication. The treatments comprised cocopeat (T₁), sawdust (T₂), sphagnum moss (T₃), coirpith compost (T₄), vermicompost (T₅), and a mixture of perlite, vermiculite, and AMF (1:1:1) (T₆). Results revealed significant variation among the media used for air layering, with vermicompost (T₅) showing the earliest root emergence (47.66 days), maximum number of rooted layers (3.00), and highest survival rate (20%) after three months. Both vermicompost (T₅) and perlite + vermiculite + AMF (1:1:1) (T₆) required the minimum duration for separation (182.00 days). The T₆ medium also produced the highest number of adventitious roots (5.33), longest root length (7.36 cm), and most side shoots (2.66). In contrast, sawdust (T₂) and coirpith compost (T₄) performed poorly across all parameters, exhibiting delayed rooting and no survival. The experiment on grafting was laid out in a CRD with two factors viz season (June, July, and August) and method of grafting (softwood, side, and veneer), comprising nine treatment combinations. Each treatment was replicated three times with five grafted plants per replication. Results revealed significant effects of both season and grafting method on the growth and survival of grafted miracle fruit plants. Grafts performed in August (S3) showed superior performance with earliest sprouting (23 days), highest number of leaves (16.16), more branches (4.46), and maximum survival (48.92%), 90 days after grafting, while grafts in June (S1) recorded the longest shoots (2.73 cm). Among the methods, softwood grafting (G1) proved most effective, producing earliest sprouting (19 days), highest leaf (17.33) and branch count (4.81) and maximum survival (55.59%), 90 days after grafting, whereas veneer grafting (G3) performed the poorest. The interaction effect between season and method was also significant. Softwood grafting during August (S₃G₁) resulted in the overall best performance, with maximum leaves (22.83), branches (6.16), and survival (73.44%), whereas side grafting during June (S₁G₂) produced the longest shoots (4.03 cm). In contrast, veneer grafting in June (S₁G₃) recorded the lowest growth and survival. The budding experiment was conducted in a Completely Randomized Design (CRD) with two factors—season and method of budding. The seasons evaluated were June (S₁), July (S₂), and August (S₃), while the methods included patch budding (B₁) and chip budding (B₂). Although the experiment initially comprised six treatment combinations, chip budding (B₂) failed to sprout or survive in any of the seasons and was therefore excluded from statistical analysis. Consequently, data analysis was carried out using CRD, considering only the patch budding treatments. Significant variations were observed among seasons, with budding performed in June (S₁) showing superior performance in all growth parameters, including the earliest sprouting (57.00 days), highest leaf number (10.80), branch count (2.56), and shoot length (3.26 cm) at 90 days after budding. The highest survival rate (93.33%) was recorded for patch budding in June, which was statistically on par with August (80.00%). Thus, patch budding carried out in June (S₁B₁) proved to be the most effective treatment, resulting in the earliest sprouting, enhanced vegetative growth, and maximum survival percentage under Kerala conditions. Overall, the study revealed that propagation success in miracle fruit varied considerably under Kerala conditions. Seed propagation was limited by the long juvenile phase of seedlings, while cuttings and air layering exhibited poor rooting and survival, making them unsuitable for large-scale multiplication. In contrast, grafting and budding performed well, with patch budding in June emerging as the most successful and reliable method, followed by patch budding and softwood grafting in August, for efficient propagation of miracle fruit under Kerala conditions.