Refinement of softwood grafting technique in Sapota (Manilkara zapota L.)

Abstract

Sapota (Manilkara zapota L.) family sapotaceae is one of the fruit trees which is adapted to humid tropical climate and diversified soil conditions. Softwood grafting in sapota has become common among farmers and horticulture nursery sector because it is an easy, as well as cheap method and helps in rapid multiplication of plants with considerable success rate. Generally, Khirni (Manilkara hexandra L.) is used as rootstock for grafting in sapota. The investigation entitled “Refinement of softwood grafting technique in sapota (Manilkara zapota L.)” was carried out at department of Horticulture, College of Agriculture, Padannakkad, Kasaragod, during 2020-2021.The study was conducted in completely randomized block design with factorial concept. The first experiment was done with the objective to find out the best practice for enhancing success percent in softwood grafting of sapota varieties under different environmental conditions with different precuring treatments having 27 treatment combinations replicated twice. The factors of first experiment were environmental conditions (open-C1, polyhouse-C₂ and polytunnel followed by shade net-C3) with cultivars (Cricket Ball-V1, Pala-V₂ and Oval-V₃) and scion precuring treatments (defoliation 10 days prior to grafting-S₁, defoliation followed by grafting on the same day-S₂ and grafting without defoliation-S₃). Interaction effect of environmental conditions, cultivars and scion precuring up to final stage of growth indicated that C3V1S3 (Polytunnel+ Cricket Ball+ Without defoliation) had maximum value with respect to growth parameters viz. girth of stem except 30 DAG(3.05),leaf area (35.42), length of leaf except 30 DAG (11.22), breadth of leaf except 60 DAG (4.32), number of leaves except 30 DAG, length of scion except 30 DAG and height of graft (34.75), fresh weight (32.06) and dry weight (15.04). C1V3S2 (Open+ Oval+ Same day defoliation) recorded lowest value with respect to growth parameters viz. length of scion (16.83 cm), girth of stem (2.32 cm), number of successful grafts (3.00), success percentage (20.00 %), survival percentage (20.00 % ), leaf area (16.45cm2 ), length of leaf (7.25 cm), breadth of leaf (3.11 cm), number of leaves (except 120 DAG) and height of graft(31.13 cm). The second experiment was undertaken to study the effect of cytokinin on success of sapota grafting. Factors are different concentration of cytokinin (P₁-100 ppm, P₂-150 ppm, P₃-200 ppm and P₄-control) and different days of application (D₁-0 thday, D₂-5 thday and D₃-10thday prior to grafting). Among the individual effect of cytokinin concentration, P3- cytokinin at 200ppm was found to be highest in terms of number of successful grafts, success percentage (82.22%), survival percentage (77%), length of leaf(12.06cm ), leaf area, breadth of leaf, girth of stem at 30,90 and 120 DAG, length of scion (120,150 and 180 DAG) and number of leaves (except 60 DAG). Considering individual effect of days of cytokinin application, D1 had the maximum value on observations like length of leaf (11.80cm), number of leaf (22.62), dry weight (11.26g), fresh weight (27.05g), height of graft, leaf area and girth of stem (3.06 cm), length of scion and breadth of leaf. Considering the interaction effect between concentration of cytokinin and days of cytokinin application, P3D1 (cytokinin at 200 ppm+ 0th day prior to grafting) proved to be the best treatment combination in terms of observations like length of scion, number of leaf (24.30), height of graft, leaf area (41.27 cm2 ), breadth of leaf (30 and 150DAG), length of leaf (90 to 150 DAG) and girth of stem (90,120,180 DAG). P4D3 (control treatment+10th day prior to grafting) was found to be lowest in terms of observations like number of leaf (18.80), leaf area (21.27 cm2 ) and length of scion (13.40 cm). The results obtained from present study revealed that grafting of sapota cv. Cricket ball without defoliation of scion and kept under polytunnel condition (T21-C₃V₁S₃) as the best treatment which recorded highest graft success and survival percentage. Grafts under C3-polytunnel found to be better in growth parameters compared to open and polyhouse conditions. Among scion precuring treatments, defoliation 10 days prior to grafting-S₁ provided highest percentage of graft success. Hence, modified grafting technique can be recommended as an ideal approach for sapota propagation during off season also. Application of cytokinin at 200ppm concentration on the same day of grafting (T₇-P₃D₁) enhanced graft growth. Regarding concentration of cytokinin, at 200ppm showed higher value which was on par with P1 and P2 in terms of success and survival percentage. So, cytokinin application at 100ppm (lower dose) for graft success can be recommend as economically beneficial.