In virto multiplication and standardisation of hardening techniques in pineapple (Ananas comosus (L.) Merr.)

Abstract

Studies were conducted on in vitro multiplication and standardization of hardening techniques in pineapple (Ananas comosus (L.) Merr.) at the Tissue Culture Laboratory of the All India Co – ordinated Floriculture Improvement Project attached to the Department of Pomology, College of Horticulture, Vellanikkara during 1991 – 1993. Surface sterilization treatment was standardized for crown explants. Among the different treatments tried, treatment with Emisan 0.1 per cent for 30 minutes followed with mercuric chloride 0.1 per cent for 10 minutes was found to be the best. Explants collected in the months of January and February gave the least contamination and maximum survival percentage. MS medium with BA 5.0 mg/1 inche alone or in combination with NAA 1.0 mg/1 inche gave maximum establishment of the explants. The globular structures were formed at maximum intensity within the shortest time of 5.96 days in MS medium supplemented with BA 5.0 mg/1 inche and NAA 1.0 mg/1 inche. Among the three cytokinins tried, the fastest response and the highest intensity of globular structures was obtained with BA followed by KIN and 2ip. Maximum shoot proliferation (11.9 per culture) was obtained with basal MS medium in which cent per cent of the cultures developed vigorous dark green shoots. Rooting of the in vitro derived shoots was obtained in in vitro as well as ex vitro conditions. Hundred per cent in vitro rooting was obtained in basal MS medium as well as in media supplemented with various concentrations of IBA and NAA. The fastest rooting (in 8.54 days) was obtained in the basal medium. Rooting was also faster in liquid medium compared to solid medium. In solid medium, early root initiation and the maximum length of roots were observed with 0.65 per cent agar concentration. Among the ex vitro rooting treatments tried, treatment with the rooting powder Rooton resulted in the fastest rooting and the maximum length of the roots. Profuse rooting of the shoots was obtained without using growth regulators by keeping them in a mist chamber. Treatments were standardised for successful transfer of the plantlets to the outside environment. Hundred per cent survival of the plantlets was obtained by immersing the roots of the plantlets in sterile water for 18 hr prior to transplanting. Among the different containers tried, plantlets grown in plastic pots, in general showed maximum vigour with respect to the number of leaves, height and width of the largest leaf, followed by those in mud pots and poly bags. The maximum percentage increase in these parameters was observed for the plantlets in pro-trays. Potting mixes such as cocopeat, soilrite, biofibe and vermiculite were found to be better in inducing vigorous growth of the plantlets. Plantlets grown in plastic pots with cocopeat or plastic bags with soilrite mix, in general, grew more vigorously. A nutrient starter solution of NPK fertilizer solution once a week or one fourth strength basal MS salts was found to be sufficient to induce healthy growth of the transplanted plantlets in the early stages of growth. To induce better growth of the plantlets in the later stages, application of the NPK fertilizer solution twice a week or Hoagland’s solution once a week was found to be better. Encapsulated beads were successfully formed with the differentiating globular bodies formed from the primary explants. The globular bodies could be encapsulated using 2.5 per cent sodium alginate and 75 mM calcium chloride with a complexation time of 30 minutes. The plantlets after 90 days of growth in the greenhouse with a minimum height of 10 cm and 12 leaves were successfully transferred to soil.