STUDIES ON IN VITRO PROPAGATION OF FOUR TROPICAL FRUIT TREES

Abstract

Methods for in vitro propagation of four economically important fruit tree species are described in this study. Two of them, Artocarpus heterophyllus and Artocarpus altilis are of the family Moraceae and the other two, Aegle marmelos and Feronia limonia are of the family Rutaceae. ARTOCARPUS HETEROPHYLLLS Axillary shoot proliferatior was induced from shoot-tips of seedlings of A. heterophyllus raised in vitro. Optimal multiplication rate (average 4.3 shoots per explant) was achieved on media supplemented with BA (5mg/l) and GA3 (0.3 or 1 mg/l). Effects of TIBA, an anti-auxin, in breaking of apical dominance were inconsistent. Nodal explants also gave good shoot proliferation ( average 6. 4 shoots per explant) on media supplemented with BA (5mg/l), GA3 (0.3mg/l) and IBA (0.5mg/l). Cotyledonary nodes gave an average of 15.1 shoots per explant when cultured on media with BA (5mg/l), GA3 (0.3mg/l) and IBA (0.5mg/l). Shoot-tips from mature A. heterophyllus grew better on gelrite media than on agar media (where the latex exudate tended to clog the cut end of the explant). A multiplication rate of 3.5 could be achieved in 9 weeks from shoot-tips cultured on gelrite media with BA ( 5mg/l), IBA (0.5mg/l) and GA3 (0.3mg/l). Shoots, however, tended to be vitrified. Normal shoots were produced when BA concentration was reduced to 2mg/l. A multiplication rate of 3.5 times in 6 weeks could be achieved when shoots were subcultured onto media supplemented with BA (2mg/l), IBA (0.5mg/l) and GA3 (0.3mg/l). Shoots produced in vitro were successfully rooted on media with IBA (0. 5mg /1 ) . However, only 52.5% survival could be achieved when plantlets were planted out. Adventitious shoots could not be induced on epidermal strips, internodes, roots, leaf and cotyledon cultures of A. heterophylus. Callus produced from these explants could be maintained in the dark with the addition of PVP in the media to slow down the browning process. However, attempts to induce organogenesis were unsuccessful. ARTOCARPUS ALTILIS A. altilis shoots obtained from root cuttings were used for in vitro experiments. Shoot-tip explants gave an average of 2.8 shoots per explant when cultured on gelrite media supplemented with BA at 1mg /l. Nodal explants produced an average of 3.5 shoots per explant on media with BA ( 2mg /l ) , IBA (0.5mg/l) and GA3 (0.3mg/l). A multiplication rate of 4 times in 6 weeks could be achieved on gelrite media with BA at 1 mg/l. Rooting occurred on gelrite media with IBA (0/5mg/l), and 77% survival could be obtained on transplanting the plantlets. AEGLE MARMELOS Explants from in. vitro germinated shoots were used. Shoot-tip cultures produced an average of 4.35 shoots per explant on media supplemented with BA (1 mg/l). Kinetin was less effective compared to BA. Nodal explants gave an average of 3 shoots per explant when BA (2mg/l) was used in combination with NAA (0.2mg/l). Kinetin (1 mg/l) was more effective in the case of nodal cultures, was more effective, giving an average of 3.7 shoots per explant. Highest multiplication rate was obtained from cotyledonary node cultures, which produced an average of 17.7 shoots per explant on media with BA (1 mg/l) and NAA (0.1 mg/l). Buds from mature A. marmelos tree produced callus which differentiated into small green bud-like structures. developed into shoots when transferred to basal medium. These Adventitious shoots could be obtained from internodes, roots, cotyledon and leaf cultures of seedling A. marmelos cultured on media supplemented with BA (1 or 2mg/I). These explants directly also formed globular bud-like structures, either on the explants or on callus. These structures developed into shoots when transferred to basal medium. Only one callus line showed organogenesis on medium supplemented with BA (1 mg/l) and NAA (0.1 mg/l). Rooting occurred on media with NAA (2mg/l). Transplanting survival, however, was only 28.5%. FERONIA LIMONIA Shoot-tip explants from in vitro germinated seedlings produced an average of 3.1 shoots per explant on media with BA (2mg/l). Kinetin was less effective in inducing shoot proliferation. BA (0.5mg/l) in combination with NAA (0.05mg/l) appeared to be optimal for nodal explants, which gave an average of 3.07 shoots per explant. Cotyledonary nodes produced an average of 4.3 shoots per explant on media with BA (1 mg/l) and NAA (0.1 mg/l ). Adventitious shoots could be induced from hypocotyl, internode, root, leaf and cotyledon cultures of seedling F. limonia on BA (1 or 2mg/l). Globular bud-like structures were also produced on callus, which developed into normal shoots when transferred to basal medium. None of the callus lines, however, showed signs of organogenesis. Rooting occurred on media with NAA (2mg/l). IBA was ineffective. Transplanting was, however, unsuccessful, with mortality mainly due to dehydration. Further research would help to determine better media composition and to improve the rate of propagation. The methods employed presently to propagate the seedling materials will have to be suitably modified to propagate the explants from elite, mature trees.