| Summary: | 博士 === 國立屏東科技大學 === 熱帶農業暨國際合作系 === 107 === Introduction. Carica papaya L. is a polygamous species with three sex types: staminate, pistillate and hermaphrodite. Papaya can be propagated by sexual and asexual methods. Unfortunately, using sexual propagation hampers the preservation of favorable plant characteristics and delays the appearance of the first flowers. These shortcomings can be circumvented by asexual propagation such as grafting, cutting, and micropropagation.
Materials and Methods. In this study, grafting, cutting and in vitro propagation methods were tested. (1). In the grafting method, the aims of the study were to evaluate the effect of rootstock age and grafting season on the cleft grafting in greenhouse. The trial in ‘Tainung No.2’ and ‘Red Lady’ varieties was conducted using the Randomized Complete Block design experiment with two factors. The first factor represented 4 levels of rootstock age (1, 2, 3 and 6 months), the second factor, two grafting seasons (summer and autumn). (2). In the cutting propagation, the objectives of this study were to evaluate the effect of different substrates and growth regulators on cutting rooting of Carica papaya cv. ‘Tainung No.2’ and ‘Red Lady’. This content was carried out with two experiments. The first test was the effect of six types of substrates (sand, perlite, peat moss, vermiculite, a mixture [50:50 by volume] of perlite and vermiculite, and a mixture [50:50 by volume] of peat moss and perlite) and the second experiment evaluated effect of NAA and IBA at five concentrations (0.0, 1,000, 2,000, 3,000, 4,000 and 5,000 mg l-1). (3). In micropropagation, an efficient in vitro regeneration system was developed for the hermaphrodite papaya cv. ‘Tainung No.2’ and ‘Red Lady’ using nodal explants. Nodal explants in two varieties were cultured on modified Murashige and Skoog (MS) medium supplemented with 3 BAP concentrations (0.0, 0.5 and 1.0 mg l-1) or Kinetin (10 mg l -1) in combination with NAA (0.0, 0.1, 0.3, 0.4 and 0.5 mg l-1) for shoot induction. Then, the influence of combinations of BAP (0, 0.5, and 1.0 mg l-1) and NAA (0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 mg l-1), Casein hydrolysate (CH) concentrations (0, 50, 100, 200, 300, 400 and 500 mg l-1) on shoot multiplication and elongation from individual shoot was investigated for two varieties. For in vitro rooting, full and haft-strength MS medium in combination with different IBA concentrations (0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 mg l-1) were tested. In acclimatization stage, five types of substrates (peat moss, perlite, vermiculite, peat moss + perlite, and vermiculite + perlite) were tested for rate of survival and initial growth of ‘Tainung No.2’ and ‘Red Lady’ papaya.
Results. (1). The data in grafting experiment in ‘Tainung No.2’ and ‘Red Lady papaya indicated that the youngest age of rootstock (1-month) achieved the best results. And in both varieties, cleft grafting in summer showed better results than in autumn. The combination of 1-month-old rootstock and grafting time in summer or autumn in ‘Tainung No.2’ and ‘Red Lady’ gave the best results on the time of sprouting (8.4 or 8.4 days and 8.4 or 8.5 days, respectively), percentage of graft success (96.7 or 91.7 % and 93.3 or 88.3 %, respectively), sprouting length of scion (3.9 or 3.8 cm and 3.7 or 3.7 cm, respectively), number of new leaves per graft (3.1 or 3.1 leaves and 3.1 or 3.1 leaves, respectively). (2). In cutting propagation of ‘Tainung No.2’ and ‘Red Lady’, there were significant differences in responses of rooting to different substrates and the best results of parameters were recorded in the peat moss, and mixture of peat moss and perlite. The growth regulator data showed that propagation by cutting of ‘Tainung No.2’ at 3,000 mg l-1 IBA and ‘Red Lady’ at 4,000 or 5,000 mg l-1 IBA achieved the best results on rooting rate (85.00 and 60.00 or 65.00 %, respectively), number of roots (5.61 and 5.33 or 5.58 roots, respectively) and root length (18.25 and 11.90 or 12.83 mm, respectively). (3). In micropropagation, an in vitro regeneration system for the hermaphrodite papaya cv. ‘Tainung No.2’ and ‘Red Lady’ using nodal explants was established thought four steps: shoot induction, shoot elongation and multiplication, in vitro rooting, and acclimatization. In the shoot induction, percentage of explants that produced shoots (65% or 66.67 % and 93.33% or 86.67 % respectively), mean number of shoots (2.08 or 2.31 shoots and 1.79 or 1.81 shoots respectively) and shoot height (2.16 or 1.82 mm and 2.24 or 1.95 mm respectively) in ‘Tainung No.2’ and ‘Red Lady’ were record by modified MS medium consisted with 0.5 or 1.0 mg l-1 BAP in combination with 0.1 mg l-1 NAA. For shoot elongation and multiplication, the best results was achieved on full-strength MS supplemented with 0.5 mg l-1 BAP, 0.2 mg l-1 NAA, and 200 or 300 mg l-1CH in ‘Tainung No.2’ and with 0.5 mg l-1 BAP, 0.1 mg l-1 NAA, and 200 - 400 mg l-1CH in ‘Red Lady’. In vitro rooting step, the best result of microshoot rooting achieved on ½ MS medium containing 1.5 mg l-1 IBA in Tainung No.2 and on ½ MS medium supplementing 2.0 or 2.5 mg l-1 IBA in ‘Red Lady’. For acclimatization in greenhouse, 85 % and 88.33% of ‘Tainung No.2’ and ‘Red Lady’ plantlets were successfully acclimatized on potting medium consisting of peat moss: perlite (1:1). After 40 days of acclimatization, plantlets grew normally and vigorously and plantlets were successfully established on field.
Conclusion. Plantlets propagated from grafting, cutting, and micropropagation in this study grew normally and vigorously on field. These results in asexual propagation should be recommended for commercial production of ‘Tainung No.2’ and ‘Red Lady’ papaya plantlets.
|
|---|
