الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
Taro is an important staple food crop grown throughout many Pacific Island countries parts of Africa, Asia and the Caribbean for its corms and nutritious leaves (Revill et al., 2005). As such taro is grown under intensive cultivation as a starch crop (Jianchu et al., 2001).
Conventional method of taro is being used via vegetative propagated plantlet for the field cultivation. The division of offshoots Taro is not always suitable for this cultivation due to the weakness and susceptibility to pathological agents. Taro is one of the principle root crops that have shown great promise in generating income within the rural communities. However, the limited availability of proper planting material has imposed an emerging problem. To address the problem, in vitro micropropagation was adopted with the objective of making Taro planting material available to farmers. Application of plant tissue culture in Taro in of great advantage for mass propagation and development of disease resistant cultivars in Taro.
5.1. First stage (Establishment of an aseptic culture of Taro)
5.1.1. Sterilization of the explants
The aim of this experiment was to suggest the best sterilization treatment of shoot-tip or / and meristem tip of Taro to give the highest survival percentage, and minimized the contaminated culture. Different treatments of sterilization were used as a combination of three factors, sterilized agents (Clorox, HR2RoR2R and Ethanol); period and excision time. Our finding indicated that three treatments gave no contamination, they are:
1- E-OH 70%/ 5sec. + Clorox 10%/ 20min used to sterilized the meristem ( survival is 20%).
2- Clorox 70%/30min to sterilize the shoot tip then Clorox 10%/10 min to sterilize the meristem (10% survival).
3- Clorox 70%/30min to sterilize the shoot tip then E-OH 70%/ 5sec to sterilize the meristem (80% survival).
5.1.2. Growth of the shoot tip of Taro:
The excised shoot tip explants were at size ~ 5 mm and then transferred to a previously sterilized nutrient medium (MS) - medium supplemented with different combination of BA (0.0, 0.5, 1.0, 1.5, 2.0) and NAA (0.0, 0.1, 0.2, 0.5) data showed that
1- Increasing (BA) concentrations due to increase the growth index of shoot tip
2- Growth index increased with time, but this rate was higher with increasing of BA concentrations with 0.5 mg/l of NAA.
3- The combination of 2.0 mg/l of BA plus 0.5 mg/l NAA gave 66.7% of shooting with no roots formation.
5.2. Second stage (multiplication stage):
This stage aimed to increase the number of new formed shoots of Taro as well as to improve their growth. In the view of the earlier mentioned results (in the previous stage) shoot tips proliferated of initiation stage were taken a 5 mm in length were cultured on MS medium which augmented with 2 mg/L BA + 0.5 Mg/ L NAA were used as propagules in the following experiments.
5.2.1. Effect of different concentrations of BA on multiplication of taro.
This experiment was made in as an attempt to quantity the
possible proliferation rate using different concentrations of BA. Results
showed that the using 3mg/L of BA significantly increase the
proliferation rates of shoots (3.5 shoot /explant), with 100% of shooting
percentage and no callus or roots were formed. But this number of shoot
decreased as well as BA increased to 4 or 5 mg/L (shoot number was
2/explant) otherwise 2 mg/L of BA gave 3 shoot / explant.
5.2.2. This experiment was conducted to study the effect of the combination of BA with NAA on multiplication rate. Our finding show that the combination of 3 mg / L of BA with 0.25 or 0.5 mg / L of NAA produced 3.5 shoots / explant after 8 weeks, it dose means that, addation of NAA to BA due to increase the rate of multiplication and its vigour.
5.2.3. Experiment was conducted to study the effect of consecutive of subculture on the multiplication rate of taro culture in vitro, Results show that consecutive subcultures had an effect on the rate of multiplication of taro cultures in vitro. The rate of shoots was gradually increased monthly. By the end of 16 weeks (Fourth subculture) we gotted 194 shoots means 4.5 shoot / explant as a rate of multiplication.
5.3 Third stage (In-vitro rooting):
The in vitro rooting of shoots derived from tissue culture is necessary for the establishment stage in vivo. To encourage root formation on new-formed shoots, the auxins NAA and IAA were used. After 4 weeks from culturing on rooting medium, percentage of root formation, number of rooted shoots as well as number of roots per shoots and length of roots were recorded. Results indicated the percentage of root formation doesn’t affected by the presence of auxins, so hormone free medium gave a 100% root formation the presence of auxin regardless of auxin concentration. The number of roots with the different concentrations of different type of auxin is not significant. Meanwhile, the lengths of the roots are affected by the type of auxin.
5.4 Fourth stage (Adaptation stage):
This experiment was conducted to study the optimal transplanting medium for in vitro derived taro plantlets. The in vitro derived plantlets about 5 cm. in height were cultured in plastic pots. 8 transplanting media were used, pots was maintained under a plastic tunnel. Survival percentages were recorded after 4 weeks of transplanting.
Data revealed that planting medium contained only sand gave the lowest survival percentage of taro plantlets (15%). Meanwhile, the highest percentage of survival taro plantlets (95%) was obtained when the medium contained vermiculite & perlite and sand (1:1:1).
5.6 Molecular analysis of tissue culture derived plantlets of Taro:
Two kinds of plant materials were used. Genomic DNAs of 60PthP materials were extracted and compared by RAPD-PCR, using five random oligonucleotide primers. Generally all cases showed that the RAPD-fingerprints produced with different were almost identical.