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close this section of the library Sharma, Rosalene Sharina

View the PDF document Optimizing protocols in the use of seeds for conservation and propagation in taro (Colocasia esculenta var. esculenta)
Author:Sharma, Rosalene Sharina
Institution: University of the South Pacific.
Award: Ph.D.
Subject: Taro -- Oceania -- Propagation , Taro -- Seeds -- Harvesting , Taro -- Seeds -- Postharvest technology, Taro -- Oceania -- Protection , Taro -- Seedlings
Date: 2011.
Call No.: pac SB 211 .T2 S3952 2011
BRN: 1184885
Copyright:Under 10% of this thesis may be copied without the authors written permission

Abstract: Taro (Colocasia esculenta var. esculenta) is a culturally and economically important food crop in the the South Pacific region. Following the increased threats to taro germplasm from pest and disease, and climate change, there was a need to collect, improve and conserve the regional taro varieties. Seed conservation was considered as a possible conservation strategy for taro, useful for the conservation of taro genes. This thesis aimed to investigate the use of taro seeds as a material for conservation and propagation. Protocols were developed to optimize flowering, seed production and germination, seedling establishment into field, post-harvest seed handling, and conservation strategy using seeds. This was carried out by researching the environmental and physical conditions that was best suited to achieve maximal results. In addition, this work also aimed to investigate possible seed transmission of virus and determine the risks associated with seed transfer. Taro (Colocasia esculenta var. esculenta) of the PNG cultivar was used for the purpose of this study. Gibberellic acid at a concentration of 500 ppm was used to promote flowering and hand pollination was carried out to promote fertilization. Long day lengths, warm temperature, high humidity and adequate water and nutrient supply favoured successful flowering, fertilization and fruiting in taro. Taro seed germination favoured a temperature range of 25 – 31 oC, red and white light, a range of substrates (petri dish method, potting mix and sterile soil), planting depth of 0 – 20 mm, and a range of 0 – 100 ppm of gibberellic acid to enhance and promote uniform germination. Sufficient amount of water was also required, with low or high water provided to seeds, the seedlings would have been affected by damping off - a major problem of taro seedlings due to its very delicate and tiny nature. Successful seedling establishment required five major developmental stages starting from initiating seed germination, transferring to glasshouse, individual transplanting of seedlings, then to 50 % nursery shade and finally establishing into field. Stepping from one stage to next was necessary to acclimatize the seedlings to the natural strength of the light. The viability of taro seeds lasted for about 30 days. Harvesting mature seeds, extracting and cleaning seeds gently, drying well before storage to avoid fungal contamination, least exposure to the different environments to avoid temperature vi fluctuations are some of the major rules that contribute towards optimizing seed production. This further contributes to maximizing seed viability after. Taro seeds maintained variable viability with different storage methods for limited time, but the storage in a fridge at 5 oC gave the best results. This research also confirmed that the Qiagen kits worked well to extract DNA and RNA from taro seeds. Thus, exchange of virus-free taro seeds across the Pacific region can be made feasible. Nevertheless, the results presented here show that the protocols developed in the study can be used for optimizing flowering, seed production, germination and conservation of taro seeds, the establishment of the seedlings in the field, and the use of the latest molecular technique (PCR) to detect either the presence or absence of a particular virus in the seeds. This research will also benefit the Pacific Island countries to increase taro production (of their suitability) for subsistence livelihood and for export.
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