Slow growth culture for in vitro maintenance of taro

Taro, popularly known as 'gabi' in the Philippines, is one of the rootcrops with great economic potential. It is primarily grown for its corms which are used as roof vegetable and the leaves as leaf vegetable. In 2002, it was reported that there is an increasing demand for taro because of its many uses as a raw material for food and health products. The Philippine Root Crop Research and Training Center in Leyte [Philippines] has already developed in vitro culture technique for taro propagation. However, the technique would produce overgrown plantlets after 2-3 months incubation, a situation which increases the risk of microbial contamination. Thus, Acedo and Dacara (PRCRTC) aimed to develop a slow growth culture technique that can keep plantlets of different taro varieties for more than a year without affecting its morphological stability and in vitro performance study on the effects of growth retardants such as abscisic acid (ABA) and mannitol at different concentration on in vitro plant development of taro was done as well as evaluation of the viability, morphological stability, and performance of in vitro-stored taro germplasm materials. Root growth of VG-1 was not very much affected by ABA treatment at 2.0 mg/L, 4.0 mg/L, and 10.0 mg/L concentrations. However, all the ABA-treated cultures exhibited reduced shoot growth than the control during the 3rd month of incubation. For NSIC G-7, ABA-treated cultures had longer roots than the control after 2 months of incubation. Based on the concentrations used, ABA was not suitable in achieving the desired growth rate reduction in taro shoot tip cultures. Mannitol concentrations lower than 4% were not effective in reducing growth rate of taro cultures. For VG-4, shoot formation at 4.5% mannitol level significantly differed with that of the control in terms of root formation. Also increasing the concentration caused a corresponding delay in both root and shoot formation. Explants taken from plantlets grown in medium with 5-5.5% mannitol concentrations were not suitable for medium-term culture maintenance. Results showed that 4.5% mannitol was the best medium additive for medium-term in vitro maintenance of taro since the plantlets exhibited the desired slow growth and were able to resume normal growth after a year of maintenance without adversely affecting the morphological traits.