Genetic Improvement of Taro (Colocasia esculenta var esculenta) through in-vitro mutagenesis

Abstract

Mutation breeding has been applied for many years for the improvement of crops. According to the   FAO/IAEA mutant variety database, there are at least 2300 mutant varieties released officially   worldwide. Taro (Colocasia esculenta) is vegetatively propagated, hence induced mutations offer the best way to induce variability in breeding program. In-vitro culture technique has also been applied to recover  mutated cells through repeated in- vitro multiplication and to accelerate the breeding time. In the in-vitro culture media test, Murashige and Skoog medium supplemented with Indole –3-acetic acid (10 mgL^-1)  was found optimum for initiation and growing of taro. Benzylaminopurine (2 mgL^-1) or Thidiazuron (0.9  mgL^-1) was found optimum for multiplication of taro. In the radiosensitivity test, shoot tips were  irradiated from 0 to 60 grays of a ¹³⁵Co gamma irradiation source and cultured on MS Medium   supplemented, with 10 mgl^-1 Indole –3-acetic acid. The effective mutation dose (LD₃₀) that causes 30% reduction in growth was found to be 7.65 grays. 300 shoot tips were irradiated with 7.65 grays and  multiplied for four generations. A population of more than 30,000 in-vitro plantlets of taro has been  reached. A low-cost alternative substrate (60% composted scum + 40% fly ash) for hardening of tissue-cultured plantlets of taro was identified. 3500 plantlets were already hardened and used to optimize screening protocols for disease resistance against Phytophthora colocasiae.

Key words: taro, mutation breeding, in-vitro culture, Phytophthora Leaf Blight resistance.