Genetic Diversity and In-vitro Regeneration of Taro (Colocasia esculenta (L.) Schott.) Germplasm in Kenya

Abstract

Taro (Colocasia esculenta) is a clonally propagated aroid and is largely grown in humid tropical areas worldwide. This crop was first domesticated in South-east Asia, spreading throughout the world and is now an important crop in Asia, the Pacific, Africa and the Caribbean. Besides, it is the most important edible species of the monocotyledonous family Araceae. Almost all parts of the taro plant are utilized. The corms are baked, roasted, or boiled and are a good source of carbohydrates. Its leaves are frequently consumed as a vegetable representing an important source of vitamins, and even petioles and flowers are utilized in certain parts of the world. Taro production is majorly affected by low genetic diversity and lack of quality planting materials. This study aimed at assessing genetic diversity and developing an In-vitro regeneration protocol for Kenyan Taro germplasm. First, the genetic diversity of all 186 samples were classified into four major groups (A, B, C and D), using the statistical R software and a simple circular phylogenetic tree was generated, showing within population variation than among the population variation. Secondly, an efficient protocol for direct organogenesis was established for two Taro varieties (Dasheen and Purple wild), using sterilized upper part of the corm and the base of the petioles. These explants were evaluated for their potency for shoot induction on varied concentrations of 6- Benzylaminopurine (BAP) concentrations that included 0, 0.5, 1, 2 and 3 mg/l. The highest shoot induction was observed on media supplemented with 2 mg/l BAP for both Dasheen and Purple wild varieties while the lowest was on media with 0.5 mg/l for both varieties. The highest rooting response that also gave the shortest roots was observed in media supplemented with 0.5mg/l IBA (12.867) for Dasheen and 11.933 for Purple wild variety. Apical meristems excised under a microscope and cultured in callus induction medium showed swelling and formation of embryo-like structures within the first four weeks of culture. The first stages of callusing, including swelling of the embryo and colour change were seen after 8 weeks of culture. After subsequent subculturing into similar media for 4 weeks, callus became more distinguishable from swollen embryos. The callus texture was more visible after two weeks and friable and compact calli could be seen. Calli was best formed in media containing 10 µM 2,4-D and 2 µM TDZ for both Dasheen and Purple wild varieties. However, Dasheen had the highest formation of 77.8% and Purple wild had 71.1%. This regeneration protocol is very important for future Taro production to enhance quality and quantity planting materials.