Botany and genetics of New Caledonian wild taro, Colocasia esculenta

Taro, Colocasia esculenta (L.) Schott, is considered to be an introduced crop in New Caledonia and has been cultivated since its introduction by Melanesian farmers. Wild germplasm exists on the main (continental) island and is represented by three easily distinguished morphotypes: a morphotype with purple leaves, another with green leaves, and a third with green leaves and a purple vein junction on the lamina. All three morphotypes are diploids (2n = 2x = 28) and have well-established wild populations in many valleys and gulches of the main island. The morphotype with purple leaves has all typical traits of a wild genotype (inedible corms; long, thin stolons); the other two produce edible corms. The purple and the green morphotypes flower and produce fertile pollen. The spathes of the green morphotype can be more than 40 em long and the spadix is characterized by an extremely long appendix atypical for Pacific taros. Isozyme analysis conducted using four enzyme systems (EST, PGM, PGI, SkDH) indicated that New Caledonian wild taros differ from most widely grown local cultivars and Pacific cultivated and wild genotypes. Evidence presented in this study suggests that C esculenta is an endemic species to New Caledonia. Cultivars were probably introduced as clones from what is now Vanuatu by early Melanesian migrants and were not domesticated locally from existing wild forms, which appear to be genetically distant from other Melanesian wild taros. (Résumé d'auteur