Xanthosoma sagittifolium, or tannia, is a tropical flowering plant from the family Araceae. It produces an edible, starchy corm. X. sagittifolium is native to tropical America where it has been first cultivated. Around the 19th century, the plant spread to Southeast Asia and Africa and has been cultivated there ever since. X. sagittifolium is often confused with the related plant Colocasia esculenta (taro), which is similar both in appearance and its uses. Both plants are often collectively named 'cocoyam'.
Tannia is among the world’s most important tuber crops and feeds 400 million people worldwide. There are multiple varieties, the two most common being the red flesh and the white flesh variety. They were selectively bred to improve pest and disease resistance, to shorten the time it takes to reach maturity and to improve the cooking quality.
Common names
Common names for X. sagittifolium include tannia, new cocoyam, arrowleaf elephant's ear, American taro, yautía, malanga, and uncucha. Cultivars with purple stems or leaves are also variously called blue taro, purplestem taro, purplestem tannia, and purple elephant's ear.
Ecology
Root rot is the most important disease in tannia. The oomycete Pythium myriotylum is probably the main causal agent of the root rot disease. Other organisms that could be involved are Phytopthora ssp., Fusarium ssp., Penicillium ssp., Botrydioplodia ssp., Erwinia ssp. and Pseudomonas ssp. Symptoms are stunted growth, wilting, chlorotic and withered leaves and a poor root system. The disease leads to low yields or even complete crop failure. The disease spreads through soil and planting material. The pathogens can persist for a long time in the soil, often forcing farmers to give up planting tannia in infected fields for at least five years. Wetland, floodings and poorly drained soils are associated with the appearance of root rot disease. As long as the field is not yet infected, the best method to control the disease is to use disease-free...
