HISTOLOGICAL AND BIOCHEMICAL CHANGES IN CORMS OF COLOCASIA ESCULENTA INFECTED BY BOTRYODIPLODIA THEOBROMAE AND SCLEROTIUM ROLFSII

Anatomical studies of the healthy corms of Colocasia esculenta showed an outer corky layer and inner cortex of mainly parenchymatous cells. The ethanol soluble carbohydrates were extracted and identified as maltose, sucrose, glucose and fructose. The two cultivars ‘ikpong’ and ‘cocoindia’ used in these studies also contain appreciable quantities of lipids, proteins and oxalate. The major carbohydrate component of the corm was starch. The two organisms , Botryodiplodia theobromae and Sclerotium rolfsii which were the most important rot pathogens of C. esculenta penetrated and colonised the corm tissue intercellularly and intracellularly. The infected cells were cleared of most of their starch grains and the cells disintegrated within ten days of inoculation. Apart from destroying the histological structure of the corms, the carbohydrate, protein and lipid contents were reduced on infection by both organisms. However, the oxalate content increased after infection by S. rolfsii.