Effect of Genotype, Age and Soil Moisture on Cyanogenic Glycosides Content and Root Yield in Cassava (Manihot esculenta Crantz)

Abstract

Cyanogenic glycosides in cassava roots and leaves can be indirectly harmful if presented at high concentrations because they are transformed into cyanide which is toxic to humans. Low cyanogenic potential should be added in breeding programs for food security in the future to reduce any bitter taste and to reduce intoxication in cases of consumption of improper processed roots. This experiment investigated the effects of genotype, plant age, soil moisture and interactions of these factors on the content of cyanogenic glycosides in both the roots and leaves of cassava and on other agronomic traits indicating plant growth. The experiment was established using a factorial randomized complete block design with three replications containing two varieties, two soil moisture conditions and three plant harvesting periods. The varieties chosen for this experiment—Hanatee (HNT) and Kasetsart 50 (KU50)—were different in cyanogenic potential. Plants were harvested at 4, 5, and 6 months after planting (MAP). The drought-stressed group was subjected to drought from 3 to 4 MAP and was irrigated at 5 mm d-1 from 4 to 5 MAP and then was subjected to drought again from 5 to 6 MAP; The well-irrigated group was irrigated at 5 mm.d-1 for the whole experiment. The results showed that root cyanogenic glycosides levels , as presented in the form of total free cyanide, were high under drought stress and a difference between the content of root cyanogenic glycosides of HNT and KU50 could occur under drought stress. However, drought stress caused a reduction in plant growth including root yield, and re-watering for 1 mth was not enough to recover cassava growth significantly.