Phytochemical compounds in cassava (Manihot esculenta crantz) var. Medan and Pontian influenced by sources of fertilizer

The level of phytochemicals in crops is affected by several factors such as genetic differences and environmental conditions. Nowadays health conscious consumers are interested in optimizing the nutritional composition of foods produced through environmentally friendly. Therefore, a study was conducted with the objectives of determining the phytochemical contents of Manihot esculenta as affected by varieties and sources of fertilizer. Planting materials collected from MARDI Jalan Kebun were used in this study. Genomic DNA was extracted from leaf samples using GeneAll Plant DNA extraction kit and a total of eight simple sequence repeats (SSR) primers were used. The genetic similarities among the planting materials were estimated using the Jaccard’s coefficients. The study revealed that number of polymorphic loci is three which is equal to 36.5% of polymorphism between 30 samples (15 Medan and 15 Pontian). The low degree of variation represent that most of these samples were somaclonal materials. The Jaccard similarity matrix ranged betweeen 0.60-1.00, indicating a close relationship among the cassava genotype. The field experiment was conducted at Field 10. Six treatments were arranged in randomized complete block split-plot design with three replications. The main plot was fertilizer sources consisting of vegetable waste vermicompost (2.32 %N: 1.54%P: 1.06%K), empty fruit bunch compost (1.46%N: 1.47%P: 2.58%K) and inorganic fertilizer (15%N: 6.55%P: 12.45%K). The sub plot based on Medan and Pontian varieties. The physiological activities were observed at 4 and 7 months after planting. The young leaves and tuber were harvested 9 months after planting and analyzed for the phytochemical compounds. The highest yield and the largest tuber diameter were observed in inorganic fertilizer treated-plants. The highest chlorophyll obtained from vermicompost-treated plant. Among varieties, the highest yield was obtained from Pontian. There were positive interactions between the fertilizer sources and varieties in terms of yield, tuber diameter, relative chlorophyll content, stomatal conductance and photosynthetic rate. The findings also showed that cassava treated with VWV gave the best performance on the ascorbic acid, total carotenoids, total phenolic compounds, and total flavonoid and antioxidant activities whereas, inorganic fertilizer increased the level of cyanogenic glycosides in tuber and leaves. Total phenolic and flavonoid content was found significantly higher (P≤0.01) in the VWV treatment than those in mineral fertilizer and EFBC. Total phenolic compounds increased by 15 % in the VWVtreated leaves and tuber compared to EBFC. Among varieties, Medan contained higher phytochemical content compared to Pontian. The DPPH and FRAP scavenging activity had shown that Medan with the application of VWV exhibited a higher percent of inhibition. Application of vermicompost and EFBC can enhance antioxidant activities. Medan leaves exhibited significantly higher antioxidant activity than Pontian. Cyanide content in all treatments showed significant differences for both leaves and tuber. Relatively a lower amount of cyanogenic glycoside content was found in cassava where compost had been applied. In this study it is clear that fertilization and variities have a pronounced influence on yield, physiological activities and phytochemical contents in cassava.

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