Root Yield and Starch Synthase Type IV Gene Activity under Different Micro Nutrient Fertilizer and Harvest Ages on Cassava (Manihot esculenta Crantz)

Abstract The important part of cassava root is starch which is probably controlled by starch synthase type IV (SSIV) gene. The information of micro nutrient and harvest age related to the activity starch synthase type IV (SSIV) gene is still very rare. The objectives of this study were to evaluate root fresh weight of cassava, to compare yield of storage root, and to evaluate the activity of starch synthase type IV (SSIV) gene by real-time quantitative polymerase chain reaction (RT-PCR) applied by micro nutrient fertilizer. Treatments were arranged by factorial (3 × 3) in randomized complete block design (RCBD) with three replications used as block. The first factor was three different dosages of micro nutrient fertilizer as 0, 20, and 40 kg/ha. The second factor was harvest ages as 7, 8, and 10 months after planting (MAP). The micro nutrient fertilizer mainly contents of 5,888 ppm Fe and 1,368 ppm Zn. Variables were leaf number (LN), leaf fresh weight (LFW), leaf dry weight (LDW), stem fresh weight (SFW), stem dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), skin root fresh weight (SRFW), skin root dry weight (SRDW), starch content, and activity of SSIV gene. The result showed that RDW of cassava applied by 40 kg micro nutrient/ha was significantly increased at 10 MAP. The increase in RDW was due to mainly high SSIV gene activity. Additionally, the SSIV gene activity caused by 20 kg micro nutrient/ha treatment showed almost as twice as those by 40 kg micro nutrient/ha. Keywords: Real-time PCR, Root dry weight, Root yield, Starch, Stem dry weight