Storage effects on genomic DNA in rolled and mature coca leaves

Abstract

Rolled and mature leaf tissue was harvested from Erythroxylum coca var. coca Lam. (coca) to determine a method for storage that would maintain DNA with high quality and content up to 50 days. Harvesting coca leaf tissue under Andean field conditions often requires storage from 3 to 10 days before extraction where tissue integrity is lost. All samples of rolled and mature coca leaf tissue were harvested and separately stored fresh in RNAlaterTM for 50 days at 4°, −20°, and 23°C, while similar samples were air-dried for 72 h at 23°C or ovendried for 72 h at 40°C after storage, before extraction. Triplicate samples of each tissue type were extracted for DNA at 10-day intervals and showed that DNA integrity and content were preserved in leaf tissue stored at 4° and −20°C for 50 days. Rolled and mature leaf tissue stored at 4°, −20°, and 23°C showed insignificant degradation of DNA after 10 days, and by day 50, only leaf tissue stored at 4° and −20°C had not significantly degraded. All air- and oven-dried leaf tissue extracts showed degradation upon drying (day 0) and continuous degradation up to day 50, despite storage conditions. Amplified fragment length polymorphism analysis of DNA from rolled and mature leaf tissue of coca stored at 4° and −20°C for 0, 10, and 50 days showed that DNA integrity and content were preserved. We recommend that freshly harvested rolled or mature coca leaf tissue be stored at 4°, −20°, and 23°C for 10 days after harvest, and if a longer storage is required, then store at 4° or −20°C.