Isolation and purification of functional total RNA from different organs of cacao tree during its interaction with the pathogen Crinipellis perniciosa

Witches' broom disease, caused by Crinipellis perniciosa, is one of the major fungal diseases causing severe losses to cacao tree (Theobroma cacao L.) plantations in South America. One of the challenges associated with the understanding of the cacao and Crinipellis interaction in genomic studies is the isolation of intact nucleic acids. In this report, we describe a new, successful, and reliable procedure for the isolation of RNA from tissues of cacao tree, both infected and uninfected by Crinipellis. This protocol overcomes the problems associated with the very high amount of polyphenols and polysaccharides present in cacao organs that are not easily removed by conventional extraction procedures. The protocol requires few reagents, uses ultracentrifugation and inexpensive consumables, and can be easily applied in any laboratory. This method produced high-quality RNA that was suitable for subsequent purposes, such as reverse transcription PCR and cDNA library construction. We also report the first evidence of RNA isolation from cacao organs infected by C. perniciosa such as meristems and fruits.