Citrus sp. and Poncirus trifoliata are without a sequenced genome. One of the only sources of sequence information for these two organisms currently comes from what are known as Expressed Sequence Tags or ESTs. ESTs are short sequencer reads of expressed RNA taken from various types, tissues, and treatments. The laboratory of Timothy Close has assembled these sequences into a meaningful database named HarvEST Citrus. This is written and maintained in the FoxPro language by Steve Wanamaker and currently exists at version number 0.38 (http://harvest.ucr.edu/). The core of the HarvEST assembly package is the CAP3 assembly engine (Huang and Madan, 1999) to which some modifications and default parameter changes have been made.

Constituent libraries in the HarvEST Citrus database include libraries such as UCRC, USDA, and UCRPT. These stem from such organisms as Citrus sinensis (sweet orange),Citrus jambhiri (rough lemon), and Citrus unshiu (satsuma or mandarin). Various tissues, including the calyx abscission zone, seeds, and fruit juice sacs from trees of immature, mature, or 18-year ages are present in these constituent libraries. Further, treatments such as normal, 24 hours after CMNP application, and fruit subject to storage are also represented. On average, a mean of 1,600 sequences are present in each of the 40 odd constituents with a median count of around 1,000 sequences. The current total number of Citrus sinensis sequences is 78,611 and Poncirus trifoliata is 14,378 (Thu Dec 9 10:25:37 PST 2004). As the count and diversity of the Poncirus and sweet orange libraries increase, any sequencing errors will be greatly reduced via the redundancy of high-quality, overlapping sequences.

Huang X, Madan A (1999). CAPS: a DNA sequence assembly program. Genome Res 9: 868-877.