Genome Evaluation of Cucumber in Relation to Cucurbit Family

Abstract

Cucumber is the only crop in Cucurbitaceae family with 2n = 2x = 14 chromosomes, while the majority of other crops in this family have chromosome number of n = 10 ~ 12. The cucumber genome size is estimated to be around 367 Mb, which is relatively smaller than melon and watermelon genomes. Comparative genetics and genomics revealed that the cucumber genome has a high level of synteny among chromosomes and sequence identity when compared to melon and Cucumis hystrix, both of which are members of genus Cucumis. With the rapid development and reduction in cost of sequencing technologies, the genomes of other Cucurbitaceae family members such as melon, watermelon, pumpkin/squash, wax gourd, bottle gourd, bitter gourd, and sponge gourd, have been sequenced in the recent years. The gene number in cucumber is comparable to that of melon, watermelon, and bottle gourd, which is significantly less than that of the other three cucurbit species, according to gene annotation for these genomes. Furthermore, the availability of these genome sequences has enabled extensive phylogenic and synteny comparison of cucurbit species using comparative genomics, which is critical for understanding the genome structure and evolution of various species with different chromosome number.