**Abstract**

Rapid progress has been made in classical genetics and traditional breeding in cucumber for various quantitative and qualitative traits which greatly benefited the development of superior varieties suitable for open field and protected cultivation. The different breeding methods like plant introductions, hybridizations, pedigree selection, recombination breeding and marker assisted selection have been employed successfully in developing superior varieties and F1 hybrids. The development of new varieties with earliness, high-yield and resistance to diseases (powdery mildew, downy mildew and tolerant to virus) through selection of superior parental lines followed by hybridization and marker assisted introgression of desired genes was a game changer in cucumber breeding. The exploitation of gynoecious sex along with parthenocarpic traits in traditional breeding has made revolution in cucumber cultivation throughout the world which enabled the adoption of cucumber crop by farming community on large scale. Molecular markers technology could be exploited to overcome the obstacle of traditional breeding by accelerating the breeding cycle and selection of desirable traits. The high density genetic maps for various traits have been constructed in cucumber to detected quantitative traits loci (QTLs) for genetic enhancement in different market classes of cucumber. Therefore, this chapter highlighted the concepts of genetic foundations for advancement made in cucumber breeding.

**Keywords:** cucumber, traditional breeding, classical genetics, molecular breeding
