| Due to the narrow genetic base of cucumber (Cucumis sativus L.), molecular polymorphism is relatively low. Thus, the identification and characterization of additional polymorphic markers would allow for their expanded use in genetic assessment. Experiments were designed to develop SSR, SCAR and SNP markers, and optimize reaction conditions for PCR. A set of 110 SSR markers was constructed using methodology included in the GeneTrapper(TM) kit, to select plasmids harboring microsatellites. Of these markers, 58 (52%) contained di-nucleotide repeats, 21 (19%) possessed tri-nucleotide repeats, 3 (2.7%) contained tetra-nucleotide repeats, 4 (3.6%) enclosed penta-nucleotide repeat, 3 (2.7%) contained hexa-nucleotide repeats, and 21 possessed composite repeats. In addition four SCARs and two PCR markers based on SNPs were developed.;Yield increase in processing cucumber is positively correlated with increases of number of lateral branches (MLB). Experiments were designed to independently confirm previously determined marker linkages to MLB, and to determine their utility in marker-assisted selection (MAS). Markers linked to MLB were used in MAS of BC1 and BC2 plants to produce BC2MAS and BC3MAS progeny. Statistical analysis showed no significant differences (p < 0.001) between means of phenotypic (BC2PHE = 3.02, BC3PHE = 3.29) and marker-aided (BC2MAS = 3.12, BC3MAS = 3.11) selection. However, both phenotypic and MAS populations were significantly higher than the random control (BC2RND = 2.27, BC3RND = 2.41).;A set of 171 recombinant inbred lines (RILs) were developed from a narrow cross in processing cucumber using lines G421 and H-19. A 131-point genetic map, having the predicted seven linkage groups and spanning 706 cM, was constructed from genetic analysis of 171 RILs and 216 F2 individuals. QTL analysis of MLB in three environments revealed four location-independent factors that explained 42% of the observed phenotypic variation. Sex expression was influenced by QTL corresponding to F and de and a third locus on linkage Group 6. QTL neighboring ll were important genetic determinants for fruit number per plant, MLB, and fruit length:diameter ratio. Molecular markers developed, and information regarding response to MAS and the genetic regions underlying the expression of yield components will assist processing cucumber improvement programs. |
