Segregation and linkage of several genes in cucumber

Gene linkage was investigated in 11 families using 18 genes in cucumber (Cu cumis sativus L.). The genes studied were B (black spine), B-3 (Black spine -3), B-4 (Black spine-4), bi (bitterfree cotyledons), Bt (bitter fruit), Bt -2 (bitter fruit-2), D (dull fruit skin), df (delayed flowering), de (deter minate habit), F (female sex expression), gl (glabrous foliage), lh (long h ypocotyl), ns (numerous spines), pm-h [powdery mildew (Sphaerotheca fuligin ea Schlecht.:Fr.) resistance expressed on the hypocotyl], as (small spines) , Tn (tuberculate fruit), u (uniform immature fruit color), and w (white im mature fruit color). A major objective of this study was to measure linkage s of genes for fruit bitterness (Bt and Bt-2), and spine color (B-3 and B-4 ) relative to previously studied loci: B, bi, D, de, df, F,gl, Ih, ns,pm-h, ss, Tn, u, and w. The Fz progeny of LJ 90430 x PI 173889 segregated 13 bit ter fruit : 3 nonbitter fruit, indicating that different genes are controll ing fruit bitterness in these lines. Bt-2 is proposed as the gene controlli ng bitterness of fruit in LJ 90430. It is a separate locus from Bt, that ca uses bitter fruit in PI 173889. Several new gene linkages were found: bi-Bt , (Bt-2)-de, D-(Bf-2),D-ns, gl-F,ss-(Bt-2), Tu-(Bt-2), and u-(Bt-2). The Bt gene appears to be linked to bi and may be located on linkage group I. Bt- 2 appears to be linked with several genes that could connect linkage groups I and IV. Bt-2 mas linked to re, Tu, D, and ss, that are all on linkage gr oup IV. Bt-2 was also found to be linked loosely to de, that is on linkage group I. No linkages were found between B-3 and B-4 and the genes evaluated in this study. Weak linkages (> 25 cM) between several gene combinations [ (Bt-2)-de, de-ns, de-ss, de-Tu, de-u, ns-F, and ss-F] provided more evidenc e that linkage group I and IV may be Linked. Due to the weak linkages, more information needs to be obtained using larger populations and more markers to confirm these findings.