AFLP and SRAP Markers Linked to the mj Gene for Root-knot Nematode Resistance in Cucumber

Root-knot nematodes (Meloidogyne spp.) are an important worldwide pest of cucumber (Cucumis sativus L.). Molecular markers linked to the Javanese root-knot nematode (M. javanica) resistance gene mj in cucumber may aid marker assisted selection. One-hundred AFLP (EcoRI-MseI) and 112 SRAP were used to screen resistant and susceptible parents for polymorphisms to develop molecular markers linked to the mj gene. Of the 100 AFLP primers, 92 produced bands and two yielded candidate markers (E-ATT/M-CAA and
E-AAC/M-CTG). These two bands were cut off from polyacrylamide gel, cloned and sequenced. Primers
designed from the sequences did not yield polymorphic bands between the parents. In addition, the sequences
did not contain any restriction site or indel to be used to convert them to CAPS or SCAR markers. The two
sequences obtained from polymorphic AFLP markers were used primarily to design D1F, D1R, D17F and
D17R primers. SRAP forward and reverse primers were used in combination with these four specific primers
to search for polymorphisms between parents. Of the 112 primer combinations 11 yielded polymorphisms
between parents. MapMaker Exp 3.0 software was used to analyze the 11 markers. Two markers were
identified that flanked the mj gene at distance of 16.3 and 19.3 cM. The results indicated that these markers
should be useful to develop molecular markers flanking the mj gene.