A lettuce plant with quantitative Bremia lactucae resistance or plant part thereof comprising an allele conferring resistance to Bremia lactucae, but lacking a second allele genetically linked to the allele conferring resistance in Lactuca saligna, wherein the second allele confers a trait selected from the group consisting of adventitious shoots, reduced plant diameter and bubbled leaves, said lettuce plant or lettuce plant part (i) comprising a chromosomal segment comprising RBQ6 QTL of Lactuca saligna that confers quantitative resistance to Bremia lactucae, wherein the RBQ6 QTL has the L. saligna allele of markers LE3118 being detectable using the primer pair comprising SEQ ID NO:7 and SEQ ID NO:8, and LE9214 being detectable using the primer pair comprising SEQ ID NO:9 and SEQ ID NO:10; and lacking a second QTL of L. saligna that confers reduced plant diameter or bubbled leaves, wherein the second QTL has the L. saligna allele of marker LE0420 being detectable using the primer pair comprising SEQ ID NO:11 and SEQ ID NO:12; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9045; or (ii) comprising a chromosomal segment comprising RBQ5 QTL of Lactuca saligna that confers quantitative resistance to Bremia lactucae, wherein the RBQ5 QTL has the L. saligna allele of markers LK1475 being detectable using the primer pair comprising SEQ ID NO:1 and SEQ ID NO:2, and LE1276 being detectable using the primer pair comprising SEQ ID NO:3 and SEQ ID NO:4; and lacking a second QTL of L. saligna that confers adventitious shoots, wherein the second QTL has the L. saligna allele of marker LE0350 being detectable using the primer pair comprising SEQ ID NO:5 and SEQ ID NO:6; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9046. (i) comprising a chromosomal segment comprising RBQ6 QTL of Lactuca saligna that confers quantitative resistance to Bremia lactucae, wherein the RBQ6 QTL has the L. saligna allele of markers LE3118 being detectable using the primer pair comprising SEQ ID NO:7 and SEQ ID NO:8, and LE9214 being detectable using the primer pair comprising SEQ ID NO:9 and SEQ ID NO:10; and lacking a second QTL of L. saligna that confers reduced plant diameter or bubbled leaves, wherein the second QTL has the L. saligna allele of marker LE0420 being detectable using the primer pair comprising SEQ ID NO:11 and SEQ ID NO:12; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9045; or lacking a second QTL of L. saligna that confers reduced plant diameter or bubbled leaves, wherein the second QTL has the L. saligna allele of marker LE0420 being detectable using the primer pair comprising SEQ ID NO:11 and SEQ ID NO:12; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9045; or (ii) comprising a chromosomal segment comprising RBQ5 QTL of Lactuca saligna that confers quantitative resistance to Bremia lactucae, wherein the RBQ5 QTL has the L. saligna allele of markers LK1475 being detectable using the primer pair comprising SEQ ID NO:1 and SEQ ID NO:2, and LE1276 being detectable using the primer pair comprising SEQ ID NO:3 and SEQ ID NO:4; and lacking a second QTL of L. saligna that confers adventitious shoots, wherein the second QTL has the L. saligna allele of marker LE0350 being detectable using the primer pair comprising SEQ ID NO:5 and SEQ ID NO:6; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9046. lacking a second QTL of L. saligna that confers adventitious shoots, wherein the second QTL has the L. saligna allele of marker LE0350 being detectable using the primer pair comprising SEQ ID NO:5 and SEQ ID NO:6; wherein a sample of seed comprising the chromosomal segment was deposited under ATCC Accession Number PTA-9046.