We performed QTL mapping for loci governing C. elegans longevity, in 4 interstrain crosses (Bristol-N2, RC301, and CL2a Bergerac-BO, and Bristol-N2DH424) revealing 4- 11 significant QTLs each, and a total of 13 life-span loci (each p<0.01; most LOD scores >8). Four of these longevity QTLs were backcrossed 20 generations to introgress the Bergerac-BO allele into the other parental background. Recombinants arising in the last two generations were rendered homozygous for the introgressed region and were tested for longevity and stress resistance. Each QTL showed retention of the longevity phenotype -- conferring allelic effects on median life-span of 1.5-3.5 days at 20 C; three of these were also backcrossed 3 generations in the opposite direction, with similar allelic trait effects. Each QTL tested also produced marked allelic differences for two or three of the four stress-response traits tested: resistance to thermal stress, hydrogen peroxide, paraquat, or ultraviolet irradiation. Of these stresses, thermotolerance correlated best with longevity (r = 0.91), followed by peroxide resistance (r= 0.72), paraquat resistance (r= 0.67) and UV resistance (r= 0.19). The QTL on chromosome IV,
lsq4b, is associated with thermotolerance and paraquat resistance (each showing a 1.7-fold allelic effect on median survival), as well as longevity (1.27-fold effect on median life span) -- all traits mapping within the same 0.9-Mb region -- whereas this locus affects peroxide tolerance only weakly, and UV resistance not at all. Segmental stress-resistance, as observed, contradicts the "general stress resistance" phenotype proposed previously for several long-lived mutants.1 The longevity QTL has now been narrowed to 0.23 Mb, positioned on the physical map by a combination of Anchor-PCR Display2 and SNP typing; it comprises 22 known protein-coding genes, 6 snRNA genes, and 19 predicted genes. Further partitioning of this QTL interval is underway.