PARENT OFFSPRING REGRESSION ESTIMATES OF HERITABILITY FOR SALT TOLERANCE DURING GERMINATION IN TOMATO

Salinity impositions can markedly delay and decrease germination rates of tomato (Lycopersicon esculentum Mill.) seed. Wide phenotypic variability in plant growth and germination responses to salinity stress has been reported, but scant documentation concerning genotypic variation for salt responsiveness has restricted breeding efforts. This study evaluated the heritability of germination performance under salinity stress by parent-offspring regression. Germination distribution data were collected for F2 and F3 seeds derived from a cross between a salt-sensitive (UCT5) and a salt-tolerant (PI 174263) cultivar under moderately high salinity levels (150 mM synthetic sea salt). Individuals germinating at different response time intervals were recovered and advanced to produce F3 and F4 progeny seeds. Progeny families were evaluated for mean times to selected germination quantiles of 25, 50, and 75% under salt stress and the family means were regressed on the individual parental values. Heritability estimates for the F2:3 regression at the selected quantiles were 0.78, 0.76, and 0.58, respectively. These results were comparable with the F3:4 regression estimates of 0.65, 0.73, and 0.58, respectively. The similarity of the estimates obtained in both parent-offspring regressions suggests the absence of significant dominance genetic effects and when considered with the moderately high heritabilities estimated (r = 0.58-0.78), reasonably rapid response to selection in early segregating generations would be expected for this important seed trait in tomato.