Studies On Cold Tolerance Evaluation In Recombinant Inbred Lines (Rils) And QTL Detection For Cold Tolerance Of Tomato (Solamum Lycopersicum)

Tomato(Solanum lycopersicum)is an important thermophilous vegetable and sensitive to low temperature.New cold resistant tomato cultivars can expand the cultivation scope and increase the annual output.In this study an Recombinant Inbred Line(RIL)population with 146 individuals derived from a cold sensitive cultivated tomato Solanum lycopersicoides XF98–7 and a wild cold-tolerant accession S.pimpinellifolium LA2184 was employed to evaluate the cold tolerance of tomato in two apparent indexes——the relative germination ratio(RGR)in 10±1°C and chilling index(CI)in 2±1°C.The data indicated that the two apparent indexes showed significant difference in the parental lines,and approximately normal distributions were observed in RGR and CI among the RIL population,so the RGI and CI well demonstrated the cold tolerance of tomato.On the basic of two apparent indexes,the peroxidase(POD)activity relative increase ratio and chlorophyll content relative increase ratio were induced to evaluate the tomato cold-tolerance.Significant difference was observed in the parental lines,and the RIL population followed approximately normal distribution or single peak continuous distribution in two physiological indexes.When four indexes compared,low correlations——only 0.226 and-0.361,were observed in CI and the two physiological indexes.Besides of that,21.3% and 16.0% of the RIL population displayed values deviating from the normal range.We concluded that,in consideration of the low correlations of the four indexes,the uniformity of the data and the operability of the experiment,POD activity and chlorophyll content were not suitable to evaluate the cold tolerance of tomato in large population.A molecular linkage map that contained 120 simple-sequence repeat(SSR)markers was conducted based on the RIL population.The molecular linkage map had 15 linkage groups,with a total distance of 256.8 cM,the maximum interval of 8.30 cM,the minimum interval of 0.18 cM,and average interval of 2.14 cM.Composite interval mapping method was used to conduct the quantitative trait locus(QTL)analysis of the RGR and CI of the RIL population.Five QTLs controlling RGR and four QTLs for CI were detected with genetic contribution ranged from 0.95% to 19.55%.