COLD TOLERANCE OF INBRED LINES DEVELOPED FROM SWEET, NORMAL AND SWEET-X NORMAL SOURCES

New inbred sweetcorn lines were developed from sweetcorn and normal so urces. Studies were made on differences in the cold tolerance of sweet corn and normal lines in the germination stage and on whether the pres umably better cold tolerance of normal lines could be used to improve that of inbred sweetcorn lines. The experiments were set up in the Mar tonvasar phytotron where the temperature was maintained at +8-degrees- C for 10 days, followed by +13.5-degrees-C for 20 days. Selected, unda maged seed with 100% germination ability was used in the experiments. The following conclusions can be drawn from the results: 1. Sweetcorn lines are significantly poorer for two cold tolerance properties and s weetcorn lines developed from sweetcorn x normal sources for four cold tolerance properties compared with normal lines. The lower % emergenc e of sweetcorn lines is probably due in part to the fact that the thin ner pericarp provides less protection against fusarium infection durin g germination. 2. Among the 5 cases examined, new sweetcorn lines whic h were better than both parental forms for several cold tolerance prop erties were found in two cases, while in two other cases the new sweet corn lines were poorer. It can be concluded that the cold tolerance of sweetcorn lines can be improved using normal sources, but that the de gree of improvement is influenced by the cold tolerance of the parenta l lines rather than by the endosperm type.