A CHILLING RESISTANCE TEST FOR INBRED MAIZE LINES

A laboratory germination test based on exposure of seeds to a temperature regime derived from natural conditions was developed to determine chilling resistance in maize (Zea mays L.). Seven inbred lines were exposed to a temperature regime approximating Ottawa, Ontario's (Lat. 45 degrees 24'N, Long. 75 degrees 43'W) spring climate. Seeds were subjected to a range of maximum (16 h) and minimum (8 h) temperatures corresponding to the dates spanning 15 April (10.3/0.4 degrees C) to 30 May (21.0/9.1 degrees C) in controlled temperature germinators. A control germination test used a constant 25 degrees C. The percent germination, percent viability, and average time taken to germinate were measured. The results of all three parameters corresponded in indicating which line was chilling susceptible, and the percents germination and viability in which lines were chilling tolerant. Field trials were sown in Ottawa in the early spring of 1992 and 1993 and percent of emergence and average time to emergence were recorded. The line demonstrated to be most chilling susceptible by the laboratory germination test and those lines selected to be most chilling tolerant by the laboratory percent germination and viability assays corresponded to those classified as such by the field percent emergence.