LOW-TEMPERATURE EMERGENCE POTENTIAL OF SHORT SEASON CORN HYBRIDS GROWN UNDER CONTROLLED ENVIRONMENT AND PLOT CONDITIONS

One important reason for limited progress in selecting corn (Zea mays L.) with superior cold tolerance during germination and early growth is the unpredictable occurrence of cold, wet test springs. Breeders need an efficient laboratory test paralleling field emergence under such climatic conditions. Laboratory screening data from 30 corn hybrids with under 2400 corn heat unit ratings were compared to field emergence data in Atlantic Canada to evaluate the usefulness of a laboratory test as an indicator of cold tolerance. Hybrids were ranked by mean percent emergence using 1985-1989 field data collected from seven locations in the Atlantic region. From daily observations on seed germinated in a germinator at 11-degrees-C, mean times to 50% root and coleoptile initiation, and 1-cm coleoptile were calculated using probit analyses. Field emergence ranked from 1 (highest percent) to 30 was compared to ranking of time to 50% 1-cm coleoptile in the laboratory (one represented most rapid growth). Of the top 15 hybrids (by 1-cm coleoptile), 11 fell in the top half of the hybrids ranked by field emergence. Removal of hybrids with low numbers of field observations, all made during the unusually warm spring of 1989, improved the comparison. These results indicate that time to 50% production of a 1-cm coleoptile is a useful screening parameter to select corn hybrids with superior cold tolerance during germination and early growth.