Laboratory studies indicate that varieties of cotton (Gossypium hirsutum L.) differ in their ability to tolerate chilling temperatures, but limited field data is available. We conducted this study to (1) compare results of a laboratory assay (Bradow, J.M. 1991. Cotton Cultivar Responses to Suboptimal Postemergent Temperatures. Crop Sci. 31:1595-1599) with cotton productivity in the field; and (2) determine if differences occur between the laboratory measurements for ability to predict field performance. The study was conducted at Clemson University's Pee Dee Research and Education Center near Florence, SC on a Norfolk loamy sand soil. In 1991 and 1992, six cotton varieties (DPL 20, DPL 50, DPL 90, DPL 5690, Coker 315, and Paymaster 145) were planted in mid-April, early-May, and mid-May. Emergence rates and lint yield were measured.

The laboratory assay used is described elsewhere in this proceedings (Bradow J.M. and P.J. Bauer. 1994. Suboptimal Temperature Stress on Cotton I. 1994 Beltwide Cotton Production Research Proceedings). The relationship between shoot length, root length, shoot weight, and root weight from the laboratory study with emergence rate and lint yield was determined by calculating linear correlation coefficients for each cultivar within each planting date each year. For the analysis, data for the 15, 20, and 25°C temperature treatments were standardized to percent of the 30°C treatment for each cultivar.

Emergence rates did not differ among these six cultivars either year at any planting date; thus, none of the laboratory measurements, at any temperature treatment, correlated with emergence rate. Also, none of the laboratory measurements were related to final stand.

No relationship occurred between the laboratory growth measurements at 15 and 25°C and lint yield. Also shoot length, shoot weight, and root weight in the 20°C did not correlate with cotton yield at any planting date either year. However, root length at 20°C was positively correlated with lint yield when the seedlings were exposed to chilling stress in the field and differences between the cultivars occurred for lint yield. Those cultivars which were more sensitive to suboptimal temperature (i.e. had more root length inhibition) in the laboratory assay had lower yield than the other cultivars in the field.