Studies On Turf Characteristics Of Nannong Kentucky Bluegrass

Kentucky bluegrass (Poa pratensis.L) has been widely used for turf establishment in golf course, playing fields, courtyard and airport, because there are long-green periods, soft-qualities, brilliant-colors, strong cold-tolerance and great tiller density. However it can hardly survive from heat and drought stress for its non-heat tolerance in the transitional zones in summer. A new line (Nannong line) Kentucky bluegrass with strong heat tolerance was screened and bred by Nanjing Agricultural University. A compareson of characteristics between Nannong line and commercial varieties of Kentucky bluegrass with field trials, and compared their differences in peroxidase (POD) zymograms, growth and turf characteristics, summer surviving and heat tolerance.The peroxidase zymograms showed that Nannong line had 13 isozyme bands, 6 bands were the same and 7 bands were different from the other varieties. The information of POD isozymes in different varieties was analyzed by cluster analysis. It showed that the 17 varieties might be classified into 3 groups. The relationship between Nannong line and the other varieties was relatively far, it could form a group alone, Merit as well. The Nannong line may be regarded as an independent material.The Nannong line has a moderate leaf texture, color, length, chlorophyll content and growth rate, however there were high coverage, tiller density, weighted quality, more numbers of intemode and strong abilities of rhizome, tillering and oversummering as with commercial varieties. The growth of Nannong line was better than the other varieties from early spring returning green, summer stress and early autumn. Coverage, tiller density and characteristics of per tiller were better than the other varieties in summer. These traits showed that there was better adaptability to summer heat and drought stress in Nannong line. The Nannong line may be an excellent variety, which could be used in the high temperature regions.The physiological responses to heat stress of Kentucky bluegrass varieties were different in summer. Coverage, tiller density, turf quality, leaf chlorophyll and water content declined markedly (p<0.05) with the swelling and persisting stress of heat and drought, the turf quality and leaf water content in mid-August declined about 12.1% - 49.8% and 14.2% -27.6% as compared with in mid-June, respectively. Similarly, the activities of SOD andPOD in leaves declined about 36.5%-55.0% and 46.9% -65.7%, respectively, and the MDA content increased about 19.8%- 88.7%. The declined degree of turf quality, leaf water content, SOD and POD activities, and the increased degree of MDA in summer significantly(p<0.05) differed among the varieties. Changes degree in Nannong line and Midnight(W) was less than the other varieties, such .as in Bluechip and Sobra. Turf quality of Nannong line and Midnight(W) in summer was higher than the other varieties. The results of correlation analysis indicated that the decline degree of POD activity was significantly (p<0.05) and negatively correlated with turf quality under high-temperature and drought stress in field. It was suggested that maintaining higher POD activities and leaf water content might be an important indicator associated with tolerance of heat and drought stress in Kentucky bluegrass.