Study On Heat Tolerance And Turf Quality Of Eighteen Tall Fescue Varieties

The pot experiment was adopted to comprehensively evaluate and compare heat tolerance of eighteen tall fescue varieties in this article. Eighteen tall fescue were under the high temperature stress of 38 ℃/2 8 ℃ (day/night) at six levels of different heat stress in the artificial climate cabinet, the stress time was zero day, two days, four days, six days, eight days and ten days repectively. The survival rate and scorching degree, relative electric conductivity rate, the total content of chlorophyll, the accumulation of MDA and proline and the activity of superoxide dimutase. Turf quality of tall fescue was evaluated combining with field experiment at the same time, the results showed that:1 .Changes of plant morphology of tall fescue under high temperature stress was behind of the changes of physiology. With the stress time prolonging, the degree of scorchimg and numbers of plant death were increased. At the same time the change of leaf color was from green to yellow even fading and the change of leaf texture was from hard to soft. All materials showed the normal growth at stress two days, light scorchimg at stress 4 days, middle scorchimg at sress 6 days, serious scorchimg at stress eight and ten days, while the survival rate of most materials were 100%, 100%, 85%, 50%, 20% respectively. But the survival rate of tall fescue "98-1" were 70% and 50% at stress eight days and ten days respectively.2.Among the measured physiological indexes of eighteen tall fescue varieties, the relative electrical conductivity rate, the accumulation of MDA and proline were all increased; meanwhile, the total content of chlorophyll were decreased with the prolonging of stress time. The activity of SOD became higher at beginning and lower later.3.Various indexes of evaluating tall fescue heat tolerance existed definite pertinency. Among them, the relative electrical conductivity rate, the accumulation of MDA and the changes of proline were high significant positive correlation, the correlation coefficients were 0.674, 0.715, 0.937. The total content of chlorophyll were high significant negativecorrelation to the relative electric conductivity rate, the accumulation of MDA and proline, the correlation coefficients were -0.550, -0.859, -0.858 respectively. The activity of SOD was high significant negative correlation to the relative electric conductivity rate and was significant negative correlation to the content of proline, the correlation coefficients were -0.412, -0.223 respectively. The index of field turf quality was high significant negative correlation to the relative electric conductivity rate, the correlation coefficients was -0.564. It was high significant positive correlation to the total content of chlorophyll, the accumulation of proline and the activity of SOD, the correlation coefficients were 0.278, 0.318, 0.476 respectively.4. Eighteen tall fescue varieties were divided into three heat tolerance classes according to the cluster analysis: the first calss was Tall fescue "98-1". the second class were Tall fescue"98-5", New star, Houndog, Mustang, Pixie, Coyote and Crossfire, the third class wereRelf, Primitive group, Plantation, Spring wind, Dynasty, Arid, Deminion, QG I , Tall fescue"98-2"and Barlexas.5. Because of comperatively short green period , light color, low oversummering rate, faster growth rate and regenative rate of Relf and QG I , which were not suitable to eatabolish turf in this region. The new Tall fescue"98-l" and "98-5", Newstar, Houndog, Mustang, Coyote, Pixieand and Crossfire comprehensive assessment were higher (7.3, 7.0, 7.2, 7.2, 7.0, 7.1, 7.0, 7.3 respectively) and superior to the two control varieties (Barlexas was 7.0, primitive group was 6.4). Tall fescue "98-1", "98-5" may be thinked of as new varieties to popularize. The tested eighteen tall fescue varieties could seedle, tiller, head, flower, set seeds and mature in this experimental region. They all completed a growth and development period of approximate 290 days. The germination rate of seeds collected after maturing were approximate eighty-two percent.6.Tallfescue"98-l"and"98-5", Newstar, Houndog, Mustang, Coyote and Crossfire's heat tolerance were relative strong and turf quality were relative perfect combining field experiment with pot experiment, so they can fit for establishing on large scale in southern transitional zone of our country.