The Evaluation Of Cold Resistance On Four Bermudagrass Cultivars (Lines)

Cynodon dactylon L.is a typical warm-season turfgrass, it has been widely used in domestic and foreign because of its many advantages. However, due to its poor cold tolerance, the promotion and utilization is limited in the colder regions of China. In this study, breeding new bermudagrass cultivars with longer green period, stronger cold resistance is the target. The research objects are the new bermudagrass line'Dwarf Abortion Bermudagrass'with radiation breeding in Huazhong Agriculture University and the new line'HN019'by selected which its cold tolerance performance better in field. And we choose the bermudagrass cultivars of'Tifway' and'Princess'which are widely used in lawn engineering as comparison.The physiological and biochemical indexes which related to cold tolerance are measured under low temperature stress in artificial and natural cooling conditions, and their phenology and leaf tissue structure in different periods was observed. Then we do a comprehensive evaluation of cold resistance on the four bermudagrass cultivars(lines), research results are as follows:1.The phenology of four bermudagrass cultivars(lines) were observed, showed that all cultivars(lines) are turning green in late March, the change range of 3-4 days, were not significant. All cultivars(lines) are turning yellow in mid-November to early December, which'Dwarf Abortion Bermudagrass' turning yellow of the latest, than other cultivars(lines) for nearly 13-15 days later, the green phase of it is the longest. Four bermudagrass cultivars(lines) of the green phase on the length in the order: 'Dwarf Abortion Bermudagrass'>'Princess'>'Tifway'>'HN019'.2.Under low temperature stress in artificial, the physiological and biochemical indexes of the four bermudagrass cultivars(lines) changed in the same tendency, but there were differences in varieties. Judging from the overall level, Electrolyte leakage and MDA content of 'Dwarf Abortion Bermudagrass' are in the smallest, proline, soluble sugar and soluble protein content and SOD activity of'Low Abortion Bermudagrass'are in larger, while the Electrolyte leakage and MDA content of'HN019'are in larger, proline, soluble protein content and SOD activity of'HN019'are in small, the physiological and biochemical indexes of'Princess'and'Tifway' are in the middle.On the stress temperature found that when the Electrolyte leakage is the largest under 5℃, the most serious injury in plants.The cold tolerance of four bermudagrass cultivars(lines) obtained by fuzzy subordination method in descending order is:'Dwarf Abortion Bermudagrass'>'Tifway'> 'Princess'>'HN019'. 3.Under the natural cooling process, the physiological and biochemical indexes of the four bermudagrass cultivars(lines) trend are more consistent, there are differences in varieties. On the whole,'Dwarf Abortion Bermudagrass'with the minimum Electrolyte leakage, its soluble sugar and soluble protein content and SOD activity are highest. Electrolyte leakage and MDA content of'HN019'are larger, its proline, soluble sugar and soluble protein content is less. Electrolyte leakage of 'Princess'is the biggest, but less MDA content, its proline and soluble sugar content are in larger.'Tifway' has the largest MDA content, more soluble protein and chlorophyll content.And we can see, all cultivars(lines) in December have the most severe cold injury. The cold tolerance of four bermudagrass varieties (strains) obtained by fuzzy subordination method in descending order is:'Dwarf Abortion Bermudagrass'>'Princess'>'Tifway'>'HN019'.4.On the principal component analysis of the physiological and biochemical indexes measured, found that the correlation among the indexes are not identical during artificial and natural cooling process of low temperature stress. But the same is, Electrolyte leakage and MDA content always show strong positive correlation, Electrolyte leakage and proline, soluble protein content also show some positive correlation, Electrolyte leakage and chlorophyll content show negative correlation. MDA and proline content always show a strong positive correlation. Proline content and soluble protein content, SOD activity always present a certain degree of positive correlation. Integrated artificial and natural cooling process of low temperature stress in the principal component analysis of various indexes, we can see, MDA, proline, soluble protein content, Electrolyte leakage and SOD activity and the relationship between cold hardiness of bermudagrass is relatively close, as Identification of important indicators of bermudagrass cold tolerance, soluble sugar and chlorophyll content could be used as reference for bermudagrass cold-tolerance.5.On leaf epidermis of the four bermudagrass cultivars(lines) in different periods were observed and analyzed, found that the length and width of stomata with decreasing temperature trends decrease, while the stomatal density increase with decreasing temperature trends, and found that the cultivars(lines) which with the smaller stomatal width and density have the stronger cold tolerance.6.On leaf cross sections of the four bermudagrass cultivars(lines) were observed and analyzed,found that the differences of four cultivars(lines) leaf thickness, the thickness of the lower epidermis, midrib vascular bundle diameter, large vascular bundle diameter and small vascular bundle diameter were significant levels. And found that the cultivars(lines) which with greater leaf thickness, smaller diameter of the midrib vascular bundle and smaller diameter of large vascular bundle have the stronger cold tolerance.7.Combination of the physiological and biochemical indexes changes in low temperature stress of artificial and natural cooling process, as well as on the leaf structure of observation and comparison, the comprehensive evaluation of four bermudagrass cultivars(lines) cold tolerance in descending orde: 'Dwarf Abortion Bermudagrass'> 'Princess' and 'Tifway'>'HN019'.