| Festuca arundinacea Schreb. is a typical cool-season turfgrass with a longest green-period, and it has been widely used at home and abroad because of its advantages such as resistance to moisture, resistance to drought, resistance to salinity, resistance to trampling, and as well as resistance to pests and diseases and so on. In this study, the objects are five excellent mutant lines (number followed by 'HN002','HN003','HN004', 'HN005' and 'HN006') with radiation breeding in Huazhong Agricultural University, and the primitive is Festuca arundinacea cv. Fine Lawn (No. 'HN001').This study mainly compared six lines'difference from the DNA polymorphism, physiology and microstructure of heat-resistance, providing certain reference value for choosing new turf-type tall fescue cultivars with strong heat-resistance to hot and humid areas of the Yangtze River. The main research contents and conclusions are shown as follows:1. ISSR markers detected genetic relationships of five excellent mutant lines and the original, and the result to clustering by UPGMA showed that their differences were obvious to distinguish; genetic similarity (GS) of HN001 and mutant lines was only 0.53, which was obviously different on molecular level; GS of the mutant lines was from 0.60 to 0.82, GS reached 0.82 both HN002 and HN006, indicating that their difference was small, while obvious during other mutant lines.2. Materials were treated five days in the artificial climate chamber under 40℃, and every day we all need to take samples at the same time, the first day (26℃) being CK; A comprehensive evaluation on heat-tolerance of six lines was given based on six measuring changes of seven physiological parameters containing the injury rate, the activity of superoxide dismutase, MDA, chlorophyll, soluble sugar, free proline and soluble protein content, and then we found that six lines had significant differences.The result was:'HN001' (0.1080), 'HN002'(0.0836), 'HN003'(0.0369), 'HN004'(0.0359), 'HN005' (0.0877), 'HN006'(0.0758), and its heat resistance in descending order was: 'HN001'>'HN005'>'HN002'>'HN006'>'HN003'>'HN004'.3. The seven physiological parameters were measured at six levels, and the stress temperatures respectively were 33℃,36℃,39℃,42℃and 45℃in the artificial climate chamber,26℃being CK, and the stress time was one day. A comprehensive evaluation on heat-tolerance of six lines was given based on seven physiological parameters'changes, and found the result was:'HN001'(0.0706),'HN002'(0.1154), 'HN003'(0.0324), 'HN004'(0.0459), 'HN005'(0.0747),'HN006'(0.0696), and it indicated that the order of heat resistance from high to low was: 'HN002'>'HN005'>"HN001'>'HN006'>'HN004'>'HN003'.4. Under 40℃and different high temperatures'stress, all the parameters of six lines had obvious difference in the rate of increase or decrease, the peaks and contents and so forth. In two high temperature stress ways, the injury rate, MDA and proline content showed all increased, and six lines'differences become more pronounced with increased stress; the total content of chlorophyll showed an down-up-down trend, some differences of Ch1 content were in the different treatment levels; soluble protein content was firstly increased and then decreased, in the constant temperature process the peak of the soluble protein content come into the fourth day, and the difference was obvious, while, in the different high temperature treatments'process, their contents'peaks didn't appear at the same time, and their performed difference was more visible when the stress temperature was 45℃; the general changing trend of the activity of the superoxide dismutase increased at first and then decreased, and they had shown a significant difference at each processing level; the overall trend of soluble sugar content was decreasing with increased stress time under 40℃stress, while, it was increased and then decreased in different high temperature treatments, but all reflected six lines'differences at different levels.5. Under natural high temperature, six lines'differences of microstuctures at the cellular level was also more significant. Observations of leaf stomata showed that, the stomatal density of HN003 and HN004 with poor heat-resistance was relatively larger, the numbers per mm2 reaching 100.66 and 94.62, and the stomatal density of other lines with strong heat resistance such as HN001, HN002 and HN006 was significantly smaller than HN003 and HN004, their numbers per mm2 in turn were 77.94,61.25,56.97.6. By observing leaf epidermal cells we found that, the epidermal long cells of HN003 and HN004 were significantly different (P<0.01) from HN001, and they were also different from other lines; their short cells existed also a lot of differences, and the mutants'differences were more obvious, especially compared with HN001.7. Observations of leaf tissues'thickness indicated that, leaf thickness and leaf epidermal thickness of HN004 and HN003 were significantly less than other lines, and the thicknesses of the epidermis under their leaves were significantly greater than other lines; and the thicknesses of their leaves'sclerenchyma had little difference (P>0.05).8. Vascular observations showed that, large vascular diameter of HN003,HN004 and HN006 was significantly different(P<0.05) than the other three lines, the middle and small vascular diameter of six lines was little significant (P>0.05). |
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