| Zoysia is an important warm-season turfgrass which played significant role in the environmental greening and ecological management. Zoysia mainly distributed in tropical and subtropical regions, intolerance to low temperature, therefore improving cold resistance is quite important for broadening the application and reforming turf character of Zoysia. Cold resistance is a complicated quantitative trait controlled by polygene, due to different genetic background, there is obvious difference of cold resistance among species and cultivars of Zoysia germplasm. The research of physiological response at different low temperature treatments and the construction of genetic linkage map were fundamental for mapping quantitative trait locus (QTL) related to cold resistance, gene clone, marker assisted selection (MAS) breeding, and cultivating new lines of Zoysia with high cold resistance. In this study, an F1mapping population consisting of86individuals were derived from a pseudo-testcross of two Zoysia japonica’Muroran’X’Tawarayama Kita’ which had the distinct discrepancy in the environment.The semilethal temperature (LT50) of leaves and stolons of two parents and F1population were analysed under the condition of artificial low temperature treatment. A total of306SSR (Simple Sequence Repeat) markers were employed in constructing a molecular genetic map for Zoysia japonica and mapping QTL for traits included the content of soluble sugar, soluble protein and the activity of superoxide dismutase (SOD) associated with cold resistance at0℃low temperature treatment.The main results were as follows:cold resistance of two parents was obviously different, and cold resistance of Muroran is strongger than that of Tawarayama Kita. Cold resistance of F1population presented continuous distribution.1The relative electric conductivity of vitro leaves and stolons of two parents possessed a slowly increased-sharply increased-slowly increased change in response to the temperature declined, corresponded with Logistic equation to calculate the LT50of Zoysia japonica, the LT50of leaves and stolons of Muroran were lower than those of Tawarayama Kita, the LT50of leaves and stolons of F1population were consistent with cold injury in the field,LT50can be used to evaluate cold resistance of plant.2Under low temperature stress, the proline and soluble sugar content of two parents of Zoysia japonica both increased in some degrees, as the temperature declined, the content of soluble sugar of Muroran increased more than that of Tawarayama Kita. SOD activity of two parents decreased firstly, then increased, and decreased at last, while the trends of malondiadehyde (MDA) content changed is reversed as the SOD. At0℃, the SOD activity and the MDA content represented very significant difference (P<0.01) between parents. The content of soluble protein of parents increased slowly along with the temperature declined.3At0℃treatment for2days, the soluble protein content of F1population had negative correlation with leaf LT50(P<0.05), the soluble sugar content and the SOD activity of F1population negatively correlated with leaf LT50(P<0.01).4A genetic linkage map containing306SSR markers was consructed at LOD=4.0by the use of mapping software Join Map3.0, with306SSR markers were grouped into29linkage groups. It spaned2082.8cM in length,with an average map density of6.81cM, the number of markers in linkage groups varied from3to25, the length of linkage groups ranged from16.2cM to180.3cM.5Interval mapping method was employed in mapping and analyzing the contribution and effection of the QTLs related to the traits of cold resistance of86individuals, which was carried out by MapQTL4.0A total of4QTLs associated with the traits of cold resistance were detected, and they distributed on4linkage groups, the score of LOD ranged from2.19to2.42, and the phenotypic variation explained by individual QTL varied from12.4%to13.8%, one QTL for the soluble protein content was detected in the interval b06m13-c985located on linkage group10, one QTL for the soluble sugar content was detected in the interval bOlj11-b07a08located on linkage group13, two QTLs for the SOD activity were detected, one in the interval c02a20-b10k17located on linkage group17, the other in the interval b01c18-NAC1030located on linkage group29. |
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