Analytical Relationship Between Summer And Heat Tolerance And Identification Of ISSR And RAPD Markers Associated With Summer Tolerance In The Clones Of Tall Fescue

Tall Fescue (Festuca arundinacea Schreb.) is a major cool-season forage, turf, and eco- grass. Heat stress usually is regarded as one of the major reason for the inhibition of grass growth and decline of turf quality in summer. Understanding the difference between summer and heat stress is beneficial for breeding criterion planning. Eleven summer-stress tolerant clones(TF01-TF11), seventeen non-tolerant clones(TF12-TF28), eight winter-stress tolerant clones (TF31-TF38)and two other clones (TF39 and TF42)were selected originally from single plants of Plantation, Triple A, Shanghai Dwarf Tall Fescue and 98-19 cultivars and lines at two test sites (Funing County of Jiangsu Province and Shanghai China) in four years (2006-2009). In the study, heat tolerance of the clones and their offspring has been identified, and turf quality of the offspring was evaluated. We also identified ISSR and RAPD markers associated with heat tolerance and summer tolerance in tall fescue. The object of our study was to detect the correlationship between heat tolerance and summer tolerance and obtain some molecular markers related to summer tolerance in tall fescue.The research has led to the following results:1)Twenty-six of the clones were submitted to control temperature (22℃) and high temperature stress (A 28-day poikilothermic heat stress of 40℃/28℃for day/night 12h each followed by a 7-day homoeothermic of 40℃day/night) for 35 d. Chemical efficiency (Fv/Fm) were measured every seven day during the temperature treatment; while relative electricity conductance (EC) of cell memberan leakage, leaf cholorophyll content and visual quality of the grass were measured at 0, 28 d and 35 d of the treatment. Two groups of heat-tolerant and non-tolerant were classified according to the pooled ratings of the characteristics measured above. Results showed that TF05,TF04,TF11,TF10,TF02,TF03,TF01,TF06 of the 11 summer-stress tolerant and TF20,TF27,TF28,TF13,TF26,TF22and TF23 of the 15 summer-stress non-tolerant clones were belong to the heat tolerant group, and no significant correlationship between heat stress and summer-stress tolerance was detected by independent test (Chi square test).2) Thirty tall fescue materials were identified including 11 first generation progenies of summer-stress tolerance clones, 17 offpsring of non-tolerance clones and 2 first generation progenies of introduced species as controls. Thirty tall fescues were under the temperature stress of 40℃/28℃(day/night) for 28 days and then 40℃/40℃(day/night) for 14 days. The tested materials were divided into three heat tolerance classes according to the evaluation of heat tolerance indicators. And then the correlationship between summer tolerance of clones and heat tolerance of their first generations was analyzed. Evaluation showed: TF1, TF3, TF6, TF9, TF10, TF14, TF15, TF17, TF19, TF21, TF27,'Plantation'and'JaguarⅢ'were the first heat tolerance class. TF18, TF20, TF23, TF26, TF28 were the second class. TF2, TF4, TF5, TF7, TF8, TF11, TF12, TF13, TF16, TF22, TF24 and TF25 were the third class. 45% first generation progenies of summer-stress tolerance clones were the first class while 55% first generation progenies were the second or the third class. 35% first generation progenies of non-tolerance clones were the first class while 65% first generation progenies were the second or the third. The percentage of the first class had no significant differences between first generation progenies of two different summer tolerance groups. It had no significant correlation of the phenotype summer tolerance of clones and the heat tolerance of first generation progenies.It is reasonably inferred that heat stress might be one of the reason for grass growth inhibition but not a primary reason for the death of grass in fields in summer. Summer stress tolerance is a more significant criterion over heat tolerance for tall fescue turfgrass breeding.3) A field trial to evaluate turf quality of the maternal progenies of 17 newly selected clones (TF01-TF11, TF33-TF38, and TF42) was implemented in Shanghai between October 2009 and May 2011, in which 19 materials including some of the 17 initial source germplasms for selection, commercial cultivars, blends, and old lines were also tested as controls. Results showed that the maternal progenies of clones TF06 and TF34 were the top two lines with improved overall competitive nature and turf quality. Turf-grass of TF06 progeny displayed less damage in summer,highest reliving coverage(93%)in next spring, medium grow habit and leaf texture, and a special grey-green leaf color, while TF34 exhibited better tolerance to both summer and winter stresses with 85% reliving coverage in next spring, lower grow habit, finer leaf texture and darker green leaf color. In addition to the two prominent clonal progeny, the first generation progenies of TF05 and TF36 were ranked top 10 due to better overall turf qualities. These four clones would be deserved propagating vegetative for turf demonstration on public greens and also could be utilized to develop new synthetic selections in further breeding program. It is also inferred that clone selection and its first generation progeny screen for good turf quality is an effective approach for tall fescue turf-grass breeding.4) By the bulked segregant analysis (BSA), we identified one marker related to summer summer stress tolerance from 100 ISSRs and 800 RAPDs. A dominant SCAR marker T_SC856 was successfully developed from the UBC856 sequence, which was a charecteristic for summer stress non-tolerant clones. Further, the SCAR marker was tested in clones differing in summer-stress tolerance from new populations, and it exhibited 77% consistence with the phenotype. Surly, with more markers obtained in the future, marker-assisted selection could be applied to summer summer stress tolerance improvement of tall fescue.