Germplasm Screening And Heat Resistance Evaluation Of Different Population Of Wild Poa Pratensis In Shanxi

Heat stress is one of the main environmental factors limiting the growth of Poa pratensis.The experiment to collect from Shanxi 49 different habitats of wild Poa pratensis as materials, after screening of its main morphological characteristics, and combined with the osmotic adjustment substances, enzyme activity, photosynthetic characteristics and chlorophyll fluorescence parameters and other indicators, the group wild Poa pratensis heat resistance was evaluated. The results were as follows:In order to evaluate the genetic differences of wild poa pratensis populations collected from Shanxi province, a experiment was carried out of study the diversity of 13 main morphological characteristics from 49 wild poa pratensis germplasm resources by principal component and cluster analysis. The results showed that the morphological characteristics had extremely significantly difference and abundant morphological variation among wild populations (P<0.01). The variation coefficient of morphological characteristics reached 88.49%, which including most information of morphological characteristics. These germplasm resources can be comprehensively evaluated based on the information above, forty-nine wild poa pratensis germplasm resources were clustered into 6 groups by cluster analysis, and each group had its respective characters. The populations of I include (YQ-03, JX-05, NW-12, NW-09, NW-08, QS-25, NW-13, WZ-21, WT-46, NW-18, WT-47, HY-35, WT-44 and HY-36)and IV (TL-30, XZ-49, WT-48 and WT-45) were better, and could be used as the key selection object of grass breeding in the future.The different poa pratensis germplasm under high temperature stress, changes of antioxidative enzyme activities, membrane lipid peroxidation, cell membrane permeability and osmotic adjustment substances of these wild germplasm seedlings with different heat tolerance which were treated at different temperature for different days respectively were determined. The results showed that the contents of malondialdehyde (MDA) in different germplasm with different heat tolerance were increased continuously with high temperature going up. However, the growing rate of the electrolytic leakage and contents of MDA in germplasm of heat resistance was smaller than that in germplasm of heat sensitivity. The superoxide dismutase (SOD), peroxidase(POD) activities and soluble protein content show a transien rise and then reduce with high temperature rising. But the growing rate of the SOD, POD activities and soluble protein content in germplasm of heat resistance was larger than that in germplasm of heat resistance was smaller than that in germplasm of heat sensitivity. The contents of free proline and soluble sugar were increased continuously with high temperature going up. However, the growing rate of the contents of free proline and soluble sugar in germplasm of heat resistance was larger than that in germplasm of heat sensitivity. The above results indicated that there were better capability in maintaining cell osmotic adjustment, synthesising and stabling protein and eliminating reactive oxygen species in germplasm of heat resistance, this is one of all physiological base which germplasm of heat resistance had high heat tolerance. The SOD, POD activities, MAD content,soluble protein, soluble sugar and free proline contents were selected as physiochemical indexes of evaluating on heat tolerance of different poa pratensis germplasm. In twenty-five days of stress, the different between the populations significantly (P<0.05), and without stress when compared to, the increase in MDA content was smaller for HY-35 populations; soluble sugar content accumulated more populations of WZ-21, LS-28, and HY-35 QS-25 population groups tend to intermediate level; soluble protein accumulation of more ranking group QS-25, HY-35, LQ-40 ranking group increase was least; more pro accumulation of WZ-21 and YY-41 populations; SOD increased more WT-48 and QS-25, HY-35 populations; Ju group POD activity greatly. GL-42, and HZ-02,QS-25 populations CAT activity higher QS-25,HY-35.With the extension of stress time, all populations poa pratensis chlorophyll content decreased;the HY-35 and LQ-40 populations of smaller increase in HZ-02 population increased considerably; different populations poa pratensis Pn, Gs, Tr and Ci values showed a downward trend, which can be explained Pn decrease was mainly due to stomatal factors. The value of HY-35 population and QS-25 population was small; HY-35 and WT-48 populations of Gs value was smaller; the value of Tr was QS-25 and HY-35 by a smaller population, YX-43 population was larger; the value of Ci by small populations WZ-21 and HY-35 populations. Pn-PAR response curves between 2000-2500 umol.m-2·s-1 there was a saturation point, when the saturation point was reached high intensity PAR cause Pn decline; to twenty-five days QS-25 and TL-30 populations showed better populations; Pn-CO2 within the measuring range not reached saturation point, indicating wild poa pratensis under specific PAR can withstand higher concentrations of CO2. which QS-25 and WT-48 population performance better.The chlorophyll fluorescence parameters Fo, Fv/Fm, Y (?), qP, NPQ and ETR measured values can be effectively monitored by a plant injured at high temperature stress environment. With prolonged stress time Fo value increased, Fo greater the greater the damage; photochemical efficiency (Fv/Fm) decreased with the increase of stress time, which was the best performance of the WT-48 population, the smaller amplitude decrease, the stronger the heat resistance; electron transport rate (ETR) also decreased; Y (2), qP decline, indicating that poa pratensis under heat stress, PSII photosynthetic system damage, resulting in effective electronic transfer activity was reduced; The increase of NPQ value was protection mechanism of poa pratensis against high-temperature environment, NPQ explain the higher poa pratensis body heat energy consumed, the more damage can reduce the temperature stress after 25 days HY-35 and LQ-40 populations NPQ increased the most.Cluster analysis of different populations poa pratensis heat resistance classification system, based on cluster analysis showed that each of the populations poa pratensis was divided into two categories, of which category I include QS-25, LQ-40, TL-30, WY-14, NW-09, WT-48, HY-35 and WZ-21 populations, and the remaining population as a class II comprises HZ-02, YX-43, LS-28, XZ-49, YY-41 and GL-42 population.Through various populations poa pratensis in different heat resistance index membership function was calculated,the results show that the best performance was QS-25 population, the worst was LS-28 population. By heat resistance from strong to weak lined for QS-25, WZ-21, HY-35, LQ-40, TL-30, WT-48, NW-09, WY-14, YY-41, GL-42,YX-43, HZ-02, XZ-49, LS-28.Shanxi wild populations in poa pratensis growth characteristics and heat resistance studies have been more excellent heat wild populations,provide a theoretical basis and method for subsequent poa pratensis resistance breeding.