Research On Physiological Response Mechanism In Kentucky Bluegrass To The Inoculation Of Rhizoctonia Solani

To explore the physiological response of Kentucky bluegrass (Poa pratensis L.) to the inoculation of Rhizoctonia solani, two Kentucky Bluegrass cultivars,’Midnight’ and’ Blue Peacock’, which reported as resistant and susceptible cultivars, respectively, to Rhizoctonia solani were inoculated by Rhizoctonia solani in this study. During the inoculation period, the roots activity, roots biomass,SOD, CAT and POD activity were tested and analyzed comparatively. In addition, the disease strains, disease incidence and disease index were calculated and the relative conductivity, relative water content, contents of MDA, proline, chlorophyll, Protein, SOD, CAT, POD, PAL and CHI in the leaf tissues of turfgrasses were tested and analyzed comparatively.The results indicated that:1.In the root, the roots activity and roots biomass in treat group were significantly lower than the control group (P<0.05).The activity of SOD and CAT had much difference between ’Midnight’ and’ Blue Peacock’. But the changes trends of SOD and CAT activity were similar. They were increased first and then declined until significantly lower than the control in the roots of ’Midnight’(P<0.05). However, the activity of SOD and CAT were increased a little and then declined quickly until significantly lower than control (P<0.05). The POD activity was significantly increase first and then decreased until significantly lower than control in the roots of ’Midnight’(P<0.05), while there was a continuously reduce in the root of ’Blue Peacock’.2.1n the leaf tissues, the disease index, relative conductivity, contents of MDA, proline and chlorophyll were all significantly increased after inoculation while the content of Protein and relative water content,chlorophyll were gradually decreased compared to no-inoculation(P<0.05). During the 7 days after inoculation, disease index, relative conductivity, contents of MDA and proline increased higher in’ Blue Peacock’ than that in’ Midnight’. Moreover, the degree of reduction of chlorophyll content was higher in’ Blue Peacock’ than that in ’Midnight’. Correlation analysis showed that significant positive correlation were found between contents of MDA, proline, relative conductivity and the change of disease index, whereas significant negative correlation were exhibited between chlorophyll,Protein content and the change of disease index. And compared with unvaccinated grasses, the grasses of Midnight had a higher activity of SOD,CAT and POD than Blue Peacock after the first increased. However,the changes of POD acticity in interspecific were oppositd.In addition, there were a similar change trend and vastly interspecific difference between two cultivars in PAL and chitinase actieity.There were increases of PAL and chitinase activity and then decreased after the first rise in Midnight.But the Blue Peacock had emerged a continued slow rise which was a very different situation.3. Correlation analysis showed that:the indexs of root showed that there were all significant correlation (P<0.05) among them. In Midnight grass,the order of relevant relationship between disease index and other indexes from high to low is:MDA content> proline content> chlorophyll content> root POD activity>root biomass>root CAT activity>root SOD activity>relative water content>leaf POD activity> leaf CAT activity> leaf PAL activity>relative conductivity> leaf SOD activity> leaf CHI activity> soluble protein content; while in the Blue Peacock grass,the order is proline content> root POD activity>root activit>chlorophyll content> MDA content> relative water content>root CAT activity>root POD activity> leaf CHI activity> root biomass> leaf POD activity> leaf CAT activity>leaf PAL activity> leaf SOD activity> relative conductivity> soluble protein content.4. On the overall activity of antioxidant enzymes in Kentucky bluegrass, there are a higher SOD, CAT and POD activity in the leaf samples than the root samples.Above all, compared with susceptible cultivars Blue Peacock, the response mechanism in disease-resistant cultivar Midnight is faster.stronger,better and suffer is lighter after infected of Rhizoctonia solani during the duration of the experiment.