The Relationship Between Blast Resistance Of Hybrid Rice Or Their Parent And Enzyme Activities Or MDA Content

Rice blast, caused by Magnaporthe grisea (Hebert) Barr, is one of the most important rice disease that widely occurred in all rice belts of the world. A variety of physiological species and the quick evolution of them usually result in loss of resistant characteristics of a new rice variety with single resistant gene in some years after its expansion. It proved that breeding, selection and cultivation of the disease resistant varieties were the most economic and efficient disease control measures after wide practice. A few researches showed that respiration rate, membrane lipid peroxidation, phenylpropanes metabolism and its relative substance metabolism were very important to resist pathogens in defense reaction. Investigation and analysis of the relationship between hybrid rice and their parent resistance to blast is theoretically and practically significant for breeding and selection of new rice resistant varieties and efficient use of rice blast resistant varieties.In this study, we used Magnaporthe grisea race P_12-2-3 which was incompatible with Luhui615, Gangyou615 and compatible with R18, Gangyou18, Gangyou46A as materials. The relationship between hybrid rice or their parent and biochemical parameters including the activities of peroxidase (POD), catalase (CAT), phenylalaine ammonia lyase (PAL) and the content of malondiadehyde (MDA) were studied after inoculation. Furthermore, we determined these parameters of new restorer line HR6 and its hybrid rice combinations Gangyou46A/HR6, Jin23A/HR6, YixiangA/HR6,216A/HR6, new restorer line HR9 and its hybrid rice combinations Gangyou46A/HR9, YixiangA/HR9, Jin23A/HR9,216A/HR9, ZhongjiuA/ HR9 to prove undermentioned results.The results showed that there were differences of enzyme activity and MDA content changes in 5 varieties by determining Luhui615, R18, Gangyou615, Gangyou18 and Gangyou46A.The POD activities of Luhui615, Gangyou615 were significantly higher than Gangyou46A, R18,Gangyou18, and PAL activities had no significant difference before inoculation; the POD,PAL activities of 5 varieties appeared up-trend first and down-trend late, but the rising rates and maximums of Luhui615,Gangyou615 were bigger than Gangyou46A,R18, Gangyou18 after inoculation. The CAT activities were not obviously different in 5 varieties before inoculation, but after inoculation the CAT activity of Luhui615 appeared down-trend first and up-trend late, Gangyou615 kept slowly up-trend all the time, Gangyou46A,R18,Gangyou18 were rapidly rising, and 5 varieties kept same trends after inoculated 72h.The MDA contents had no obviously different either in 5 varieties before inoculation, but after inoculation the MDA contents of 5 varieties appeared up-trend first and down-trend late, the rising rate of Luhui615,Gangyou615 were significantly bigger and the maximums appeared earlier(24h), the rising rate of Gangyou46A,R18,Gangyou18 were bigger,but the maximums appeared late(48h),also all the MDA contents kept same trends after inoculated 72h.The POD,PAL,CAT activity changes,the MDA content changes and the rice blast resistance of HR6, Gangyou46A/HR6, Jin23A/HR6, YixiangA/HR6,216A/HR6, YixiangA/HR9, Jin23A/HR9, ZhongjiuA/HR9 were almost coherent to Luhui615 and Gangyou615,while HR9,Gangyou46A/HR9, 216A/ HR9 were almost coherent to Gangyou46A,R18 and Gangyou18. It proved that POD, PAL, CAT activities and MDA content were nearly correlative with rice blast resistance, so do blast resistance of hybrid rice with that of their parent.After inoculation,POD activity on 48h was positively relative with blast resistance,the correlative coefficient was 0.9328 and the regressive equation was: Y_POD=15.9506—0.0214X_POD2;PAL activity on 24h was also positively relative with blast resistance, the correlative coefficient was 0.9530 and the regressive equation was: Y_PAL= 14.4819—0.3561X_PAL1;CAT activities on 24h and 48h were negatively relative with blast resistance and correlative coefficients were-0.9098 and-0.6469,as well as the regressive equation Y_CAT =-0.9154+0.0602X_CAT1+0.0417X_CAT2;MDA content on 24h was positively relative with blast resistance, the correlative coefficient was 0.9864 and the regressive equation was: Y_MDA= 12.2032-0.0365X_MDA2 by further correlative analysis.So POD,PAL,CAT activities and MDA content could be considered as auxiliary indexes of blast resistance.