| Rice blast(Magnaporthe grisea( Hebert) Barr(the anamorph is Pyricularia grisea ( Cooke) Sacc.) is one of the most important rice disease that widely occurred in all rice belts in the world. A variety of physiological species and the quick evolution of the physiological species usually res -ult in loss of resistant characteristics of a new rice variety with single resistant gene in some yea- rs after its expansion. It is widely accepted that breeding, selection and cultivation of the disease resistant varieties are the most economic and efficient disease control practice. Investigation and analysis of the chemical mechanisms of rice resistance to blast is of theoreticcally and practically significant for efficient use of rice resistant varieties, chemical control practice, resistant gene clo- ning, breeding and selection of new rice resistant varieties, etc.hi this study, we used a pair of near isogenic lines (NIL) of rice, C101 and CO39. The 5-leaf-stage rice seedlings were inoculated with Magnaporthe grisea(race 70-15). C101 and 70-15 is incompatible combination, while CO39 and 70-15 is compatible one. After inoculation, the assay of the following physio-biochemical parameters in the rice leaves was carried out: soluble sugar, soluble protein, malondiadehyde (MDA) , ascorbic acid (ASA) and the activities of ASA peroxidase, the phenylalanine ammonia lynase(PAL), peroxidase(POD), polyphenoase (PPO) , superoxide dismutase ( SOD) , catalase(CAT), lipoxygenase(LOX), the POD isoenzyme, the esterase (EST) isoenzyme, and the relationship between the rice resistance and the above parameters were analyzed.The results of our study showed that most of the above physio-biochemical parameters of C101 were regularly significantly different from those of CO39. The major results are as following: the activities of POD, PPO, PAL in C101 weresignificantly higher than those in CO39 and the increase of the activities was higher in C101 than in CO39, although all the enzyme activities rose and then descended both in C101 and CO39; The activity of APX in C101 and CO39 appeared up-trend first and down-trend late, but the rising rate was higher and the net increase was bigger in C101 than in CO39, and the activities decreased significantly in CO39 48h after inoculation; The ASA content in C101 was not significantly different from its control (un-inoculated seedlings), while the one in C039 decreased and then increased; The activities of SOD and CAT in C101 decreased during the early stage increased during the late stage after inoculation. However, the net decrease of the activities of SOD and CAT was greater in C101 than in CO39, the activities of CAT in CO39 was relatively stable; The activities of LOX had no significant difference in C101 and CO39 before inoculation. However, these activities increased and then decreased both in C101 and CO39 after inoculation, and were obviously higher in inoculated C101 than the corresponding control during 18-48 hours after inoculation, and the net increase was greater in C101 than in CO39.There were 2 activity peaks in C101 corresponding to 18 and 48 hours after inoculation; The number of bands of POD isoenzyme in C101 and CO39 was the same, but the POD isoenzyme activity increased, and the color of some bands became darken 3 hours in C101 and 18 hours in CO39 after inoculation, farthermore, the activities of POD were obviously higher inC10l thaninCO39;The banding patterns of esterase (EST) isoenzyme were no different between C101 and CO39; The content of soluble protein both in C101 and CO39 decreased and then increased, reached their maxima at 48h and 72h corresponding to C101 and CO39 after inoculation; The content of soluble sugar were higher in C101 than in CO39, and it was positively correlated with the resistance of rice to blast; The content of malondiadehyde(MDA)was higher in C101 than in CO39, and the content reachedmaximum at 24hs and 36hs corresponding to C101 and CO39 after inoculation. According to the above results, we primarily concluded:1. The...
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