Study On Induced Disease-resistant Effect And Biochemistrial Mechanism To Rice Bacterial Leaf Blight By Weak Virulent Strains On Rice Varieties

Rice bacterial leaf blight caused by Xanthomonas oryzae pv.oryzae is one of three big rice diseases in our country. This research embarked from the overlapping protection theory, used the weak virulent strains screened from our laboratory to carry on the experiment, studied its induction effect and the function mechanism, provided some theory basis for the using value and the application prospect of the chosen strains.Took the strain 0163(Hubei, xianning), Gd1358(Guangdong), Js97(Zhejiang), B5 (Wuhan), Pxo280(the Philippines) and so on 10 weak virulent strains as the females, we had separated 21 mono-cell clones, compared their toxicities in 23 rice varieties, then had screened five weakest virulent mono-cell clones "0163-1, Pxo280-1, Gd1358-1, Js97-2, B5d4" as the resistant induction strains.Continuously in 2 years' induction experiment, 5 weak virulent strains performed very low toxicity; The statistical analysis indicated that, the induction effects of all tried strains, existed difference in 1ï¼…level compared with the diseases, namely had all had the remarkable induced disease-resistant effect.Looking from the average induction effect, the induced disease-resistant effect of 0163-1 was first(average relatively effect 46.65ï¼…), higher than Keshade(38.95ï¼…) and Xiaojunling (31.25ï¼…); BSd-4(32.88ï¼…) and Pxo280-1(32.15ï¼…) were the second, the same as two disinfectants functions; Gd1358-1(29.35ï¼…) and Js97-2 (24.23ï¼…) were the third, hypervirulent strain IV3-1(23.35ï¼…) also had certain induced effect, but was lower than the weak poisonous strains.Compared with 5 strains' induced effect, obviously the induced effects of 0163-1, B5d-4, and Pxo280-1 were stabler, as same as the two disinfectants functions, so they had certain application prospect.Of different strain in the different year and the different variety, the induced disease-resistant effect had certain amplitude variation, it explained that environmental factor such as meteorology, sludge fertilizer mutually influented the relations between the strain and the host greatly. In view of this, in order to guarantee the weak virulent strain' induced disease-resistant effect, we'd better to select several different weak virulent strains and mix them according to certain proportion.Took 0163-1 as the representative, atomizing clear water(CK) and atomizing hypervirulent strain IV3-1 as the comparison, after atomization, divided 12h, 24h, 48h, 72h, 96h and gathered the rice leaf samples, determined the changes of its related physiological and biochemistry factors, researched "the induced disease-resistant mechanism", finally it indicated: 1) 0163-1 could, in 24h, stimulated H₂O₂ content of the plant to reach the high point;2) After atomizing 0163-1, the CAT activity of the rice had been suppressed enormously in 12～72 hour(compared with the CK), it explained the induced disease-resistance of the rice were negatively correlated with the CAT activity in the early stage;3) 0163-1 processing could, in 2 days, rapidly induced APX activity of the rice to reach to 48 units, remarkably higher than CK and the IV3-1 processing. This indicated that, rapidly enhancing the rice' APX activity, was an important disease-resistant induction mechanism of 0163-1;4) After atomizing with 0163-1, rice in 48h, the malondiadehyde(MDA) content was higher than the normal level(CK), but atomizing with IV3-1, although in the 12th hour, the MDA content was the highest, but afterwards it was continuously in the 4～6 units low levels. This indicated that, atomizing with 0163-1, before 72 hours, effectively stimulating the MDA content to elevate, was correlated with the induced disease-resistant mechanism.5) After atomizing with 0163-1, it could induce the rice's POD activities in 48h to reach the high point, obviously, stimulating the rice's POD activities to the highest level, was 0163-1 's important inducing mechanism.6) After 0163-1 processing, the polyphenoloxidase(PPO) activity was higher than CK in the first 72 hours, compared with IV3-1, 0163-1 could stimulate rice earlier to appear the PPO activity peak. This indicated that, to stimulate the rice's PPO activity to the peak, was correlated with the induced disease-resistant mechanism of 0163-1.7) 0163-1 processing, could stimulate the phenylalanine ammonia lynase PAL activity of the rice in 72 hours to reach to the high level. It told us this was one of the induced disease-resistant mechanisms of 0163-1.8) In view of the fact that the soluble protein content of 0163-1 processing was bigger than IV3-1 and the CK processing, we could extrapolate, comprehensively stimulating "the correlated disease-resistant enzymes to activate and the correlated protein content to increase", was the important mechanism of 0163-1 inducing plant disease-resistance.