The Spatial Distribution Pattern And Evaluation Of Varieties Resistance And Biochemical Mechanism Of Their Resistance To False Smut In Rice

Rice false smut caused by Ustilaginodea virens (cooke) Tak is a worldwidefungal disease in rice, which its occurrence and damage globally tends to more andmore serious. The disease is not only greatly decrease the yield and quality of rice, butits ustiloxins may also cause poisoning to human and animals.The most convenient and effective method among the three methods of isolatingUstilaginodea virens was the vibrating method. XBZ medium was the best method toget chlamydospores through screening for the six media. Based on chlamydosporesthrough vibrating cultured in PS liquid on shaking bed at 130r/min under 26℃darkconditions for 7 days, conidia were largely obtained.Occurrence information of rice false smut on paddy at Hengnan in 2006 wasinvestigated. According to statistics, 20 hills per small plot at total 100 plots in eachpaddy lot were checked. The data from 12 varieties checked were analysed by thespatial distributing aggregation indexes determination of DPS software. The resultsshowed that the spatial distributing of rice false smut subjected to aggregationdistributing pattern.The main components analysis displayed that disease grains of the average eachpanicle among three components was the main component. Then the main componentused as clustering analysis in 114 varieties with cluster-average method. 114 ricevarieties were clearly divided into 6 groups at 0.5220 threshold level, in which 88, 9,7, 6, 3 and 1 varieties were classfied intoⅠ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵgroup, respectively.Based on above classification, resistant scale of the rice cultivars against false smut asthe field evaluation may be divided into 6 scales, viz. 0: 0.00～0.09disease grains ofthe average each panicle(highly resistant, HR); 1: 0.01～0.30(resistant, R); 3:0.31～0.40(moderate resistant, MR); 5: 0.41～0.50(moderate susceptibility, MS);7:0.51～1.10(susceptibility, S); 9:＞1.10(highly susceptibility, HS). The regression analysis was respectively based on per panicle disease gains, thesterile gain rate, 1000-grain weighty and yield loss rate of 15 cultivars. The resultsshowed that relationship between per panicle disease grains and the sterile grain ratewas obviously negative, and between per panicle disease grains and both 1000-grainweighty and yield loss rate was significantly positive, respectively.PAL,POD,PPO activity of 12 cultivars, 1d, 3d, 5d, 7d after inoculating conidiaof rice fasle smut with the injection at 7～10d before heading was detected. The resultsshowed that these enzyme's activity quickly enhanced and changed in the resistantcultivars after inoculability, but sIowly in the susceptibilitycultivars.