Study On Fungicide Control And Pathogenic Characteristic Of Stem Rot Of Rice In Soda Saline-alkali Land

Stem rot of rice is widespread and serious disease in rice growing areas where is sodasaline-alkali paddy field in west Jilin. Rice yield decreases markedly which is directlycaused economic loss, it is now causing increased concern among growers. Because of thespecial land, previous chemical control is not work. In order to effectively control stem rot,the systematic study on stem rot of rice in soda saline-alkali land in this thesis, andunderstood characteristic of stem rot.A systematic study was made on characteristics of incidence, pathogenic morphologyand identification, biological characteristics on stem rot of rice in soda saline-alkali land. Atthe same time, effective fungicides were screened preliminarily for the disease.The disease spot was found from the end of June to early July, viz. at early tilleringstage of rice. The disease was serious and developed in July and August. Sclerotialproduction were in August and September. The conidia were not found in field, but theconidia were produced in special condition indoor. Sclerotium diameter was243.74μm,which were bigger than that of Sclerotium in non-saline-alkali land. The sexualreproduction of the pathogen were not found after field investigation and room culture.Molecular biological identification showed that the pathogen was Magnaporthesalvinii. This result further confirmed morphological identification. The ITS of strains fromdifferent areas was the same with that of the strain from different rice cultivar.There were significant differences in biological characteristics of the pathogen of stemrot of rice between the soda saline-alkali and the non-saline-alkali land. Compared withacid soil and cold region, the growth of pathogen was the fastest under the condition ofalternating light and dark. The pathogen could grow at15℃to30℃, pH3.5to10.5. Thebest condition for mycelium growth was30℃, pH4and8.The optimum carbon andnitrogen sources were rhamnose and calcium nitrate, respectively. The optimumcarbon/nitrogen ratio was60/1,30/1,20/1. The trace elements zinc sulfate acceleratedmycelial growth. The pathogen could growth best in Corn Meal Medium. The testedgrowth substance inhibited mycelium growth. The mycelial lethal temperature was50℃.The sclerotium lethal temperature was60℃.Seven fungicides were screened for the diseases with methods of mycelium growthrate indoor, included iprodione50%WP, prochloraz25%EC, triadimefon10%DP,prochloraz25%EW, carbendazim50%WP, bacillus subtilis2.5%AS and propiconazole 25%EC. The results of field trials showed that iprodione50%WP, prochloraz25%EC,prochloraz25%EW and propiconazole25%EC exhibited high control effect.The above results will further integrally lay the foundation for the studying of thedisease development law and the integrated management of the rice stem rot in sodasaline-alkali land.