| Stem blight of Eleocharis dulcis is an important fungal disease caused by Phoma bellidis. In recent years, the disease which occurred in E.dulcis planting area in Tuanfeng County, Hubei Province, seriously reduced corm production. Based on previons work,phytotoxins from the pathogen were separated and the effect of phytotoxins on the ultrastructure of host cells was explared. Moreover the occurrence of disease in the field was investigated and field control technology of disease was researched. Main results of the study are shown as follows:1.The crude phytotoxins was extracted from the liquid culture of P.bellidis by ethyl acetate and concentrated by rotary evaporation. The best extractior solvent for crude phytotoxins is 20% methanol. Developing solvent EAC∶HAc∶DD H2O=(15∶1∶2) had best separation effect in 24 different TLC developing solvents. The crude phytotoxins could be separated into 14 components by the solvent. Component T12 and T13 respecting RF value 0.93 and 0.95 respectively showed the highest toxicity. High performance liquid chromatography was used to further detect T12 and T13. The chromatogram showed that T12 and T13 contained 8 and 26 components, respectively.The result of biological activity assay with components the 8 peaks corresponding to from the T13 indicated that T13-4 and T13-5 which the retention time of each was 2.65 min and 2.8 min showed higher toxicity than other components in T13. Percentage composition of T13-4 and T13-5 was 25.62% and 70.72%, respectively.2.Concentraction of 0.02g/ml crude phytotoxins were inoculated onto stems of resistant(Yang Dian) and susceptible E.dulcis(Lushan)cultivars. Cell ultrastructures of E.dulcis stem treated with crude phytotoxins were observed at 3, 6, 12 and 24 hpi. The results indicated that cell ultrastructures was normal after resistant E.dulcis stems treated for 3hpi. Bubble appeared in the mitochondria, chloroplasts and nuclei after resistant E.dulcis stems treated for 6hpi. At 12 hpi, wall separation, cell membrane deformation and chloroplast lamellar structure was destroyed. At 24 hpi, cell death was observed. After susceptible E.dulcis stems treated for 3hpi, Cell wall separation and plasma membrane were found.After 6hpi, chloroplast lamellar structure disintegrated.At 12 hpi, cellmembrane structure disintegrated and cell death was observed.3.The results of field investigation in 2014 ~2015 showed that. Early August is the early speriod of the disease. Disease index got up quickly in late September. The highest disease index was investigated during mid and last October. Disease index of 2014 and2015 is 6.11 and18.01 at peak period, respectively. DPS software was used to analyze the correlation between meteorological factors and disease index in two years. The results showed that the disease index of P.bellidis was negatively correlated with the average daily temperature.4.Resistance of different E.dulcis varieties to P.bellidis was evaluated by inoculatione with spore suspensions and phytotoxins from P.bellidis on E.dulcis stems.The results showed that Lushan, Shaoguan Maba, Baoying, Qizhou, Sanjiang-98 and Chaozhou were susceptible. While varieties Guilin-2, Yiyang, Jiangxi, Xiangtan, Yang Dian were resistant. The results of field resistance indentificationg in 2014~2015 showed that, among the 34 E.dulcis varieties, Xinku-2 showed susceptible, Lianjiang and Anhui showed resistant. Xiangtan, Yang Dian and Guilin-2 showed good resistance in field resistance test and laboratory tests.5.In 2014, fungicides were chosen for chemical control at Tuanfeng county. After spaying for 10 d and 20 d, The results showed that the control efficacy of 10%difenoconazole WDG(1500 times diluted) is 98.72% and 94.79%, respectively. The control efficacy was more higher than 70% mancozeb WP(700 times diluted) and 25%carbendazim WP(500 times diluted). |
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