| Chinese water chestnut (Eleocharis dulcis) belongs to Cyperaceae, a perennial herb in shallow water. It is native to southern China and India. The incidence of Chinese water chestnut stem blight was20%-40%, serious fileds reached70%in TuanFeng county of hubei province in2009-2012. We identified the causal agent of Chinese water chestnut stem blight by molecular biological methods, occurrence and control techniques.The main results were as followed:Genomic DNA of TF2010-1was extracted, sequences of rDNA-ITS and mtSSU were obtained. The sequence length is538bp and522bp respectively. Comparison with sequences in Genbank showed above95%and86%similarity with colletotrichum sp. respectively.We studied the occurrence of Chinese water chestnut stem blight in2012and2013in Tuanfeng County, Hubei province. The results showed, sympom appeared at the end of July to early August each year, in which case the severity was light and the disease developed slowly; the rate accelerated on early September.Correlation analysis showed that the development of the disease in2012and2013were closely related to meteorological factors respectively. Disease index was negatively correlated with a daily average temperature (R22012=0.72, R22013=0.44, P<0.05) and positively correlated with cumulative rainfall (R22012=0.81, R22013=0.68, P <0.05).The results of overwintered test showed that plant debris in the refrigerator4℃,25℃, outdoor soil surface and soil at10cm122d, the separation rates of C.eleocharidis were23.61%,5.56%,7.78%and3.33%, buried in soil at20cm122d after treatment, C.eleocharidis on plant debris were not isolated at all. The pathogen rates of corms showed that the skin disease and the skin healthy corms were100%and55%, the frequency of C. eleocharidis in isolated tissues were28.7%and18.03%respectively.Four fungicides can significantly improved seed germination rate. The germination rate of25%carbendazim WP500x and10%difenoconazole WG1000x reached96.67%、92.22%respectively; followed by400g/L flusilazole EC8000x and250g/L azoxystrobin SC1000x, the germination rate were83.33%and80%respectively. Studies on various clove treatments before the second nursery, the results showed, effect of250g/L azoxystrobin SC2000x and10%difenoconazole WG1000x、2000x were the best, disease index were4.70,4.47,1.90; effect of250g/L azoxystrobin SC1000x and400g/L flusilazole EC5000x were the worst, disease index were38.27and26.93respectively. Studies on effect of different fungicides on control of stem blight of Eleocharis Dulcis indoor, the results showed,250g/L azoxystrobin SC1000x,10%difenoconazole WG1000x were the best, followed by25%carbendazim WP500x,400g/L flusilazole EC8000x was the worst. Studies on effect of different fungicides on control of stem blight of Eleocharis Dulcis in filed in2012and2013,the results showed,10%difenoconazole WG1000x was the best, efficacy was78.06%～91.91%, the worst was25%carbendazim WP500x, efficacy was26.96%～61.52%.Studies on resistance evaluation of different varieties of E.dulcis to stem blight throughout the2011to2013growing seasons,we have selected two stable and high resistant varieties:Yangdian and Baoying, disease index were0.13to13.20and0.53to16.40respectively; two high susceptible varieties:Chaozhou and Lianjiang, disease index were22.87to38.33and30.48to42.50respectively. Other varieties were unstable, there were some differences between years.Studies on effect of various varieties and fungcides treatments on control of stem blight of E. dulcis, the results showed,10%difenoconazole WG1000x was significantly better than25%carbendazim WP500x and sprayed two times higher than the effect of only once. There were some differences bettween various varieties, disease index of Yangdian and Baoying were significantly lower than Tuanfeng and Yiyang. In all combinations, Yangdian sprayed10%difenoconazole WG1000x2times has the lowest disease index. |
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