“黑麦草-水稻”草田轮作对湘西稻田纹枯病发生的影响

Effects of Ryegrass-rice Rotation on the Occurrence of Rice Sheath Blight in Xiangxi Paddy Field

2015~2016年在湘西水稻两熟制地区开展了冬种黑麦草对水稻纹枯病越冬病原菌存活力及后作水稻纹枯病发生程度的影响研究。结果显示:冬种黑麦草处理土表越冬菌核在冬春季轮作后,菌核萌发率到第二年5月显著下降至58. 49%,而冬季休闲处理萌发率达80. 0%;冬种黑麦草处理越冬稻兜上菌丝的存活率到5月显著下降至43. 0%,而冬闲田也有一定程度下降,但差异不显著,到第二年5月存活率仍可达68%。可见,冬种黑麦草田无论是越冬菌核萌发率还是越冬稻兜菌丝存活率均显著低于冬闲田。在后作水稻纹枯病发生方面,冬种黑麦草田发病初期,稻纹枯病病株率及病情指数分别比冬闲田低3. 60%和1. 25;水稻生长发育后期,冬种黑麦草田稻纹枯病病株率及病情指数与冬闲田差异程度增加,分别比冬闲田低24. 17%和6. 42。上述研究表明,冬种黑麦草可以显著降低土壤中越冬菌核的萌发率及残留于稻兜的菌丝体存活率,有效减轻后作水稻纹枯病的发生。

The effects of winter cropping ryegrass on the survival of Rhizoctonia solani overwintering in winter fallow areas and the occurrence degree of rice sheath blight of subsequent rice was conducted from 2015 to 2016 at Xiangxi. Our results showed that ryegrass significantly reduced the survival rate of Rhizoctonia solani overwintered within the timespan of winter and spring. The germination rate of sclerotium laid in the surface layer of soil in the ryegrass-cultivating field was only 58. 49%,which was much lower than that in the control field( about 80%). In addition,the survival rate of mycelia in rice stubble overwintered in the ryegrass-cultivating field( 43%) was significantly reduced,compared to that in the control field( 68%). Variance analysis revealed that both germination rate of sclerotium and survival rate of mycelia in the ryegrass-cultivating field was significantly lower than that in the control field when the overwintering process concluded.Considering the occurrence of rice sheath blight of subsequent rice,the disease incidence and disease index in the ryegrass-cultivating field was 3. 6% and 1. 25 lower than that of the control field,respectively. However,at the late period of rice growth and development,disease incidence and disease index in the ryegrass-cultivating field was 24. 17% and 6. 42 lower than that in the control field,respectively. Together,winter cropping ryegrass significantly reduced germination rate of sclerotium and survival rate of mycelia,which alleviated the occurrence degree of rice sheath blight of subsequent rice.