“多花黑麦草-水稻”轮作对稻瘟病发生程度的影响

Effects of“Italian ryegrass-rice”Rotation on the Occurrence of Rice Blast

2016~2017年在湘西水稻两熟制地区开展了冬种黑麦草对稻瘟病菌越冬存活力及后作水稻稻瘟病发生的影响研究。结果显示,冬种黑麦草田残留稻兜上的稻瘟病越冬菌丝随越冬时间的推进,存活率从2016年12月的72.80%显著下降到2017年4月的52.80%,冬闲田无明显下降。从越冬病菌产孢量看,冬种黑麦草田稻兜的稻瘟病菌产孢数量从2016年12月至2017年4月均在显著减少,冬闲田则从2016年12月至2017年2月减少显著,2017年2月到4月降低不显著;比较同一调查时间冬种黑麦草田与冬闲田越冬病菌产孢量,发现冬种黑麦草田的越冬病菌产孢量均比冬闲田显著降低。在冬种黑麦草对后作水稻稻瘟病发生的影响上,在同一调查时间,无论是病叶(穗)率还是病情指数,冬种黑麦草田均显著低于冬闲田,其中2017年7月、8月和9月冬种黑麦草田的病叶(穗)率分别比同时期冬闲田的病叶(穗)率低52.83%、26.97%和20.61%,病情指数分别低66.82%、45.48%和39.84%。冬种黑麦草对后作水稻稻瘟病发生的控制以2017年7月最高,为40.05%,8月和9月的控病率分别为31.26%和28.49%。综合以上结果,在稻区实施冬季种植黑麦草,不仅能够显著降低稻瘟病越冬菌丝的存活率,而且也显著降低越冬病菌的产孢数,有效减少后作水稻稻瘟病的初侵染源,并在一定程度上降低后作水稻稻瘟病的发生。

The effects of winter cropping Italian ryegrass on the survival of Magnaporthe oryzae overwintering and the occurrence of rice blast in the late-grown rice of subsequent rice were conducted from 2016 to 2017 in Xiangxi.Results showed that the survival rate of Magnaporthe oryzae mycelia in rice stubble overwintered in the ryegrass-cultivating field reduced from December 2016(72.80%)to April 2017(52.80%).However,the mycelia survival rate of the control was not reduced.The sporulation capacity of Magnaporthe oryzae for ryegrass-cultivating field was decreased significantly from December 2016 to April 2017.The sporulation capacity for winter fallow field was only decreased from December 2016 to February 2017.The amounts of spores for ryegrass-cultivating field were significant lower than that for winter fallow field.In addition,the occurrence rate of rice blast,the disease incidences and disease indexes for the ryegrass-cultivating field were significantly lower than that of the control field.The disease incidences of the ryegrass-cultivating field in July,August and September were 52.83%,26.97%and 20.61%lower than that of the control field,respectively.The disease indexes in July,August and September were 66.82%,45.48%and 39.84%lower than that of the control field,respectively.The disease control rate was highest in July 2017 at 40.05%,with the disease control rates in August and September at 31.26%and 28.49%,respectively.Taken together,winter cropping ryegrass can not only significantly reduce the survival rate of Magnaporthe oryzae mycelia,sporulation capacity and efficiently decreased initial infection sources,but also alleviate the occurrence of rice blast for subsequent rice.