Study On The Field Occurrence Dynamics, Resistance Resource Evaluation And Damage Loss Of Cyst Nematodes In Upland Rice

The rice cyst nematode,Heterodera elachista,also known as the Japanese cyst nematode,is a parasitic nematode which mainly harms rice in the hilly areas of South China in recent years.The nematode mainly endangering the root of rice,significantly reducing the utilization rate of rice to water,reducing the yield of rice and decreasing the quality of rice.In general,it can cause the loss of rice yield 7%-19%.With global warming and changes in rice planting and management system,its potential threat is increasing.In the past2016-2017 years,the field dynamics,screening of resistant germplasm resources and damage loss were studied in 3 aspects,and the following results were obtained.1)In 2016,the field dynamics of H.elachista in rice seedling field and direct seeding field were investigated in 2016.It was found that the number of spores appeared at 3 peaks in the seedling field,respectively at the end of the tillering stage,the heading stage and the filling stage,and the temperature decreased after October 2nd,and the number of spores in the rice rhizosphere had no significant changes;the direct seeding field was found.There were 2 peaks in the number of spores,namely,jointing booting stage and yellow maturity stage.The number of cyst sac decreased slightly before harvest in October 2nd.In 2017,the occurrence of the cyst nematode of upland rice in the late rice field of different resistance was investigated.It was found that there were 1 peaks in the tillering stage of the cultivated susceptible variety,the number of spores in the tiller period of rice,and the 1 higher levels of >200(>200 cyst /L soil)after the booting period of rice,and 73 in the drought resistant cultivar.After the tillering,the number of cyst nematode in Upland Rice has been at a low level(<50 cyst /L soil).2)H.elachista is a new pathogenic nematode of rice in China.For screening resistant resources in breeding to H.elachista,the resistance of 51 rice cultivars from Hunan Province,China was evaluated in the greenhouse and field using average number of cyst per plant,relative resistance index(RRI)and Pf/Pi ratio.No cultivar was immune and highly resistant to H.elachista.Among the 24 middle-season rice cultivars,only Guangliangyou 2010 showed resistance to H.elachista based on average number of cyst per plant in greenhousetest,and Guangliangyou 2010,Zhunliangyou 527 and Guangliangyou 1128 showed resistance to H.elachista based on RRI evaluation.Among the 27 late rice cultivars,10cultivars(Shengtaiyou 9712,Zhunliangyou 608,Nongxiangyou 204,Yueyou 9264,Yueyou3700,Zhongzheyou 1,Yueyou 27,Xiangwannuo 1,Heyou 50 and Yliangyou 9918)were resistant to H.elachista based on average number of cyst per plant.However,Xiangwannuo1,Heyou 50 and Yliangyou 9918 were moderately susceptible based on RRI evaluation.Using Pf/Pi ratio as the evaluation index,9 late resistant cultivars screened from greenhouse based on RRI evaluation were basically consistent with field resistance.The results indicated that RRI is an efficient index for evaluating the resistance of rice cultivars to rice cyst nematode.3)In 2016,the damage of H.elachista to late season rice was studied by inoculation with different density of dry rice cyst in the field.The results showed that,with the increase of inoculation density,the chlorophyll of rice decreased with the increase of inoculation density,and the results of the harvest time showed that with the increase of the number of spores,the dry weight,the number of effective tillering,the grain weight and the weight of the grain showed a decreasing trend.The yield loss of rice inoculated with 200 plants per plant and 400 plants per plant was 19.3% and 24.2% respectively.In this paper,through the study of the germplasm resources of the cyst nematode,the dynamics of the field and the influence of the inoculation amount on the agronomic characters and yield of the different upland rice cyst nematode,some rice varieties with excellent resistance to H.elachista were screened,and the regularity of the occurrence of the parasite in the field was understood.The economic threshold is of great significance for further prevention and control of the disease and guiding the comprehensive control of H.elachista...