Identification Of Nematodes In Rice Root And Pathogenicity Of Rice-root Nematode And Root-knot Nematode To Rice

During 2004 ~ 2007, plant nematodes were identified from rice roots in Fuzhou and Wuyishan, Fujian and in Sanya, Hainan, China. The population combination of rice root nematode (Hirschmanniella) were compared in the field at Jinshan, Fuzhou and Sanya, Hainan. Research problems included the resistance of rice varieties to Hirschmannielld spp., infection process and outbreak condition of rice root nematode disease, risk analysis for root knot nematode to rice. The research results were below:Seventeen species, seven genera of plant nematodes were identified, which were Hirschmanniella oryzae, H. mucronata, H. microtyla, H. gracilis, H. mexicana, H. thornei, H. belli, H. anchoryzae, Macroposthonia xenoplax, Macroposthonia sp., Tylenchorhynchus agri, Pratylenchus zeae, P. pratensis, Helicotylenchus dihystera, H. crenacauda and Aphelenchus avenae. M. xenoplax, T. agri, P. zeae and H. crenacauda were new recorde species on the rice in China. H. thornei and H. anchoryzae were new recorde species on the rice in Fujian province and H. gracilis and H anchoryzae were new recorde species on the rice in Hainan province.Investigation of rice root nematode (Hirschmanniella) populations in the field showed that compound population at Jinshan Fuzhou was different with that at Sanya, Hanan. The dominate species were H. oryzae at both places, rate in the population was 79．6 % and 56．9 % respectively, while accessory species were H. mucronata, H. microtyla, H. gracilis, H. thornei, H. belli, H. mexicana, H. anchoryzae. Rate of accessory species in the population was different markedly, rate of H. mucronata and H. gracilis was 6．9 % and 2．3 % in the Jinshan population, while was 26．5 % and 21．5 % in the Sanya population. Experiment proved that resistance of same rice varieties to Hirschmanniella spp. was different at different places in according to rate of accessory species in the population.54 early rice cultivars, 151 late rice cultivars, 16 rice combinations and 9 samples from 5 wild rice species tested were not immune to rice root nematodes (Hirschmanniella). The ability of resistance to nematode infection and propagation was different in rice varieties, therefore population level in the rice roots were different markedly. Although rice varieties tested were susceptible to H. oryzae, they showed some selectivity to the other species, and species combination mode in the root of rice varieties was different. The disease tolerance of rice varieties to Hirschmanniella spp. was different. Some rice varieties were serious nematode populations level in the roots but yield loss was low, and some rice varieties were not marked nematode populations level but yield loss was high . The cultivated medium, inoculating time, inoculating population level, rice sowing density, fertilization level and stadium of nematode were factors of affecting invasion of rice root nematodes. The results of inoculation showed that it was more convenient for invasion of Hirschmanniella spp. in the soil than in the sand. The infection ability of J2 was strongest of the instars, while the ability of female was weakest. It certain that there were coordination between rice root nematode and nutrition of soil, and they affected the yield of rice.Chlorophyll of rice leaves and POD, CAT, PAL, TAL, PPO activity of rice roots changed markedly after invading rice root nematode, while carotinoide didn't change. Souble protein and MDA raised after innovating with rice root nematode at first invasion stage and then lowed. Activity of POD and PPO was low at first invasion stage and up to the highest at yellow ripening stage. Change of PAL and TAL activity in resistance variety, Fenghuazhan-1 was more remarkable than susceptible variety, Jiangxisimiao.Inoculation experiment approved that Hirschmanniella spp. could invade the embryo and roots, but couldn't invade sprouts at embryo stage. Therefore, seed germination and rate of rice establishment didn't change markedly.Tiller number, height of rice plant, heavy of roots increased at first invasion stage. And decline appeared at booting stage, with weakening , yellowing, delaying the flowering time and lightening color of leaves .Hirschmanniella spp. could cause yield loss of rice, especially reduced the number of panicles and grain weight. Losses of the conventional rice were more than the hybrid rice at the same invasion level.Meloidogyne arenaria and M. incognita from the other hosts could invade rice. J2 of M. incognita could invade rice and form root knots in the irrigation soil, while development and propagation of nematode were normal in the condition of discontinuous irrigation soil, caused yield loss, and the nematode was not well development and propagation in the continuous inundation. The inoculation level was higher, yield loss was the more.