Studies On The Distribution And Occurrence Of Cyst Nematodes On Rice In Guangdong Privonce

Rice is one of the most important staple crop in the world.At present,only six species of cyst nematodes can parasitize on rice,among them are Heterodera elachista and Heterodera luodingensis.In this paper,The existence of the combined infection by these two cyst nematodes on rice in Guangdong Province and the cyst nematodes distribtion on rice have been investigated.Combined with field surveys and pot experiments,the occurrence regularity of H.elachista in Guangdong Province has been studied.The host range of H.luodingensis was determined by pot trial.The resistance of 34 varieties of rice to H.elachista and H.luodingensis was identificated.The main results are as follows:The investigation results of cyst nematodes on rice showed that 127 samples of rice roots and soil collected,23 samples had H.elachista,and the detection rate of H.elachista was 18%.the occurrence of cyst nematodes on Qingyuan City and Jiangmen City was relatively common,the detection rate of H.elachista were 47% and 42%,followed by Zhaoqing City,the detection rate of H.elachista was 22%;Yunfu,Zhanjiang,Shantou had moderate occurrences,the detection rate of H.elachista were7.7%,6% and 2%.And cyst nematodes have not been found in Guangzhou.The cyst nematodes collected in Qingyuan,Zhaoqing,Shantou,Jiangmen were H.elachista;the cyst nematodes collected in Jiangmen,Yunfu,Zhanjiang were H.luodingensis after molecular identification and morphological observation.The combination infection of H.elachista and H.luodingensis was existed in Jiangmen.The pot experiment on occurrence regularity of H.elachista results showed that when average daily temperature around 28 ℃,the H.elachista needs about 24 days to complete a life cycle,it takes about 22 days to complete a life cycle when the averageIVdaily temperature around 34 ℃.In the pot experiment in Guangzhou city,H.elachista occur 6-7 generations a year,during early rice season,the cyst nematodes can occur 3generations,the number of J2 in the soil have three peaks,mainly from June.There are3-4 generations on late rice,3 peaks of J2 in the soil,a large number of white females and cysts began increased in early October.The number of cysts produced by late rice is significantly more than the number of cysts produced by early rice.The field fixed-point investigation results of H.elachista showed that when the average daily temperature was 30 ℃,it takes about 25 days for the H.elachista to complete a life cycle,and it takes longer time when the temperature was lower.In the field of Qingyuan,H.elachista can occur 4-6 generations a year,early rice occurs 1-2generation,more J2 produced in the soil from mid-May,and more cysts are produced in the rice roots in late June.Late rice occurs 3-4 generations,more J2 in the soil from the beginning of September,and a large number of cysts are produced in the rice roots in the late part of October.The occurrence of H.elachista in late rice is more serious than that of early rice.The results of the determination of host range of cyst nematode H.luodingensis showed that in 6 grass family,the H.luodingensis can only complete the life cycle on rice and corn,Rice is its optimal host,and corn is its bad host.The resistance identification results of rice varieties on H.elachista showed that Baohan 1 is high resistance to H.elachista,Zhenghan 10,Luodao 998,Lianjing 4 and other 13 rice varieties showed medium resistance,19 Xiang,Huangsizhan among the14 rice varieties showed middle sense,Hengfengyou 426,Quanliangyou 1822 and other 6 rice varieties showed high sensitivity.The identification results of rice varieties on H.luodingensis showed that Guinongzhan,Lianjing 4,Wushansimiao,Luodao 998,4 rice varieties showed medium resistance,6 rice varieties such as Ribenqing,Guijingsimiao showed medium sensitivity,24 rice varieties such as Jinjing818,Zhenghan 10 showed high sensitivity.The four rice varieties Lianjing 43 Guinonzhan Wushansimiao Luodao 998 showed a certain resistance to H.elachista and H.luodingensis.In this paper,the distribution of cyst nematode on rice in Guangdong Province have been conducted through the investigation.The occurrence of cyst nematode H.elachista on rice has been studied by the method of inoculation in greenhouse and field survey.The host range of cyst nematode H.luodingensis was determined.Lianjing43,Guinogzhan,Wushansimiao and Luodao 998 are resistance to H.elachista and H.luodingensis.