| China is the biggest rice cultivating and consumption country in the world.It has approximately 29 million hm2 rice planting areas.As well as other countrys,China is suffering from a new noxious weed in rice cultivating field,called "Weedy rice".Estimated by related national farming departments,in recent 20 years,almost one ninth of rice areas were affected by weedy rice in China.What's more,weedy rice has spreaded all over the 6 rice planting zones.Cause of the more powerful abilities of survival and competition than cultivated rice,weedy rice is triggering a serious influence on the planting and production of cultivated rice.For example,there are about 200 thousand hm2 direct-seeded rice lands infected by weedy rice in Jiangsu province which has 2 million hm2 rice planting areas.Weedy rice caused a 20%decrease of yield on average.Some fields faced a more serious situation with an awful decrease of yield about from 60%to 80%,even 100%.Based on our research,the occurrence frequency of weedy rice in Liaoning,Heilongjiang and Jilin provinces were between 14%and 52%on average per year,30%or some in Jiangxi and Guangdong provinces.Those provinces is the mainly areas of production of commodity rice in china and facing a great challenge from weedy rice.Management is in emergency.At present,related studies concerned about manegement and prevention have obtained some achivements.However,due to the extreme similarity between weedy rice and cultivated rice in physiological mechanism and morphology traits,even the same hereditary basis with AA genotype,few breakthrough was made in prevention and management work.Upon these,the most important reason is that we lack of a systematic and comprehensive study on Chinese weedy rice.In China,every research institution basicly used the weedy rices come from local or near places as the research materials.Each institution lacked a germplasm resources bank that contains the whole Chinese weedy rice samples.Because a complete germplasm resources bank is the material base of establishing a systematic and comprehensive study on Chinese weedy rice.Furthermore,with that bank,more in-dcpth studies will be carried out,for instance,analysing the diversities of the ecotypes of weedy rice,studying the proportion and distribution of indica-japonica weedy rice,finding out the relationship between weedy rice and cultivated rice and whether the relationship is regionalism or not,exploring and discussing the origin of Chinese weedy rice.As a consequence,so comprehensive and systematic research will be benefit for more in-depth study,establishing the theoretical base for prevention and management.In the period of 2 years from 2011 to 2012,our study surveyed the situation of weedy rice happening in 4 provinces of south of China,Hainan,Guangdong,Fujian and Jiangxi.68 sites were surveyed totally and over 1500 samples were collected.With the previous work,we supplement and complete the weedy rice's germplasm resources bank of China.From the bank,130 sample sites were selected randomly,which contained 58 sites distributed in Jiangsu Province and 72 sites spreaded in other 22 provinces.Among samples in each site,2 to 6 weedy rice accessions and 1 cultivated rice accession were picked up by random.Finally,431 samples were used in this study,including 10 accessions of common rice race for comparison,66 accessions of local cultivated rice and 355 accessions of weedy rice(205 accessions from Jiangsu,150 accessions from other 22 provinces).In 2011,205 weedy rice samples were planted in the paddy field of Jiangpu farm of Nanjing Agricultural University,while other samples were planted in the same field in 2012.Following,we did these research:First,total 44 morphological traits were determined in two physiological phases.Systematic clustering analysis studied the diversities of ecotypes of weedy rice in China.Combining with Arcgis software,we studied the geographical distribution of weedy rice's ecotypes.Second,two methods,Cheng Index and InDel fingerprint,were took into the study on the indica-japonica classification of weedy rice,with the indica rice 93-11 and the japonica rice Nipponbare and other indica/japonica rices as compared control.Statistics analysed the proportion of different indica-japonica types of weedy rice in each sample site and studied the law of geographical distribution of each indica-japonica type.Through Arcgis software,the spread law of indica-japonica weedy rice was discussed.Third,correlation analysis studied the correlation between Cheng Index and InDel Molecular Index,discussing the applicability of these two identification methods in the research on weedy rice's indica-japonica types.Fourth,compared the geographical distribution indica-japonica type between weedy rice and cultivated rice,we analysed and discussed the correlation between weedy rice and cultivated rice,exploring the origin of weedy rice in China.In the study,we firstly did the research on 205 accessions of weedy rice from Jiangsu province.Euclidean Distance clustering analysis of 38 morphological traits for 205 accessions and 58 populations showed that weedy rice was not independent occurrence in 13 cities,but mutual spreading.The geographical distribution of these weedy rices illuminated that indica and indica-clinous weedy rice spreaded all over Jiangsu Province.This supported the result that weedy rice was under a situation of mutual spreading.The result of indica-japonica classification by Cheng Index indicated that indica and indica-clinous weedy rice were the main types in Jiangsu province,taking 54.15%and 42.4%respectively.A small amount of weedy rice were japonica(0.48%)and japonica-clinous(2.93%)and spreaded in 4 cities,Huaian city,Suzhou city,Yancheng city and Yancheng city.Analysing the phenomenon that japonica and japonica-clinous weedy rice occured,the natual gene flow from cultivated rice to weedy rice may be the main reason.Then offsprings with fertility occurred.Upon these weedy rice samples that used in this study,we discussed the ecotype of weedy rice in China.From the germplasm resources bank of weedy rice,among 23 provinces,four cities were randomly choosed in each province,spreaded in four geographical directions.From each city,1 weedy rice population was selected randomly for this study;in which 2 to 4 weedy rice samples were randomly picked up from the samples of population.At last,totally 220 accessions of weedy rice from 23 province were choosed as the research materials and planted in the paddy field of Jiangpu farm of Nanjing Agricultural University.44 morphological traits were determined.Because of the missing data of 12 traits,32 traits' data were remained in this study.Results of hierarchical clustering analysis,one-way analysis of variance and principal component analysis showed that there are four ecotypes of Chinese weedy rice,Group I with a high plant heigh and an early flowering phase,Group ? with a high plant heigh and a late flowering phase,Group III with a small plant heigh and an early flowering phase,Group IV with a small plant heigh and a later flowering phase.A geographical distribution law was uncovered through analysing the distribution of these 4 ecotypes.In south of Yangtze River,the main ecotype of weedy rice there was the weedy rice with a high plant height,while the weedy rice with a small plant height mainly spreaded in north of Yangtze River.Otherwise,the diversity of weedy rice ecotypes in south of Yangtze River was significantly richer than that in north of Yangtze River.The last part of this study was that we used both Cheng Index(a traditional method)developed by Kaisheng Cheng and InDel Molecular Index(a new method)developed by Baorong Lu to classify the indica-japonica type of Chinese weedy rice completely and systematically,studying the law of geographical distribution of weedy rice by geographical information technology.296 accessions were contained in this study,including 10 accessions of common rice for comparison,66 accessions of cultivated rice and 220 accessions of weedy rice.These cultivated rices and weedy rices were sampled from 23 provinces,totally 89 sample sites.The result of Cheng Index was that indica and indica-clinous weedy rices occupied a higher percentages than japonica and japonica-clinous weedy rice among 220 weedy rices,accounting for 33.6%and 40.0%repectively,while japonica and japonica-clinous weedy rice took a less percentage,accounting for 10.9%and 15.5%repectively.With the result of identification work by Cheng Index,study on geographical distribution of weedy rice indicated that there was a significant spread law on indica-japonica weedy rice existed in China.Based on the Yellow River as a boundary to separate north and south of China,then in south of China indica and indica-clinous weedy rice were the main types,while japonica and japonica-clinous weedy rice were the main types in north of China.The Yunnan-Guizhou Plateau experienced a similar situation in high latitude area,like north of China,where japonica and japonica-clinous weedy rice were the main types.At the same time,34 InDel primers were used into identifying the indica-japonica type of 220 accessions of weedy rice.Calculated the indica genotype frequency(Fi)and japonica genotype frequency(Fj)of all accessions,the result showed that there were 3 main types of weedy rice in China,typical indica weedy rice(48.6%),typical japonica weedy rice(30.9%),indica weedy rice(17.3%).Japonica weedy rice and intermediate type and japonica-clinous weedy rice occupied less amount,with the primer one 1.8%,the second one 0.9%and the last one 0.5%.No indica-clinous type existed.Upon the result of identification work by InDel Molecular Index,geographical spread study based on Arcgis software illuminated that weedy rice had a remarkble spread law that indica type spreaded in south of China and japonica type spreaded north of China.Accuracy ratio statistic analysis showed the result that both two identification methods were 100%corrected,suggested the reliability and accuracy of the identifying result of both two methods.Consistency analysis and correlation analysis demonstrated that the identification results of Cheng Index and InDel Molecular Index had a high consistency ratio of 93.2%,.The Pearson Correlation Index of these two methods can reach to 0.842,with Sig.(2-tailed)of 0.000.Consequently,the result told the truth that both two methods can explain the differentiation of indica-japonica type of weedy rice accurately. |
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