Effects of Seed Rate on Root Twining Power and Seedling Quality of Machine-transplanted Super Rice

Fei TENG，Defeng ZHU，Huizhe CHEN，Xueqing CAl，Yicheng XU

1.China National Rice Research Institute/State Key Laboratory of Rice Biology，Hangzhou 310006，China；

2.Beijing Agricultural Machinery Testing and Extension Station，Beijing 100079，China

Effects of Seed Rate on Root Twining Power and Seedling Quality of Machine-transplanted Super Rice

Fei TENG1，2，Defeng ZHU1*，Huizhe CHEN1，Xueqing CAl1，Yicheng XU1

1.China National Rice Research Institute/State Key Laboratory of Rice Biology，Hangzhou 310006，China；

2.Beijing Agricultural Machinery Testing and Extension Station，Beijing 100079，China

In order to investigate the effects of seed rate on root twining power and seedling quality ofmachine-transplanted superrice cultivars，Yongyou 12 and Zhongzheyou No.1，total 6 seed rates were arranged，and the growth characteristics，quality and root twining power of machine-transplanted rice seedlings were studied.The results showed that seed rate had great effects on root twining power and quality of rice seedlings；with the increase of seed rate，the root twining power of rice seedlings was increased，but the quality of rice seedlings was significantly reduced；under the condition of high seed rate，rice seedlings were weak with less accumulate dry matter and nonuniform growth，and the proportion of weak seedlings was higher.When the seed rate of both rice cultivars was reduced by 10 g/tray，the average seedling height was increased by 0.5 cm，leaf age was increased by 0.1，stem base diameter was increased by 0.1 cm，and root number per plant was increased by 0.3.When the seed rate was increased by 10 g/tray，the accumulated dry matter per plant was reduced by 5.1 mg.With the increase of seed rate，the seedling quality of Zhongzheyou No.1 was decreased rapidly，and the proportion of weak seedlings was increased rapidly.However，Yongyou 12 has a larger elasticity in seed rate.When the seed rate reached to 50 g/tray，blanket seedlings of Yongyou 12 were nursed with uniform growth and higher quality，but the shoots were sparse with lower leaf area index.However，when the seed rate was up to 50 g/tray，blanket seedlings of Zhongzheyou No.1 were nursed with uniform growth and higher quality，as well as higher-density shoots.From a comprehensive point of view，the optimum seed rates of Yongyou 12 and Zhongzheyou No.1 were 65 and 50 g/tray，respectively.

Rice；Super rice；Mechanical transplanting；Seed rate；Blanket seedling；Seedling quality

W ith social and economic development，rural labor transfer and aging，mechanized production of rice，especially mechanical transplanting technology，is developed more and more rapidly.The comparison of different planting patterns and production characteristics show that mechanical transplanting is development direction of rice industry in China.Mechanical transplanting has been applied in China for several years，and the cultivation area of machine-transplanted rice accounts for 40%of the total cultivation area.There are also some factors constraining the promotion of mechanical transplanting in China.Mechanical transplanting is difficult to be applied in double cropping rice and hybrid rice，so the cultivation area of machine-transplanted double cropping rice and hybrid rice is smaller.The main aspect restricting the promoting of mechanical transplanting in rice is nursing［1-2］.Mechanical transplanting is characterized bylarge seed rate and uniform seedling age，and it has higher requirements for seedling management［3-7］.In the cultivation of hybrid rice，if seed rate is higher，seedling quality will be lower，and the advantage of hybrid rice will not be better played；if seed rate if lower，it is difficult for rice roots to twine together，affecting the effectofmechanical transplanting. The ideal seedlings for mechanical transplanting should have uniform and robust growth and strong root twining power［8-12］.

In recent years，there are great differences in optimum seed rate for mechanical transplanting among different rice-growing regions.It is considered that seed rate has close relationships with seedling quality and root twining power.With the increased seed rate on trays，seedling quality is trended to be reduced.Under the condition oflow seed rate，although seedling quality is high，root twining power is weak，and seedling roots are easy to get loose and damaged［11-17］. The relationships between seed rate of different rice cultivars，especially super rice cultivars，and seedling growth and quality are still unclear，and there are no quantitative indicators for evaluatingroottwining powerofnursed seedlings.In this study，different seed rates were arranged，and the effects of seed rate on seedling growth，quality and root twining power of indica and japonica super hybrid rice were investigated，providing theoretical basis and technical support for mechanical transplanting of hybrid rice.

Materials and Methods

Overview on test site

The test was conducted in the Fuyang experimental base of China Rice Research Institute （30.1°N，120.0°E），which is the main ricegrowing area in the middle and lower reaches of the Yangtze River.

Experiment design

The test materials were indicajaponica hybrid rice cultivars，Yongyou 12 and Zhongzheyou No.1.They are recognized as super rice cultivars by the Ministry of Agriculture，and are also dominant rice cultivars in Zhejiang Province.

The rice seedlings were nursed on trays（580 mm（L）×280 mm（W）× 28 mm （H））with seedling substrate（Jinhai，Hangzhou）.Total 6 seed rates were arranged，including 35，50，65，80，95 and 110 g dry seeds/tray.The rice seeds were soaked on May 27，and sowed on May 30.There were 6 replicates for each seed rate treatment.

lndicator measurement and methods

Growth and dry matter accumulated amount In each treatment，the average leaf age was surveyed 18 d after the sowing.According to the average leaf ages，total 20 plants were sampled for each treatment with 3 replicates.The plant height，root length，root number，yellow leaf number and seedling base diameter were measured.The seedling plants were dried at 105℃and then at 80℃to constant weight，and then weighed.

Uniformity of plant height After a certain time （19 d），three seedling blocks in size of 6 cm ×6 cm were sampled from each treatment.In each seedling block，the heights ofall seedlings were measured.The average seedling height，along with coefficient of variation，was calculated.According to variation coefficientof seedling heightand proportion of seedlings lower than half of the average height，the uniformity of seedling height was observed.

Variation coefficient of seedling height= （Standard deviation of seedling height/Average seedling height）×100%.

Leaf area and SPAD value After a certain time （19 d），three seedling blocks in size of 6 cm ×6 cm were sampled from each treatment.In each seedling block，the fully expanded leaf green degrees of all seedlings were measured using chlorophyllmeter（SPAD-502，Japan）.Theeffectof seed rate on seedling chlorophyll content was analyzed.Subsequently，the seedling leaves with length higher than 2 cm in each seedling block were cut off，and their leaf areas were measured using leaf area meter（LI-3000A，LI-COR Inc.）.

Leaf area index（LAI）=Total leaf area per tray/Tray area.

Root twining power At the 3.5-leaf stage，the entire seedling block was removed from each tray.One end of each seedling block was fixed，and the other end was snapped with a large splint.Subsequently，the seedling block was pulled horizontally by an electronic dynamometer till the seedling block was loosened and broken.The maximum tensile strength was also the root twining power.There were 3 replicates for each treatment.

Data processing and analysis

The data were processed and analyzed using Excel and SAS.The variance analysis was conducted using LSD multiple comparisons.

Results and Analysis

Seedling growth

The seed rate of rice on trays showed significant effect on growth of rice seedlings （Table 1）.With the increase of seed rate，the seedling heights，base diameters，leaf ages and root numbers of both rice cultivars were all trended to be decreased. When the seed rate was reduced by 10 g/tray，the average seedling height was increased by 0.5 cm，leaf age was increased by 0.1，seedling base diameter was increased by 0.1 cm，and root number per plant was increased by 0.3.Under the condition of low seed rate （35-50 g/tray），seedling growth was better，base diameter was larger and roots were more developed.However，under the condition of high seed rate （95-110 g/tray），seedling quality，as well as plant height，leaf age，base diameter and root number，were all reduced greatly.When the seed rate was up to 65 g/tray，yellow leaves appeared in the lower part of seedlings. When the seed rate exceeded 80 g/tray，more withered leaves appeared in the lower part of seedlings，and seedling quality was also reduced rapidly.

Dry matter accumulated amount

With the increased seed rate，dry matter accumulated amount in shoots ofseedlingswasreduced （Fig.1）. When the seed rate was increased by 10 g/tray，the dry weight of single seedling was reduced by 5.1 mg.The critical seed rate for reduced seedling dry matter accumulated amount was different between the two rice cultivars.When the seed rate of Yongyou 12 was increased to 80 g/tray，the drymatter accumulated amount in seedling shoot was significantly reduced；but when the seed rate of Zhongzheyou No.1 was increased to 65 g/tray，the dry matter accumulation amount in seedling shoot was greatly reduced.It indicates that indica super hybrid rice Zhongzheyou No.1 is more sensitive to seed rate，but indicajaponica super hybrid rice Yongyou 12 has larger elasticity in seed rate.

Table 1 Effects of different seed rates on morphological characteristics of rice seedlings

Seedling growth uniformity

According to variation coefficient of seedling height and proportion of seedlings lower than half of the average height，the uniformity of seedling growth was evaluated（Table 2）.Under the condition of low seed rate（30-65 g/tray），the seedling height variation coefficient and proportion of seedlings lower than half of the average height of Yongyou 12 were 11.59% and 0.0%，respectively.However，when the seed rate was increased to 80-110 g/tray，the seedling height variation coefficient and proportion of seedlings lower than half of the average height were 18.6%and 01.8%，respectively. At the low seed rate （30-65 g/tray），the seedling height variation coefficient and proportion of seedlings lower than half of the average height were 19.7% and 0.7%，respectively.But when the seed rate was up to 80-110 g/tray，the seedling height variation coefficient and proportion of seedlings lower than half of the average height were 22.3% and 2.8% ，respectively.When the seed rate was lower than 65 g/tray，there were basically no dwarf seedlings in Yongyou 12.However，when the seed rate was only up to 50 g/tray，dwarf seedlings appeared in Zhongzheyou No.1.The seedling height variation coefficient of Zhongzheyou No.1 was larger than that of Yongyou 12，so the growth uniformityofZhongzheyouNo.1was worse than that of Yongyou 12.Too high seed rate will affect growth uniformity of rice seedlings，resulting in higher proportions of dwarf seedlings and weak seedlings.

Leaf area and SPAD value

With the increased seed rate，seedling leaf SPAD values of both rice cultivars were trended to be decreased（Fig.2）.There was a negative correlation between seedling leaf SPAF value and seed rate.

As shown in Fig.3，with the increased seed rate，the leaf area index was increased first and then decreased.Under the condition of low seed rate，increasing seed rate showed significant effect on increasing leaf area index.However，under the condition of high seed rate，increasing seed rate almost showed no effect on leaf area index.When the seed rate was increased to 65 g/tray，the leaf area indexes of both rice cultivars all reached the peaks.However，when the seed rate was further increased，the leaf area indexes were decreased. This might be because that too high seedling density reduced seedling quality，leading to reduced leaf area.

Root twining power

Root twining power is an important indicator evaluating nursed seedling quality.The greater the root twining power is，the more difficult the seedling block’s loosening is.As shown in Fig.4，there was a positive correlation between root twining power and seed rate.The regression analysis showed that root twining power waslogarithmically linearly related to seed rate（r＞0.98，P＜0.05）.It suggests that increased seed rate can inevitably increase root twining power.However，under the condition of high seed rate，when the seed rate was increased further，the increment of root twining power became small.Under the condition of same seed rates，the root twining powers of Yongyou 12 were higher than those of Zhongzheyou No.1 by 9.26% （35 g/tray），24.11%（50 g/tray），32.6%（65 g/tray），33.81%（80 g/tray），34.74%（95 g/tray）and 41.09%（110 g/tray），respectively.Therefore，the root twining power of Yongyou 12 was greater under various seed rates.

Table 2 Seedling uniformity under different seed rates

Discussion

Effect of seed rate on seedling root twining power

Mechanical transplanting and supporting cultivation techniques of rice is one of the development directions of modern，intensive and largescale agriculture，and it has wide application prospect［18］.Tray seedling is one of the most important steps in mechanized cultivation of rice.On trays，rice roots twine together.When they are removed，seedling block is difficult to be loosened.Tray seedling is the basis for mechanical transplanting of rice.Root twining power is closely related to seed rate.Yu et al.［19］found that when the seed rate was low，individual advantages of seedlings were more obvious，but the root twining power was weak；when the seed rate was high，seedling quality was poor，which was not conducive to survival of transplanted seedlings.This study found that there was a logarithmic linear relationship between root twining power and seed rate.When the seed rate was low，increasing seed rate could significantly increase the root twining power；but when the seed rate was further increased，the increment of root twining power became small. The lowest seed rates required by the two rice cultivars to nurse blanket seedlings were all 50 g/tray.However，at the lowest seed rate，the seedling shoots were sparse，increasing missing rate of seedlings during transplanting.When the seed rate was increased to 95 g/tray，seed rate showed smaller effect on root twining power，but the seedling quality was reduced greatly.Even worse，the seed costs were increased.

Effect of seed rate on seedling quality

Different scholars achieve different conclusions about effect of seed rate on seedling quality.Fang et al.［20］found that when the seed rate was 80 g/tray，the seedling quality was best. Zhang et al.［21］considered that substrate seedling could nursed robust seedlings meeting requirements by mechanical transplanting under the condition of low seed rate （300-400 g/m2）.Li et al.［22］and Peng et al.［23］found that the optimum seed rate was 150-180 g/tray for mechanical transplanting of Wuxiangjing 14.In this study，the effect of seed rate on seedling quality of rice was investigated.The results showed that under the condition of low seed rate（＜50 g/tray），the seedlings were robust with uniform growth and small difference in seedling height，but the leaf area index was relatively low.However，under the condition of high seed rate（＞110 g/tray），the seedlings were weak with nonuniform growth，higher proportions of dwarf and weak seedlings and reduced leaf area index.It suggests thatincreased seed rate can increase root twining power.However，the seedling quality is reduced，and the proportion of dwarf and weak seedling is increased，affecting the growth uniformity of rice seedlings.Although the variation trends of various indicators were almost the same between the two rice cultivars，the critical seed rate for reducing seedling quality was different.When the seed rate was increased to 80 g/tray，the seedling growth was restricted， and the seedling quality was reduced.However，the seedling quality of Zhongzheyou No.1 began to be reduced when the seed rate was increased to only 65 g/tray.In conclusion，Zhongzheyou No.1 is more sensitive to seed rate，and its seedling quality is effected more greatly by seed rate；Yongyou 12 has a large elasticity in seed rate. From a comprehensive point of view，the optimum seed rates for Yongyou 12 and Zhongzheyou No.1 are 65 and 50 g/tray，respectively.

Conclusions

Seed rate has great effects on root twining power and seedling quality of rice.Increasing seed rate can effectively increase root twining power and leaf area index of rice seedlings.However，seedling quality and growth uniformity are worsened，and weak and dwarf seedlings are increased.The indica hybrid rice Zhongzheyou No.1 is more sensitive to seed rate.

Under the condition of low seed rate，increasing seed rate can significantly improve root twining power and leaf area index.However，the seedling quality and SPAD value are greatly reduced.Under the condition of high seed rate，continuously increasing seed rate shows small effects on seedling quality and root twining power，and the change tendencies of various indicators become small.

When the seed rate reaches 50 g/tray，blanket seedlings of Yongyou 12 will be nursed.However，since the seed rate is relatively low，seedling shoots are sparse，and leaf area index is small.The lowest seed rate for Zhongzheyou No.1 to obtain blanket seedlings is also 50 g/tray.On the contrary，its seedling quality and leaf area index are all better.Comprehensively considering root twining power，seedling quality and production costs，the optimum seed rates of Zhongzheyou No.1 and Yongyou 12 are determined as 50 and 65 g/tray.

［1］CHEN HZ（陈惠哲），ZHU DF（朱德峰），XU YC（徐一成）.Development of rice mechanized transplanting technology in north China（北方水稻机插秧技术发展）［J］.North Rice（北方水稻），2011，01:1-3，8.

［2］ZHU DF（朱德峰），CHEN HZ（陈惠哲）. Development of mechanical transplanting in rice and food security（水稻机插秧发展与粮食安全）［J］.China Rice（中国稻米），2009，06:4-7.

［3］SHAO WJ（邵文娟），SHEN JH（沈建辉），ZHANG ZJ（张祖建），et al.Effects of seedbed fertilizing on quality and flexibility of rice seedlings nursed with Towlayer plastic film for mechanical transplanting（水稻机插双膜育秧床土培肥对秧苗素质和秧龄弹性的影响）［J］.Journal of Yangzhou university（扬州大学学报），2004，02:22-26.

［4］MA J（马均），SUN YJ（孙永健），GOU YC（苟永成），et al.Study on the sowing density and seedling-age of machinetransplanted hybrid rice with pot-mat seedling（杂交稻钵形毯状育秧机插不同播种密度与秧龄研究）［J］.China Rice（中国稻米），2011，03:11-14.

［5］YAO X（姚雄），YANG WY（杨文钰），REN WJ（任万军）.Effects seedling raising methods and seed rates on machinetransplanted long-age rice seedling（育秧方式与播种量对水稻机插长龄秧苗的影响）［J］.Transactions of the CSAE（农业工程学报），2009，06:152-157.

［6］SHEN JH（沈建辉），CAO WX（曹卫星），ZHU QS（朱庆森），et al.Effects of different seedling raising methods on rice seedling quality by mechanical transplanting（不同育秧方式对水稻机插秧苗素质的影响）［J］.Journal of Nanjing Agricultural University（南京农业大学学报），2003，26（3）:7-9

［7］XU GL（徐光良），MA RR（马荣荣），SHU QY（舒巧云），et al.The Factors having an effect on seedling quality of hybrid rice（杂交水稻秧苗素质的影响因素研究初报）［J］.Hybrid Rice（杂交水稻），2001，16（2）:31-32.

［8］YU ZY（于忠云），HONG F（洪芳），CAI LG（蔡连贵），et al.Cultural techniques of rice seedling growing in plastic plate and covered with plastic film for transplant with machine（机插水稻塑盘覆膜旱育秧技术）［J］.China Rice（中国稻米），2007，13（1）:54-55.

［9］SUN YZ（孙永中）.Technical key points of mechanical and standardized seedling of rice（水稻机械化规范化育秧技术要点）［J］.Shandong Agricultural Mechanization（山东农机化），2009（6）:14-14.

［10］XU GC（徐国臣），JIAO WC（焦维成），ZHANG XW （张喜武），et al.Transplanting characteristics of plastic traynursed japonica rice seedlings and high-yielding and high-efficiency cultivation techniques（粳稻塑盘旱育抛秧特点及高产高效栽培技术）［J］.Crops（作物杂志），2003，2:011.

［11］XU YC（徐一成），ZHU DF（朱德峰），ZHAO S（赵匀），et al.Effects of broadcast sowing and precision drilling of super rice seed on seedling quality and effectiveness of mechanized transplanting（超级稻精量条播与撒播育秧对秧苗素质及机插效果的影响）［J］.Transactions of the CSAE（农业工程学报），2009，25（1）:99-103.

［12］CHEN HZ（陈惠哲），ZHU DF（朱德峰），WANG G（王广），et al.Effects of mechanical transplanting of rice seedlings nursed on trays on growth and yield formation of rice（稻草机插秧盘育秧对水稻秧苗生长及产量形成的影响）［J］. China Rice（中国稻米），2013，19（4）: 19-22.

［13］LI ZH（李泽华），MA X（马旭），XIE JF（谢俊锋），et al.Experiment on precision seedling raising and mechanized transplanting of hybrid rice under low seed rate in double cropping area（双季稻区杂交稻机插秧低播量精密育秧试验）［J］.Transactions of the Chinese Society of Agricultural Engineering（农业工程学报），2014，30（6）:17-27.

［14］ZHANG LY（张来运），ZHANG GL（张国良），DING XW（丁秀文），et al.Effect of different seed rate on matrix raising seedling quality and yield of machine transplanted rice（不同播种量对水稻基质育秧秧苗素质的影响）［J］.Jiangsu Agricultural Sciences（江苏农业科学），2013，08:66-67.

［15］覃建国，王朝勇.水稻不同播种量对秧苗素质影响的研究 ［J］.中国科技信息，2007，06:69-70.

［16］CUI SY（崔世勇）.Research on the Seeding rate of Mechanized rice transplantation（水稻机插秧的育苗播种量研究）［J］.Agricultural Science&Technology and Equipment（农业科技与装备），2012，03:29-30.

［17］DUAN CY（段春燕），SONG LC（宋立臣），ZOU SD（邹胜东）.Effect of different seed rate on seedling quality and yield of rice（不同播种量对水稻秧苗素质及产量的影响）［J］.Modernizing Agriculture（现代化农业），2010，12:20-21.

［18］HE WH（何文洪），CHEN HZ（陈惠哲），ZHU DF（朱德峰），et al.Effect of different seed rate on machine-transplanted seedling quality and yield of rice（不同播种量对水稻机插秧苗素质及产量的影响）［J］.China Rice（中国稻米），2008，03:60-62.

［19］YU LH（于林惠），DING YF（丁艳锋），XUE YF（薛艳凤），et al.Factors affect-ing rice seedling quality of mechanical transplanting rice（水稻机插秧田间育秧秧苗素质影响因素研究）［J］.Transactions of the CSAE（农业工程学报），2006，22（3）:73-78.

［20］FANG L（方利），HUANG YD（黄义德），ZHANG JM（张健美），et al.Research on the cultivation technique of stronger rice seedlings（机插水稻双膜育秧培育壮秧技术研究）［J］.Journal of Anhui Agricultural Sciences（安徽农业科学），2004，32（2）:218-219.

［21］ZHANG WX（张卫星），ZHU DF（朱德峰），LIN XQ（林贤青），et al.The effects of different sowing densities and raising materials on seedling quality of mechanical transplanting rice（不同播量及育秧基质对机插水稻秧苗素质的影响）［J］.Journal of Yangzhou University（A-gricultural and Life Science Edition）（扬州大学学报:农业与生命科学版），2007，28（1）:45-48.

［22］LI SF（李世峰），LIU RR（刘蓉蓉），WU JL（吴九林）.Effects of different seed rates and transplanting densities on yield formation of machine-transplanted rice（不同播量与移栽密度对机插水稻产量形成的影响）［J］.Crops（作物杂志），2008，1:71-74.

［23］PENG CQ（彭长青），LI SF（李世峰），BIAN XM （卞新民），et al.Study on quantitative planting practice of machine transplanted rice（机插水稻精确定量栽培调控技术研究）［J］.Acta Agricultural Shanghai（上海农业学报），2006，22（1）:20-24.

Responsible editor：Tingting XU

Responsible proofreader：Xiaoyan WU

超级稻机插播种量对秧苗成毯性与秧苗素质的影响

滕飞1，2，朱德峰1*，陈惠哲1，蔡雪青1，徐一成1
（1.中国水稻研究所/水稻生物学国家重点实验室，浙江杭州310006；2.北京市农业机械试验鉴定推广站，北京100079）

为探明水稻机插不同播种量条件下秧苗成毯及质量的差异，以超级稻品种甬优12和中浙优1号为试验材料，设置6个秧盘播种量，研究秧苗生长特性、秧苗质量及成毯性。研究结果表明，不同播种量对秧苗成毯性及秧苗素质的影响显著，播种量的增加可显著提高秧苗根系盘结力，但其秧苗素质明显下降，秧苗细弱，干物质积累量减少，同时其秧苗整齐度较差，小苗弱苗比例增多。2个品种秧盘播种量每下降10 g，平均秧苗株高提高0.5 cm，叶龄增加0.1个，秧苗基部增粗0.1 cm，单株秧苗根数增加0.3根；秧盘播种量每提高10 g，平均单株干物质下降5.1 mg。随着播种量的增加，中浙优1号秧苗素质下降较快，小苗比例迅速提高，甬优12播种量弹性则相对较大。甬优12在播种量达到50 g/盘时可实现秧苗成毯，秧苗生长整齐，秧苗个体素质也较优，但其秧盘地上部生长稀疏，叶面积指数较小；而中浙优1号播种量为50 g/盘时，秧苗成毯及秧苗素质各项指标均较优，秧苗生长整齐、紧密。综合各指标研究结果考虑，甬优12和中浙优1号最适播种量分别为65及50 g/盘。

水稻；超级稻；机械插秧；播种量；秧苗成毯；秧苗素质

国家水稻产业技术体系项目（CARS-01-04A）；国家科技支撑计划项目（2012BAD07B02）；科技部科研院所技术开发研究专项（2013EG134237）；中央级公益性科研院所基本科研业务费专项基金（2012RG005-3）。

滕飞（1990-），男，江苏盐城人，硕士，研究方向：水稻机械化种植技术，E-mail：493861676@163.com。*通讯作者，博士，研究员，博士生导师，从事水稻高产栽培方面的研究，E-mail：cnrice@qq.com。

2015-08-22

Supported by National Rice Industry Technology System（CARS-01-04A）；National Key Technology Research and Development Program （2012BAD07B02）；Ministry of Science and Technology’s Special Fund for Technology Development and Research of Research Institutes （2013EG134237）；National Nonprofit Institute Research Grant of CATAS-TCGRI（2012RG005-3）.

*Corresponding author.E-mail:cnrice@qq.com

Received:August 22，2015 Accepted:November 3，2015

修回日期 2015-11-03