Pengfei DONG,Jianfeng CHANG,Lianfu HUANG,Chaohai LI

Collaborative Innovation Center of Henan Grain Crops,Agronomy College of Henan Agricultural University,Zhengzhou 450002,China

Maize,an important crop and feed,plays a vital role in the national economy of China.High quality is the guarantee of high yield of crops.The difficult point in maize breeding is how to find and i dentify a good hybrid line.A rapid and comprehensive method holds the key to new maize variety breeding.

In general,variance analysis and stability analysis are always used to assess hybrid maize.Because of the sidedness of statistical survey,it may ignore some related information of other traits[1-3].The application of multifactorcomprehensive appraisalis aimed to make comprehensive and objective evaluation on character index of hybrid maize.In order to provide a reliable basis for utilizing new combinations,this study was carried outto assessthe comprehensive traits of 15 hybrid maize cultivars using mul ti-factorcomprehensive appraisal technique.

Materials and Methods

Materials

Among the 15 hybrid maize cultivars we selected,five were approved representative maize hybrids:Nongda 108,Zhendan 958,Xianyu335,Yedan 13 and Yudan 610;the other 10 cultivars ND1,ND2,ND3,ND4,ND5,ND6,ND7,ND8,ND9 and ND10 were proven to yield over 5%more than Zhendan 958.

Experiment design

Randomized complete block design was adopted to conduct the field experiments in the scientific and educational park of Henan Agricultural U niversity,three repetitions were set for each treatment.Six rows were designed in every plot,and the rows were 6 m long each and spaced 0.6 m to each other.So the planting density was 60 000 seedlings/hm2.The repetitions were separated by aisles of 1 m wide,surrounded by four or more rows of protecting plants.

Measurement items and methods

Ten plants those grew well and were similar in size were selected from everyplotto measure theirplant height and ear height at silking stage.The plant height was the distance from ground to male spike,and the ear height was the distance from ground to the first fruit cluster.Maize seeds in each plot was separately harvested at maturity to calculate maize yield per plot.

Statistical analysis

All the data were analyzed using Excel 2007.

AssessmentFactorsand the Mathematical Model of Comprehensive Multi-factors Appraisal Technique

Assessment factors

Based on the principle of multifactors appraisal system,all the assessment factors were selected[1,3-4].Among them,high yield was selected as the primary factor because it directly determines the quality of a maize cultivar.Otherassessmentfactors were as follows:ear length,ear diameter,kernel rows per cob,kernels per row,1 000-grain weight,percentage ofgrain weight,plantheight,ear height,growth period,disease resistance and anthesis-silking interval(ASI)(Table 1).

Building the mathematical model of multi-factor comprehensive appraisal

Multi-factorcomprehensive appraisal can assess each factor of things those are affected by many factors,using nonnegative real number as the index.The formula was given as follows:

Wherein,Ris the fuzzy transformation matrix which represents the membership degree of selected evaluation index;A(a1,a2,…,a12)is the weight coefficient of each character;B(b1,b2,…,b15)is the comprehensive evaluation index(Table 1).According to the standards proposed by Konget al.[1-3,5-7],the weight coefficients of these traits were determined.Then,the highest and the lowest levels of each assessment factor were calculated based on the mean of each cultivar(Table 2).

Calculation ofthe membership function(UX)of each factor and establishment of fuzzy transformation matrix R

The membership function is given as follows:

Table 2 Statistic analysis on the assessment factors of maize cultivars

Wherein,U(X)represents the membership function of hybrid maize.Xis the eigenvalue of each trait,Xmaxis the maximum eigenvalue andXminis the minimum eigenvalue.Finally,the fuzzy transformation matrixRwas obtained from eigenvalues ofthe traits as follows:

Comprehensive evaluation set B

Based on the weight distribution setA= (0.02,0.02,0.03,0.03,0.03,0.03,0.01,0.03,0.06,0.12,0.02,0.6),the comprehensive evaluation setB=(0.365,0.187,0.760,0.249,0.395,0.423,0.516,0.339,0.341,0.297,0.291,0.500,0.637,0.480,0.314)was obtained using the formulaB=A×R,.

Table 3 The comprehensive evaluation on tested hybrid maize cultivars

Results and Analysis

Based on the principle of multifactor comprehensive appraisal,the comprehensive evaluation indices have positive correlation with the quality of tested varieties.According to the multi-factor comprehensive appraisal,the 15 hybrid maize cultivars were listed here in the order of comprehensive performance from better to poorer:Xianyu 335,ND 8,ND 7,ND 9,ND 1,Yundan 610,Nongda 108,ND4,ND 3,ND 10,ND5,ND6,Yedan 13 and Zhengdan 958.

Discussion and Conclusion

Many studies have demonstrated that multi-factor comprehensive appraisal can objectively and completely assess maize cultivars and overcome the sidedness of other methods which just depend on yield[2].There are some other important factors should be took into account such as disease,insect pests,weeds,lodging,broken rates,high temperature,drought,floods and rains.

Multi-factor comprehensive appraisal merely analyzes the repeated means at a single or several sites,which cannot make comprehensive judgment on the fine varieties in some regions.Long-term filed trials at several regions are necessary for comprehensively evaluating a crop variety.

Reasonable membership function and weight coefficient are important in multi-factor comprehensive appraisal,which directly affect the results[1].In fact,different agronomic traits and weight coefficients are adopted by researchers.So it is important to determine the range of weight coefficient according to breeding objectives and actual production in our studies,which provides the basis for the application ofmulti-factorcomprehensive appraisal.

In order to make the results more persuasive and reliable,approved representative hybrid maize cultivars should be introduced as the control for evaluating new cultivars using multifactor comprehensive appraisal.

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