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Volume 8, Issue 4, August Issue - 2020, Pages:402-417


Authors: Ajay Verma, G.P. Singh
Abstract: Nonparametric measures of stability had been compared based on ranks of genotypes as per BLUP and BLUE of wheat genotypes evaluated in North Eastern Plains Zone of the country. Sismeasures, as per the BLUP of yield for the first year, identified G5, G1, G7 as the stable genotypes whereas corrected yield measures CSis selected G4, G5, G7, G1. Values of measures NPi(s) settled for G7, G5, G4 wheat genotypes. The significance of Kendall’s coefficient of concordance resulted in an overall similarity of the ranking of genotypes as per nonparametric measures. Spearman coefficients had observed positive correlations by Sis, CSis & NPi(s) with other measures. CV expressed close affinity with CCV, NPi(2), NPi(3), NPi(4) & Si6, CSi3 , CSi6 whereas SD, CSD, NPi(1) associated with Z1, Z2, Si1, Si2, Si3, Si4, Si5, Si7, CSi1, CSi4,CSi5 ,CSi7 in Biplot graphical analysis.  BLUE’s of the yield shown G1, G2, G4, G5, G7 genotypes selected by Sis. Values of CSis identified G2, G4, G5, G6 genotypes, as opposed to G4, G5, G7 by NPi(s). Positive correlation exhibited by Sis, CSis&NPi(s) with other nonparametric measures. CV placed with NPi(2), NPi(3) & NPi(4), Si3, Si6 measures in biplot analysis. Largest cluster expressed by Z1, Z2, SD, CSD,CCV, Si1, Si2, Si4, Si5, Si7, CSi1, CSi2,CSi3,CSi4, CSi5, CSi6,CSi7 measures. BLUP’s of yield values for the second year (2017-18) revealed that Sis selected G1, G12, G13 genotypes while CSis favouredG13, G1, G4 genotypes. Lower values of NPi(s) identified G1, G4, G12, and G13 genotypes. Direct and positive relationships expressed by Sis, CSis & NPi(s) measures. Maximum measures clustered together i.e. SD, CSD, CCV, NPi(1), Si1, Si2, Si4, Si5, Si7, CSi1, CSi2, CSi3, CSi4, CSi5, CSi6,CSi7. Based on BLUE’s values, Sis measures pointed for G13, G1 G4 while G1, G13, G4 selected by CSis values. Lower values of NPi(s) achieved by G1, G4, G11, G13 genotypes. Sis, CSis & NPi(s) had achieved strong and weak relations with other measures. Measures Z1, Z2, SD, CSD, CCV, NPi(1), Si1, Si2, Si4, Si5 , Si7, CSi1, CSi2, CSi3, CSi4, CSi5 CSi6, CSi7 clubbed in bigger cluster. Nonparametric measures would be quite useful to researchers especially breeders to make the selection of genotypes in the presence of genotype X environment interactions.
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Full Text: 1 Introduction High yield and stable genotypes have been identified by breeders for diverse environmental conditions to sustain a good harvest of the crop (Pour-Aboughadareh et al., 2019). Multi-environment trials (MET) have been established as inevitable to recommend promising genotypes for different locations of the country (Vaezi et al., 2018). Genotype x Environment (GxE) interaction effects decrease the association between genotypic and phenotypic values and also masks the selection of the desirable genotypes (Mohammadi et al., 2016). Stability analysis methods are categorized into two parametric and non-parametric groups (Huhn & Leon, 1995; Farshadfar et al., 2014; Golkar et al., 2020). The parametric approach is based on statistical assumptions about the distribution of genotype, environment, and GEI effects (Khalili & Pour-Aboughadareh, 2016). Moreover, nonparametric showed robust behavior without specific assumptions (Rasoli et al., 2015). Mostly breeding experiments utilized parametric methods for assessing the stability of genotypes. Recent studies showed the use of nonparametric approaches as the performance of genotypes had been judged by ranks. Additionally, these methods reduce the bias factor due to outliers and simple to use and interpret (Zali et al., 2011;  Ahmadi et al., 2015; Khalili & Pour-Aboughadareh, 2016; Vaezi et al., 2018; Pour-Aboughadareh et al., 2019). A large number of nonparametric procedures has been compared in the literature to interpret the stability and genotype x environment interactions analysis (Deli?  et al., 2009; Balali?  et al., 2011; Karimizadeh  et al., 2012; Mahtabi  et al., 2013; Mortazavian & Azizinia, 2014; Ahmadi et al., 2015; Khalili & Pour-Aboughadareh, 2016; Vaezi et al., 2018; Pour-Aboughadareh et al., 2019 ). With this in mind, the objectives of the present study were (1) to analyze stability based on BLUP and BLUE values of genotypes by nonparametric methods (2) to differentiate genotypes performance possessing high yield along with adaptations as per BLUP and BLUE across environments, (3) to find out the similarities or dissimilarities among the nonparametric measures. 2 Materials and Methods Seven promising wheat genotypes were evaluated under field trials at sixteen major locations of the zone for 2016-17 whereas fifteen genotypes were tested at thirteen locations during 2017-18 cropping seasons of the country. Recommended agronomic practices had followed to have a good harvest of wheat genotypes. Parentage details and environmental conditions were reflected in tables 1 & 2 for ready reference.  Huehn (1990 a & b) proposed seven nonparametric methods for assessing GxE interaction and stability analysis. Xij de­notes the yield of ith genotype in jth environ­ment where i=1,2, ...k, , j =, 1,2 ,..., n and rank of the        ith genotype in the jth environment by rij, and ri as the mean of ith geno­type. Sabaghnia et al. (2012) proposed the correction for the yield of ith genotype in jth environment as (X*ij=  Xijxi .+ x..  ) as X*ij, was the corrected phenotypic value; Xi  was the mean of ith genotype in all environments and X.. was the grand mean. Generally used seven statistics based on ranks of genotypes yield and corrected yield was expressed as follows: Si1=2Sjn-1Sj'=j+1n½rij-rij'½[n(n-1)] Si7=Sj=1n(rij-ri)2Sj=1n|rij-ri| Si3=Sj=1n(rij-ri)2ri. Si4=Sj=1n(rij-ri)2n Si5=Sj=1n|rij-ri|n Si6=j=1n|rij-ri|ri. Si2=Sj=1n (rij-ri')2(n-1) ri 1nj=1nrij. Ziv=Siv-E {Siv}2Var{Siv}, v=1,2
Nonparametric measures for stability analysis proposed by Thennarasu (1995) as NPi(1), NPi(2), NPi(3) and NPi(4) based on ranks of corrected means of genotypes. Ranks of genotypes as per corrected yield X*ijdenoted by  r*ijwith average of ranks and median byri * and M*di. NPi1=1nj=1n½rij*-Mdi* ½ NPi3=S(rij*-ri.*)2/nri. NPi2=1nSj=1n½rij*-Mdi*½Mdi NPi4=2n(n-1)Sj=1n-1Sj'=j+1mrij*-rij'*ri.
Further, Nassar & Huehn (1987) proposed a test to judge the significance of Si(1) and Si(2) measures. The degree of had been assessed by correlation among genotypes ranking. Spearman’s rank correlation values used to test the degree of similarity among measures (Piepho & Lotito, 1992) as: rs=1-6i=1ndi2n(n2-1) where di denotes the difference between ranks for ith genotype and sum over the number of pairs. 3 Results and Discussion 3.1 First year 2016-17 3.1.1 Analytic analysis based on BLUP’s High yielder genotypes were G6, G5, G4, whereas Geometric Adaptability Index (GAI) selected G6, G5, G4 genotypes. Average of ranks (MR), standard deviation of ranks (SD), and coefficient of variation of ranks (CV) were calculated as per ranks based on yield. MR identified for G7, G5, G4 while the consistent yield of G5, G1, G7 expressed by values of SD (Table 3). Genotypes G7, G5, G4 pointed out by values of CV. Sabaghnia et al. (2012) proposed two ranking methods according to mean and standard deviation of ranks while Mortazavian & Azizinia (2014) reported the advantages of these nonparametric procedures in stability studies. Median of ranks (Med) pointed towards G7, G5, G4 wheat genotypes. Measure Si1 selected G5, G7, G1 as opposed to G5, G1, G7 by Si2values. G7, G5, G1 genotypes considered by Si3 & Si4 measures, next two Si5 & Si6 pointed towards G5, G7, G1 genotypes while Si7 favored G1, G7, G5 genotypes. Average ranks as per corrected yield values (CMR) selected G6, G5, G4, and corrected standard deviation (CSD) observed suitability of G1, G6, G9 genotypes. Coefficient of variation as per corrected yield (CCV) values found G5, G7, G1 while median values (CMed) G2, G1, G3 genotypes. Measures based on ranks as per corrected yield CSi1, CSi2, CSi3, CSi4 & CSi5pointed towards G5, G7, G1 while G5, G7, G4 by CSi6 and CSi7 identified G1, G7, G4 wheat genotypes (Table 4). The mentioned strategy determines the stability of genotype over the environment if its rank is similar over other environments (biological concept). Many authors that have used the corrected Huehn’s (1990b) nonparametric measures of stability and demonstrated the association of these measures with the biological concept of stability (Sabaghnia et al., 2012; Mahtabi et al 2013). Measures NPi(1), NPi(2), NPi(3), NPi (4), consider the ranks of genotypes as per yield and corrected yield simultaneously, found G7, G5, G4 as suitable wheat genotypes while Z1 & Z2 settled for G2, G4, G1 genotypes.  Kendall ’s coefficient of concordance, W was used as an additional tool to evaluate the degree of agreement among non-parametric measures and mean yield. Perfect agreement among rankings of the measures across the environments denoted as W = 1, while zero value indicated total disagreement (Vaezi et al., 2018). Calculated values of W = 0.56 and for its significance values of c2 statistic = 100.8 (Table 4). The calculated value was less than the table value of  c2 (0.05, 290) = 124.3 (135.8), which resulted in an overall similarity among nonparametric measures. Z1 and Z2 values were calculated for each genotype, as per the ranks of adjusted yield, and then summed: Z1 sum = 10.20 and Z2 sum = 11.99 (Table 4). Both these statistics were distributed as c2 and were less than the critical value of c2 (0.05, 29) = 42.6. This indicated the non-significant differences among genotypes as per ranks of CSi1 and CSi2 measures (Kilic et al 2010). Moreover the no individual Z values more than the critical value of c2 (0.05, 1) = 3.84as observed by Hameed et al., 2020. 3.1.2 Association analysis Mean yield had expressed both positive and negative correlations with measures (Table 11). Highly significant positive correlation with GAI, MR, CMR measures and very weak relationships expressed with Si1, Si2, Si4, Si5, Si7, CCV, CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 measures. GAI had a highly significant positive with MR & CMR only. Positive association of MR observed with CV, Med, CCV, CSi6, NPi(3), and NPi(4) measures. SD & CVexpressed highly significant positive correlations with measures. Med expressed only positive correlations with measures. Values of Si1, Si2, Si3, Si4, Si5, Si6, Si7 maintained direct relationships with exception of CMed.   Measure CMR maintained highly significant negative with CMed and weak correlation with Z1 & Z2 values. CSD & CCV measures showed highly significant direct relationships with CSi1,CSi2,CSi3,CSi4,CSi5,CSi6, CSi7,NPi(1), NPi(2), NPi(3),NPi(4). Weak and very weak relationships were observed for CMed measure. CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 had displayed highly significant to significant correlation with other measures (Hameed et al., 2020). Similar behavior is managed by measures NPi(1), NPi(2), NPi(3), and NPi(4)as reported by Rasoli et al. (2015). Z1 & Z2,normalized forms of CSi1& CSi2measures,were related in negative manner. 3.1.3 Biplot graphical analysis Biplot analysis of nonparametric measures had been carried out to explore any type of association among studied measures. Loadings of the first two principal components axes (PCA) of ranks of nonparametric measures were shown in figure 1 (Mohammadi et al., 2016). Two separate groups of Yield with GAI and MR with Med were displayed in the graphical analysis.  Measure CV expressed close affinity with NPi(2), NPi(3) & NPi(4), CCV, Si6, CSi3,CSi6. Bigger cluster consisted of Z1, Z2, SD, CSD, NPi(1), Si1, Si2, Si3, Si4, Si5, Si7, CSi1, CSi4,CSi5,CSi7 measures. 3.1.4 Analytic analysis based on BLUE’s Maximum yield and GAI selected G6, G1, G4 genotypes while MR identified G5, G7, G4, and consistent performance of G4, G5, G2 judged by SD. Lower values of CV identified G4, G5, G7, and median settled for G5, G4, G7 genotypes (Table 5).  Si1 favored G4, G5, G1 and Si2 for G4, G5, G1 whereas as per Si3 values G4, G5, G7 & Si4 found G4, G5, G1 as suitable genotypes and G4, G5, G2 by Si5 while as per Si6 values G5, G4, G7 were genotypes of choice. Lastly by Si7, G4, G2, G1 would be of stable performance genotypes. CMR exhibited G6, G5, G7 as desirable ones and consistent yield would be of G4, G2, G5 by CSD values while CCV pointed for G5, G4, G6, and CMed for G2, G3, G7 wheat genotypes (Table 6). Genotypes G4, G2, G5 mentioned by CSi1 and CSi2 found G4, G5, G2 as suitable genotypes; CSi3 & CSi4 settled for G4, G2, G5 genotypes while G4, G5, G2 selected by CSi5 values & CSi6 settled for G6, G5, G4. Lastly, CSi7 pointed towards G5, G2, G7 as genotypes of choice. Values of NPi(s) identified G5, G4, G7 wheat genotypes for considered locations of the zone. Measure Z1 selected G1, G7, G6 while for Z2 genotypes G1, G7, G5 would be of choice. Calculated values of Kendall’s coefficient of concordance W = 0.45 and values of c2 statistics = 80.5 was less than the critical value. Values of Z1 sum = 5.08 and Z2 sum = 5.35 were less than the critical value of c2 (0.05, 29) = 42.6. This indicated the non-significant differences among genotypes as per the ranks of CSi(1) and CSi(2) measures. However, individual Z values showed HD3043 &MACS6677were significantly unstable (Table 6). 3.1.5 Association analysis Spearman’s rank correlation analysis among all possible pairs of considered measures was tabulated. The yield had expressed significant positive relation with GAI and negative correlations were seen with most measures (Table 12). Significant indirect relations of GAI were observed with MR, Med. Significant positive correlations were expressed by SD and CV measures, while weak negative with CMed, Z1, Z2. Med had a highly significant positive with NPi(2). Measures Si1, Si2, Si3, Si4, Si5, Si6, Si7 maintained direct relationships with measures exception of CMed and Z1 only.  CMR maintained significant positive to moderate positive with measures.  Highly significant direct relationships shown by CSD & CCV with CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7, NPi(1), NPi(2), NPi(3) & NPi(4)  measures. Weak and highly significant positive relationships were observed for values of CMed measure. CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 measures had displayed highly significant to significant direct correlations (Table 12). The same nature of relations was also expressed by NPi(1), NPi(2), NPi(3), and NPi(4) measure. Z1 was negatively related to Z2. 3.1.6 Biplot graphical analysis Loadings of the first two principal components axes (PCA)           of ranks of nonparametric measures were shown in figure 2. Both significant PAC’s accounting for 80.2% of the variance of the original variables. Two separate groups of Yield with GAI and MR with Med were displayed.  Measure CV expressed close affinity with NPi(2),NPi(3), NPi(4), Si3,Si6 measures. Largest group consisted of Z1, Z2, SD, CSD, CCV, Si1, Si2, Si4, Si5, Si7, CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 measures. 3.2 Second year of study 3.2.1 Analytic measures based on BLUP’s (2017-18) The mean yield of genotypes showed G12 was the highest yielding with 46.7q/ha followed by G2 and G8, with remarkable differences among the studied genotypes (Table 7). GAI selected G12, G2, and G9 as desirable genotypes. MR pointed towards G4, G7, G11 and SD settled for G13, G1, G12, whereas CV for G1, G13, G4 as stable genotypes, while G12, G2 based on MR, G8, G5 based on SD and G2, G8 based on CV, were most unstable wheat genotypes for studied locations of this zone. G13, G1, G12 were the stable genotypes as per values of Si1, Si2, Si3, Si4, Si5, Si6, and Si7, however G8, G5 would be genotypes of unstable yield. CMR selected G9, G8 & G11; CSD observed suitability of G13, G1 & G4 and G13, G1 & G9 were the stable genotypes by CCV.  Genotypes G8, G9, G11favoured by CMed criterion.  CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, and CSi7 values pointed for G13, G1, G4 as stable genotypes, and G10, G6 would be undesirable ones (Table 8). NPi(1) selected G13, G1, G12; while measures  NPi(2), NPi(3), NPi(4) pointed towards G1, G13, G4 as desirable wheat genotypes at the same time reflected G2 & G12 would not be able to express stable yield performance for the locations of this zone. Values of Z1 found G7, G15, G3 whereas G15, G7, G3 would be genotypes of choice as per Z2. Values of W = 0.51 and c2 statistic = 215.7 showed an overall dissimilarity among ranking of genotypes as per considered non parametric measures (Table 8).Values of Z1 sum = 19.6 and Z2sum = 20.9 were less than the critical value of c2 (0.05, 29) = 42.6. This indicated the non-significant differences among ranks as per CSi(1) and CSi(2) measures. Genotypes DBW233, WH1218, DBW39expressedvalues more than the critical value of c2 (0.05, 1) = 3.84to showthe unstable performance. 3.2.2 Association analysis Significant positive Spearman’s rank correlation of Yield observed with GAI, CMR while negative with MR, CV, NPi(3), and NPi(4) measures (Table 13).GAI showed mostly negative correlations with measures. MR expressed weak, moderate and significant positive relationships. SD and CV had maintained highly significant positive and weak negative correlations.  More degree of positive as compared to negative correlation expressed by Med. Measures Si1, Si2, Si3, Si4, Si5, Si6, Si7 maintained direct relationships as evident with positive values. CMR, CSD, CCV & CMed had developed only direct relationships with one or two exceptions.  Highly significant, significant, and moderate positive correlations had seen for CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 measures. Highly significant and significant direct relationships were achieved by NPi(1), NPi(2), NPi(3), and NPi(4). A weak negative correlation was observed between Z1 and Z2 values. 3.2.3 Biplot graphical analysis The first two principal components axes (PCA) contributed more than 80% of the variance of the original variables. Biplot analysis of nonparametric measures had displayed five clusters in figure 3. Three separate clusters each of two measures were observed as Yield with GAI, MR with Med, and CMR with Cmed.  NPi(2), NPi(3), NPi(4), Si6 & Si3 expressed close affinity with CV measure. Largest cluster comprised of SD, CSD, CCV, NPi(1), Si1, Si2, Si4, Si5, Si7, CSi1,CSi2,CSi3 ,CSi4, CSi5,CSi6,CSi7 measures. 3.2.4 Analytic measures based on BLUE’s (2017-18) Genotype G12 was the highest yielding (48.9q/ha) followed by G2 and G9 (Table 9). GAI values pointed for G12, G3, and G9 genotypes. MR identified G11, G4, G15 and G13, G1, G4 selected as per SD whereas CV found G4, G13, G1 as stable genotypes. Genotypes G10, G5 asper MR, G1, G10 based on SD and G2, G5  by values of CV, would be of unstable yield. Si1, Si2, Si3, Si4, Si5, Si6, and Si7observed maximum yield achievable by G13, G1, G4 genotypes, however G5, G10 would show inconsistence yield. Genotypes G8, G9 & G11   settled by CMR values, CSD found G1, G13 & G4 as genotypes of consistent yield and G13, G1 & G4 were of stable performance as per CCV.  Genotypes G8, G11, G12 favored by CMed values.  CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 measures identified G1, G13, G4 as stable genotypes             (table 10). NPi(1) selected G1, G13, G11; while measure  NPi(2) settled for G13, G1, G15, and last two NPi(3), NPi(4) pointed towards G1, G4, G13 as desirable wheat genotypes. Z1 observed suitability of G9, G11, G12 whereas G13, G12, G9 would be genotypes of choice as per Z2. Calculated W = 0.58 and values of c2 statistic = 244.1 observed overall similarity among the ranking of genotypes. Values of Z1 sum = 15.1 and Z2 sum = 17.3 were less than the critical value of c2 (0.05, 29) = 42.6. The stable yield performance of genotypes reflected by lower Z values of genotypes as compared to the critical value. 3.2.5 Association analysis A significant positive correlation of yield had been observed with GAI & CMR and negative correlations of moderate to the weak degree with others (Table 14). GAI expressed only positive relations of moderate nature. Moderate to weak direct relationships maintained by MR values. SD expressed significant direct relations with CV, Si1, Si2, Si3, Si4, Si5, Si6, Si7, CSD, CCV, CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7, NPi(1), NPi(3), NPi(4) measures. Significant positive correlations of CV were observed with measures while weak with CMR, CMed, Z1, Z2 values. Med had achieved moderate to weak positive correlations. Si1, Si2, Si3, Si4, Si5, Si6, Si7 maintained direct relationships of moderate to a higher degree with measures.   CMR maintained moderate to weak direct relations with measures.  CSD & CCV expressed highly significant and significant positive values with measures, while CMed maintained a weak positive correlation. Measures CSi1, CSi2, CSi3, CSi4, CSi5, CSi6, CSi7 had displayed only direct highly significant to significant correlation with measures. Strong and weak relations were expressed by NPi(1), NPi(2), NPi(3), and NPi(4). Weak negative correlation was seen between Z1 & Z2. 3.2.6 Biplot graphical analysis The loadings of the first two principal components axes (PCA) of nonparametric measures were shown in figure 4. More than 82% of the variance of the variables accounted for two significant PAC’s. Biplot analysis of nonparametric measures had displayed five clusters. Three clusters each of two measures were observed as Yield with GAI, MR with Med, and CMR with CMed.  Measures NPi(2),NPi(3),NPi(4), Si6 & Si3clubbed with CV.  Large cluster comprised  of  Z1, Z2, SD, CSD, CCV, NPi(1), Si1, Si2, Si4, Si5, Si7, CSi1,CSi2,CSi3,CSi4, CSi5,CSi6,CSi7 measures. Acknowledgments Authors sincerely acknowledge the training by Dr J Crossa and financial support by Dr. A.K Joshi & Dr RP Singh CIMMYT, Mexico along with the hard work of the staff at coordinating centers of AICW&BIP project to carry out the field evaluation and data recording. Conflict of Interest No conflict of interest among authors for this study.
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