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A sequential clustering strategy for classifying gene bank accessions

By: Franco, J.
Contributor(s): Díaz, J [coaut.] | Eberhart, S.A [coaut.] | Taba, S [coaut.] | Villaseñor, J [coaut.] | Crossa, J [coaut.].
Material type: materialTypeLabelArticlePublisher: 1997ISSN: 1435-0653 (Revista en electrónico).Subject(s): Analytical methods | Classification | Gene banks | Gene pools | Maize | Sampling | Statistical analysis | Tropical maize CIMMYT | Zea mays AGROVOC In: Crop Science v. 37, no. 5, p. 1656-1662Summary: Statistical classification methods such as Normix, applied to groups previously formed (a priori groups) using hierarchical methods, ean improve the a priori groups and give estimation of probabilities Far membership. In this study, we used data from the evaluation of 29 maize (Zea mays L.) races to (i) apply Normix to the a priori groups formed by the Ward method (Normix after Ward), (ii) use tile upper tail approach and a likelihood ratio test to estimate the optimal number of groups, and (iii) use three geometrical and statistical criteria (Mahalanobis distances, multivariate statistics, and trace and determinant of the within- and among-group variability matrices) to compare the groups obtained from Ward per se and the Normix after Ward method. Results indicated that the reclassification of accessions by Normix substantially improved the a priori groups obtained by Ward in four ways: (i) the average Mahalanobis distance between groups was larger among Normix than among Ward groups; (ii) the ratio of variability between groups to variability within groups is increased after Normix compared with that obtained after Ward; (iii) the generalized variance within groups is decreased in Normix compared with Ward; and (iv) the correlation coefficients between variables are increased after Normix compared with those correlation values obtained by Ward. Results suggested that the groups Foamed by the Normix after Ward procedure allows (i) a good estimation of the optical group numbers, (ii) formation of more compact and separates: groups than the a priori groups formed by Ward per se, and (iii) estimation of the probability of accession membership to the groupsCollection: CIMMYT Staff Publications Collection
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Article CIMMYT Knowledge Center: John Woolston Library

Lic. Jose Juan Caballero Flores

 

CIMMYT Staff Publications Collection Available
Total holds: 0

Peer-review: Yes - Open Access: Yes|http://science.thomsonreuters.com/cgi-bin/jrnlst/jlresults.cgi?PC=MASTER&ISSN=0011-183X

Statistical classification methods such as Normix, applied to groups previously formed (a priori groups) using hierarchical methods, ean improve the a priori groups and give estimation of probabilities Far membership. In this study, we used data from the evaluation of 29 maize (Zea mays L.) races to (i) apply Normix to the a priori groups formed by the Ward method (Normix after Ward), (ii) use tile upper tail approach and a likelihood ratio test to estimate the optimal number of groups, and (iii) use three geometrical and statistical criteria (Mahalanobis distances, multivariate statistics, and trace and determinant of the within- and among-group variability matrices) to compare the groups obtained from Ward per se and the Normix after Ward method. Results indicated that the reclassification of accessions by Normix substantially improved the a priori groups obtained by Ward in four ways: (i) the average Mahalanobis distance between groups was larger among Normix than among Ward groups; (ii) the ratio of variability between groups to variability within groups is increased after Normix compared with that obtained after Ward; (iii) the generalized variance within groups is decreased in Normix compared with Ward; and (iv) the correlation coefficients between variables are increased after Normix compared with those correlation values obtained by Ward. Results suggested that the groups Foamed by the Normix after Ward procedure allows (i) a good estimation of the optical group numbers, (ii) formation of more compact and separates: groups than the a priori groups formed by Ward per se, and (iii) estimation of the probability of accession membership to the groups

Genetic Resources Program

English

9710|Crop Science Society of America (CSSA)|EE|R97-98ANALY|Maria|anterior|Fdo|FINAL9798|1

MX-CP 1998 FRANCO D rf

CCJL01

CIMMYT Staff Publications Collection

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