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Comparison of models for analysis of cultivar phenotypic stability

Lindolfo Storck

Departamento de Fitotecnia, Universidade Federal de Santa Maria, 97119-900 Santa Maria, RS, Brasil

ABSTRACT

An analysis of the phenotypic stability of the yield of a group of 33 maize cultivars assessed in 19 locations in Rio Grande do Sul, was carried out with a non-linear model, the Gompertz growth curve. Five linear models were adjusted for comparison with each other and with the non-linear model, which was used as the control. Four of the linear models assessed were segmented in different ways and one, a model of quadratic regression, was continuous. The discontinuous bi-segmented model (Storck, Doctoral Thesis, ESALQ, USP, Piracicaba, SP, 1989) was considered the best because: a) it showed independence between the angles of the two segments; b) the hypothesis tests for the second segment are independent of the discontinuity; c) the estimated values adjust well to the Gompertz growth curve; d) the estimates of the parameters are more disperse. The model also fits better in a wide range of situations, over a complete growth curve, over the first and the second halves of the curve and over the initial third and middle of the curve.

Keywords: cultivar; phenotypic.

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