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Thesis (M.S.)—University of Nebraska—Lincoln, 1949. Department of Agronomy.


Copyright 1949, the author. Used by permission.


This investigation was divided into the following parts:(1) a study of the association between certain quantitative characters in individual plants of an F2 population and their respective F3 progenies, (2) calculation of heritability estimates for certain quantitative characters, and (3) a study of within plot variances of F1, F2, and F3 populations.The material consisted of two corn single crosses.

The parent-progeny association of six characters was estimated for the corn single crosses Wf9x38-11 and Wf9x30A.The characters studied were: (1) days from planting to pollen shedding, (2) plant height, (3) ear height, (4) ear length, (5) ear diameter, and (6) yield.

Coefficients of correlation between F2 plants and their F3 progeny means were highly significant for days to pollen shedding, plant height, and ear height in both the Wf9x38-11 and Wf9x30A crosses.The correlation coefficient for yield was highly significant for the latter, but not for the former cross.

Within-plot variances for the F1 generation of the Wf9x38-11 cross and the F3 generation of both crosses for six characters were determined.The variances were much greater for the F3 generation than the F1 generation. This indicates that segregation of factors for the characters studied had taken place; and after two generations of self-pollinating, some genetic variation still remained.

Heritability estimates were obtained for six characters by the following three methods: (a) the ratio of the heritable variance to the total phenotypic variance; (b) the regression of F3 progeny means to the F2 parent plants; and (c) the ratio of the heritable coefficient of variation squared to the total phenotypic coefficient of variation squared.

Heritability estimates were highest for plant height and ear height and lowest for days to pollen shedding and yield.Heritability estimates, in general, were highest for the cross in which the parent lines exhibited the greatest difference in phenotypic values for a given character.

Advisor: E. F. Frolik