The pathways through which the three yield components operate to produce their phenotypic associations with grain yield reveal their direct and indirect contributions (Table 2) and are demonstrated diagramatically. The path coefficient analysis showed that spike number and 100-grain weight having positive and high inter-relationships with grain yield had both high direct and indirect effects through each other. The grain number inspite of its negative but non-significant correlation with grain yield had a high direct effect (0.9843). When the indirect influences of this character were examined, these were found to be negative thus nullifying its direct effect. Hence the selections for high performance for this character will adversely affect the other important variables. Considering the magnitude of direct and indirect contributions, in the material studied, for selection purposes, the effective grain yield components were spikes per plant and 100-grain weight and not the grain number. The results were in agreement with those of VIRK and SINGH (1972) even though the present material included F₂ segregating generations of as many as nine crosses. The inclusion of the segregating populations did not materially alter the inter-relationships of these yield components in wheat.

Fig.1. Diagrammatic representation of factors influencing grain yield in wheat.

Summary

The phenotypic correlations in 20 wheat populations consisting of eleven diverse varieties and nine F₂ populations were partitioned to determine the direct and indirect contributions of important yield components viz., spike number, 100-grain weight and grain number towards grain yield. The correlation and path coefficient study gave similar results and it was found that spike number and 100-grain weight showing positive and highly significant correlations with yield had displayed high direct and indirect influences and were the real grain yield components in contrast to grain number.

Literature cited

DEWEY, D. R. and K. H. LU 1959. A correlation and path coefficient analysis of components of crested wheat grass seed production. Agron. J. 51: 515-18.

GANDHI, S. M., A. K. SANGHI, K. S. NATHAWAT and M. P. BHATNAGAR 1964. Genotypic variability and correlation coefficients relating to grain yield and few other quantitative characters in Indian wheat. Indian J. Genet. 24: 1-8.

SIKKA, S. M. and K. B. L. JAIN 1958. Correlation studies and the application of discriminant function in aestivum wheat for varietal selection under rainfed conditions. Indian J. Genet. 22: 181-86.

VIRK, D. S. and S. C. ANAND 1970. Studies on correlations and their implications in selection in wheat. (T. aestivum L.). Madras Agric. J. 57: 713-17.

VIRK, D. S. and S. B. SINGH 1972. Path coefficient analysis of grain yield in wheat (T. aestivum L.) Wheat Information Service 33-34 : 6-8.

WRIGHT, S. 1921 Correlation and causation. J. Agric. Res. 20: 557-87.

(Received April 18, 1972)

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