Graduate Thesis Or Dissertation
 

Heritabilities and associations of seed yield components and seed yield in tall fescue (Festuca arundinacea, Schreb.)

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  • Estimates of heritability and associations of tiller number, seed number, seed weight, and seed yield were determined in two groups of tall fescue. Group E was early maturing and had eight parental clones, while group I was intermediate in maturity and had nine parental clones. The parents and five progeny groups were included in the study: first generation selfed progeny (S₁), open-pollinated progeny, polycross progeny, single-cross progeny, and selfed progeny from the single-crosses (F₂). Each entry consisted of ten plants in a nine foot row, with three feet between rows. The plants were established in the field in October 1962, in a randomized block design with four replications. Data were collected during the summers of 1963, 1964, and 1965. Group E plants had slightly higher seed yields than group I plants. This yield advantage was mainly the result of heavier seeds in group E. The parents and the open-pollinated, polycross, and single-cross progeny were generally highest in performance for all four characteristics, while the S₁ progeny were intermediate and the F₂ progeny were lowest in performance. The open-pollinated and polycross progeny were limited in their usefulness for evaluating breeding material since there were no significant differences among the open-pollinated progenies in 13 of 24 analyses of variance and there were no significant differences among the polycross progenies in 12 of 24 analyses of variance. Six methods (regression of the S₁ progeny on the parents, two times the regression of the open-pollinated progeny on the parents, two times the regression of the polycross progeny on the parents, regression of the single-cross progeny on the mid-parents, regression of the F₂ progeny on the mid-parents, and mean squares from the diallel analysis) of estimating heritability were compared for both populations. There were large differences in the heritability estimates among years and among methods. Two methods, 2([superscript b][subscript OP.P]) and [superscript b][subscript SX.MP'] generally resulted in higher heritability estimates than the other four methods. The "average heritability" (averaged across six methods and three years) for tiller number, seed number, seed weight, and seed yield were .187, .371, .506, and .193 respectively for group E and .567, .417, .622, and .374 for group I. The correlation and path-coefficient analysis for groups E and I indicated that tiller number had the largest direct effect in 1963, while seed number was most important in 1964 and both were equally important in 1965. Seed weight had relatively small effects all three years. All indirect effects were minor in both populations. The correlations and the direct and indirect effects for the parent, single-cross and F₂ generations were more variable and they were not always in agreement with the direct and indirect effects for the combined data of the parents and five progeny groups. There were large negative indirect effects in the individual generations which were not evident for the combined data of the parents and five progeny groups. Group E could be improved most by breeding for increased seed number while selection for yield would be most worthwhile in group I. However, maximum improvement could be made by combining the attributes of the two populations. The high seed weight of group E could be incorporated into group I and seed number of group E could be increased by crossing plants of group E with plants of group I.
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file details ThomasJohnnyR1967.pdf 2017-08-23 Pubblico Scaricare