Top Crosses Research Articles

Performance and Phenotypic Stability of Different Hybrid Types in Winter Rye 1

Our objective in this study was to determine which type of hybrid cultivar in rye (Secale cereale L.) offers optimum chances of combining high yield performance, with satisfactory yield stability. Nine single crosses, 33 three-way crosses, 33 two-component-mixtures of three-way crosses, and 33 double crosses, forming genetically balanced sets of material, were tested. Additionally, 33 top crosses were included in this study which were not genetically balanced with the other material. All entries were grown at two locations in South Germany and one location in North Germany in 1976 and 1977 (Exp. 1); 24 of these entries were tested at two additional sites in North Germany (Exp. 2). The average performance of single and threeway crosses did not differ; the three-way crosses yielded 0.5 q/ha less than the three-way cross mixtures in Exp. 1 and surpassed the double crosses by 0.5 and 1.4 q/ha in Exp. 1 and Exp. 2, respectively. Phenotypic stability generally increased from three-way to top crosses. However, the differences in average stability between hybrid types were small as compared to the remarkable variability within each type. Taking into account performance, stability, and economy of seed production, a double cross or an equivalent form with a two-line synthetic as pollinator parent is probably the most favorable hybrid type for rye at present.

Predicting Double‐Cross Sugarbeet Hybrid Performance1

Thirty‐five double crosses, 15 single crosses, and six red beet top crosses were developed from six inbred lines and used to tesl; five methods of predicting double‐cross sugarbeet (Beta vulgaris L.) hybrid performance. The mean of the four nonparental single crosses of any double cross was found to be the most consistent method for predicting root yield and percent sucrose. Percent purity was best predicted by the mean of all six single crosses of the parents iinvolved in any double cross. However, predictive capabilities of five methods studied were not greatly different. There was little relationship between the correlation cofficients and the percentage of accurately predicted top performing hybrids.

Comparative Performance of Top Crosses and S 1 Progeny for Improving Populations of Corn ( Zea mays L.) 1

Forty-five introduced strains, two Northern U.S.A. single crosses, and their double cross were all crossed to form a synthetic variety which was randomly mated for three generations. Randomly chosen S0 plants were selfed and top crossed to a double cross tester. The top-yielding 11% of the S1 lines based on S1 performance and top-yielding 11% of the $1 lines based on top cross performance were developed into two subsynthetics in which random mating was practiced for three more generations. In the following cycle, mean yields were significantly higher in the S1. progeny from the synthetic based on S1 progeny performance than from the synthetic based on top cross performance. Conversely, mean yields were significantly higher in the top crosses from the synthetic based on top cross performance than from the synthetic based on St line performance. The next generation of each sub-synthetic was progagated by intennating the top-yielding 21%, based on S1 performance and top cross performance, respectively. Samples of seed were drawn from each generation of the subsynthetics and parent synthetic and tested at two locations. These tests indicated that a highly significant yield improvement was made with the first cycle of selection by both methods of evaluation, but there was no significant difference between the two methods. The second cycle of selection was not effective.

Heterosis and Combining Ability in Varietal Top Crosses of Upland Cotton, Gossypium birsutum L.1

Crop ScienceVolume 4, Issue 6 cropsci1964.0011183X000400060028x p. 646-649 Article Heterosis and Combining Ability in Varietal Top Crosses of Upland Cotton, Gossypium birsutum L.1 P. A. Miller, P. A. MillerSearch for more papers by this authorJ. A. Lee, J. A. Lee Professor of Crop Science, North Carolina State, and Research Geneticist Crops Research Division, ARS, USDA, respectively Raleigh, N. C.Search for more papers by this author P. A. Miller, P. A. MillerSearch for more papers by this authorJ. A. Lee, J. A. Lee Professor of Crop Science, North Carolina State, and Research Geneticist Crops Research Division, ARS, USDA, respectively Raleigh, N. C.Search for more papers by this author First published: 01 November 1964 https://doi.org/10.2135/cropsci1964.0011183X000400060028xCitations: 17 1 Contribution from the Department of Crop Science, North Carolina Agr. Exp. Sta., Raleigh, in cooperation with the Crops Research Division, ARS, USDA Journal Paper 1792, North Carolina Agr. Exp. Station. The assistance of Alfred Jones and J. C. Williams, now of the Crops Research Division, ARS, USDA, Tifton, Georgia, and the University of California at Davis, respectively, in the collection of a portion of the field data is greatefully aknowledged. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume4, Issue6November–December 1964Pages 646-649 RelatedInformation

Results of one cycle of recurrent selection in rye

A sufficiently variable rye population was subjected to one cycle of recurrent selection for combining ability in order to ascertain whether this complex property can be repatterned. Some hundreds of clones derived from this population were toperossed to an other unrelated variety used as tester. Through visual selection, more than half of these clones were rejected. The topcross progenies of the remaining clones were subjected to a comparative test whereby, as was to be expected, a considerable degree of variability was demonstrated. From the best 10% and the poorest 10% that is from those which surpassed the general average by at least 1.5 standard deviation units or remained below that average by at least 1.5 σ, narrowed populations were built up. This was done with the aid of reserve seed which in the year in which the top cross was made had been obtained from these clones, either through compulsory selfpollination or by allowing the clones to fertilize each other in isolation. The two subpopulations obtained through selection in opposite directions further indicated as “high” and “low” were crossed “en masse” with the same tester variety as the first time. In addition a large number of randomly taken individuals from the “high” synthetic were cloned and toperossed to this common tester. On testing the top crosses carried out “en masse”, the “high” synthetics clearly yielded more than the “low” ones. In one trial it was even found that the “high” synthetic surpassed our standard variety Petkus by approximately 20%. It is possible, therefore, to segregate a population into two fractions of different combining ability. The optimistie pieture to be derived from the foregoing trials unfortunately is shaded by the results of the individual test crosses pointing to a shift of the frequency distribution in a negative sense in regard to the original population. The influence of the year may be mentioned as a possible cause of this contrast and also the fact that in the original population a close visual selection had been practised while those obtained from the synthetic resulting after one cycle were derived from individuals which had been taken entirely at random.

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A Comparison of Reciprocal Top Crosses in Corn1

A Comparison of Reciprocal Top Crosses in Corn¹