This study was undertaken to see if a method of handling segregating populations could be employed which combined the positive attributes of the traditional pedigree and-bulk methods. Derived F5 lines from the pedigree, bulk, and what is identified as a modified bulk method, were obtained from three winter wheat crosses. The effectiveness of the methods, representing different cycles of phenotypic selection, were evaluated in terms of plant height, plant ideotype and indirectly kernel weight and grain yield. To assess differences in levels of heterogeneity in relation to possible line x environment interactions, the material was grown at three diverse experimental sites. The modified bulk method was as effective as the pedigree method in establishing the desired semi-dwarf height level. Due to the competitive advantage of taller plants, dwarf and semi-dwarf height levels were eliminated in the unselected populations resulting from the bulk method. Although differences were observed for kernel weight between methods, no consistent trends for this trait were established when crosses and locations were considered. Based on the combined mean values of the F5 lines for each method across and within locations, the modified bulk method was superior for grain yield in only one cross. However, when individual F5 lines were compared, a higher percentage of lines obtained from the modified bulk method were superior across and within locations in two of the crosses. Data from this study suggests that to reduce the variety x environment interaction it is important to maintain a level of genetic heterogeneity within varieties. The modified bulk method does appear to be an efficient compromise in handling segregating populations when compared to the traditional pedigree and bulk methods. It is also more efficient in terms of maximizing limited resources which can be important in developing countries where funds and trained scientist are limited.

Includes abstracts of the annual meetings of the American Society of Agronomy; Soil Science Society of America; Crop Science Society of America ( - of its Agronomic Education Division).