The relationship of sodium dodecyl sedimentation test values to breadmaking quality of early generation dryland wheat lines

[摘要] English: Currently, high numbers of genotypes are unnecessarily being carried from generation to generation in the early generations of wheat breeding programs, only to be discarded in the advanced generations because of not reaching the strict quality standards. If a simple and reliable test could be used as an indication for baking quality in the early generations of the program, a more effective way to do culling of poor quality lines would be possible. Advanced (elite) and early generation material (F4) were evaluated to determine the influence of genotype and environment on the variation detected in SDS sedimentation. Firstly, nine intermediate hard red wheat elite lines and two intermediate hard red cultivars were evaluated for three consecutive years over eight locations in the Eastern Free State. Secondly, six F4 populations and two hard red cultivars were evaluated for one season at three locations in the Eastern Free State. Single plants in the F2 generation were selected by taking SDS sedimentation into consideration (selected group) and without taking SDS sedimentation into consideration (unselected group) and the influence of selection on the subsequent F4 generations was determined. The following conclusions were reached in the study: · There is a significant correlation between baking volume and SDS sedimentation. SDS sedimentation is therefore a reliable predictor of baking volume. · SDS sedimentation successfully discriminated between the genotypes in both the F4 and elite material. The contribution by genotype was high enough to make effective selection for SDS sedimentation possible. The large genotype x year effect on performance in contrast to the genotype x location effect in the elites, indicated that testing of genotypes across years may be more important than testing of genotypes across locations. · There were significant differences between the groups where selection was done on SDS sedimentation (selected) and groups where selection was done without taking SDS sedimentation into consideration (unselected groups) in most of the populations. The difference in SDS sedimentation between selected and unselected groups for most populations remained constant from the F2 to the F4 generation. Early generation SDS sedimentation selection would therefore effectively enhance baking quality in later generations. This would decrease the amount of lines that have to be evaluated in later generations and would have practical and financial advantages for a breeding program. · In both the elite and F4 material, there was a strong relationship between SDS sedimentation and dough strength, presumably because gluten responsible for the dough strength includes the glutenin, which takes part in the flocculation action of the SDS sedimentation process. SDS sedimentation selection in the early generations of a breeding program can therefore result in excessive dough strength in subsequent generations of certain crosses if a trait evaluating dough strength does not accompany SDS sedimentation selection. · The relationship between protein quantity (content) and SDS sedimentation varied, possibly due to difference in the glutenin quantity and quality between the genotypes. The negative correlation between SDS sedimentation and grain yield was highly significant. This could possibly be attributed to the influence of protein content, because it is well known that a negative association exists between protein content and grain yield, which was also evident in the study. · Mixing development time and hardness index (F4 generation) and grain yield and mixing development time (elite material) are the most definable independent variance predictors for SDS sedimentation in the F4 material. Therefore, mixing development time has a large influence on SDS sedimentation or is related to the same aspect, presumably gluten. · To perform effective SDS sedimentation selection in early generations, testing at one to two locations is adequate. A further increase of locations will result in a very small increase in precision, but would have large practical and financial implications and is therefore not recommended. The gains in precision obtained by increasing the number of years were substantially more than by increasing the number of replications. It is recommended that four to five years is essential for reliable SDS sedimentation selection. This can be done by selecting in the F2 to F5 generations in a breeding program, which will result in a decrease in variation and an improvement in SDS sedimentation stability. This will result in a drastic decrease in the effect of genotype x environmental interaction, which will make further selection later in the breeding program for SDS sedimentation selection unnecessary.

[发布机构] University of the Free State