Identification of genetic variation in bread wheat quality characteristics in the Western Cape

[摘要] English: 1. The objective of this study was to select environmentally stable parental lines,and to determine the heritability of quality characteristics, the correlationbetween these characteristics, the combining ability of these qualitycharacteristics, and the selection response.2. A parental trial was planted at two diverse environments namely langgewensand Tygerhoek, to determine the influence of environment on the differentquality traits and parents. locality had a significant influence on most of thecharacteristics (FPC, EX, FCL, MDT, FA, LFV, BSI,TKM and yield) whereas HlM,FSTand FOT were not influenced by the environment.3. A correlation matrix performed on the collected data from the two localitiesshowed that correlations tend to be environment specific. There were noconsistent correlations between characteristics across envi ronments.4. As expected, locality had a significant influence on most of the qualitycharacteristics. Parents should be selected on average performance acrosslocalities. Kariega, SST 57 and Palmiet showed the least interaction with theenvironment and should therefore be considered as parents. Gamtoos was thebest parent for FA and FST, but because of the 1B/1R translocation's negativeeffect on quality, this cultivar should be avoided as a parental line to improvequality.5. At langgewens a diallel trial was conducted, on the parents and the F2 progeny,to determine the correlations, heritability, combining ability and selectionresponse of the different quality characteristics.6. Significant effects were found over the four replications for some of the qualitycharacteristics. From this trial, Palmiet, Kariega, Nantes and SST57 were foundto perform very well. Nantes and Kariega were involved in almost all the bestperforming F2 combinations and even though the progeny was F2, someheterosis was stiII evident.7. Significant GCA was found for all the traits except FN, FCL and SDS. SCA wassignificant for FN, HLM and LFV, which could be an indication of heteroticeffects in these traits.8. To produce the best progeny, parental lines with the highest GCA for a specifictrait should be used. High GCA effects is an indication of additive gene action,which again indicates high heritability. Kariega, Nantes, SST 57 and Palmietproved to be the best cultivars to improve the different quality and yieldcharacteristics.9. The best specific combination to produce progeny with desirable millingcharacteristics was Nts/Kar, whereas Kar/Gmt proved to be the best specificcombination to improve the rheological characteristics simultaneously. W92-1/Nts can be used to develop desirable progenies for LFV. SST57/Kar proved tobe the best combination to improve TKM. The SCA of W92-1 proved to bemostly influenced by the environment.10. The GCA:SCA ratio was calculated to determine whether a character showsmore additive or non-additive gene action. The following characteristicsshowed additive gene action: TKM, EX, BFY, FCL, HLM, GPC, LFV, MDT andFPC. The remainder of the characteristics showed very little variation betweenadditive and non-additive gene action, except for FN, where the SCA was muchhigher.11. To further confirm the above findings, the additive gene action was determined.Results were in agreement with previous findings, stating that TKM, EX and BFYwas mainly under additive control, FCL, HLM, GPC, LFV, MDT and FPC showedmainly additive but also non-additive gene action and FN and SDS were undernon-additive genetic control.12. A phenotypic correlation matrix was performed to determine whether a positiveor negative correlation exists between the quality and yield characteristics.Significant positive correlations were observed between HLM and TKM, EX andMDT, GPC and LFV and FPC, SDS and LFV, BFY and LFV, EX and MDT, FPCand LFV and FCL and MDT. This implies that selecting for one of these traitswill simultaneously improve the other traits in a desirable environment. None ofthese correlations correlated with findings in the parental trial. Significantnegative correlation existed between TKM and GPC and EX and FCL, implying aselection for one trait will influence the other trait negatively.13. A genetic correlation matrix was also performed. Significant positive geneticcorrelations were observed between SDS and FN (0.858*), MDT and HLM(0.815*) and LFV and FPC (0.824*) indicating that an increase in one of thesecharacteristics will result in an increase of the other character as well,irrespective of the environment. In the phenotypic correlation matrix thesecorrelations were positive as well, but non-significant.14. The broad and narrow sense heritability was calculated for the quality and yieldcharacteristics. The narrow sense heritability varied from as high as 0.7089 forTKM to 0 for SDS and FN. These findings again indicate a good success inselecting for higher TKM. The broad sense heritabilities were relatively high formost of the characters, indicating a significant environmental influence in thenon-additive or heterotic effects of these genes.15.lndirect selection was calculated to find out whether it is possible to achievemore rapid progress through selection for a correlated response than fromselection for the desired character itself. None of the indirect selections showedhigh response to selection for TKM and GPC, therefore to improve thesecharacters, selection should be applied directly. Direct selection would bebetter to improve FCL, because of the negative correlations with thecharacteristics. None of the indirect selected characters could improve all theother characters simultaneously, but selection for HLM and MDT improved allthe characteristics except FCL. Direct selection procedures should rather beused to improve specific quality characteristics. Indirect selection would be bestto select for SDS and FN.

[发布机构] University of the Free State