The inheritance and influence of low molecular weight glutenin subunits on the breadmaking quality of South African wheat cultivars

English: 1 The aim of this study was to study: a) The inheritance of LMW-GS in 50 F2 lines of eight different Tugela crosses. b) The effect of the different LMW-GS on breadmaking quality using F2:3 derived lines in order to determine the usability of the LMW-GS as markers for baking quality. c) The usability of F2:3 derived lines in early generation selection for the improvement of breadmaking quality. 2 a) The cultivar and the F2 progeny of the eight crosses were screened in a gliadin-free background using a simplified one-dimensional procedure of Singh et al (1991). The HMW and LMW glutenins were run on a single gel. b) The F2:3 derived lines of eight different Tugela crosses were evaluated for breadmaking quality using the procedures of the American Association of Cereal Chemistry (AACC). 3 The results were as follows: a) Only four percent of the F2 progeny of the eight Tugela crosses, contained no bands on the A genome. b) Banding patterns were expressed simultaneously in the F2 progeny and in the pure breeding cultivars. This contrasted with the findings of Gupta and Shepherd (1990b), who found that only one banding pattern for each chromosome was expressed in pure breeding cultivars. c) Due to interaction between the parent types, new banding patterns were formed by recombination. d) Some cultivars had no matching combinations in the B- and 0 genome. Polymorphisms are common in wheat and new banding combinations are quite possible. e) It would seem that none of the "normal" inheritance patterns (eo-dominant) were followed, but rather that there is some kind of suppression of banding patterns in the F2 lines on some of the genomes. f) The quality results showed many differences between the crosses of Tugela and the parent, Tugela. It was already possible in the early generation (F 2:3) to observe an improvement in the reduction of the stability of the dough of Tugela. g) The complexity of the LMW-GS patterns made it difficult to correlate between certain LMW-GS and certain quality parameters. 4 The conclusions from this study: a) The inheritance of LMW-GS in South African wheat material is much more complex than expected. b) The South African material did not always follow the inheritance and banding patterns as described in the nomenclature of Gupta and Shepherd (1990b). c) The differences in LMW-GS composition should explain most of the differences in breadmaking quality in the Tugela crosses, because there was little or no differences in the HMW-GS composition. d) Early generation quality tests (F2:3) could give an indication of the advances made in the improvement of breadmaking quality, although it is very difficult and much more research is needed. e) The unexpected segregation patterns in the F2 progeny, together with multiple combination expression will make marker-assisted-selection on ground of LMW-GS difficult at this early stage. f) The contribution by the parents to the LMW-GS were so diverse, that no single banding pattern could be identified, which definitely influenced the baking quality. g) Until the nomenclature system of Gupta and Shepherd (1990b) is updated with these possible unique South African LMW-GS patterns, the correlation of LMW-GS data with quality results will be very difficult.