The gliadin composition of South African wheat cultivars

Abstract

English: The aim of this study was to identify the gliadin subunit composition of South African wheat cultivars and to use these banding patterns to determine genetic relationships between cultivars. • Due to its solubility in 70 percent ethanol, gliadin was extracted from the wheat kernels and by using a simplified one-dimensional gel electrophoresis procedure the different gliadin subunits separated according to their relative mobilities on the gel. The gliadins were then analysed with the help of the "Geldac"-system to identify their banding patterns according to the nomenclature of Konarevet al (1979). Further analyses was made with the help of the "Phylip"-system. • The results were as follows: • α-Gliadin combinations of bands 3 and 5, bands 1 and 5, bands 2 and 7 and bands 5 and 7 were found frequently. In some of the cultivars novel bands sometimes occurred between the existing band combinations. • β-Gliadin combinations of bands 3 and 4, bands 3 and 5, bands 1, 3 and 5 and bands 1 and 4 were found frequently. Novel bands also occurred between the existing band combinations. • ϒ-Gliadincombinations of bands 1, 4 and 5 and bands 2 and 5 were found frequently. Novel bands sometimes occurred between these bands. • ω-Gliadincombinations of bands 1, 2 and 3, bands 7, 8, 9 and 10, bands 2, 4 and 5, bands 2, 3 and 4, bands 2, 3 and 5 and bands 1, 2 and 4 were found frequently. In some cases other bands occurred between these combinations and in some cases one of the bands were missing Bands not included in the nomenclature system used also occurred at the following positions: between the α7- and β1-positions, between the β5- and y1-positions, as well as between the y5- and (l) ω-positions. • In the genetic distance analyses it was found that high degrees of similarity and low genetic distances exist between the cultivars tested. • The conclusions of this study are: • It is possible to distinguish between near-isogenic lines with the help of gliadin banding patterns, as was seen in the cases of Betta, Betta DN, Gamtoos, Gamtoos DN, as well as Tugela and Tugela Dn. • Gliadin banding patterns can be used as a means of cultivar identification on its own. Sufficient genetic information can be obtained from the banding patterns for this purpose, but if more information on quality is needed it is best to use the gliadin classification system in combination with HMW and LMW glutenin classification systems. • A dangerously high level of intercrossing and inbreeding has occurred in the South African wheat cultivars when measured by gliadin patterns. No genetically unique cultivars are found and it is therefore suggested that wheat cultivars from other genetic systems should in the future be used as parents in breeding programmes in order to lower the high level of inbreeding.

Afrikaans: Die doel van die studie was om die gliadien samestelling van Suid-Afrikaanse koring kultivars te bepaal en om hierdie bandpatrone te gebruik om die genetiese verwantskappe tussen die kultivars te bepaal. • As gevolg van die oplosbaarheid van gliadiene in 70 persent etanol was dit moontlik om die gliadiene uit koring te ekstraheer. Die gliadiene is daarna met behulp van 'n eenvoudige een-dimensionele gel elektroforese procedure geskei. Die verskillende gliadien subeenhede skei op grond van hul relatiewe mobiliteite op die gel en is daarna geanaliseer met behulp van die "Geldoc"- sisteem om hul bandpatrone te identifiseer met behulp van die nomenklatuur van Konarevet al (1979). Verdere analises is met behulp van die "Phylip"- program gedoen. • Die resultate was as volg: • α-Gliadien kombinasies van bande 3 en 5, bande 1 en 5, bande 2 en 7 en bande 5 en 7 het gereeld voorgekom. In sommige van die kultivars het nuwe bande soms tussen die bestaande bandkombinasies voorgekom. • β-Gliadien kombinasies van bande 3 en 4, bande 3 en 5, bande 1, 3 en 5 en bande 1 en 4 het dikwels voorgekom. In sommige van die kultivars het nuwe bande soms tussen die bestaande bandkombinasies voorgekom. • y-Gliadien kombinasies van bande 1, 4 en 5 en bande 2 en 5 het dikwels voorgekom. Nuwe bande het somtyds tussen die bandkombinasies voorgekom. • ω-Gliadien kombinasies van bande 1, 2 en 3, bande 7, 8, 9 en 10, bande 2, 4 en 5, bande 2, 3 en 4, bande 2, 3 en 5 en bande 1, 2 en 4 het algemeen voorgekom. In sommige gevalle het ander bande tussen die bande voorgekom en in geval van sommige van die kombinasies was een van die bande soms afwesig. • Bande wat nie met behulp van die oorspronklike nomenklatuursisteem benoem kon word nie het op die volgende posisies voorgekom: tussen die α7- en β-posisies, tussen die β5-en y1-posisies en tussen die y5- en ω1-posisies. • By genetiese afstandsbepalings is gevind dat hoë mates van genetiese ooreenstemming en klein genetiese afstande tussen die verskillende kultivars wat getoets is voorkom. • Die gevolgtrekkings van die studie was die volgende: Dit is moontlik om met behulp van gliadien bandpatrone tussen nabyisogeniese lyne te onderskei. • Gliadien bandpatrone kan op hul eie vir kultivar identifikasie gebruik word. Genoegsame genetiese inligting kan verkry word vanaf die gliadien bandpatrone vir hierdie doel, maar as meer inligting op kwaliteitsaspekte verkry moet word is dit beter om die gliadien identifikasie sisteem te kombineer met die van HMWen LMWgluteniene. • 'n Gevaarlike hoë vlak van inteling kom voor by die Suid-Afrikaanse koring kultivars as waarnemings op grond van gliadien bandpatrone gemaak word. Geen geneties unieke kultivars is gevind nie en dit word daarom voorgestel dat koring kultivars van ander genetiese oorsprong in die toekoms as ouers in teelprogramme gebruik moet word om sodoende die hoë vlakke van inteling te verhoed.