The domestic requirement for wheat in South Africa is approximately 2.8 million tons and annually the shortfall on local production is imported to meet the demand. During the past 25 years two distinct wheat marketing mechanisms characterised the wheat industry, impacting significantly on both research and industry. In 1996 the single channel marketing system through the Wheat Board made way for a liberal marketing environment in which market forces of supply and demand determine price. This refocused most research activities on factors to lower input costs and risks, while increasing the profitability of wheat production. Significant challenges were experienced with much stricter milling and baking quality requirements impacting on not only the development of adapted wheat cultivars for South African conditions, but also on fertiliser and cultivar recommendations, as well as production practices. Minimum tillage, preharvest sprouting, as well as the threat of Russian wheat aphid and stripe rust were some of the pertinent challenges faced during this time. Significant scientific breakthroughs of international importance were made with regard to the physiological and biochemical nature of insect resistance and plant defence as well as the transfer of resistance genes from alien species. This review provides an overview of the most pertinent wheat research undertaken from 1983 to 2008.

Russian wheat aphid, Diuraphis noxia (Mordvilko), feeding injury on ‘Betta’ wheat isolines with the Dn1 and Dn2 genes was compared by assessing chlorophyll and carotenoid concentrations, and aphid fecundity. The resistant Betta isolines (i.e., Betta-Dn1 and Betta-Dn2) supported similar numbers of aphids, but had significantly fewer than the susceptible Betta wheat, indicating these lines are resistant to aphid feeding. Diuraphis noxia feeding resulted in different responses in total chlorophyll and carotenoid concentrations among the Betta wheat isolines. The infested Betta-Dn2 plants had higher levels of chlorophylls and carotenoids in comparison with uninfested plants. In contrast, infested Betta-Dn1 plants had the same level of chlorophyll and carotenoid in comparison with uninfested plants. Our data provide essential information on the effect of D. noxia feeding on chlorophyll and carotenoid concentrations for Betta wheat and its isolines with D. noxia-resistant Dn1 and Dn2 genes.

Russian wheat aphid (RWA;Diuraphis noxiaKurdjumov) resistance on the 1D chromosome of wheat has been the subject of intensive research. Conversely, the deployment of theDn4derived RWA resistant varieties diminished in recent years due to the overcoming of the resistance it imparts in the United States of America. However, this resistance has not been deployed in South Africa despite reports thatDn4containing genotypes exhibited varying levels of resistance against the South African RWA biotypes. It is possible that there may be certain genetic differences within breeding lines or cultivars that influence the expression of resistance. The aim of this study was to identify single nucleotide polymorphism (SNP) markers associated with resistance to South African RWA biotypes. A panel of thirty-two wheat lines were phenotyped for RWA resistance using four South African RWA biotypes and a total of 181 samples were genotyped using the Illumina 9K SNP wheat chip. A genome wide association study using 7598 polymorphic SNPs showed that the population was clustered into two distinct subpopulations. Twenty-seven marker trait associations (MTA) were identified with an average linkage disequilibrium of 0.38 at 10 Mbp. Four of these markers were highly significant and three correlated with previously reported quantitative trait loci linked to RWA resistance in wheat. Twenty putative genes were annotated using the IWGSC RefSeq, three of which are linked to plant defence responses. This study identified novel chromosomal regions that contribute to RWA resistance and contributes to unravelling the complex genetics that control RWA resistance in wheat.