Genetic mapping of leafspot resistant QTLs, and introgression into West African adapted and US-high oleic peanuts

Leaf spot disease is a very important disease in Ghana and the US. Breeding for resistance to this disease is difficult as it is controlled by many recessive genes. Wild species have been identified to habor resistant genes to leafspot disease but the differences in their genomes compared to cultivated species makes trait transfer difficult. The development of TxAG-6 through the cross [A. batizocoi x (A. cardenasii x A. diogoi)]4x has helped to circumvent this drudgery in breeding. Leaf spot disease resistance have been identified in BC3 populations of a cross between Florunner and TxAG-6. RFLP and SSR genetic linkage maps of this population have also been constructed in order to map QTLs of disease resistant from this population. RFLPs are not ideal markers because of slow turnaround time, need for large amounts of DNA, and use of radioactivity. Although SSRs have been preferred over RFLPs, genotyping with SSRs is also quite laborious, making Single Nucleotide Polymorphisms (SNPs), the markers of choice in genotyping. In this study a SNP based genetic linkage map has been constructed for the BC1 population of which markers have been used to genotype 317 BC3 individuals. These were used in conjunction with leaf spot data collated from Ghana, Burkina Faso and US in identifying leaf spot resistant QTLs. QTLs for Early and Late leaf spot have been identified. Crosses were also made to transfer leaf spot resistant genes from BC3 lines into Spanish peanut varieties in West Africa and the US. These materials were advanced to the F3 stage and evaluation for leaf spot disease done in Ghana. Several lines have been identified to be resistant to leaf spot disease, selected materials will be advanced further and subsequently released as leaf spot resistant materials in the future.