Genetic Diversity Among Genotypes With Bacterial Wilt Resistance And Molecular Markers Related To Resistance In Peanut (Arachis Hypogaea L)

Bacterial wilt (BW) caused by Ralstonia solanacearum is a major biotic factor affecting peanut (Arachis hypogaea) production in China and several other countries in Asia. This soil-borne disease is difficult to control with chemicals. Even rotation of peanut with other non-host crops and biological control could be useful, they are less feasible in most developing countries because the arable land per capita is limited and efficient biocontrol agents are aot available. Therefore planting varieties with resistance is the best approach for controlling this disease. In the past three decades, extensive efforts have been made in peanut breeding for BW-resistance and many resistant cultivars have been released in China. However, yield of the released resistant cultivars is relatively lower compared to the susceptible cultivars with similar ecological adaptation, and seed quality is also poor especially for oil and oleic acid contents. Only a few peanut germplasm lines with bacterial wilt resistance have been successfully used in peanut breeding programs up to now. Obviously, the genetic background of parents in breeding programs was narrow, which might have impeded the progress of breeding. Hence, a better understanding of the genetic diversity of the available BW-resistant germplasm accessions is a prerequisite for more efficient improvement for the resistance. Molecular markers linked to bacterial wilt resistance genes would facilitate more efficient pyramiding of genes related to disease resistance, yield and seed quality. This would compliment classical breeding programmes and also provide the basis for map-based cloning of genes for bacterial wilt resistance.In this study, the DNA polymorphisms among 31 peanut genotypes with various levels of resistance to bacterial wilt including 4 botanical types of the 2 subspecies of A.hypogaea were assessed by SSR and AFLP analysis. Polymorphisms in morphological characters and seed chemical composition were also analysed. The results indicated that there were considerable polymorphisms in the peanut genotypes with bacterial wilt resistance based on SSR and AFLP analysis. The SSR-based genetic distance was bigger than the AFLP-based genetic distance among the 31 genotypes. The cluster based on SSR data was very similar to that based on AFLP data. Considering the botanical type, origin and pedigree of the genotypes involved in the study, the clusters based on SSR data was more consistent with that based on morphological and seed quality characters. However,...