Genetic Diversity Of Peanut (Arachis Hypogaea L.) Genotypes Resistant To Rust Disease And Molecular Markers For Rust Resistance

China is the largest country for peanut (Arachis hypogaea L.) production, consumption and export worldwide, accounting for 40% of global production and export. Peanut industry has greatly contributed to the supply of vegetable oil and protein, increase of farmers' income and development of sustainable agriculture. Rust disease caused by Puccinia arachidis Speg. has been a destructive disease of peanut in south and central parts of China and could cause yield loss up to 50%, decrease oil content and increase aflatoxin contamination. Breeding for rust-resistant cultivars has been the most effective control approach but the progress in breeding has been very limited. Most peanut germplasm lines identified as resistant to rust in the cultivated peanut belonged to the var fastigiata with close genetic linkage between rust resistance and undesirable agronomic traits. Less application of modern molecular approaches in resistance identification and selection has also impeded the breeding for resistance to rust in peanut. Hence, it is highly necessary to intensify research on germplasm evaluation and improve the breeding technology. In this study, the DNA polymorphism among different peanut genotypes with resistance to rust was assessed by SSR approach. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) analysis were employed to identify DNA markers linked to rust resistance based on the segregation of resistance in F₂ population of a cross combination made of resistant and susceptible genotypes. The identified markers were also verified in segregating plants of F₃ generation. The results were as followings.1) The genetic diversity was assessed in 34 peanut genotypes with resistance to rust using 16 ploymorphic SSR primer pairs. The average genetic distance among the peanut genotypes ranged from 0.03 to 0.98 with an average as 0.69. The 34 peanut genotypes were divided into different groups based on the clustering results.2) Based on the segregation of resistant and susceptible plants in the cross Yuanza 9102×ICGV86699, the rust resistance in ICGV86699 was controlled by one single dominate gene. As ICGV86699 was developed by using two diploid species of Arachis with different inheritance and components of resistance to rust compared with other resistant germplasm belonging to var fastigiata, it was a unique genotype for breeding as well as for gene cloning in the future.3) An F₂ segregating population derived from Yuanza 9102×ICGV86699 was used to identify DNA markers for resistance to rust in peanut by AFLP approach. Two markers linked with the resistance to rust, M3L3 and M8L8, were identified. The genetic distances of the two markers with the resistance gene were 10.9 cM and 7.86 cM respectively. Forty-seven plants in F₃ generation were used to verify the reliability of the markers, and the two markers were correlated with the performace of the resistance with a fit ratio of 100% and 87% respectively. Therefore, the identified markers were applicable in breeding.