Genome-Wide Association Analysis Identified Quantitative Trait Loci (QTLs) Underlying Drought-Related Traits in Cultivated Peanut (Arachis hypogaea L.).

Drought is a destructive abiotic stress that affects all critical stages of peanut growth such as emergence, flowering, pegging, and pod filling. The development of a drought-tolerant variety is a sustainable strategy for long-term peanut production. The U.S. mini-core peanut germplasm collection was evaluated for drought tolerance to the middle-season drought treatment phenotyping for pod weight, pod count, relative water content (RWC), specific leaf area (SLA), leaf dry matter content (LDMC), and drought rating. A genome-wide association study (GWAS) was performed to identify minor and major QTLs. A total of 144 QTLs were identified, including 18 significant QTLs in proximity to 317 candidate genes. Ten significant QTLs on linkage groups (LGs) A03, A05, A06, A07, A08, B04, B05, B06, B09, and B10 were associated with pod weight and pod count. RWC stages 1 and 2 were correlated with pod weight, pod count, and drought rating. Six significant QTLs on LGs A04, A07, B03, and B04 were associated with RWC stages 1 and 2. Drought rating was negatively correlated with pod yield and pod count and was associated with a significant QTL on LG A06. Many QTLs identified in this research are novel for the evaluated traits, with verification that the pod weight shared a significant QTL on chromosome B06 identified in other research. Identified SNP markers and the associated candidate genes provide a resource for molecular marker development. Verification of candidate genes surrounding significant QTLs will facilitate the application of marker-assisted peanut breeding for drought tolerance.

Development of trinucleotide (GGC)n SSR markers in peanut (Arachis hypogaea L)

Cultivated peanut (Arachis hypogaea L.) is an oilseed crop of economic importance. It is native to South America, and it is grown extensively in the semi-arid tropics of Asia, Africa, and Latin America. Given an extremely narrow genetic base, efforts are being made to develop simple sequence repeat (SSR) markers to provide useful genetic and genomic tools for the peanut research community. A SSR-enriched library to isolate trinucleotide (GGC)n SSRs in peanut was constructed. A total of 143 unique sequences containing (GGC)n repeats were identified. One hundred thirty eight primer pairs were successfully designed at the flanking regions of SSRs. A suitable polymerase was chosen to amplify these GC-rich sequences. Although a low level of polymorphism was observed in cultivated peanut by these new developed SSRs, a high level of transferability to wild species would be beneficial to increasing the number of SSRs in wild species.