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Cultivated peanut (Arachis hypogaea L.) is one of the most widely grown oilseed crops worldwide, however the events leading to its origin and diversification are not fully understood. Here, by combining chloroplast and whole genome sequence data from a large germplasm collection, we show that the two A. hypogaea subspecies (hypogaea and fastigiata) likely arose from distinct allopolyploidization and domestication events. Peanut genetic clusters were then differentiated in relation to dissemination routes and breeding efforts. A combination of linkage mapping and genome-wide association studies allowed us to characterize genes and genomic regions related to main peanut morpho-agronomic traits, namely inflorescence architecture, inner integument color, growth habit, pod/seed weight, and oil content. Together, our findings shed light on peanut evolutionary history and provide an important genomic framework resource for the genetic improvement of this crop.

The peanut rich in oleic acid in seed oil, also known as high oleic peanut, renders its products superior in human healthy diet, long shelf life and high oxidative stability in food and oil processing. High oleic peanut varieties in China are derived from a handful of high oleic donors with limited genetic background. Improvement of high oleic peanut cultivars by integrating key target traits is crucial for both food security and germplasm enhancement. Several superior high oleic peanut lines have been developed by marker assisted backcrossing in our breeding program. The objective of present study is to characterize bacterial wilt disease resistance and yield related traits in these novel peanut lines. The two-year disease nursery survival rates were used as an indicator for bacterial wilt resistance, and the diagnostic markers identified by QTL mapping were used for molecular verification. Genetic background of high oleic peanut lines was estimated by 40 K genotyping by target sequencing (GBTS) SNP panel. Preliminary and regional yield tests were performed for selected breeding lines in 2021. As a result, an elite high oleic peanut accession Yuhua183 was identified, inheriting the superior characteristics of its recurrent parent such as resistance to bacterial wilt, high shelling percentage and early maturity. The development of Yuhua183 broadened the genetic background of high oleic peanut germplasm, providing valuable genetic resources for peanut breeding and further utilization.

Background: Oil and protein content, as well as fatty acid composition, are important quality traits in peanut. Elucidating the genetic mechanisms underlying these traits may help researchers to obtain improved cultivars through molecular breeding techniques.Results: Whole-genome resequencing of an RIL population of 318 lines was performed to construct a high-density linkage map and identify QTLs for peanut quality. The map, containing 4561 bin markers, covered a length of 2032.39 cM with an average marker density of 0.45 cM. A total of 109 QTLs for oil content, protein content, and fatty acid compositions were mapped on the 18 peanut chromosomes. The QTL qA05.1 was detected in four different environments and exhibited a major phenotypic effect on the content of oil, proteins, and six fatty acids. The genomic region spanned by qA05.1, corresponding to a physical interval of approximately 1.50 Mb, contains two polymorphic SNPs between two parents that could cause missense mutations. The two SNP sites were employed as KASP markers and validated using lines with extremely high and low oil contents; these sites may be useful in the marker-assisted breeding of peanut varieties with high oil contents.Conclusions: A high-density genetic map with 4561 bin markers was constructed, and a major and pleiotropic QTL located on LG05 was stably detected for oil, protein and fatty acids across four different environments.

To determine the effects of the hours after pollination and the treatment durations on triploid production and reveal the effective stages of embryo sac chromosome doubling by high temperature exposure. At least three catkins were sampled, and 80 ovules were used for the determination of the embryo sac developmental process. Catkins (2-74 h after pollination) were treated to induce embryo sac chromosome doubling. Cytological observations revealed that the embryo sac development was a consecutive and asynchronous process. Fertilization occurred 50 h after pollination. In the offspring seedlings, 167 triploids were detected and the highest efficiency of triploid production was 87.0%. Among all the induced triploids, the most effective treatment period of inducing embryo sac chromosome doubling is from 26 to 50 h after pollination, and 121 triploids were obtained, representing 72.46% of the sum of all triploids. GLM-Univariate analysis indicated significant differences among the hours after pollination (F = 4.516, p = 0.045). However, the differences between the treatment durations (F = 0.077, p = 0.791) were not significant. Correlation analysis between the proportion of each embryo sac's developmental stage and the percentage of triploid production indicated that the third mitotic division may be the most effective stage for 2n female gamete induction.

To reveal the mechanism of low triploid production, meiotic observation, induction of 2n pollen by colchicine, hybridization of colchicine-induced 2n pollen and pollen germination were conducted in Populus tomentosa clone 5088. Meiosis of the PMCs was initiated 24 h after it was cultured in the greenhouse. Results showed that the meiosis developed in a consecutive, asynchronous process. Analysis of the occurrence rate of colchicine-induced 2n pollen using the GLM-univariate revealed significant differences among the dominant meiotic stages (F = 45.822, P = 0.000). Significant differences also occurred among various colchicine injection times (F = 10.150, P = 0.004). The most effective stage for colchicine-induced 2n pollen occurred between the zygotene to diakinesis substages. Sixty-eight triploids were confirmed with both flow cytometric analysis and chromosome number-counting among the 3346 offspring. The highest triploid induction rate was 13.2%—significantly lower than the expected triploid production rate of 47.0%—indicating that the colchicine-induced 2n pollen was weak during fertilization. We found positive correlation between the efficiency of triploid production and the frequency of colchicine-induced 2n pollen (r = 0.961, P = 0.001) which suggests that the triploid production rate increased as the occurrence rate of colchicine-induced 2n pollen increased. Analysis using the GLM-univariate indicated that both pollen types (F = 87.50, P

To determine the effects of the hours after pollination and the treatment durations on triploid production and reveal the effective stages of embryo sac chromosome doubling by high temperature exposure. At least three catkins were sampled, and 80 ovules were used for the determination of the embryo sac developmental process. Catkins (2–74 h after pollination) were treated to induce embryo sac chromosome doubling. Cytological observations revealed that the embryo sac development was a consecutive and asynchronous process. Fertilization occurred 50 h after pollination. In the offspring seedlings, 167 triploids were detected and the highest efficiency of triploid production was 87.0%. Among all the induced triploids, the most effective treatment period of inducing embryo sac chromosome doubling is from 26 to 50 h after pollination, and 121 triploids were obtained, representing 72.46% of the sum of all triploids. GLM-Univariate analysis indicated significant differences among the hours after pollination (F = 4.516, p = 0.045). However, the differences between the treatment durations (F = 0.077, p = 0.791) were not significant. Correlation analysis between the proportion of each embryo sac’s developmental stage and the percentage of triploid production indicated that the third mitotic division may be the most effective stage for 2n female gamete induction.