Seventy peanut cultivars were planted at two locations to study peanut kernel Cd accumulation. Six entries (8.57%) had a maximum kernel Cd concentration exceeding the European Union allowable upper limit of 0.20 mg/kg. Ten low Cd peanut entries with a maximum kernel Cd concentration below 0.10 mg/kg were tentatively obtained. Location, genotype and their interaction significantly affected peanut kernel Cd accumulation, with location contributing most of the variability (96.67%) and cultivar alone only accounting for 1.69%. Significant positive correlation was detected between kernel protein content and kernel Cd concentration. Negative and positive Spearman rank correlation was also found for SPAD readings and leaf spot ratings with kernel Cd concentration, respectively. The output of this study provides a basis for exploring the mechanisms underlying low Cd accumulation in peanut kernels and for mining relevant genes/QTLs through association analysis.

Peanut is a world-renowned oilseed and food crop. Improving its biochemical quality traits is of great signi cance not only for meeting edible oil and food needs, but also for producing clean renewable energy. Identi cation of peanut genotypes with high and stable oil content in coastal areas is of economic importance, as the high oil trait of peanut bred in inland areas are di cult to fully express in coastal areas. Two peanut genotypes were grown at two sites in the coastal area. One of the genotypes was identi ed as with high oil and low carbohydrate, while the other, low oil and high carbohydrate. We noticed that number and total area of oil bodies were higher in high oil peanut than in low oil peanut, and that peanut with higher protein content had larger total protein body area. A novel nding of the present study was that number and area of starch grains were higher in peanut with high total soluble sugar (TSS) and sucrose contents than in peanut with low TSS and sucrose. Regarding the ultrastructural properties associated with oil, protein and TSS/sucrose contents, signi cant and highly positive correlations were detected between total oil body area and number of oil bodies, between total protein area and maximum protein body area, and between total starch grain area and number of starch grains. This study laid the foundation for further exploration of the mechanisms shaping peanut seed biochemical quality through transcriptomic, metabolomic and hormonal analysis. Peanut CultivationBoth peanut genotypes were planted under polythene lm mulch at two locations, Dongdichi (L1) and Pengxi (L2), at the Shandong Peanut Research Institute Laixi Experimental Station. Peanuts were sown on May 22 and 24, 2022, and harvested on August 30 and September 12 of the same year, respectively. Routine cultural practices were observed(Wan 2003). Biochemical Quality AnalysisOil, protein, TSS and sucrose contents of peanut kernels were analyzed using near infrared re ectance spectroscopy (NIRS)(Wang and Zhang 2013). Transmission Electron Microscopy ObservationMature peanut pods with brown mesocarp, whose maturity was determined by hull-scrape method, were sampled from both peanut genotypes grown at L2 on August 31, 2022. Each genotype had 3 biological replicates.

Wild Arachis species are of great value to the genetic improvement of the cultivated peanut; however, incompatibility hinders the utilization of the species outside section Arachis. Endogenous phytohormone imbalance was hypothesized but is yet to be confirmed. Using UPLC-ESI-MS/MS, we were able to determine the phytohormone levels in flower bases 3 days after pollination and pegs/pods 5 and 10 days after soil penetration. The results showed that as far as the significantly changed phytohormones were considered, with the advancement of reproductive development, the proportion of down-regulated auxins and cytokinins gradually increased. Significantly reduced levels of gibberellins in pegs/pods were also recorded. The study suggested that to get desirable results in overcoming incompatible obstacles in wide crosses in Arachis, early post-pollination application of hormone mixtures incorporating auxins, cytokinins and gibberellins should be beneficial.

Peanut is a world-renowned oilseed and food crop. Improving its biochemical quality traits is of great significance not only for meeting edible oil and food needs, but also for producing clean renewable energy. Identification of peanut genotypes with high and stable oil content in coastal areas is of economic importance, as the high oil trait of peanut bred in inland areas are difficult to fully express in coastal areas. Two peanut genotypes were grown at two sites in the coastal area. One of the genotypes was identified as with high oil and low carbohydrate, while the other, low oil and high carbohydrate. We noticed that number and total area of oil bodies were higher in high oil peanut than in low oil peanut, and that peanut with higher protein content had larger total protein body area. A novel finding of the present study was that number and area of starch grains were higher in peanut with high total soluble sugar (TSS) and sucrose contents than in peanut with low TSS and sucrose. Regarding the ultrastructural properties associated with oil, protein and TSS/sucrose contents, significant and highly positive correlations were detected between total oil body area and number of oil bodies, between total protein area and maximum protein body area, and between total starch grain area and number of starch grains. This study laid the foundation for further exploration of the mechanisms shaping peanut seed biochemical quality through transcriptomic, metabolomic and hormonal analysis.

In recent years, soil-borne diseases including pod rot have become increasingly rampant with climate change, causing serious yield and quality losses to peanut. Resistance breeding is considered an effective measure for pod rot management. Nine peanut cultivars with various degrees of resistance were used to study leaf/shell anatomical and shell biochemical features, main agronomic traits and leaf spot disease ratings in relation to pod rot score. All four anatomical features, viz., leaf palisade cell number, cell width, index and shell lignin staining area, were negatively correlated with peanut pod rot score at 0.01 levels. However, a robust association between shell lignin content and pod rot score was not established. Given the stable and strong correlation between these anatomical features and pod rot scores and high heritability estimates of these features, the pre-existing resistance may be identified even in the absence of disease. This study provided useful selection indicators for screening for resistance to pod rot in peanut. Association analysis of peanut pod rot resistance is being carried out at our laboratory using several natural populations phenotyped in multiple environments. Particular attention will be paid to the relationship between resistance and these indicators from a genetic perspective.