Castor (Ricinus communis L.), known as castor oil plant or castor bean, is a non-edible oilseed crop. In the present study, the genetic diversity among 54 samples (3 wild and 51 cultivated) collected worldwide was evaluated using inter-simple sequence repeats (ISSRs) and random amplified polymorphic DNA (RAPD) markers. A total of 9 ISSR primers produced 83 high-resolution bands with 61 (74.53%) as polymorphic. The percentage of polymorphic bands per primer and the genetic similarity coefficient ranged from 54.55% (UBC-836) to 100% (UBC-808) and from 0.74 to 0.96, respectively. A total of 11 out of 20 RAPD primers amplified unique polymorphic products with an average percentage of polymorphic bands of 60.98% (56 polymorphic bands out of a total of 90 bands obtained). The percentage of polymorphic bands per primer ranged from 25% (OPA-02 and B7) to 90.91% (B21) with the genetic similarity coefficient ranging from 0.73 to 0.98. The unweighted pair group method with arithmetic averages (UPGMA) dendrogram using two molecular markers divided 54 castor genotypes into three groups. Furthermore, based on morphological data, all 54 castor varieties were grouped into three main clusters. The genetic diversity analysis based on two molecular makers showed that most varieties from China were closely related to each other with three varieties (GUANGDONGwild, ZHEJIANGWild, and HANNANWild) belonging to a wild group separated from most of the cultivated castor samples from China, India, France, and Jordan. These results suggested that the cultivated castor contains a narrow genetic base. Accordingly, we recommend that wild castor genetic resources be introduced for breeding novel castor varieties. Furthermore, the Vietnam, Malaysia, Indonesia, and Nigeria accessions were clustered into the same group. The results of principal coordinate analysis (PCoA) and UPGMA cluster analysis were consistent with each other. The findings of this study are important for future breeding studies of castor.

Soil salinity is one of the major environmental factors, influencing agricultural productivity of crops. As a non-edible and ideal oilseed crop, castor (Ricinus communis L.) has great industrial value in biofuel, but molecular mechanisms of salt stress regulation are still unknown. In this study, the differentially expressed genes (DEGs) for differential salt tolerance in two castor cultivar (wild castor : Y, cultivated castor 'Tongbi 5': Z) were identified. 12 libraries were sampled for Illumina high-throughput sequencing to consider 132,426 nonredundant unigenes and 31,221 gene loci. Multiple phytohormones and transcription factors (TFs) were correlated with salt-tolerance and differently enriched in these two genotypes. The type 2C protein phosphatases (PP2C) homologs were all upregulated under salt stress. Importantly, IAA (1), DELLA (1) and Jasmonate zim domain (JAZ) (1) were also identified and found to be differentially expressed. Based on the co-expressed module by regulatory networks and heatmap analysis, ERF/AP2, WRKY and bHLH families were prominently participate in high salt stress response of wild and cultivated castor. Finally, these results highlight that the hub DEGs and families were more accumulated in cultivated castor than those in wild castor, providing novel insights into the salinity adaptive mechanisms and genetic improvement in castor.

H. pedunculosum, a well-known alpine plant, is widely distributed in high-altitude regions and can survive in the extreme environment of the Tibetan Plateau (TP). In this study, we used proteomic technologies to study the tolerance mechanism of H. pedunculosum to high altitudes, namely, 2800 m, 3000 m, 3100 m and 3300 m. A total of 52 proteins were successfully identified and classified into eleven groups based on their molecular functions, i.e., cytoskeleton dynamics (3), energy (5), carbohydrate metabolism (9), photosynthesis (11), protease (2), transcription (5), stress and defense (6), molecular chaperones (3), protein synthesis (2), other materials metabolism (2) and unknown function (4). These results indicated that the chloroplast pathway as well as the production of signaling, the ROS-scavenging pathway and the Calvin cycle pathway may collectively mediate adaptation to high altitudes in H. pedunculosum. Based on these findings, we concluded that the high level of expression of some proteins, such as oxygen-evolving enhancer proteins, calreticulins, and S-adenosyl-l-homocysteine hydrolase, might confer H. pedunculosum with greater tolerance to the complex environment associated with high altitudes. In addition, we surmised that high altitudes can induce protein changes in H. pedunculosum.