Genetic improvement of a neglected and underutilised oilseed crop: sesame (Sesamum indicum L.) through mutation breeding

Sesame, an Underutilized Oil Seed Crop: Breeding Achievements and Future Challenges

Sesame seeds and their edible oil are highly nutritious and rich in mono- and polyunsaturated fatty acids. Bioactive compounds such as sterols, tocopherols, and sesamol provide significant medicinal benefits. The high oil content (50%) and favorable mono- and polyunsaturated fatty acid balance, as well as resilience to water stress, make sesame a promising candidate crop for global agricultural expansion. However, sesame production faces challenges such as low yields, poor response to agricultural inputs, and losses due to capsule dehiscence. To enhance yield, traits like determinate growth, dwarfism, a high harvest index, non-shattering capsules, disease resistance, and photoperiod sensitivity are needed. These traits can be achieved through variation or induced mutation breeding. Crossbreeding methods often result in unwanted genetic changes. The gene editing CRISPR/Cas9 technology has the potential to suppress detrimental alleles and improve the fatty acid profile by inhibiting polyunsaturated fatty acid biosynthesis. Even though sesame is an orphan crop, it has entered the genomic era, with available sequences assisting molecular breeding efforts. This progress aids in associating single-nucleotide polymorphisms (SNPs) and simple sequence repeats (SSR) with key economic traits, as well as identifying genes related to adaptability, oil production, fatty acid synthesis, and photosynthesis. Additionally, transcriptomic research can reveal genes involved in abiotic stress responses and adaptation to diverse climates. The mapping of quantitative trait loci (QTL) can identify loci linked to key traits such as capsule size, seed count per capsule, and capsule number per plant. This article reviews recent advances in sesame breeding, discusses ongoing challenges, and explores potential strategies for future improvement. Hence, integrating advanced genomic tools and breeding strategies provides promising ways to enhance sesame production to meet global demands.

Associations of the Seed Fatty Acid Composition of Sesame (Sesamum indicum L.) Germplasm with Agronomic Traits and FAD2 Variations

Sesame is an important oilseed crop grown for human consumption in many countries, with a high commercial value due to its high oleic/linoleic acid ratio (O/L ratio). However, its properties may vary among different accessions. In the current study, 282 sesame accessions were evaluated to determine the effects of agronomic traits and genotypes on the O/L ratio. The O/L ratio was positively correlated with the oleic acid (C18:1), stearic acid (C18:0), and myristic acid (C14:0) concentrations, as well as the capsule zone length (CZL), capsule width (CW), and capsule length (CL), and negatively correlated with the linoleic acid (C18:2) and linolenic acid (C18:3) concentrations, the days to maturity (DTM), days to flowering (DTF), and the height of the first capsule-bearing node (HFC) (p < 0.05). In addition, the O/L ratio was affected by the FAD2 haplotype, as the Hap2 and Hap3 sesame accessions had lower O/L ratios. Therefore, we suggest that the increase and decrease in the contents of C18:1 and C18:2 are associated with the FAD2 haplotype. A total of 25 agronomic traits and fatty acid compositions were compared via statistical analysis, and accessions with a high O/L ratio were selected. The results of this study can be used as a basis for further research on the development of new sesame varieties through enhancing nutritional functionality.

Sensitivity of genotypically diverse rice varieties to radiation and the related changes to antioxidant enzyme activities

PURPOSE

Radiation mutagenesis, which typically involves gamma rays, is important for generating new rice germplasm resources. Determining the appropriate radiation dose range is critical for the success of radiation mutagenesis. Clarifying the sensitivity and tolerance of genotypically diverse rice varieties to gamma irradiation as well as the radiation-induced changes to reactive oxygen species (ROS) generation and antioxidant enzyme activities is crucial for increasing the utility of radiation mutagenesis in rice breeding programs.

MATERIALS AND METHODS

The seeds of the following four rice varieties with different genotypes were used as test materials: indica Zhe 1613, glutinous indica Zhe 1708, japonica Zhejing 100, and glutinous japonica Zhenuo 65. Additionally,60Co was used as the source of gamma rays. The rice seeds were irradiated with 14 doses (0, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, and 750 Gy). Non-irradiated seeds were used as the control. The seedling survival rate for each variety was recorded at 3, 7, 14, and 28 days after sowing. Moreover, the median lethal dose (LD50) and critical dose (LD40) were calculated according to the seedling survival rates at 28 days after sowing. The seedling superoxide anion (O2•-), hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents and the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities were analyzed at 7 days after sowing.

RESULTS

As the radiation dose increased, the seedling survival rate decreased. The seedling survival rate also decreased significantly as the number of days after sowing increased. Among the rice genotypes, the rank-order of the radiation tolerance was as follows: indica Zhe 1613 > glutinous indica Zhe 1708 > japonica Zhejing 100 > glutinous japonica Zhenuo 65. The LD50 values were 426.7 Gy for Zhe 1613, 329.2 Gy for Zhe 1708, 318.3 Gy for Zhejing 100, and 316.6 Gy for Zhenuo 65. Increases in the radiation dose resulted in significant increases in the seedling O2•- and H2O2 contents, but only up to a certain point. Further increases in the radiation dose caused the seedling O2•- and H2O2 contents to decrease. The H2O2 content for each variety peaked when the radiation dose was very close to the LD50. We propose that the radiation dose associated with the highest H2O2 content (±50 Gy) should be used as the recommended dose for the gamma irradiation of rice. The radiation dose that resulted in peak seedling O2•- contents in the analyzed rice varieties was very close to the LD40. In all rice varieties, the MDA content increased as the radiation dose increased. The SOD, CAT, POD, and APX activities increased as the radiation dose increased within a certain range (less than 600 Gy for Zhe 1613 and 400 Gy for the other varieties), but there were slight differences among the rice varieties.

CONCLUSIONS

Genotypically diverse rice varieties vary regarding their sensitivity to gamma irradiation. Our findings suggest that ROS generation and antioxidant enzyme activities are important factors associated with the radiation mutagenesis of rice. The close relationship between the activities of key antioxidant enzymes, such as SOD, POD, APX, and CAT, and the LD50 and LD40 may be exploited to enhance radiation mutagenesis through the use of plant growth regulators.

Neglected and Underutilised Crops: A Systematic Review of Their Potential as Food and Herbal Medicinal Crops in South Africa

The African continent harbours many native species with nutraceutical and pharmaceutical potential. This study reviewed underutilised crops in South Africa to determine their potential as food and herbal medicinal crops. Over 5,000 species have been identified and earmarked for their medical attributes in formal and informal setups. Researchers, plant breeders and policymakers have mostly ignored the development potential of these crops. Consequently, their value chains are poorly developed. In South Africa, there is a wide range of neglected and underutilised crops, which were historically popular and used by communities; however, over the years, they have lost their status within farming systems and been relegated to the status of neglected and underutilised. Recently, driven by the need to transition to more sustainable and resilient food systems, there has been renewed interest in their potential as food and herbal medicinal crops to establish new value chains that include vulnerable groups. They are now gaining global attention, and their conservation and sustainable utilisation are now being prioritized. The review confirmed that several of these crops possess nutraceutical and pharmaceutical properties, highlighting their potential for development as food and herbal medicines. However, current production levels are too low to meet the requirements for industrial development; research and development should focus on all aspects of their value chain, from crop improvement to utilisation. A transdisciplinary approach involving a wide range of actors is needed to develop the identified neglected and underutilised crops' potential as food and herbal medicinal crops and support the development of new and inclusive value chains.