Ricinus communis is a monophyletic species belonging to the Euphorbiaceae family with many medicinal and industrial applications. Castor bean has a mixed reproductive system that includes cross-pollination and self-pollination. However, there are no reports on the ability of castor oil to produce seeds asexually through apomixis. The purpose of this study was to eva‎luate the ability of seed production by different reproductive methods including apomixis, self-pollination, and open pollination in castor, to investigate the effect of seed production type on the diversity of the morphological, physiological, and phytochemical characteristics of castor progeny, and to measure the expression levels of genes effective in castor apomixis. This research was conducted over three years, from 2018 to 2020, at the research farm of the University of Technology. In this research, 33 genetic germplasm populations collected from various regions of the world were randomly cultivated in an augmented design over two years, and seed production was carried out by three methods: apomixis, self-pollination, and open pollination. Then, in the third year, the seeds of the progeny of 14 selected genotypes obtained using these three reproductive methods were planted in a randomized complete block design with three replications. The results of the analysis of variance for each year indicated wide variation between genotypes in most of the studied traits and in each reproductive method. Results of data analysis revealed that castor bean has the ability for a wide range of apomixis for seed production and the highest percentage of apomixis ability in the first and second years was 86.30% and 92.31%, respectively. Apomixis ability was positively correlated with yield components, seed oil content, and leaf rutin content. In addition, apomixis reproduction enables the preservation of superior castor bean genotypes with enhanced phytochemical traits, yield, and oil quality. Also, according to the progeny eva‎luation results, inbreeding depression for most traits than apomictic progenies (IDA) was higher (more negative) compared to inbreeding depression than open-pollinated progenies (IDO). Additionally, the highest inbreeding depression was for seed yield per plant, and the genotypes Isfahan and Benin had the highest IDA (-53.78%) and IDO (-76.95%) for seed yield per plant. In contrast, apomixis advantage was positive for most traits, and apomixis advantage relative to self-pollinated progenies (AAS) was higher (more positive) than apomixis advantage relative to open-pollinated progenies (AAO). The highest apomixis advantage was for seed yield per plant, and the highest AAO (424.51%) and AAS (333.85%) for this trait were observed in the Benin genotype. Therefore, the progenies resulting from apomixis reproduction were superior in most of the studied traits, which is perhaps due to the accumulation of undesirable alleles in self-pollinated progenies (inbreeding effects) and the segregation of desirable characteristics in open-pollinated progenies (segregation effect). The expression levels of the apomixis candidate genes, including Helic, SERK, LEC1, BBM, ABI3, FUS3, WUS, and GLC, increased in apomixis vs. open-pollination reproduction, and the greatest expression difference was observed for Helic and ABI3, which promoted somatic embryogenesis in earlier stages of seed development. Based on the results of the molecular study and the changes in the expression of the studied genes (related to apospory), it is likely that the type of apomixis in castor bean is apospory.

محمدرضا سبزعليان دستجردي , مهدي رحيم ملك

مجيد طالبي

بدرالدين ابراهيم سيدطباطبايي , احمد ارزاني , رضا درويش زاده