Agronomic responses of rice to putative polyploid-inducing plant extracts: a screening study

Rice productivity improvement is an urgent priority to secure food availability in Indonesia, and polyploid induction using antimitotic compounds provides a promising strategy. This study evaluated agronomic responses of four rice genotypes (Cibogo, F4 Sb × Cb, F4 Sb × Ch, and Ciherang) following in vivo seed soaking with natural antimitotic extracts from Gloriosa superba, Catharanthus roseus, and Elephantopus scaber at varying concentrations. Seeds were treated with standardized antimitotic solutions and key traits-tiller number, plant height, panicle production, leaf number, panicle weight, and stomatal characteristics-were assessed. The results revealed clear genotype-specific and dose-dependent responses. The 10% G. superba treatment consistently enhanced tiller formation, plant height, and panicle production across most genotypes, and produced "giant rice" phenotypes in F4 Sb × Cb. Cibogo showed the heaviest panicles under 10% E. scaber and 15% G. superba, while Ciherang performed best at lower doses, particularly 5% C. roseus and 5-10% G. superba. In contrast, stomatal density and size remained relatively stable, indicating that stomatal traits are not reliable standalone markers of polyploidization. Collectively, these findings highlight the agronomic potential of G. superba-particularly at ~10%-as a candidate natural antimitotic extract to improve yield-related traits. However, because direct cytological verification (e.g., flow cytometry and/or chromosome counting) was not performed in this study, the observed responses should be interpreted as polyploid-like or putative outcomes that require validation in future work.