Phenotypic characterization of flag leaf and pollen germination behavior in relation to grain yield in selected Oryza nivara populations in Sri Lanka

The flag leaf, the most important functional leaf in the rice plant, positively influences the photosynthetic process and yield components. Meanwhile, pollen germination is a critical indicator of species compatibility for successful seed setting. This study analyzed the correlation between flag leaf traits and panicle traits and pollen germination characteristics of six wild rice (Oryza nivara) populations. Plants from six populations (N1 to N6) were collected from different geographical locations and established in a common garden. Morphological traits of the flag leaf were evaluated shortly after heading and yield traits were measured at the maturity stage. Agro-morphological, reproductive, and physiological traits related to grain yield were recorded. Data were analyzed using one-way ANOVA, followed by Duncan’s multiple range test (p<0.05), least significant difference (LSD) (p<0.05), and Pearson’s correlation test (p≥0.05 to p<0.001). The Kilinochchi (N6) population recorded the highest significant values for flag leaf length (26.58 ± 0.49), flag leaf area (23.04 ± 1.22), number of seeds per panicle (71.40 ± 3.52), panicle length (24.55 ± 0.38), 100-seed weight (1.76 ± 0.027), and pollen germination (65.74 ± 3.51) compared to other populations. The Anuradhapura (N1) population had the highest ratio of fertile seeds per panicle (0.75 ± 0.023). The Kurunegala (N3) population showed the lowest seed fertility (0.11 ± 0.012) after removal of the flag leaf, showing a 71.8% reduction in seed fertility compared to the intact flag leaf. According to Pearson’s correlation analysis, the highest positive correlation was observed between flag leaf length (r = 0.79, p < 0.001) and panicle length, followed by chlorophyll content (r = 0.26, p < 0.05) and pollen germination (r = 0.36, p < 0.01) with the ratio of fertile seeds per panicle. Results suggested that flag leaf length, chlorophyll content, and pollen germination could be the best yield-attributing indicators for selecting O. nivara wild rice populations to adopt in rice pre-breeding studies.