The differences in parental genotypes can lead to significant heterosis influenced by genetic control. Understanding genetic control enables the effective utilization of genetic resources to improve various traits in the local rice. The presented research sought to evaluate four rice F1 hybrids (KBP × PTT1, PTT1 × KBP, KBP × HKL1, and HKL1 × KBP) and their parental cultivars for the genetic variation on agronomic traits. The crossing of local rice (Oryza sativa L.) cultivar Kum Bangpra (KBP) occurred with two improved rice cultivars, viz., Pathum tani1 (PTT1) and Hawm Khlong Luang 1 (HKL1). A completely randomized design with five replications ensued for conducting the rice experiment. Significant (P < 0.001) differences appeared among F1 hybrids and their parental cultivars for the flowering date, plant height, tillers per plant, and panicles per plant. The F1 hybrids of PTT1 as parent showed greater values for plant height, tillers per plant, and panicles per plant, and the F1 hybrids of HKL1 as parent showed more branches per panicle, spikelets per panicle, higher grain size, and grain weight. Significant heterosis was evident in F1 hybrids for most agronomic traits, except flowering date and seed set. Only the F1 hybrid Kum Bangpra × PTT1 revealed maternal effects. Using an improved rice cultivar as a parent for crossing with the local Kum Bangpra led to significant differences in F1 hybrids for gene control and inheritance, including maternal effects; therefore, the final selection should focus on that promising cross.

Keywords: Rice (Oryza sativa L.), parental genotypes, local rice cultivar Kum Bangpra, direct and reciprocal crosses, F1 hybrids, purple rice, agronomic traits

Key findings: Genotypic variations in F1 hybrids for agronomic traits were significant by utilizing improved rice cultivars PTT1 and HKL1 in crosses with the local rice cultivar KBP. The F1 hybrids of the parental cultivar PTT1 showed higher productivity at the vegetative stage, and the F1 hybrids of the parent cultivar HKL1 exhibited higher productivity at the reproductive stage.