Abstract
Eleusine indica (L.) Gaertn., commonly known as goosegrass, is a widely distributed weed species in the Poaceae family. Its success as an agricultural weed is associated with its prolific seed production, strong competitiveness with cultivated crops, extended germination period, and ability to thrive under a wide range of environmental conditions. This study investigated reproductive and genetic variation among E. indica populations collected from different habitats. A total of 45 mature plants were sampled from three habitat types and evaluated based on seven reproductive morphological characteristics. Genetic diversity was examined using the psbA–trnH intergenic spacer (IGS) region, with 18 representative samples selected for sequencing. Significant differences (p < 0.05) were observed among habitats for spike length, peduncle length, and seed length, suggesting the influence of environmental conditions and adaptive responses. Roadside populations exhibited shorter spike and peduncle lengths, whereas farm and wasteland populations produced relatively larger reproductive structures, indicating morphological responses to habitat disturbance intensities. Analysis of the psbA–trnH sequences revealed low genetic variation, with only two haplotypes identified among the samples. Similarly, limited polymorphism was detected among Eleusine species, including E. indica, E. multiflora, and E. coracana, indicating a high degree of genetic similarity and conservation within the genus. The findings indicate low reproductive variation and low genetic diversity of E. indica across the three habitats, as revealed by the psbA–trnH IGS marker, might be due to the close genetic relationship among populations and the limited resolution of this chloroplast marker in detecting intraspecific variation.