Allelopathic effects of Hyptis suaveolens leaf extract on germination and early seedling growth of two local varieties (gero and dauro) of Pennisetum glaucum L.

Allelopathy is a biological phenomenon in which plants release chemical compounds that influence the germination, growth and development of neighboring plants. Hyptis suaveolens is an invasive aromatic species known to produce allelochemicals capable of suppressing the establishment of cultivated crops. This study evaluated the allelopathic effects of aqueous leaf extracts of Hyptis suaveolens on the germination and early seedling growth of two local pearl millet (Pennisetum glaucum L.) varieties, Gero and Dauro. The research was conducted between April and August 2026 at the Biological Science Laboratory, Sa'adu Zungur University, Bauchi, Nigeria. Fresh leaves of H. suaveolens were collected; shade-dried, pulverized and extracted using distilled water. Four extract concentrations (0%, 2%, 4% and 8%) were evaluated in a Completely Randomized Design (CRD) with three replicates for each treatment. Thirty viable seeds of each millet variety were used per replicate. Germination percentage, cumulative germination, plant height, leaf number and seedling vigor index were determined, while data were analysed using two-way Analysis of Variance (ANOVA) and Tukey's Honestly Significant Difference (HSD) test at a 5% probability level. The results showed that extract concentration significantly affected germination percentage (F = 39.57, P < 0.001), plant height (F = 34.83, P < 0.001), leaf number (F = 28.97, P < 0.001) and seedling vigor index in both millet varieties. Germination percentage and cumulative germination declined progressively with increasing extract concentration, with the control treatment recording the highest germination while the 8% extract produced the greatest inhibition. Plant height, leaf number and seedling vigor index were also significantly influenced by the extract concentrations. Significant variety × concentration interactions indicated differential responses of the two millet varieties to the extract. Gero exhibited greater tolerance than Dauro by maintaining relatively better germination, seedling growth and vigor under increasing extract concentrations. The study concluded that Hyptis suaveolens possesses strong allelopathic properties capable of suppressing the germination and early seedling growth of pearl millet in a concentration-dependent manner. It is therefore recommended that H. suaveolens should be effectively controlled before millet cultivation to reduce its adverse effects on crop establishment. Furthermore, field-based studies should be conducted to validate these laboratory findings and identify millet varieties with greater tolerance to allelopathic stress.