Pollen morphology, viability and <i>in vitro</i> germination across diverse genotypes of marigold ( <i>Tagetes erecta</i> L.)

Abstract Pollen morphology, viability and in vitro germination are vital parameters for taxonomic classification, hybridization, artificial pollination and improving seed set in crop breeding. In the present study, we investigated the pollen morphological characteristics of four marigold genotypes using scanning electron microscopy, assessed pollen viability using Alexander’s stain and acetocarmine and evaluated in vitro germination under a light microscope using media supplemented with varying concentrations of sucrose and polyethylene glycol (PEG). Pollen grains were medium-sized (25–50 µm) and exhibited suboblate to oblate-spheroidal shapes, with a polar/equatorial ratio ranging from 0.84 to 0.88. All genotypes displayed tricolporate pollen grains with three colpi and endoaperture, and their aperture lengths were between 3.88 and 4.90 µm. Significant genotypic differences were observed in pollen viability, with the highest values recorded in IIHRMY 1-4 (96.66 ± 0.34%) using acetocarmine and in IIHRMY 2-1 (96.42 ± 0.51%) using Alexander’s stain. The optimal germination medium contained 15% sucrose and 15% PEG, with IIHRMY 1-4 exhibiting the highest pollen germination rate (54.09 ± 1.15%), followed by IIHRMY 2-1 (47.05 ± 1.27%). These findings offer valuable insights for marigold breeding programmes, particularly in selecting genotypes for efficient cross-pollination and hybrid development.