Anther Ontogeny and Pollen Development in Southern Highbush Blueberry (Vaccinium corymbosum L.)

Abstract

Southern highbush blueberry (SHB, Vaccinium corymbosum, Ericaceae) enables production in warm, low-chill regions, where breeding success depends on precisely timed pollinations. To support breeding in non-traditional environments, we characterized floral staging, anther wall ontogeny, tubule formation, and pollen development in two SHB cultivars (‘Emerald’, ‘Snowchaser’) grown in commercial orchards. Floral development was divided into seven stages: dormant buds (db), five successive floral-bud stages (botA–botE), and anthesis, based on bud size, corolla exposure and pigmentation, and anther/tubule coloration. Internal events were documented by light, confocal, and scanning electron microscopy. External cues reliably separated stages and tracked male-gametophyte phases: meiosis at botB; callose-encased tetrads at botC; permanent tetrahedral tetrads after callose dissolution at botD; bicellular tetrads from botE to anthesis, released intact via poricidal dehiscence. Anther-wall differentiation followed a consistent sequence and lacked a fibrous, lignified endothecium. We therefore propose a new Ericaceous pattern for blueberry anthers, defined by a transient non-lignified subepidermal stratum. Tubules originated apically as solid outgrowths, hollowed centrifugally to a beveled pore, developed a dorsal supportive zone, and mediated poricidal release of permanent tetrads. No qualitative cultivar differences were detected. The staging framework defines operational windows for pollination, emasculation, and pollen handling in low-chill systems.