Starch Characteristics of Popcorn Endosperms With Different Flake Patterns

Popcorn flake pattern is an important processing trait, but the role of endosperm starch development in the formation of different flake patterns remains unclear. Two popcorn hybrids with contrasting and representative flake patterns, SN16 (spherical-flake) and SN27 (butterfly-flake), were selected for comparative analyses of kernel morphology, popping characteristics, starch accumulation, starch biosynthesis-related enzyme activities, starch granule development, and starch physicochemical properties during grain filling. SN27 (butterfly-flake) showed a higher popping expansion ratio (30.0 vs. 25.0 times) and a higher kernel length-to-width ratio (1.4 vs. 1.3) than SN16 (spherical-flake), suggesting that elongated kernel shape may favor anisotropic expansion and contribute to the butterfly pattern. At maturity, compared with SN16, SN27 had 12.5% lower total starch content (51.3% vs. 58.6%) and 17.2% lower amylopectin content (41.0% vs. 49.5%), but 13.2% higher amylose content (10.3% vs. 9.1%). Differences in starch granule development were particularly evident in the outer endosperm, where SN27 exhibited smaller and more polygonal starch granules. SN16 also showed generally higher activities of starch biosynthesis-related enzymes (adenosine diphosphate glucose pyrophosphorylase [AGP], soluble starch synthase [SSS], starch branching enzyme [SBE], debranching enzyme [DBE]) during grain filling, consistent with its greater starch and amylopectin accumulation. These results suggest that the contrasting flake patterns of SN16 and SN27 are associated with coordinated differences in kernel morphology, starch accumulation, and endosperm starch structural characteristics rather than a single factor. Further validation using a broader range of popcorn genotypes is required.