Inflorescence development of Zoysia and its corresponding relationships with phenotypic characteristics

Most zoysiagrass varieties in China are commercially propagated through vegetative organs, such as stolons and underground stems. Native varieties that can be propagated by seed are scarce. The development of inflorescences in grasses represents a critical transition from vegetative to reproductive growth. The process of inflorescence development of Zoysia is closely related to the reproductive characteristics including the inflorescence density, the number of grains per spike, seed setting rate and the thousand-grain-weight and affects the final seed yield and quality. However, the inflorescence development of Zoysia has not yet been thoroughly characterized. In this study, we systematically observed the inflorescence development of zoysiagrass and divided it into eight landmark stages: vegetative formation period, growth cone elongation period, bract primordia formation period, spikelet primordia formation period, glume protuberance formation period, gynoecium and stamen formation period, anther separation and pistil stigma bifurcation period and flowering period. Unlike most grasses, the growth cone of zoysiagrass did not rapidly elongate before differentiating during the bract primordia formation stage; instead, it elongated and differentiated simultaneously. We identified a leaf stage during which the height of the new pulvinus of vertical stems is either parallel to or lower than that of the preceding pulvinus, marking the transitional phase from vegetative to reproductive growth. Growth cones formed in this leaf stage. No growth cone was found in the vertical stem of Zoysia without this phenotype after dissection. This phenotype can serve as an indicative marker for the transition from vegetative to reproductive growth in zoysiagrass. Implementing appropriate cultivation and management practices at this stage can enhance reproductive traits and ultimately improve seed yield and quality. This study provides a theoretical foundation for the establishment of high-yield cultivation technology systems for zoysiagrass and the breeding of new high-yield and high-quality seed varieties in China. • The inflorescence development of zoysiagrass is divided into eight stages. • The growth cone elongate and differentiate simultaneously unlike other grasses. • new pulvinus lower than the previous one marks turning to reproductive growth.