Effect of Harvest Seasons on the Efficiency of Ovary Culture in Panicum maximum

Cultures were made of ovaries guineagrass (Panicum maximum) harvested in different seasons to obtain plant regeneration via somatic embryogenesis. Callus formation and plant regeneration occurred when the ovaries harvested 0-7 days after anthesis (DAA) in summer were cultured on Murashige and Skoog medium with suitable hormones. However, most of the ovaries harvested in winter did not form calli when cultured similarly. To determine the reason for this difference, flowers at 0-7 DAA were collected during both seasons and observed under Nomarski differential interference-contrast optics. The ovaries collected at 0-7 DAA in summer showed normal development and matured seed set-up. In contrast, most of the ovaries collected at 0-7 DAA in winter degenerated gradually. This result suggests that embryo-sac analysis of plant materials provides important information on whether plant materials are suitable for the induction of calli.