Analysis of flowering dynamics heritability in the perennial warm-season grass Paspalum dilatatum

Understanding the flowering cycles of perennial warm-season grass species may be very important to the design of management practices and breeding. However, developmental dynamics are not well understood. As most plant traits associated with flowering dynamics do not follow a normal distribution, the use of general linear models to describe and compare these variables might be misleading. The aims of this study were (i) to find a methodology to compare panicle accumulation curves and (ii) to estimate heritabilities for flowering curve attributes. Panicle counts were recorded during a complete flowering cycle on a diverse collection of dallisgrass (Paspalum dilatatum). We compared the efficiency of different linear mixed models based on whole plot or individual plant data; then, we adjusted nonlinear regression curves for individual plants to estimate several curve attributes and compared this approach to the area under the curve. Finally, we calculated the broad-sense heritabilities of the estimated curve parameters. The following reproductive curve attributes were obtained: panicle production potential, panicle accumulation rate and days until 3, 5, 10 and 15 panicles. We found that monitoring individual plants is more efficient when studying flowering attributes. Significant differences among genotypes for several flowering cycle attributes were found. Heritabilities were very high for all flowering cycle initiation and duration attributes. We also showed that the number of days until the emergence of a given low number of panicles can be used as a highly heritable measure to characterize flowering cycles.