Submitted to: Sugar Journal
Publication Type: Abstract Only
Publication Acceptance Date: 5/10/2010
Publication Date: 6/18/2010
Citation: Edme, S.J. Assessing the quantitative and molecular changes in the Florida sugarcane breeding program. Sugar Journal.
Technical Abstract: To ascertain the genetic gains obtained through breeding sugarcane (Saccharum spp.) for Florida, a comprehensive analysis was undertaken using cultivars released over a 50-year period. Fifty genotypes, including early progenitors (e.g. POJ, NCo310 used as the base population) and cultivars (13 CL and 32 CP released from 1950 to 2000) were field-tested at the USDA-ARS Sugarcane Field station (Canal Point, FL) in a triple 5x11 a-lattice design and sampled in the plant cane and two ratoon crops (2006-2010). All sources of variation were significant for all traits, with crops contributing three times more to the total variation than genotype for stalk weight (SW), sucrose content (SC), and theoretical recoverable sugar (TRS), and with genotype playing a major role for sucrose yield (SY) and the interaction being less important. Regressing means on five decades indicated that genetic gains for this 50-year period were 0.06% yr-1 for SC, 0.05 kg Mg-1 yr-1 for TRS, and 1.16 yr-1 for SY, with a tendency towards a non significant decrease comparing the last two decades. These gains were accompanied with significant genetic and phenotypic correlations between SC and SY (rg = 0.37±0.17, rp=0.58±0.04), between TRS and SY (rg = 0.39±0.17, rp=0.60±0.04), and between SC and TRS (rg = 0.97±0.01, rp=0.98±0.002). Genetic and phenotypic relationships between SW vs SC or TRS were negative (rgSC = -0.16±0.18, rp=-0.10±0.06; rgTRS = -0.123±0.20, rp=-0.09±0.06), but not significant. The correlations between SW and SY were positive and highly significant (rg = 0.88±0.06, rp=0.69±0.03). Highly significant and moderate heritability estimates supported these results, ranging from 0.45±0.08 for TRS, 0.52±0.07 for SC and SY, to 0.64±0.06 for SW, with higher values calculated on an entry means than on a plot basis. These results ascertained that genetic improvement in breeding sugarcane for Florida rest on solid grounds with moderate heritability and strong genetic correlations among the traits. The evolution of the quantitative variation for the traits will be discussed and compared with that at the molecular level.