Breeding implications of diversifying end uses of sugarcane

Use of biomass as a renewable energy resource is particularly well advanced in maize (Zea mays L.) and wheat (Triticum aestivum L). Ethanol production from grain, while well developed, has raised serious concerns regarding such use of food sources. The emphasis now is technology development allowing use of the non-grain component of food crops. Sugarcane (Saccharum spp. hybrids), particularly in Brazil, has followed a similar pathway, yet the consequences for crop improvement are essentially unexplored. The objective of this paper is to consider three key genetic statistics to predict the likely success of crop improvement activities satisfying the demands arising from four diversified-use scenarios:- sucrose and constrained fibre, Brix and constrained fibre, Brix and moderate fibre, and total biomass. This is done without all necessary technologies and relative economic weightings that the different quality components may attract in each scenario being available. Data came from harvests of eight Progeny Assessment Trial populations and 17 harvests over 11 trials of four Final Assessment Trial populations, conducted over four years from BSES Meringa. Analyses yielded estimates of broad sense heritability (g(2)) and genetic coefficient of variation (GCV%) for Brix, commercial cane sugar (CCS), dry matter (DM), and fibre. The genetic correlations (r(G)) between the six trait pairs were computed. All g(2) values were high (> 0.66) indicating likely success for selection for all traits. The GCV% values for fibre were the only ones higher than CCS, a trait traditionally considered to suffer restricted variation. Progress from selection for some of the scenarios considered may suffer from a lack of variation in existing germplasm. The r(G) values between Brix and CCS, Brix and DM, and DM and fibre were all strong. Those between Brix and fibre, CCS and DM, and CCS and fibre were weak. None was considered detrimental to achieving the four use scenarios. A restructuring of germplasm may be necessary. There is scant knowledge of fibre-component variations, yet manipulation of these, particularly for lower lignin, appears inevitable. Technologies from the active R&D environments associated with major energy-attractive crops may be transferable. However, cost-effective analytical techniques to screen and manipulate fibre-quality components in sugarcane crop improvement programs will need development.