Breeding of Elephantgrass (Pennisetum purpureum Schum.) for Improved Biomass/Biofuel Yield and Enhanced Biosafety.

Elephantgrass is a promising feedstock for lignocellulosic biofuel production due to its high yield and biomass quality. However, the currently available cultivars and  naturalized populations can produce wind dispersed seeds, which contribute to their potential for invasiveness (Category I in the List of the Florida Exotic Pest Plant Council). Seed production is not required for establishment of new plantings, since stem cuttings are used for this purpose. Variablilty in flowering time exists in elephantgrass and selection of late-flowering acessions may suppress the production of seeds since temperature requirements are not met.

Five genetically distant accessions including high-yielding, late-flowering, non-lodging phenotypes were selected as parents in order to maximize heterosis for biomass yield and enhance biosafety. A nursery of 1600 F1 hybrids (Pseudo F2) and 20 clones from each parent was established. The 50 highest yielding hybrids and 183 hybrids from the two most contrasting parents (P3xP5) were vegetatively propagated in replicated row plots for evaluation during three growing periods. Merkeron, a commonly used elephantgrass cultivar, was included as a control. Phenotypic data were recorded to correlate different traits with biomass yield from harvests in August 2012, December 2012 and June 2013.

The 183 F1 hybrids from two contrasting genotypes showed a normal distribution for plant height, stem diameter, number of tillers, leaf width, flowering time and biomass yield. The phenotyping of these hybrids will support the identification of molecular markers for these quantitative traits to accelerate future selection cycles. Most F1 hybrids from the crosses P1xP2 and P1xP4 produced more biomass than their most productive parent. Following two harvests of replicated plots, non- or late-flowering, non-lodging F1 hybrids were identified with significantly higher biomass yield than Merkeron. The number of tillers and the plant height were the traits with the highest correlation coefficient with plant biomass. Multi-site testing in larger plots will be carried out to confirm the superior accessions for the development of high-yielding, late-flowering cultivars.