The article published in In Vitro Cellular and Developmental Biology-Plant(2009) focusses on the possibilities of using short-rotation woody crops as a better means for biofuels. Trees and wood accounts for a considerable amount of total biomass resource potential besides the other perennial energy crops as the article states “Purpose-grown trees are expected to account for 377 million dry tons of the 1.37 billion dry ton total biomass resource potential at projected yields of 8 dry tons/acre/yr.” The economic costs associated with using woody crops as a source for biofuels can be made affordable by using alternative silvicultural systems, improved breeding and biotechnology to increase production of such crops.
The basic idea behind short-rotation woody crops is to produce new shoots and trees species from the same cut stump following harvest; this process is called coppicing. This article therefore describes the benefits and limitations in using woody crops as biofuels and how their productivity gains can be increased by increased research on their tree genetics and improved silvicultural practices. The article specifically talks about using various Populus species and changing their genotypes such that they can grow in a range of sites and environmental conditions. For instance, identifying drought-tolerant genotypes based on the presence of certain leaf metabolites is one of the research goal which can help to reduce the cost and improve the breeding of Populus sp. to upland sites. The paper describes various gene modification approaches that can be used to modify the short-rotation woody crops such that their growth rate and production can be improved.
Another species that is ideal for biofuel usage is Eucalyptus with low lignin content and a short rotation time. However, Eucalyptus sp. that meets the level of productivity for biomass requirements are adapted to grow in the tropics and are sensitive to freezing temperatures. Therefore, freeze-tolerant Eucalyptus has been developed and the paper talks about the various important genes and pathways that should be understood in developing such freeze-tolerant Eucalyptus. The article focusses a big bulk of its talk on the ways to grow woody biomass in a cost-effective manner. It then talks about improving the wood itself such that more biofuels or bioenergy conversion can be done. The article mentions the two general areas for modifying wood to increase its enthanol production: 1. the polysaccharides should be made easily accessible to the enzymes which can break them down, and 2. the concentration of the compounds that inhibit fermentation of the sugars should be reduced; both of the two areas can be acquired by reducing the lignin content of the wood. The articles mentions the way to reduce lignin content and the target genes identified to do so. Finally the risk associated with using such woody trees as a potential source for biofuels are described at the end of this paper; the main problem of such genetically improved trees would be the risk of pollen transfer and the gene flow to other native trees.
I think this paper gives an in-depth idea on the various ways to modify trees at the level of genes which I found it to be very informative.
The article can be found at the link below: