The increasing demand for energy and decreasing oil production has made it imperative to find and exploit new forms of energy. Various forms of energy such as hydro power, nuclear power, wind and biomass are being used as alternative sources of energy. Biomass has emerged as a very important form of alternative energy due to its renewable nature, low impact on the environment and cost benefits. Growing energy in the form of forest trees has been found to be a sustainable model for the production of energy. However, strict regulatory policies on the felling and growth rates are required to ensure the balance in the forest cover.
Deciduous trees of the genus salix are found to grow mostly in moist soils in cold and temperate regions of the Northern hemisphere. Being a perennial crop with a life span of 20 to 25 years, its ideally suited for cultivation with the aim of harvesting for biomass. It requires low input of fertilizers and pesticides for its growth making it easy to cultivate.
The advantage of growing these energy forests can be further increased by using these tree for phytoremediation. The short rotation crops such as willows offer the double advantage of high biomass yields and removal of hazardous compounds through frequent harvests.The cleaning of polluted sites which contain heavy metals such as cadmium can be helpful in cleaning up various wastes.
Breeding programs to improve the biomass production, drought and heat tolerance and resistance towards pests are underway. With the aim of growing the plants in southern Europe which has higher temperatures, the heat tolerant strains are being sought. Leaf beetles are the major pests of willows and reduce the biomass by up to 40%. Leaf rust caused by fungi also cause loss of biomass in excess of 40%. As a result of the breeding programs, new strains which increase the biomass production by 60% have been selected for use.
Genomics based approaches which use the sequences genomes of the trees have been used to find genes associated with specific traits. Molecular markers identified by crossing have been associated with the concerned genes.It has been predicted that successful use of knowledge from genome sequencing projects will require the successful identification of polymorphisms associated with traits of interest, the frequency of superior alleles in the base breeding population and their phenotypic effect. Hence, just the sequencing of the genomes without proper understanding of the mechanisms involved in the various traits will not be of much use. Efforts to sequence EST's and studies of the expression patterns associated with different environmental conditions are being undertaken to bridge this gap.