The method, a form of micro-propagation, produced more plants which were free of disease, in a shorter time, with less labour compared to traditional willow breeding methods. The disease-free plants were exported to, and grown in, Canada, where the risk of the spread of willow borne diseases often causes a ban on importation. The research, which was strategically-funded by the BBSRC is published in the Canadian Journal of Forest Research.
The micro-propagation method used by the scientists, allowed for rapid, lab-based, multiplication and establishment of individual willow clones. The clones were, specially cultured from sterilised plant bud tissue taken from a single willow tree. A simple, single growth medium, supplemented with a plant hormone, was used to successfully culture the cuttings. Taken from the lab, the tissue-culture plants were then successfully grown in the field.
Rothamsted Research scientist Dr Elena Palomo-Rios said: "By careful optimisation of plant cuttings and media components we found we could produce almost 5000 disease-free willow clones from a single plant in only 24 weeks and showed this method could be used for a wide range of different willow types."
Traditional, field-based, plant breeding involves sexual reproduction of a male and female plant which show some desired traits. From the offspring produced plants which show the desired traits most are then bred together. This process is repeated over many generations, each time selecting and breeding together those plants that have the desired traits.
Through the traditional breeding process desired traits, such a rapid growth, high biomass, erect shoots and disease resistance, can be honed. However, reaching the necessary amount of plant material needed for large scale field testing of new varieties, in a range of environments, can be slow and labour intensive work. For example, the Rothamsted Research willow breeding scheme takes six years from the very first step in traditional breeding, to the time at which there is enough plant material to carry out replicated field tests. Additionally, while the plants can be bred for disease resistance, complete removal of plant pathogens in field-grown material is not possible.
Head of the plant transformation and tissue culture laboratory at Rothamsted Research Prof Huw Jones said: "This method significantly reduces the time required to generate the number of plants needed to carry out multisite yield tests, and for the first time allows the export of disease free material to markets that are currently inaccessible due to phytosanitary restrictions."
The scientists suggest that if micro-propagation of willow was included in the early phase of the traditional Rothamsted willow breeding scheme there is potential to reduce the timescale for breeding new varieties by four to five years.
Prof Angela Karp, who leads Rothamsted Research’s strategic research programme Cropping Carbon said: "Driven by the challenge to reduce dependency on fossil fuels and help build the bioeconomy, there has been an increasing interest in growing improved willow varieties for renewable energy and diverse bioproducts. The micro-propagation method enables fast propagation and distribution of disease-free willows from our breeding programme in the UK for multiplication, trialling and use in a wide range of countries."