Associate Professor, Faculty of Science
Research interests: Morphogenesis and plant regeneration in tissue culture Having developed programmes for the micropropagation of a wide range of herbaceous and woody plants, attention has turned to understanding the control of morphogenesis and regeneration. With geophytes, the physiological age and origin of explants as well as the chemical composition of the culture medium and the physical environment of cultures have been found to influence growth and development of new plants in the culture system. With the successful control of shoot formation, emphasis has been placed on understanding the control of the growth and development of perennating organs, e.g. bulbs and rhizomes, in order to provide suitable propagules for establishment ex vitro. With woody plants, there are still some difficulties in achieving aseptic shoot cultures and consequently in the development of micropropagation protocols. Protocols have been developed for species of tropical and temperate hardwoods, including oak and beech. Isolation and identification of bacterial contaminants have resulted in the ability to control them using specific antibiotics. Shoot regeneration from explants from mature trees continues to offer a challenge, however, as shown by success with the cloning of the Major Oak (Sherwood Forest, UK), islands of more responsive tissue exist in such veteran trees, and techniques have been developed to enhance their growth in culture. Regeneration in vitro through somatic embryogenesis has been studied for a range of plants, including date palm, peach, guajava, grapevine, Alstroemeria, potato, sweet pepper and Galanthus. This knowledge has been of value for genetic transformation studies in plant improvement programmes, providing a culture system that may be more amenable to transformation by Agrobacterium tumefaciens and improving the chances of subsequent plant regeneration from transgenic cells or callus. Biochemical changes in cells and tissues, which are associated with early stages of regeneration by somatic embryogenesis, have been investigated, e.g. the low molecular weight proteins associated with proembryogenic callus. Manipulation of natural enemies for the biocontrol of crop pests: multitrophic interactions There are many natural agents which influence the population dynamics of important crop pests, such as aphids. Entomopathogens offer considerable potential for controlling such pests, however it is essential to understand how environmental factors (biotic and abiotic) and traditional agricultural practices (e.g. use of pesticides) affect the viability and performance of such beneficial agents. A study of the effects of the fungus Erynia neoaphidis (Zygomycetes: Entomphthorales), which parasitises aphids, on the predation of aphids by ladybirds, provided evidence that ladybirds act as vectors of the fungus. Funding from the Lawes Trust allowed the expansion of this research, including a comparison of laboratory and field work at Rothamsted and Sutton Bonington and consideration of the influence of weather factors on the activity/efficiency of natural enemies of aphids. Part of this research (based at Rothamsted) has been expanded to consider the impact of the host plant on entomopathogens through direct (plant volatiles) and indirect mechanisms (induced defences). In a biorational approach, isolates of entomopathogens have been screened for their efficacy under a range of environmental conditions, and four isolates of three species of Hyphomycete fungi (Beauveria bassiana, Paecilomyces fumosoroseus and Verticillium lecanii) have been selected for further study of their sensitivity to commercially used pesticides. A degree of tolerance to selected pesticides has been found which suggests that these isolates may be of value in an Integrated Crop Management system. The effects of longer term exposure to these pesticides is being investigated.