Epsilon Open Archive

Abstract

Pathogens and pests constantly threaten plants and cause crop losses of significant economic importance for agricultural production worldwide. One way to reduce the damage caused by pathogens and pests is the development of new, resistant cultivars. However, conventional resistance breeding often suffers from limited access to suitable resistance sources. The development of gene technology has drastically increased the availability of genes conferring resistance, which can be derived from non-related plant species as well as non-plant sources. In this thesis three attempts to improve the resistance against a virus, some fungi and an insect by genetic engineering are described. In the first example an approach to develop potato with improved resistance against Potato mop-top virus was evaluated. A modified version of a gene involved in viral movement from Potato mop-top virus was transformed into potato. Transgenic plants shown to transcribe the inserted sequence were evaluated in a field trial, where increased resistance to natural infection by Potato mop-top virus could be demonstrated. The second example is the evaluation of doubled haploids of oilseed rape transformed with a chitinase and a b-1,3-glucanase gene from barley. Although the barley chitinase and b-1,3-glucanase did show some antifungal effects when evaluated in vitro, no significant effects could be demonstrated when the transgenic plants were challenged with four different oilseed rape fungi in greenhouse assays. The doubled haploids were also evaluated for stability of the transgenic inserts as well as their expression during five subsequent generations. The third example evaluates pea lectin as a possible resistance factor against pollen beetles in oilseed rape. In feeding assays with pollen beetle larvae several plant proteins with potential insecticidal activity were tested. In these assays pea lectin was shown to have significant detrimental effects both on growth and survival of the larvae. Therefore, transgenic oilseed rape plants were produced that expressed pea lectin in pollen. When pollen beetle larvae were fed anthers from these plants significant reduction in larval weight was observed as well as some effect on survival.