Drought resistance of old pea varieties - Stomata and root trait responses to drought

Summary in the original language of the document

Climate change mitigation and adaptation is imperative, and agriculture can mitigate climate change by reducing animal production and increasing the production of plant foods for human consumption. Peas (Pisum sativum) are well-adapted to Danish conditions and an increased production and consumption of peas could support a green transition of the Danish agriculture. Peas were staple foods in Denmark until the end of the 1800s and cultivars suitable for modern agriculture- and consumers could be found in the rich gene pool of old pea varieties. Unfortunately, pe as are sensitive to drought. With projected increases of droughts due to climate change, it is crucial to improve the limited understanding on pea drought responses. Expanding this knowledge is key, so we know what traits to look for in cultivars for a future climate. Also, knowledge about the links between early development and later drought responses is important with regards to the validity of early season phenotyping as a method to predict drought resistance. On this background, the aim of this thesis was 1) to investigate the initial development of the three old pea accessions Brunært fra Nakskov, SKR 154 and SKR 164, 2) to investigate the drought response of these pea accessions and 3) to compare the initial development and drought response. A rhizotube screening trial and drought experiment was conducted to investigate initial development and drought responses, respectively. Root traits (rooting depth, root dry weight, root length density and specific root length) and stomata traits (stomatal conductance, stomata size, stomata density) were recorded, as well as plant height, aboveground biomass, leaf area, number of nodules, nitrogen fixation and δ13C values. Significant accession variations were found in the plant traits specific root length, stomata size, shoot biomass, root biomass, plant height, leaf area, stomata size, stomatal conductance and number of nodules. Drought had a significant effect on a range of plant traits. The drought treatments had higher root length, smaller stomata size, higher stomata density, lower stomatal conductance, fewer nodules, lower N fixation and higher δ13C values than their well-watered counterparts. Some relations between the initial development and the drought response existed. High initial values of shoot- and root biomass, plant height, leaf area, stomata size and number of nodules corresponded with high values in these traits under drought conditions. The findings of this project added to the knowledge base on pea drought responses and showed that plant traits important to drought resistance depended on accession and water availability. Also, it indicated that early season phenotyping possibly can be predictive of performance under drought conditions. This could allow breeders to more efficiently discover pea varieties adapted to a future climate.