Effect of Agronomic Practices on Arbuscular Mycorrhizal Colonisation, Spore Density and Phosphorus Uptake in Spelt (Triticum spelta)

Abstract

Arbuscular mycorrhizae (AM) fungi form symbiotic, normally mutualistic, associations with roots and can translocate nutrients, especially phosphorus (P) to the host plant. These fungi can play an important role in agroecosystems, which is why it is important to understand how agricultural practices and genotypes affect their existence and function. There were three main components to this project. First, a systematic review of the literature was carried out to document differences in AM fungal populations, diversity and colonisation in crops grown in organic and conventional production systems; where possible, this included meta-analyses of data extracted from the literature. In addition, two field experiments were conducted. Experiment 1 (“fertiliser trial”) was conducted for two years (2014/15 and 2015/16) to find out the effect of spelt variety (Oberkulmer Rotkorn, ZOR, Rubiota and Filderstolz) and fertiliser type (compost and mineral N) and rate (50 and100 kg N ha-1 ) on AM fungal colonisation in spelt roots, spore density in the soil and grain yield, P (concentration, uptake and total) in straw and grain. Experiment 2 (“tillage trial”, 2015/16 and 2016/17) was designed to study the effect of crop protection management (conventional and organic), fertiliser type (compost and mineral N), tillage system (minimum and conventional), and spelt variety (Oberkulmer Rotkorn and Filderstolz) on the same mycorrhizal and crop parameters. Both trials were conducted under field conditions at Nafferton farm in northeast England. Twenty studies were identified in the meta-analysis, with soil spore density, AM fungi diversity, and root colonisation reported as indicators of AM fungal diversity and function. Results from the fertiliser trial indicated that lower levels of fertiliser input promote vesicle formation, while highest numbers of spores in 2015/16 were measured at high levels of compost input. The tillage trial showed that crop protection had a significant effect on spore density and was higher where organic approaches were used compared to conventional. Both minimum tillage and compost fertilisation increased spore density, whereas, both conventional tillage, and compost fertilisation enhanced AM fungal colonisation. Highest spore densities were measured where the spelt variety was Oberkulmer, while AM fungal colonisation was highest for Filderstolz. The adoption of organic approaches could be a good strategy to encourage AM fungal symbiosis especially using compost fertiliser. Selective breeding could also enhance the ability of spelt to form symbioses with AM fungi, as shown for the variety Filderstolz.