Potential for Growth Enhancement by Arbuscular Mycorrhizal Fungi in Potato

Abstract

Arbuscular mycorrhizal fungi (AMF) are important in natural and agricultural ecosystems to provide and enhance nutrient uptake, particularly phosphorus. Potato is one of the most important food crops globally in terms of total production and a phosphorus-demanding plant, which grows in symbiosis with AMF. This field research investigates the influence of crop management practices (fertiliser inputs and crop protection measures) and potato variety on species abundance, the diversity and function of AMF in potato. The suitability of mycorrhizal inoculants for growth enhancement in potato under specific management conditions in the glasshouse was also conducted. Traditional root staining by ink and vinegar method was used to quantify AMF colonisation along with three molecular techniques to measure AMF species diversity and level of infection, including terminal restriction fragment length polymorphism (T-RFLP), using AMF-specific primers FLR3 and FLR4 for LSU rDNA amplification, Illumina MiSeq Next Generation Sequencing (NGS) using universal fungal primers ITS1f and ITS2 for ITS region amplification and qPCR using AMF-specific primers AMG1F and AM1 for SSU rDNA amplification. All three molecular techniques were successful in nuclear ribosomal DNA region amplification. The results show that organic crop protection management significantly enhances AMF colonisation and the genetic diversity of the AMF community. The use of NPK fertiliser along with conventional pesticides decreased AMF colonisation, the quantity of the AMF gene, and diversity of the AMF community. The use of triple superphosphate in the field showed a negative effect on AMF colonisation, the quantity of the AMF gene, and the genetic diversity of the AMF community. The study did not demonstrate a strong relationship between AMF colonisation and phosphorus uptake or potato tuber yield. NGS results showed that potato colonised by native populations of AMF in the field were dominated by Paraglomus. Potato variety had no significant effect on AMF abundance or the diversity of the fungal community, but phosphorus uptake and potato tuber yield were significantly affected. In the glasshouse experiment, Rhizophagus was the only genus detected in inoculated plants, but colonisation was not correlated with phosphorus uptake and potato tuber yield. This study demonstrated that natural populations of AMF could effectively colonise potato in the field across a range of varieties but did not show any agronomic benefit from higher levels of AMF colonisation, even under low P conditions.