Using High-Throughput Phenotyping to Explore Growth Responses to Mycorrhizal Fungi and Zinc in Three Plant Species

Abstract

There are many reported benefits to plants of arbuscular mycorrhizal fungi (AMF), including positive plant biomass responses; however, AMF can also induce biomass depressions in plants, and this response receives little attention in the literature. High-throughput phenotyping (HTP) technology permits repeated measures of an individual plant’s aboveground biomass. We examined the effect on AMF inoculation on the shoot biomass of three contrasting plant species: a vegetable crop (tomato), a cereal crop (barley), and a pasture legume (Medicago). We also considered the interaction of mycorrhizal growth responses with plant-available soil zinc (Zn) and phosphorus (P) concentrations. The appearance of a depression in shoot biomass due to inoculation with AMF occurred at different times for each plant species; depressions appeared earliest in tomato, then Medicago, and then barley. The usually positive-responding Medicago plants were not responsive at the high level of soil available P used. Mycorrhizal growth responsiveness in all three species was also highly interactive with soil Zn supply; tomato growth responded negatively to AMF inoculation in all soil Zn treatments except the toxic soil Zn treatment, where it responded positively. Our results illustrate how context-dependent mycorrhizal growth responses are and the value of HTP approaches to exploring the complexity of mycorrhizal responses.

High‐throughput phenotyping reveals growth of Medicago truncatula is positively affected by arbuscular mycorrhizal fungi even at high soil phosphorus availability

“…This trend was also observed in the phenotyping data, with AGR and RGR values higher in the mycorrhizal plants only at low soil P availability. In terms of harvest point biomass data, this neutralization of response to AMF with high P has been demonstrated previously in this plant species (Jakobsen et al, 2016; Watts‐Williams, Jewell, et al, 2019). Some plant species respond neutrally to colonization by AMF regardless of the soil P concentration, such as wheat, barley, and tomato (Grace, Smith, & Smith, 2009; Watts‐Williams et al, 2013).…”

“…Medicago truncatula is typically well‐colonized by AMF, and can accumulate substantially more biomass when colonized by AMF than when grown in the absence of AMF, particularly under nutrient stress (Watts‐Williams et al, 2017). On the other hand, M. truncatula can display lowered AMF colonization and neutral growth responses to AMF when nutrients are highly available (Watts‐Williams, Jewell, et al, 2019). Almost all physiological studies of M. truncatula present growth responses to AMF based on the harvest time point biomass, which may mask temporal responses to AMF.…”

“…Such HTP platforms have been successfully used in previous experiments studying plant stress responses and genetic variation studies, for example, in barley (Honsdorf, March, Berger, Tester, & Pillen, 2014; Neumann et al, 2015), pea (Humplík et al, 2015), and chickpea (Atieno et al, 2017). It has also been used recently to explore the complex temporal dynamics of mycorrhizal growth responses and interaction with Zn availability, from positive through to negative in three plant species (Watts‐Williams, Jewell, et al, 2019), and to explore how mycorrhizal responses are driven by resource allocation (Riley et al, 2019).…”

Responses in Zinc Uptake of Different Mycorrhizal and Non-mycorrhizal Crops to Varied Levels of Phosphorus and Zinc Applications

“…Although the responses of different crop species and genotypes to P or Zn application have been verified to be different ( Yilmaz et al, 1997 ; Fageria, 2002 ; Watts-Williams et al, 2019 ; Qin et al, 2020 ), the negative effects of increasing P application on Zn uptake among different mycorrhizal and non-mycorrhizal crops have not been reported. In the present study, mycorrhizal crops (maize and soybean) displayed higher degrees of decrease in Zn uptake and ZnAE mediated by P application than non-mycorrhizal crop (oilseed rape).…”

Mycorrhizas for a sustainable world

“…The advent of modern high‐throughput plant phenotyping systems has allowed us to begin characterizing mycorrhizal host plant (shoot) growth responses (positive through to negative) over time (Watts‐Williams et al , ), rather than just at the harvest time point. This technology will be especially useful when it extends to root phenotyping platforms that allow for high resolution screening, and analysis of the effects of mycorrhizal fungi on root growth and morphology over time.…”