Biophysical Phenomics: Evaluation of the Impact of Mycorrhization with Piriformospora indica

Abstract

Piriformospora indica, a root endophyte with arbuscular mycorrhizal fungi-like characteristics and the added important advantage that it can grow axenically, has been proven to be a powerful new candidate symbiont for improving plant production and crop yield in sustainable agriculture, flori–horticulture and agroforestry. However, the success of any microbial inoculation in practice has to be tested for each case, because the effectiveness of symbiosis depends on complex interactions between plant, symbionts and environment. Since mycorrhizal activity has multiple effects on the physiology and vitality of the host plant at different levels, it was reasonably expected that it would affect, as well, the performance of the photosynthetic apparatus, which is highly sensitive to any environmental change. We here review an experimental approach, widely applied to address the impact of any biotic or abiotic stress on the photosynthetic apparatus, which we have further employed for the detection of the establishment of symbiosis and the evaluation of the impact of symbiosis. This testing method, called as JIP-test, is a multilevel analysis of the fast chlorophyll a fluorescence transient OJIP exhibited by all oxygenic photosynthetic organisms upon illumination, which permits a description of the behaviour/performance of photosystems II and I in terms of different structural and functional parameters; it is, thus, an in vivo vitality analysis leading to the description of the biophysical phenotype of the photosynthetic apparatus, hence termed as Biophysical Phenomics. The method provides early diagnosis and the experimentation is simple, fast and non-invasive. In our review, we give representative examples of JIP-test application revealing the beneficial impact of symbiosis with P. indica on the photosynthetic performance of the host plants, presenting also the whole data processing by the JIP-test for a chosen case study. We further demonstrate that the behaviour patterns of the photosynthetic machinery are similar upon colonisation either with P. indica or with arbuscular mycorrhizal fungi.