The agronomic management of symbiotic (S) inoculations, by means of bio-fertilizers (BF), is aimed at inducing modifications of the plant rhizosphere and thereafter of the phenotype and yield of the crop. It is here shown that the yield response of maize to a symbiotic treatment may be correlated to six easy-to-calculate indicator variables on the basis of the raw foliar pH, NIR-Spectroscopy of leaves, and the NIRS of hay litter-bags from soils. It has been confirmed, in a set of thirteen pairwise comparisons of Symbiotic (S) soil inoculated by BF vs. Control (non-inoculated soil; C), that the inoculation on average acidified the leaves by-3.7% pH units (P<0.0001). The responses in yield ranged from +25.2% to-9.2% (av.ge +3.5%; P = 0.03), but with average null responses in two centers and a significant response (+11%) in a third center. NIR-Tomoscopy scans (No. 574) were also performed on the leaves, and in addition, hay-litter-bags that had previously been buried in fields were dug up after two months, and 431 NIR-scans were acquired. The effect-size on the yield was expressed as the logarithm of the response ratio, i.e. the mean of the inoculated Symbiotic treatment divided by the mean of the non-inoculated Control for each pairwise comparison. A multiple regression model was developed to predict the symbiotic response to the treatment using six independent variables, including the squared litter-bag fingerprints, and an R 2 adj. level of 0.78 (P=0.01) was reached, with a standard error of ±4%. Validation in one external maize field, with a positive response to bio-fertilizers, demonstrates the juxtaposition of the estimated and accomplished yield. In a second experiment, with 40 pairwise comparisons, the two tested maize varieties did not respond to five types of bio-fertilizer, and the negative results were predicted at 84% (P 0.0012). The soil biota is a key factor for the application of appropriate microbial inoculants in the field, but the genotype/ genotype interactions between the microbial strain (s) and the crop cultivar (s) require prior screening to obtain the desired results.

Four strains of Arbuscular Mycorrhizal (AM) biofertilizer fungi, combined with two potato cultivars, were in-field tested in a four-replicate arrangement in a factorial experiment. As far as general combinability is concerned, cv. Agria was more responsive to different inocula (yield +5.56%, P 0.02) and to two strains in particular (+8%). On the other hand, the results with Innovator, a cultivar that yields 33% less than Agria, showed a significant reduction in the number of tubers for three AM strains, thus proving a clear genetic Biofertilizer * Cultivar interaction. The study of hay litter-bags has shown a high NIR spectral fingerprint for the Cultivar factor (81%), while the Inoculation factor showed a higher spectral fingerprint in Agria (76%) than in Innovator (65%). The Substrate Induced Respiration predicted from the NIR-SCiO spectra of the litter-bags was significantly increased after inoculation (+6.3%, P 0.04), but appeared lower for Agria (-5.4%) vs. Innovator (P 0.05), with a non-significant interaction. The obtained results show that the adaptation of the AM strains to the genetics of potato cultivars is a first step toward reducing chemical inputs, with consequent benefits for the environment, but without an excessive reduction in yield. The litter-bag technique can therefore be recommended for a simplified monitoring of the complicated plant-mycorrhizosphere relationship.

The management of the inoculation of a plant's roots, by means of biofertilizers (BF) containing arbuscular mycorrhizal (AM) fungi, is aimed at inducing modifications of the quality of the seeds. It is here shown that a seed-soil treatment can be elicited in the fingerprints of a symbiotic treatment using Near Infra Red (NIR)-SCiO NIR-SCiO spectra collections of single kernels: overall, a sensitivity of 73% and a specificity of 73% have been achieved, thus suggesting that it may be possible to assign the symbiotic origin of corn from just twenty kernels, provided that the dataset is adequately representative of the cultivar and AM. A global correlation study has shown a positive general trend (R 2 0.45) of quality vs. quantity, in the sense that an increase in yield corresponded to an increase in the spectral differences between the symbiotic spectra and the control ones, but the inverse was also true, as a result of the parasitic behaviour of the BF treatments. The efficacy of the symbiosis can be back predicted from the NIR spectra; in fact, around 90% of the positive yield outcome results were discriminated from the negative ones. A reduction in the foliar pH (R 2 0.37) and an increase in the foliar protein (R 2 0.43) were observed as immediate phenotypic signs of a productive symbiosis.The commercial raw composition of the kernels appeared to only be affected slightly by the BF treatments; thus, till now uncharted secondary compounds of the maize kernels are involved, as supported by animal performances.