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Background and Aims. The study aims to explore the impact of advancements in wheat genetics on root structure and rhizosphere biology, which are still not fully understood. Specifically, we investigated various factors including the exudation of carboxylates, colonization by arbuscular mycorrhizal fungi, microbial activity, and root architecture in winter wheat varieties that have been released between 1965 and 2020. Methods. To conduct our study, we sowed fourteen different winter wheat varieties with four replicates on acidic Andisol at field conditions. Complete root systems and soil samples were extracted using a tractor-mounted hydraulic sampler tube of 3.5 cm diameter, which reached a depth of 60 cm. Results. In this sense, succinate showed a significant increase by 21%. Mycorrhizal colonization was inversely proportional to P concentrations and all varieties showed higher microbial activity at anthesis. The longest roots were found in varieties released after the year 2000, but no significant differences were found in other root architecture parameters. There was no clear pattern observed in root architecture or biological activity as a function of the year of release. Plant genetics moderated root architecture, carboxylate exudation, microbial activity, and mycorrhizal colonization, all of which are affected by high P concentrations. Conclusions. This study investigated plant-microorganism interactions, often overlooked due to root system analysis challenges. Older wheat varieties showed higher carboxylate exudation. We identified wheat varieties with potential for improved root systems and crop efficiency.

The impact of climate change requires developing and validating models that help to project possible scenarios that must adapt to new varieties. This study seeks to validate and calibrate the Decision Support System for Agrotechnology Transfer (DSSAT) model as a tool that facilitates the characterization of the behavior of new varieties in the face of new scenarios generated by climate change. The determination of genetic coefficients of three bread wheat (Triticum aestivum L.) varieties was considered in the methodology; this was done with the database of the historical records of the Instituto de Investigaciones Agropecuarias (INIA) Wheat Breeding Program for the 2000 to 2011 period. Once the adjustment level of the model was dealt with, it was feasible to obtain genetic coefficients of three spring wheat varieties (Pandora-INIA, Kipa-INIA, and Millan-INIA); days from planting to anthesis variable exhibited RMSE values fluctuating between 3.5 and 9.7 depending on the variety. For total duration of days to maturity, 'Millan-INIA' exhibited a very good adjustment (RMSE = 0.25) as compared to 'Pandora-INIA' (RMSE = 1.35) and 'Kipa-INIA' (12.22). Furthermore, the coefficient of determination of the genetic coefficients indicates that the varieties have minimum vernalization requirements; these are similar to the photoperiod between 'Pandora-INIA' and 'Millan-INIA' and lower in the case of 'Kipa-INIA'. Thermal requirements for grain filling, biomass production, and plant height did not exhibit any important differences among varieties. Finally, the methodology allowed calibrating the DSSAT model and achieving a good predictive level of yields for the three varieties. The plant development parameters must be studied in greater detail because of the low association between simulated and observed values.

A greenhouse experiment was carried out to assess the effect of the inoculation with rhizobacterial strains on the tolerance to water stress in wheat genotypes (Triticum aestivum L.) under two different water regimes. A drought resistant (Fontagro 8) and a susceptible (Fontagro 98) genotype were studied. Soil water content was kept at 100% and 45% field capacity. The treatments were inoculations with AG-70 (Bacillus sp.), AG-54 (Pseudomonas sp.), and a mixture of both (AG-70 + AG-54); a control treatment consisting of an autoclaved nutritive solution. When applied to Fontagro 8 genotype, the AG-70 + AG-54 treatment resulted in a higher increase in shoot (88%) and root dry weight (211%) compared to the control under drought conditions. The same treatment applied on the susceptible genotype (Fontagro 98) resulted in increases of 73% and 129% in shoot and root dry weight, respectively. In addition, the inoculated plants showed significant increases in root length, stomatal conductance and chlorophyll index. The AG-54 and AG-70 treatments increased NPK contents in the drought-resistant genotype, while the AG-54 and AG-70 + AG-54 treatments increased the P content in the susceptible genotype. The treatments that showed the most positive effects on the biological quality parameters of the soil (microbial activity, microbial respiration and urease enzyme activity) were AG-54 and AG-70 + AG-54. Therefore, the use of AG-70 and AG-54, applied separately or combined, increased tolerance to water stress in both wheat genotypes and constitute a biotechnological tool for the production of crops in water-deficit ecosystems.