Influence of Sugarcane Variety on Rhizosphere Microbiota Under Irrigated and Water-Limiting Conditions.

Drought is one of the main problems linked to climate change that is faced by agriculture, affecting various globally important crops, including sugarcane. Environmentally sustainable strategies have been sought to mitigate the effects of climate change on crops. Among them, the use of beneficial microorganisms offers a promising approach. However, it is still necessary to understand the mechanisms that regulate plant-microorganism interactions, in normal situations and under stress. In this work, the rhizosphere metagenomes of two sugarcane varieties, one resistant and the other susceptible to drought, were compared under normal conditions and under water-limiting conditions. The results showed that for the drought-resistant sugarcane variety, bacteria belonging to the order Sphingomonadales and the family Xanthomonadaceae presented increased activities in terms of mobility, colonization, and cell growth. In contrast, the rhizosphere associated with the drought-sensitive variety exhibited increases of bacteria belonging to the family Polyangiaceae, and the genus Streptomyces, with modifications in DNA metabolism and ribosome binding proteins. The results pointed to variation in the rhizosphere microbiota that was modulated by the host plant genotype, revealing potential bacterial candidates that could be recruited to assist plants during water-limiting conditions.

Relationships between radiation, wildfire and the soil microbial communities in the Chornobyl Exclusion Zone.

There is considerable uncertainty regarding radiation's effects on biodiversity in natural complex ecosystems typically subjected to multiple environmental disturbances and stresses. In this study we characterised the relationships between soil microbial communities and estimated total absorbed dose rates to bacteria, grassy vegetation and trees in the Red Forest region of the Chornobyl Exclusion Zone. Samples were taken from sites of contrasting ecological histories and along burn and no burn areas following a wildfire. Estimated total absorbed dose rates to bacteria reached levels one order of magnitude higher than those known to affect bacteria in laboratory studies. Sites with harsher ecological conditions, notably acidic pH and low soil moisture, tended to have higher radiation contamination levels. No relationship between the effects of fire and radiation were observed. Microbial groups that correlated with high radiation sites were mostly classified to taxa associated with high environmental stress habitats or stress resistance traits. Distance-based linear models and co-occurrence analysis revealed that the effects of radiation on the soil microbiome were minimal. Hence, the association between high radiation sites and specific microbial groups is more likely a result of the harsher ecological conditions in these sites, rather than due to radiation itself. In this study, we provide a starting point for understanding the relationship between soil microbial communities and estimated total absorbed radiation dose rates to different components of an ecosystem highly contaminated with radiation. Our results suggest that soil microbiomes adapted to natural soil conditions are more likely to be resistant to ionising radiation than expected from laboratory studies, which demonstrates the importance of assessing the impact of ionising radiation on soil microbial communities under field conditions.