Isabel Méndez

This systematic review evaluates the scientific literature from 2010 to 2024 on the effects of climate change-induced modifications in key abiotic factors on the severity of plant diseases caused by pathogens. The review aims to provide a comprehensive overview of recent advancements in plant pathology within the context of climate change, identifying knowledge gaps and highlighting areas that require further research. A thorough database search was conducted in Scopus and Web of Science, yielding 2,459 articles. After applying PRISMA exclusion criteria, 106 articles were selected for in-depth analysis, in which 32 articles focused on water deficit stress (WDS), 27 on the combined effect of elevated temperature (eT°) and CO ₂ , 23 on eT°, 22 on elevated CO ₂ (eCO ₂ ), and the combined effects of eT° + CO ₂ , eT° + RH, eT° + CO ₂ + soil moisture, eT° + soil moisture and eCO ₂ + WDS. The review covered 60 agriculturally important crops, with wheat, grape, chickpea, and rice being the most frequently studied. Fusarium sp. emerged as the most researched fungal genus, alongside other significant pathogens such as Rhizoctonia sp. and Phytophthora sp. Across all studies, 61% reported an increase in pathogen severity, with WDS being the most critical factor, followed by the combined effects of eT° and CO ₂ . These findings highlight how soilborne pathogens influence soil dynamics and responses to climate change. The review underscores the need for further research on the multiple interactions between abiotic stress and severity, which is essential for developing mitigation strategies, such as improving soil management practices and integrated pest management, to safeguard crop health and support global food security in a changing climate.

One of the most challenging aspects of long-term research based on microorganisms is the maintenance of isolates under ex situ conditions, particularly the conservation of phytopathological characteristics. Our research group has worked for more than 10 years with Gaumannomyces graminis var. tritici (Ggt), the main biotic factor affecting wheat. In this sense we preserved the microorganisms in oil overlaid. However, several strains preserved for a long time lost their pathogenicity. These strains show white and non-infective mycelia. In this sense, we hypothesized that this is attributable to low melanin content. Melanin is a natural pigment mainly involved in UV protection, desiccation, salinity, oxidation, and fungal pathogenicity. Therefore, understanding the melanin role on Ggt pathogenicity is fundamental to developing melanin activation strategies under laboratory studies. In this study, we induce melanin activation by UV-A light chamber, 320 to 400 nm (T1) and temperature changes of 30 °C, 15 °C, and 20 °C (T2). Fungal pathogenicity was evaluated by determination of blackening roots and Ggt was quantified by real-time PCR in inoculated wheat plants. Results revealed that Ggt grown under UV-A (T1) conditions showed around 40% higher melanin level with a concomitant effect on root infection (98% of blackened roots) and 4-fold more Ggt genome copy number compared with the control (non-infective mycelia) being T1, a more inductor factor compared with T2. These findings would support the role of melanin in pathogenicity in darkly pigmented fungi such as Ggt and could serve as a basis for activating pathogenicity under laboratory conditions.

“Take-all” disease is the most important biotic factor affecting cereal productivity, causing 30–50% of crop losses. The causal agent is the ascomycete soil-borne pathogen Gaeumannomyces graminis var. tritici (Ggt). Current control measures are ineffective, because Ggt can remain saprophytic in soils for long periods. Therefore, the study of the microbiome residing in suppressive soils (SS) is a promising niche of Ggt biocontrol. Here, we evaluated the efficiency of Serratia sp., Bacillus sp., and Acinetobacter sp. isolated from SS against the incidence of Ggt on wheat. Our results demonstrated that plants inoculated with the bacterial consortium in both greenhouse and field conditions were highly efficient in Ggt biocontrol, more so than individual strains. The disease reduction was evidenced by higher biomass production, fewer copies of the Ggt genome with a concomitant curtailment of blackening of roots, a decrease of lipid peroxidation, and an increase of superoxide dismutase activity. The ability of the microbial consortium over that of single strains could be attributable to interspecies communication as a strategy to biocontrol; i.e., higher chitinase activity. In conclusion, bacterial consortia from SS are an important niche of Ggt biocontrol, serving as a model for other soil-borne pathogens.