Biology subjects

Mahmoud, R.

Publications and source records attributed to Mahmoud, R..

5 recordsLinked to original sources

bioRxiv2024

Differences in growth features between species are driving cereal-legume intercrop yield: a statistical learning approach based on aggregated dataset

Increasing crop diversification is crucial for developing more sustainable agricultural systems, and cereal-legume intercropping is a promising strategy. This study investigates the factors influencing the yield of cereal-legume intercrops using data from six field experiments in southwestern France, where durum wheat was intercropped with either faba bean or pea. We assessed how differences in plant traits between the associated species (e.g., height or biomass growth rates) are related to the intercrop productivity. Additionally, we developed a novel modeling approach, combining machine learning and mixed-effects models, to identify the key traits driving intercrop performance based on variable importance. Our results show that interspecific differences in plant traits, particularly in biomass accumu-lation rate, maximum leaf area index, and elongation rate, were the most important factors explaining intercrop yield. These traits and their differences mainly suggest that compet-itive processes shape the outcome of a mixture and highlight the importance of dynamic measurements in agronomic experiments. The relationship between species yield and trait differences was symmetric for both intercropped species. Furthermore, these relationships were scale-dependent, with trends observed at the aggregate level not always consistent at the level of individual experiments. Our study highlights the importance of considering trade-offs when designing intercropping systems for practical applications and demonstrates the value of combining machine learning with ecological knowledge to gain insights into complex agricultural systems from aggregated datasets. HighlightsO_LIJoint analysis of experimental datasets provided new insights into crop mixtures func-tioning. C_LIO_LIDifferences in growth traits between species in the mixture predicted their perfor-mance. C_LIO_LIThe strength of the correlation between performance and trait distance was similar for both species. C_LIO_LIFarmers and researchers need to consider trade-offs when designing intercropping sys-tems. C_LI

ecology↗

bioRxiv2024

Ecophysiological Behaviour Of Major Fusarium Species In Response To Combinations Of Temperature And Water Activity Constraints

Fusarium Head Blight (FHB) is a devastating fungal disease affecting cereals, caused by Fusarium species that can produce harmful mycotoxins. Fusarium species share the same ecological niche, and their population dynamic and associated mycotoxin patterns are driven by the environment. The aim of the present study was to investigate ecophysiological characteristics of the major Fusarium species causing FHB under abiotic factors. Growth and mycotoxin production of different strains of Fusarium avenaceum, Fusarium graminearum, Fusarium langsethiae, Fusarium poae and Fusarium tricinctum were characterized under a combined effect of temperature ({Theta} = 15, 20, 25 and 30{degrees}C) and water activity (aw = 0.99, 0.98, 0.97, 0.96, 0.95 and 0.94). Using innovative statistical analyses, we demonstrated that those Fusarium species greatly differ in their responses to the studied environmental constraints. Our findings indicated that {Theta}, aw, and their interaction were the major factors with a significant impact on the species behaviour. The intraspecific variation was demonstrated as less pronounced than the interspecific one. Understanding the ecophysiological requirements of Fusarium species is crucial in the context of climate change that is predicted to worsen disease outbreaks. Our data constitute a valuable knowledge base for improving the reliability and robustness of FHB prediction models and anticipating the associated mycotoxin risk. IMPORTANCEFusarium species pose a significant threat to major cereal crops, including wheat. These fungi not only reduce yield but also produce mycotoxins harmful to animals and humans. The prevalence of each Fusarium species is influenced by environmental conditions and shifts in pathogen populations, leading to changes in mycotoxin patterns have already been observed in relation to climate changes. This study revealed distinct ecophysiological behaviours, including mycelium growth and mycotoxin production, among the five major Fusarium species when exposed to varying temperature and water activity conditions. Our findings provide a valuable foundation for a more comprehensive understanding of the challenge of mycotoxin contamination and for the development of more effective mitigation strategies in the near future.

microbiology↗

bioRxiv2021

Interspecific interactions regulate plant reproductive allometry in cereal-legume intercropping systems

O_LICalls for ecological principles in agriculture have gained momentum. Intercropping systems have long been designed by growing two, or more, annual crop species in the same field, aiming for a better resource use efficiency. However, assembly rules for their design are lacking. Notably, it is still unknown whether species performances are maximized during both the vegetative and reproductive phases given the sensitivity of reproductive allocation rules to resource limitation. Interestingly, ecological theory provides expectations regarding putative invariance of plant reproductive allometry (PRA) under non-limiting conditions for plant growth. Here we examined whether and how PRA changes in response to plant-plant interactions in intercropping systems, which can inform both ecological theory and the understanding of the functioning of intercropping systems. C_LIO_LIWe analyzed a dataset of 28 field cereal-legume intercropping trials from various climatic and management conditions across Western Europe. PRA was quantified in both mixing and single-species situations. C_LIO_LIPRA was positively impacted in specific management conditions, leading to a greater increase in yield for a given increase in plant size. Variations in PRA were more beneficial for legumes grown in unfertilized mixture, which explains their use as a key component in actual intercrop systems. The response for cereals was similar but less pronounced in magnitude, and was greater under limiting resource conditions. Focusing on intercropping conditions, hierarchical competition (indicated by biomass difference between intercropped species) appears as a strong driver of the reproductive output of a given species. C_LIO_LISynthesis and applications. Plant reproductive allometry behaves in crop species in the same way as it does in wild species. However, contrary to theoretical expectations about an overall invariance of PRA, we highlighted taxon-specific and context-dependent effects of plant-plant interactions on PRA. This systematic deviation to PRA expectations could be leveraged to cultivate each species up to its reproductive optimum while accounting for the performance of the other, whether farmers objective is to favor one species or to reach an equilibrium in seed production. Sowing density and cultivar choice could regulate the biomass of each component, with specific targets derived from allometric relationships, aiming for an optimal reproductive allocation in mixtures. C_LI

ecology↗

bioRxiv2018

Early and Late Effects of Maternal Experience on Hippocampal Neurogenesis, Microglia, and the Circulating Cytokine Milieu

The maternal brain displays considerable plasticity, and motherhood is associated with changes in affective and cognitive function. Motherhood can alter the trajectory of brain ageing, including modifications to neuroplasticity and cognition. Here, we investigated the short- and long-term effects of motherhood on hippocampal neurogenesis, microglial density and morphology, and circulating cytokines, domains known to be altered with age and implicated in cognition and mood. Female rats were bred then euthanized during gestation or at various postpartum timepoints, culminating in middle age, and nulliparous rats served as age-matched controls. Hippocampal neurogenesis was significantly suppressed during gestation and the postpartum period. Interestingly, neurogenesis declined significantly in middle-aged nulliparous rats, but increased in primiparous rats across the same period. Transient postpartum adaptations to the neuroimmune environment of the hippocampus were evidenced, as Iba-1-immunoreactive microglia assumed a de-ramified morphology followed by increased density. Intriguingly, ageing-related changes in circulating cytokines were dependent on parity. These adaptations in neurogenic and immune processes may have ramifications for maternal mood and cognition across the peripartum period and beyond.

neuroscience↗

bioRxiv2017

Premarin has opposing effects on spatial learning, neural activation and serum cytokine levels in middle age dependent on reproductive history

Menopause is associated with cognitive decline, and hormone therapies (HT) can improve cognition dependent on time since menopause. Previous parity also influences cognition in later life. The present study investigated how primiparity and long-term ovariectomy influence cognition, hippocampal neurogenesis, and neuronal activation in middle-aged rats in response to the HT, Premarin. Nulliparous and primiparous rats were sham-ovariectomized or ovariectomized, administered vehicle or Premarin six months later, and trained in the Morris water maze. Premarin improved spatial learning and memory in nulliparous rats, but impaired spatial and reversal learning in primiparous rats. Primiparity increased hippocampal neurogenesis, whereas Premarin treatment decreased immature neurons in both primiparous and nulliparous middle-aged rats in a region-specific manner. Moreover, Premarin increased serum TNF and KC/GRO in nulliparous, but not primiparous, rats, whereas Premarin increased zif268 expression in the CA3 region of the hippocampus in primiparous rats. Thus, primiparity alters how Premarin affects spatial learning, neuronal activation, serum cytokines, and adrenal mass. These findings have implications for the tailored treatment of age-associated cognitive decline in women.

neuroscience↗