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Introduction: Ascochyta blight (AB) caused by the necrotrophic fungus Ascochyta rabiei is one of the most significant diseases that limit the production of chickpea. Understanding the metabolic mechanisms underlying chickpea-A.rabiei interactions will provide important clues to develop novel approaches to manage this disease. Methods: We performed metabolite profiling of the aerial tissue (leaf and stem) of two chickpea accessions comprising a moderately resistant breeding line (CICA1841) and a highly susceptible cultivar (Kyabra) in response to one of the highly aggressive Australian A. rabiei isolates TR9571 via non-targeted metabolomics analysis using liquid chromatography-mass spectrometry. Results: The results revealed resistance and susceptibility-associated constitutive metabolites for example the moderately resistant breeding line had a higher mass abundance of ferulic acid while the levels of catechins, phthalic acid, and nicotinic acid were high in the susceptible cultivar. Further, the host-pathogen interaction resulted in the altered levels of various metabolites (induced and suppressed), especially in the susceptible cultivar revealing a possible reason for susceptibility against A.r abiei. Noticeably, themass abundance of salicylic acid was induced in the aerial tissue of the susceptible cultivar after fungus colonization, while methyl jasmonate (MeJA) was suppressed, elucidating the key role of phytohormones in chickpea-A. rabiei interaction. Many differential metabolites in flavonoid biosynthesis, phenylalanine, Aminoacyl-tRNA biosynthesis, pentose and glucuronate interconversions, arginine biosynthesis, valine, leucine, and isoleucine biosynthesis, and alanine, aspartate, and glutamate metabolism pathways were upand down-regulated showing the involvement of these metabolic pathways in chickpea-A. rabiei interaction. Discussion: Taken together, this study highlights the chickpea -- A. rabiei interaction at a metabolite level and shows how A. rabiei differentially alters the metabolite profile ofmoderately resistant and susceptible chickpea accessions and is probably exploiting the chickpea defense pathways in its favour. [ABSTRACT FROM AUTHOR]

Recent studies have challenged the validity of the Redfield ratio. It is proposed that physical and biogeochemical processes govern the geographical variations in carbon : nitrogen : phosphorus (C : N : P) ratios. However, this proposal remains to be examined through concurrent observations of C : N : P ratios with physical and biogeochemical processes in various marine reservoirs. Here, we sampled the Arabian Sea for its C, N, and P content in organic and inorganic pools during the winter monsoon. We analyzed the role of convective mixing, eddies, and N2 fixation to explain the variation in observed elemental ratios. Convective mixing injected the cold water and enhanced the supply of N and P nutrients in the top layer (surface to 50–75 m) of the northern Arabian Sea. This led to a decrease in the N : P and C : P ratios in the particulate organic matter in the northern region, but C : N : P increased equatorward, averaging 245 : 32 : 1 in the top layer of the Arabian Sea. The variation in the elemental ratios in the top layer is best explained by the changes in water temperature. N2 fixation contributed negligibly to the N : P ratio of the export flux. The substantial decrease in N : P ratios of nutrients in the subsurface waters is most likely caused by the denitrifying conditions in the Arabian Sea. As the processes of convective mixing and eddies are are prevalent oceanic processes, our observations underpin that the interplay of these processes leads to changes in the elemental ratios globally. [ABSTRACT FROM AUTHOR]

Marine dinitrogen (N2) fixation fuels primary production and thereby influences the Earth's climate. Yet, its geographical distribution and controlling environmental parameters remain debatable. We measured N2 fixation rates from the two spatially and physicochemically contrasting regions of the Arabian Sea during the winter monsoon: (a) the colder and nutrient‐rich waters in the northern region owing to winter convection and (b) the warmer and nutrient‐poor waters in the southern region unaffected by winter convection. We found higher N2 fixation rates at the surface of northern region due to convective mixing driven supply of phosphate (intuitively iron also) from the underlying suboxic waters. N2 fixation was favored by high nutrient concentrations in the euphotic waters, whereas remained unaffected by nutrient availability in the aphotic waters. We conclude that diazotrophs dwelling in the euphotic zone chose phosphate over fixed nitrogen‐poor waters. However, we found that among oligotrophic waters, anticyclonic eddy extremes the barrier of fixed nitrogen supply, and thereby, elevates N2 fixation. While the Arabian Sea loses about 20%–40% of the global ocean fixed nitrogen, we estimate that N2 fixation in the Arabian Sea offsets only up to 42% of its fixed nitrogen‐loss by denitrification, but this offset could be higher if diazotrophic activity is further examined up to the deeper depths of the Arabian Sea. Plain Language Summary: Phytoplankton facilitate the removal of greenhouse carbon dioxide gas from the atmosphere. However, phytoplankton's carbon dioxide assimilation ability is largely controlled by the reactive forms of nitrogen (N, such as ammonium, nitrate and nitrite). In contrast, the N‐limited environments often create a suitable niche for diazotrophs—organisms genetically proficient to convert dinitrogen (N2) gas to a reactive form of N. Previous research has hypothesized close spatial coupling between N2 fixation and N‐loss processes because the latter result in an N‐deficit, that is, a conducive condition for diazotrophs. Here, we measured N2 fixation rates in and above the N‐loss dominated waters of the Arabian Sea. The highest N2 fixation occurred near the coast of the Arabian Sea. We found relatively high N2 fixation rates above the waters with the highest N‐loss owing to convective mixing driven supply of nutrients such as phosphate and probably iron. N2 fixation rates below the sunlit layer were consistent but low. Our study showed that physical processes substantially influence N2 fixation by affecting nutrients supply. Key Points: Winter convection elevates N2 fixation through the enhanced supply of nutrients from the suboxic waters to the surface waters of the Arabian SeaDiazotrophy offsets up to 42% of the Arabian Sea's denitrification deficitWinter convective mixing strengthens the long‐held hypothesis of coupling between N‐gain and ‐loss processes [ABSTRACT FROM AUTHOR]

Aflatoxins, carcinogenic secondary metabolites produced by the Aspergillus fungi, pose a significant threat to groundnut, making them susceptible to infection and compromising their quality. Despite extensive breeding programs, the need for more durable resistance in groundnut germplasm remains a major challenge. Targeting susceptible genes favoring Aspergillus infection in groundnut could offer a promising strategy for achieving durable resistance. The glycine-rich RNA-binding protein (GR-RBP)-coding genes, known for their involvement in plant hypersensitivity and susceptibility to A. flavus, have been studied in model plants. However, there needs to be more understanding of the GR-RBP gene family in groundnut. In this study, twenty-three Arachis hypogaea GR-RBP (Ah.GR-RBP) genes were identified, and the chromosomal location, sub-cellular localization, and regulatory elements in the putative promoter region were analyzed. Expression analysis revealed that Ah.GR-RBP.1, Ah.GR-RBP.12, Ah.GR-RBP.3, and Ah.GR-RBP.15 showed higher expression in the susceptible genotype. This paper would help to provide knowledge on potential candidate target genes for precise breeding interventions for aflatoxin mitigation in groundnut. [ABSTRACT FROM AUTHOR]