Understanding the intraspecies genetic and phenotypic diversity of the clover symbiont Rhizobium leguminosarum

Rhizobia are agriculturally important bacteria capable of forming symbiosis with legumes and fixing atmospheric nitrogen which sustainably improves plant productivity and soil fertility. The Rhizobium leguminosarum species complex is highly genetically diverse and contains five genetically distinct genospecies. Significant phenotypic diversity is also displayed within Rhizobium leguminosarum; however, no phenotypes are genospecies-exclusive. The importance of the broad genetic diversity of Rhizobium leguminosarum and its influence on phenotypic diversity and rhizosphere-associated interactions are unclear. In this thesis, Rhizobium leguminosarum symbiovar trifolii (Rlt) intraspecies diversity was investigated by assessing the genetic and phenotypic variation of white clover nodule Rlt from agricultural field managements across Europe. This thesis identified that the significant genetic diversity of Rlt can manifest in substantial transcriptional and phenotypic variation across strains, and this diversity can influence plant-mediated symbiont selectivity and competitive strain interactions. A novel multiplexed high-throughput amplicon sequencing approach, MAUI-seq, was developed to improve detection of chimeras and other erroneous sequences for confident determination of intraspecies diversity from environmental samples. Using this method, significant Rlt nodule population diversity was identified between clover genotypes due to the combined effects of plant-host filtering and geospatial variation in allele frequencies of individual genes. Investigation of multiple Rlt strain transcriptomes demonstrated that genospecies displayed differences in core genome expression which was associated with phenotypic growth traits and putative differences in bacterial metabolism. Genomic and transcriptomic variation was utilised to identify transcriptional units conserved across strains. Pairwise growth competition experiments between Rlt strains further showed that significant competitive variation is evident and potentially associated with genospecies differences. This research demonstrates that utilising multiple strains can aid identification of species-specific traits by considering the representative variation within a species. The work presented here has laid the groundwork for future investigation into the implications of intraspecies diversity for symbiotic effectiveness in the rhizobia-legume symbiosis

XVI Agricultural Science Congress 2023: Transformation of Agri-Food Systems for Achieving Sustainable Development Goals

The XVI Agricultural Science Congress being jointly organized by the National Academy of Agricultural Sciences (NAAS) and the Indian Council of Agricultural Research (ICAR) during 10-13 October 2023, at hotel Le Meridien, Kochi, is a mega event echoing the theme “Transformation of Agri-Food Systems for achieving Sustainable Development Goals”. ICAR-Central Marine Fisheries Research Institute takes great pride in hosting the XVI ASC, which will be the perfect point of convergence of academicians, researchers, students, farmers, fishers, traders, entrepreneurs, and other stakeholders involved in agri-production systems that ensure food and nutritional security for a burgeoning population. With impeding challenges like growing urbanization, increasing unemployment, growing population, increasing food demands, degradation of natural resources through human interference, climate change impacts and natural calamities, the challenges ahead for India to achieve the Sustainable Development Goals (SDGs) set out by the United Nations are many. The XVI ASC will provide an interface for dissemination of useful information across all sectors of stakeholders invested in developing India’s agri-food systems, not only to meet the SDGs, but also to ensure a stable structure on par with agri-food systems around the world. It is an honour to present this Book of Abstracts which is a compilation of a total of 668 abstracts that convey the results of R&D programs being done in India. The abstracts have been categorized under 10 major Themes – 1. Ensuring Food & Nutritional Security: Production, Consumption and Value addition; 2. Climate Action for Sustainable Agri-Food Systems; 3. Frontier Science and emerging Genetic Technologies: Genome, Breeding, Gene Editing; 4. Livestock-based Transformation of Food Systems; 5. Horticulture-based Transformation of Food Systems; 6. Aquaculture & Fisheries-based Transformation of Food Systems; 7. Nature-based Solutions for Sustainable AgriFood Systems; 8. Next Generation Technologies: Digital Agriculture, Precision Farming and AI-based Systems; 9. Policies and Institutions for Transforming Agri-Food Systems; 10. International Partnership for Research, Education and Development. This Book of Abstracts sets the stage for the mega event itself, which will see a flow of knowledge emanating from a zeal to transform and push India’s Agri-Food Systems to perform par excellence and achieve not only the SDGs of the UN but also to rise as a world leader in the sector. I thank and congratulate all the participants who have submitted abstracts for this mega event, and I also applaud the team that has strived hard to publish this Book of Abstracts ahead of the event. I wish all the delegates and participants a very vibrant and memorable time at the XVI ASC