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Abstract Plant-based agricultural systems rely heavily on inorganic nitrogen (N) fertilizers to increase yields and ensure food security for the rapidly growing global population. However, the production and overuse of synthetic fertilizers lead to significant amounts of greenhouse gas emissions, causing a critical need for the development of alternative and sustainable organic N fertilizers. Here, we demonstrate the effective use of lysed and dried bacterial biomass from the marine purple photosynthetic bacterium Rhodovulum sulfidophilum as an alternative source of N fertilizer for the cultivation of Japanese mustard spinach (komatsuna, Brassica rapa var. perviridis). To assess the suitability of this processed bacterial biomass, containing approximately 11% N, as a N fertilizer, we examined the effects of its application on plant germination and growth (measured by leaf chlorophyll, maximum leaf length, and dry weight) under two different temperature regimes, comparing it to that of a conventional N-containing mineral fertilizer. Application at rates up to four times that of the mineral fertilizer had no negative effects on seed germination and plant growth. The bacterial biomass had to be applied at approximately twice the rate of mineral fertilizer to obtain similar plant growth parameters, roughly corresponding to the predicted 62% rate of mineralization of the bacterial N. Our findings confirm the ability of plants to take up N from the lysed and dried biomass of marine purple photosynthetic bacteria, demonstrating the potential for using R. sulfidophilum as a source of N fertilizer.

Unraveling the complex genetic bases and mechanisms underlying salt tolerance is of great importance for developing salt-tolerant varieties. In this study, we evaluated 42 chromosome segment substitution lines (CSSLs) carrying chromosome segments from IR64 on the genetic background of Koshihikari under salt stress. Two CSSLs, SL2007 and SL2038, produced higher plant dry weight and grain yield than did Koshihikari under the stress condition. These CSSLs also showed lower Na+ and Cl− accumulation in the leaf and whole plant at the full heading stage, which might be related to the higher grain yield and yield components. To understand the genetic control of its grain yield and yield components, a SL2007/Koshihikari F2 population was generated for quantitative trait locus (QTL) analysis. Six QTLs for grain yield and yield-related traits were detected on chromosome 2. Using near-isogenic lines (NILs) from a SL2007/Koshihikari F5 population, qSTGY2.2 was delimited to a 2.5 Mb region and novel qSTPN2 was delimited to a 0.6 Mb region. We also detected a novel QTL, qSTGF2, for grain filling, which was considered an important contributor to grain yield under salt stress in this CSSL. Our results provide insights into mechanisms conferring grain yield under salinity stress and new genetic resources for cloning and breeding.