Efficient control of the fungal pathogens Colletotrichum gloeosporioides and Penicillium digitatum infecting citrus fruits by native soilborne Bacillus velezensis strains.

Destruction of citrus fruits by fungal pathogens during preharvest and postharvest stages can result in severe losses for the citrus industry. Antagonistic microorganisms used as biological agents to control citrus pathogens are considered alternatives to synthetic fungicides. In this study, we aimed to identify fungal pathogens causing dominant diseases on citrus fruits in a specialized citrus cultivation region of Vietnam and inspect soilborne Bacillus isolates with antifungal activity against these pathogens. Two fungal pathogens were characterized as Colletotrichum gloeosporioides and Penicillium digitatum based on morphological characteristics and ribosomal DNA internal transcribed spacer sequence analyses. Reinfection assays of orange fruits confirmed that C. gloeosporioides causes stem-end rot, and P. digitatum triggers green mold disease. By the heterologous expression of the green fluorescent protein (GFP) in C. gloeosporioides using Agrobacterium tumefaciens-mediated transformation, we could observe the fungal infection process of the citrus fruit stem-end rot caused by C. gloeosporioides for the first time. Furthermore, we isolated and selected two soilborne Bacillus strains with strong antagonistic activity for preventing the decay of citrus fruits by these pathogens. Molecular analyses of 16 S rRNA and gyrB genes showed that both isolates belong to B. velezensis. Antifungal activity assays indicated that bacterial culture suspensions could strongly inhibit C. gloeosporioides and P. digitatum, and shield orange fruits from the invasion of the pathogens. Our work provides a highly effective Bacillus-based preservative solution for combating the fungal pathogens C. gloeosporioides and P. digitatum to protect citrus fruits at the postharvest stages.

Boltzmann-type collision operators for Bogoliubov excitations of Bose-Einstein condensates: A unified framework.

Starting from the Bogoliubov diagonalization for the Hamiltonian of a weakly interacting Bose gas under the presence of a Bose-Einstein condensate, we derive the kinetic equation for the Bogoliubov excitations. Without dropping any of the commutators, we find three collisional processes. One of them describes the 1↔2 interactions between the condensate and the excited atoms. The other two describe the 2↔2 and 1↔3 interactions between the excited atoms themselves.

Shock waves from the inhomogeneous Boltzmann equation.

We revisit the problem on the inner structure of shock waves in simple gases modelized by the Boltzmann kinetic equation. In a paper by Pomeau [Y. Pomeau, Transp. Theory Stat. Phys. 16, 727 (1987)10.1080/00411458708204311], a self-similarity approach was proposed for infinite total cross section resulting from a power-law interaction, but this self-similar form does not have finite energy. Motivated by the work of Pomeau [Y. Pomeau, Transp. Theory Stat. Phys. 16, 727 (1987)10.1080/00411458708204311] and Bobylev and Cercignani [A. V. Bobylev and C. Cercignani, J. Stat. Phys. 106, 1039 (2002)10.1023/A:1014037804043], we started the research on the rigorous study of the solutions of the spatial homogeneous Boltzmann equation, focusing on those which do not have finite energy. However, infinite energy solutions do not have physical meaning in the present framework of kinetic theory of gases with collisions conserving the total kinetic energy. In the present work, we provide a correction to the self-similar form, so that the solutions are more physically sound in the sense that the energy is no longer infinite and that the perturbation brought by the shock does not grow at large distances of it on the cold side in the soft potential case.