No abstract

Bacterial speck caused by Pseudomonas syringae pv. tomato is a serious foliar disease on tomato. However, it is still unknown how organic fertilizers application mediates plant defense against foliar pathogens by altering the composition of the soil microbial community. We conducted a 2-cycle pot experiment involving chemical and organic fertilizers and tracked tomato foliar pathogen incidence. Using microbiome sequencing, we then compared the differences in bulk and rhizosphere microbial communities. The results showed that, compared with soils amended with chemical fertilizer, soils amended with organic fertilizer gradually and significantly presented a reduction in tomato foliar disease, and the bacterial richness and diversity significantly increased. Moreover, the bacterial and fungal compositions of the bulk soil and rhizosphere soil of the organic fertilizer and chemical fertilizer treatments were different from each other. More importantly, the abundance of some potentially beneficial bacteria, such as Luteolibacter, Glycomyces, Flavobacterium, and Flavihumibacter, increased in the organic fertilizer-amended soil, and these genera were significantly negatively correlated with the incidence of tomato foliar disease. These results suggest that organic fertilizers can alter the taxonomy of the soil microbiome and that some specific beneficial microbial communities may play an important role in reducing the infection of foliar pathogens by inducing plant resistance.

Three kinds of tri-metallic catalysts with core–shell structure are synthesized, in which the outer shell is alloy of Pt and Ag, and the inner core consists of Ag and Pd. Amongst, the composite catalyst with atomic ratio of Ag, Pd and Pt equaling to 1:1.4:1.2 (denoted as Ag1Pd1.4Pt1.2) has the greatest total mass activity (3310.7 mA mgmetal −1), which is much higher than commercial Pt-Ru, Pt- and Pd-based catalysts reported previously. The superior catalytic activity for methanol oxidation should be due to the high amount of Pt alloyed with the least Ag in outer shell and boundary of PtAg outer shell and AgPd inner core composed of tiny nanoclusters, endowing synergistic effect from the electronic structure, numerous defeats, and available great internal and external surface areas. In addition, Ag1Pd1.4Pt1.2 catalyst about 250 nm at mesoscopic scale shows improved stability to large extent. Meanwhile, the presence of Pd in Ag1Pd1.4Pt1.2 contributes outstanding ability against CO poisoning. This work may pave a promising way to prepare core–shell composite catalyst with high catalytic performance for fuel cell application.

Engineering non-Pt electrocatalysts that are accompanied with superior activity and durability toward methanol oxidation reaction (MOR) remains a great challenge. In this work, a lamellar and conductive ion association is easily formed by mixing Na 2 PdCl 4 , (NH 4 ) 6 Mo 7 O 24 , and cetyltrimethylammonium bromide (CTAB), designated as PdMoCTAB. Through tuning the amounts of precursors, three kinds of palladium (Pd) supported by lamellar ion association are fabricated by a facile hydrothermal method. Surprisingly, when the atomic ratio of Pd and Mo is 1.8:1, the resultant Pd/PdMoCTAB (denoted as Pd 1.8 Mo) presents great catalytic performance for MOR in an alkaline medium with a high peak current density of 2178 mA•mg metal −1 . The mechanism could be due to the high loading efficiency of Pd on the great surface of ion association, rapid mass transferring in the lamellar structure, and abundant strain defects of Pd induced by the deformation of ion association as well as the good conductivity of PdMoCTAB. Pd 1.8 Mo also shows improved stability, whereby the current density maintains 104 mA•mg metal −1 after electrochemical catalysis for 10,000 s and, after 500 cycles, the mass activity retains about 64% of the initial value. Such conductive and lamellar PdMoCTAB ion association is expected to become a promising support to load various noble metals for preparing excellent electrochemical catalysts.