Cotton leaf spot (Alternaria macrospora) is a widespread disease that occurs in the main cotton-producing area of China. In managing this disease, a novel chitosan-based biopesticide, an amphiphilic N-alkyl-O-carboxymethyl chitosan derivative, was prepared. The product was selected from variations of chitosan with different molecular structures, which were obtained via a two-step reaction. First, carboxymethyl chitosans with varying molecular sizes were obtained by etherification with chloroacetic acid; then the carboxymethyl chitosan was alkylated with C4–C12 fatty aldehyde through a Schiff-base reaction. This procedure resulted in derivatives of amphiphilic N-alkyl-O-carboxymethyl chitosan, which showed strong antifungal activities against A. macrospora , and the efficacy was determined by its molecular structure.
Locating the source(s) of the raw material used in the production of Shang bronzes with highly radiogenic lead (HRL) has been one of the most important unresolved issues surrounding metallurgy in early China. In this paper, we demonstrate that the Shang period (ca. 1600–1050 BCE) smelting slags from Yingcheng contain HRL, and the copper ores could have been acquired from Lüzudong and Bukou (6 km and 17 km from Yingcheng, respectively). This is the first discovery of HRL from Shang period smelting slags. In addition, the lead isotope signals from Yingcheng match well with those from Middle Shang period bronzes, indicating the possibility that Laiwu could be a source area for metals with HRL at the time. Our data provide a new direction for exploring the sources of ores for Shang bronzes, which can in turn inform us about the socio-political and economic organization of the Shang state.
When and under what circumstances domestication related traits evolved in soybean (Glycine max) is not well understood. Seed size has been a focus of archaeological attention because increased soybean seed weight/size is a trait that distinguishes most modern soybeans from their ancestors; however, archaeological seed size analysis has had limited success. Modern domesticated soybean has a significantly higher oil content than its wild counterpart so oil content is potentially a source of new insight into soybean domestication. We investigated soybean oil content using X-ray computed tomography (CT; specifically, synchrotron radiation X-ray CT or SRX-CT) of charred, archaeological soybean seeds. CT identified holes in the specimens that are associated with oil content. A high oil content facilitates the development of small holes, whereas a high protein content results in larger holes. The volume of small holes increased slowly from 7,500 to 4,000 cal B.P. We infer that human selection for higher oil content began as early as 7,500 cal B.P. and that high oil content cultivars were well established by 4,000 cal B.P.
Endophytic strains were isolated from different parts of a healthy "Dongzao" jujube (Ziziphus jujuba Mill. 'Dongzao') to find biocontrol agents against jujube shrunken-fruit disease caused by Alternaria alternata. The strains were screened using A. alternata strain CN193 as the target pathogen. The nutrient competition for all isolates was studied using the dual culture, and their inhibitive capability was tested by measuring the inhibition width of filter paper disks with filtrate. Influence of filtrate from the selected strains with strong inhibition of mycelial growth on spore germination was studied with hanging drop method on concavity slides. Colonization in the jujube leaves was assayed using a rifampicin-resistant mutant of strain St-zn-34 as the screening marker. Strains were identified based on their morphological, physiological, and biochemical characteristics, 16S rDNA sequencing, and phylogenetic analysis. A total of 81 endophytic strains were isolated from the stems, leaves, flowers, and fruits of winter jujube. Among these isolates, 14 strains showed strong antagonism against A. alternata. Further study showed that the filtrate of strains St-zn-9 and St-zn-34 could inhibit the mycelial growth of A. alternata, and the widths of their inhibition zone reached 6.14±0.03 mm and 8.27±0.09 mm, respectively. However, strain St-zn-34 showed stronger inhibition on spore germination than strain St-zn-9. St-zn-34 could significantly reduce the spore germination rate of A. alternata, and the spore did not germinate at all or the germ tube was very short. A rifampicin resistant-derivative of wild-type strain St-zn-34, which was designated as St-zn-34r, was obtained by transferring the strains to media with stepwise-increased rifampicin. Colonization assays indicated that St-zn-34r could colonize in jujube leaves, and the population of St-zn-34r was 1.2×103 CFU/g FW after inoculation for 30 days. Except for its salt tolerance, St-zn-34 was the closest to those of Bacillus subtilis. Thus, the strain was identified as B. subtilis.
The effects of repeated freeze-thaw cycles(F-Tc) on cell shape of fermented Bacillus subtilis and the inhibitory activity to Alternaria alternata, the primary infection pathogen of jujube fruit shrunken disease, were determined using an endophytic B. subtilis strain St-zn-34 isolated from winter jujube.The fermented broth was freeze-thawed after batch fermentation of the test strain. The population of living bacteria and bacterial endospores were determined by dilution methods of plate counting, and the inhibitory activity to A. alternata was tested by filter paper disks with filtrate of fermented broth. The shape of B. subtilis with different freeze-thaw cycles was observed under environment scanning electron microscope.Changes of pH, living bacteria, bacterial endospore counts in the fermentation broth and the inhibitory activity of filtrate at different time generally increased first and decreased afterwards. The inhibitory activity at 60 h was higher than other time points. The bacterial cells fermented for 60 h were treated with F-Tc, and the living bacteria count and inhibitory activity decreased gradually when cells of B. subtilis were freeze-thawed for 3 cycles, but it had no significant difference (P>0.05) after being freeze-thawed for more than 3 times. With the increase of freeze-thawing times, the bacteria cells became smaller than the normal cells, the surface twisted with one or more depressions, and the jelly flowed out under environment scanning electron microscope. The inhibitory activity of filtrate was determined and it showed a broad-spectrum inhibitive capability against twelve species of plant pathogens. The treatment of different temperature and proteinase to the filtrate showed that the temperature below 60℃ did not affect the inhibitive activity and had no significant difference compared with that of the control. However, the inhibition decreased with increasing of the temperature above 80℃ and was significantly lower than that of control. The inhibitory activity of filtrate to A. alternata decreased by treatment with proteinase K.Repeated freeze-thaw cycles could affect the shape of B. subtilis and reduced the inhibitory activity of filtrate to A. alternata.
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