Seasonal variation of airborne fungi of the Tiantishan Grottoes andWestern Xia Museum,Wuwei,China

In this study,a systematic survey of cultural airborne fungi was carried out in the occurrence environments of wall paintings that are preserved in the Tiantishan Grottoes and the Western Xia Museum,China.A bio-aerosol sampler was used for sampling in four seasons in 2016.Culture-dependent and-independent methods were taken to acquire airborne fungal concentration and purified strains;by the extraction of genomic DNA,amplification of fungal ITS rRNA gene region,sequencing,and phylogenetic analysis,thereafter the fungal community composition and distribution characteristics of different study sites were clarified.We disclosure the main environmental factors which may be responsible for dynamic changes of airborne fungi at the sampling sites.The concentration of cultural airborne fungi was in a range from 13 to 1,576 CFU/m^(3),no significant difference between the two sites at the Tiantishan Grottoes,with obvious characteristics of seasonal variation,in winter and spring were higher than in summer and autumn.Also,there was a significant difference in fungal concentration between the inside and outside of the Western Xia Museum,the outside of the museum was far more than the inside of the museum in the four seasons,particularly in the winter.Eight fungal genera were detected,including Cladosporium,Penicillium,Alternaria,and Filobasidium as the dominant groups.The airborne fungal community structures of the Tiantishan Grottoes show a distinct characteristic of seasonal variation and spatial distribution.Relative humidity,temperature and seasonal rainfall influence airborne fungal distribution.Some of the isolated strains have the potential to cause biodeterioration of ancient wall paintings.This study provides supporting information for the pre-warning conservation of cultural relics that are preserved at local sites and inside museums.

Responses of arbuscular mycorrhizal fungi to straw return and nitrogen fertilizer reduction in a rainfed maize field

Straw return can be used to reduce fertilizer input and improve agricultural sustainability and soil health.However,how straw return and reduced fertilizer application affect beneficial soil microbes,particularly arbuscular mycorrhizal fungi(AMF),remains poorly understood.Here,we conducted a five-year field experiment in a rainfed maize field on the Loess Plateau of northwestern China.We tested four treatments with straw return combined with four nitrogen(N)application rates,i.e.,100%,80%,60%,and 0%of the common N application rate(225 kg N ha^(-1)year^(-1))in this region,and two reference treatments(full or no N application),with three replicates for each treatment.Mycorrhizal colonization was quantified and AMF communities colonizing maize roots were characterized using Illumina sequencing.Forty virtual taxa(VTs)of AMF were identified in root samples,among which VT113(related to Rhizophagus fasciculatus)and VT156(related to Dominikia gansuensis)were the predominant taxa.Both root length colonization and AMF VT richness were sensitive to N fertilization,but not to straw return;furthermore,both gradually increased with decreasing N application rate.The VT composition of the AMF community was also affected by N fertilization,but not by straw return,and the community variation could be well explained by soil available N and phosphorus concentrations.Additionally,60%,80%,and full N fertilization produced similar maize yields.Thus,our study revealed the response patterns of AMF to straw return and N fertilizer reduction and showed that straw return combined with N fertilizer reduction may be a promising practice to maintain mycorrhizal symbiosis concomitantly with crop productivity.

Ethylene Production and 1-Aminocyclopropane-l-Carboxylate （ACC） Synthase Gene Expression in Tomato （ L ycopsicon esculentum Mill.） Leaves Under Enhanced UV-B Radiation

Tomato （Lycopslcon esculentum Mill.） plants grown in a greenhouse were irradiated with two different levels of UV-B, namely 8.82 （T1） and 12.6 kJ/m^2 per day （T2）. Ethylene production, 1-aminocyclopropane-1-carboxylate （ACC） content, 1-（malonylamino） cyclopvopane-1-carboxylic acid （MACC） content, gene expression of ACC aynthase （EC 4.4.1.14）, and ACC oxidase activity in tomato leaves were determined. The results Indicated that ACC content, the activity of ACC synthase and ACC oxidase, and ethylene production Increased continuously under low doses of UV-B radiation, whereas at high doses of radiation these parameters Increased during the first 12 d and then started to decrease. The MACC content increased continuously over 18 d under both doses of UV-B irradiation. The changes in ACC content, ACC synthaae activity, ACC oxidase activity, the transcriptional level of the ACC synthase gene, and ethylene production were consistent with each other, suggesting that ACC synthase was the key enzyme in ethylene biosynthesis and that ethylene production in tomato leaf tissues under UV-B radiation could be regulated by the expression of the ACC synthase gene. The results also indicate that the change in ethylene metabolism may be an adaptive mechanism to enhanced UV-B radiation.