Performance of common buckwheat(Fagopyrum esculentum M.) supplied with selenite or selenate for selenium biofortification in northeastern China

Selenium(Se)deficiency commonly occurs in soils of northeastern China and leads to insufficient Se intake by humans.A two-year field study of Se biofortification of common buckwheat supplied with 40 g Se ha^(-1)as selenite(Se(IV)),selenate(Se(VI)),or a combination(1/2 Se(IV+VI))was performed to investigate Se accumulation and translocation in plants and determine the effects of different forms of Se on the grain yield,biomass production,and Se use efficiency of plants and seeds.Se application increased seed Se concentrations to 47.1–265.1μg kg^(-1).Seed Se concentrations following Se(VI)or 1/2 Se(IV+VI)treatment exceeded 100μg kg^(-1),an amount suitable for crop Se biofortification.Se concentration in shoots and roots decreased with plant development,and Se translocation from root to shoot in Se(IV)-treated plants was lower than that in plants treated with 1/2 Se(IV+VI)and Se(VI).Both grain yield and biomass production increased under 1/2 Se(IV+VI)treatment,with grain yields reaching 1663.8 and 1558.5 kg ha^(-1)in 2015 and 2016,respectively,reflecting increases of 11.0% and 10.3% over those without Se application.The Se use efficiency of seeds and plants under Se(VI)treatment was significantly higher than those under 1/2 Se(IV+VI)and Se(IV)treatments.Thus,application of selenate could result in higher Se accumulation in buckwheat seeds than application of the other Se sources,but the combined application of selenate and selenite might be an alternative approach for improving buckwheat grain yield by Se biofortification in northeastern China.

Alterations of the oral and gut mycobiome and cytokines during long-term follow-up of COVID-19 convalescents

Dear Editor,A large number of COVID-19 patients experience body-specific conditions such as fatigue,sleep disturbances,anxiety,depression,and dyspnea after the disease has subsided,which is called“long COVID-19”.1 Studies have confirmed reduced microbial diversity,enrichment of opportunistic pathogens and depletion of beneficial symbiotic bacteria in patients with COVID-19.2,3 Long-term dysregulation of the microbiota has also been observed in recovered patients.4 Nevertheless,long-term fungal microbiota follow-up was still blank.

CH_4 and N_2O emissions from double-rice cropping system as affected by Chinese milk vetch and straw incorporation in southern China

Chinese milk vetch(CMV) and rice straw(RS)were incorporated into soil to substitute for synthetic N fertilizers and to maintain soil fertility. However, little is known about the integrated impacts of CMV and RS incorporation on CH_4 and N_2O emissions in double-rice cropping systems in southern China. A field experiment was conducted to estimate the integrated impacts of CMV and RS incorporation in the early-and late-rice seasons on CH_4 and N_2O emissions. All treatments received uniform N inputs, 6%–37% of which was replaced by CMV and RS crop residue. CMV and/or RS incorporation produced equivalent or slightly more grain yield, while reducing N2 O emissions by 3%–43%. However, both CMV and RS incorporation increased CH_4 emissions. Annual CH_4 emissions ranged from 321 to 614 kg·hm^(–2)from CMV and RS amendment treatments, which were 1.5–2.9 times higher than that from synthetic N. Compared with single synthetic N fertilizer, incorporation of CMV and/or RS increased GWP and yield-scaled GWP by 45%–164% and45%–153%, respectively. Our results demonstrate CMV and RS amendments replacing N fertilizer, maintained stable yield, mitigated N_2O emission, but enhanced CH_4 emission. Further study is needed on crop residue management in double-cropping rice systems.

The diazotrophic community in oat rhizosphere: effects of legume intercropping and crop growth stage

In this study, the abundance, diversity and structure of the diazotrophic community in oat rhizosphere soil in three cropping systems and at two oat growth stages were investigated using real-time PCR and Illumina MiSeq sequencing. The nifH gene abundance in oat-soybean intercropping (OSO) and oat-mungbean intercropping (OMO) was significantly greater than that in sole oat (O), but the nifH gene abundance significantly decreased at the later stage in all the treatments. Alpha diversity indices in OSO and OMO were higher at the heading stage, but lower at the maturity stage than that in O. Bradyrhizobium and Skermanella were the dominant genera identified in all samples, with an average proportion of 35.8% and 12.4%, respectively. The proportion of dominant genera showed significant differences and varied with cropping system and growth stage. Principal component analysis showed that growth stage had a stronger effect than intercropping on the diazotrophic community structure. However, Mantel test and redundancy analysis showed there was no environmental factor significantly correlated to the diazotrophic community structure. Our results demonstrate that intercropping had a weaker effect than growth stage on the abundance, diversity and structure of the diazotrophic community in oat rhizosphere soil.